Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Steam => Topic started by: Capricorn on October 26, 2007, 01:32:45 pm
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Looking for info on model steam turbine engines. Would appreciate any links or discussion on topic.
Thanks, Capricorn
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Hi Cap,
I recently designed and made my own, this was designed to run from air, but should be able to run from steam with a little modification to material selection. It all depends on what you want to 'do' with it. They are fairly easy to make, mine took about 3 days for the basic engine plus another one to match it to the generator.
http://www.youtube.com/watch?v=KW6V7JWbQwk
If you are looking to power a model boat, maybe a few less pockets on the rotor to make it smaller, but you would need a reduction gearbox on it, as props don't really like running at over 30-40,000 rpm, which is easily obtainable from a turbine.
John
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Thanks John,
I'm watching the video now, it will take an hour on our connection. Have you seen the tesla turbine video on youtube too? I haven't got the link handy but it was good, if you want to see it and can't find it let me know. I thought about a tesla too, but it seems it may be a bit touchy
I do plan to power a boat with it, a 10 ft long, 100 lbs fletcher class destroyer. I'm going to need something in the range of 1/4 hp (approximate). It's preliminary, I wanted to use steam, decided to go with electric, but now am back on steam again. I plan to use a couple 16.4 oz tanks of propane for fuel. The principle is very simple, and the turbine can be done I think, but the system controls get complex fast.
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John,
Finished watching the video, it screams. Any info on it, like rpm, power output etc. I've seen a few turbines and they usually run a generator like yours, but I've not found out how much power they produce, can you put a watt meter on it? Cap
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Hi Cap,
The main problem with turbines are the bearings. The ones I use are shielded stainless and are rated by the manufacturer at max 45K.
Even the ceramic bearings that NASA uses don't go to the full potential of a high speed turbine, and you would need a second mortgage to buy a pair. That is why I have put a load on mine to stop it reaching that sacred number.
If you can supply a watt meter ?? it can be connected.
At about 40psi mine runs at what I suspect is somewhere between 35 & 40k loaded with generator. My tacho only goes up to 29k so I can't measure it accurately above that. Without the load I am positive the motor would shatter within a few minutes running as I suspect from previous very short duration unloaded testing it would easily exceed 100k.
Turbines for model boats were still being manufactured up until I think the late eighties, so maybe someone has some info on how they performed.
Tesla turbines are a total waste of space as far as I am concerned, they were just a by product of his experimentation and are as far as I know very 'greedy' engines, it is that they are easy to produce coupled with impressive looks is the reason they have caught on.
For the size of ship you are contemplating I am sure that a couple, or even one of the pocket type turbines geared down to about 20 to 1 would power your model easily. Keeping them supplied with the volume of steam that is required would be your main problem.
John
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For turbine bearings check the WREN site for model gas turbines cos in toy aero construction, SELF built
model gas turbines IDLE at around 40K.
Ian
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John, thanks for taking the time to respond. It's a bit of a nutty project but I enjoy it. I'll definitely have to keep the revs down, in fact I wasn't anticipating over 20K, but I imagine that's where you get the power, low torque x many rpms. (the watt meters are fairly common now, gadget with 2 wires on each end and a LC screen, you just put it between your generator and load, it reads out volts, amps, watts, and records high point, sort of expensive, about 50$ US I think).
Yes the steam supply is one of the big concerns, and then matching it with the turbine consumption. I need to get out the old physics book and steam tables. One item I'm not sure about either is whether it's worth putting in a condensor to try to retain warm water for feeding the boiler, or if I should just use that space for a second boiler.
See attached "preliminary" drawing. That's just one version of the turbine, though you can't see much, it's goofy, with the exhaust ducts, would be difficult to build.
I think the propane tanks can put out 11000 btu's for 4 hours, so two tanks could put out as much as heat as needed if it can be accomodated, and then converted to steam. (Like 176000 btu's for a half hour heh, heh, that's 34 hp) at 1% effeciency that's 1/3 hp, but I'm afraid the thing would melt or explode.
What do you think? Cap
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Circlip,
I think you will find that the type of ceramic bearings used in model gas turbine engines have very limited life, around 30 hours at my last query about them. That is why they are so cheap.
Cap,
I am no expert on boiler design, but with the available output you have I would definitely consider a flash boiler. That would certainly be man enough to keep a small turbine running, in fact it just might be too much, your main problem as far as I can see is getting rid of the heat produced. If you want to see how I made my basic designed pocket turbine you should be able to find it here
http://freeforums4u.com/viewtopic.php?t=244&mforum=homemodelengine
You might have to register to view the pics, but if you want to build one at least it will give you a good basic understanding, but for your use I would consider building one with solid end shields, and duct the spent steam away thru a pipe, one can easily be knocked up in a couple of days. For gearing down from this sort of speed a good quality worm gear system could easily do it, that is 1 worm gear and a 20 tooth pinion.
No complicated gearboxes. This type can also be reversed either from another nozzle blowing the wheel from the opposite direction, not very efficient, to machining a set of reversing pockets on the side of the wheel, more efficient, or even two rows of pockets, one for forwards one for reverse on the top face, separated by a wall, most efficient, but would need two sets of tangential exhausts.
John
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Ian,
Thanks for the link, I looked through it some. I'll eventually have to select bearings but probably get relatively cheap ones, with an auto oiler and just replace them as needed.
John2, thanks for the info, I'll look. It's exactly the sort of thing I need, see something that works and not stray too far from it. A small computer fan(s) may not be adequate for taking the heat out, but if I insulate it hopefully most will go up the stack, may end up like a blow torch, direct it aft and get some more thrust.
Will look at both sites and respond, takes a while. Thanks all for input/discussion. Any other ideas info much appreciated. Cap
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Yes, thats the price of fame in the turbine world, I think if the aero set get up to 30hrs between rebuilds they
would be ecstatic, they usually replace the bearings quite regularly but only in the interests of safety. This is
even using forced lubrication and while the aero side has been 'sorted' it will still take a few years to make a
Successful model marine unit. If you can trace links to the Saito units of a few years ago you can see the problems
a 'Manufacturer' had. John has given you a clue as to the problem in terms of steam consumption of turbines
by stating you would probably need flash steam at 'small' sizes, the high speeds associated with them are due
to the need for EFFICIENCY. If you can get hold of some of the old Model Engineer mags dealing with this you
will be amazed at the experimentation to try to achieve this, - nozzle size ,venturi shape, injection angle - there's
no EASY quick fix. The peripheral speed of the rotor also tends to be a bit troublesome, if it runs too fast the rotor
disk can explode - this is a function of rotational speed and disc diameter, are you getting a basic insight? If you
can get hold of a copy of Experimental Flash Steam by J H Benson & A A Rayman it certainly makes interesting
bedside reading cos due to temp and pressure of steam it makes even 'slow' reciprocating engines glow red hot!
Hope I haven't put you off, bearings are going to be the LEAST of your problems.
Ian
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Ian, Thanks, I'm sure you are correct about the difficulty, I'm sure the nozzles are touchy as well as much of the rest. On the other hand I'm not planning to run the thing for extended periods, or often, it's more the building of it that interests me. Obviously a successful maiden voyage is hoped for but I'm okay with whatever the result, just hope I don't get seriously injured :(. Thanks for the sources too, thats what I need, I'm not a great researcher so I appreciate getting help finding these things. Cap
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Senility creeping in, - you'll get there eventually, but article on model steam turbines is in JULY edition of
MODEL BOATS - THIS YEAR.
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Ian, I'm working on it. Senile... only in the early stages. I'm working on finding the article but I don't subscribe so I don't know what the chances are (do you know the title of the article?).
I am getting a basic insight into the steam powered turbine world. I have an idea of the scope, it's big. Any design suggestions, sketches?
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I have the article. I can scan it and email it to you if you like. It's three pages.
Colin
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Thanks Collin that would be great. My home email is in my wifes name, [email protected], accessible through the forum I imagine. You can send her gift ideas too, only gifts for me though ;D.
Any collaboration on this project is welcome, I may not have the machinest skills for some parts of it, not to mention equipment. Electronics/computers as well, although I'm working on that.
Cap
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On the way! Hope you find it interesting.
Colin
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Thanks much Colin, I do find it interesting and will keep looking for info myself as well. It would be nice to bypass all the design, trial and error over the years. Cap
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Years and years ago someone used to advertise a model turbine every month in Model Boats. Cheap and simple, he said. Did anybody try one?
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Jonty, I'll bet it was pre 'Trade descriptions act' ? Cap, just to show how simple steam turbines are;-
MODEL STEAM TURBINES, How to design and build them, by H H Harrison. Originally published by
Percival Marshall, (stop laughing silver surfers!) - re published by MAP - Argus books Ltd. Don't know
why people have found it sooo difficult?
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Could someone explain to a person who knows nothing about steam why it's impossible/impractical and/or inefficient to make a model turbine that spins at sane revs?
I mean, if there was a solution that works around 2k-3k rpm then surely people would be ditching reciprocating engines for turbines at least as fast as the RN did...and possibly luring more people into (what for me, at any rate) is the most romantic and potentially most rewarding method of propulsion available.
Curious, Andy
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Hi Andy,
I think you are getting slightly confused here. As far as I know (and I await correction), surface warships use mainly gas turbines, basically the same as used in aircraft, but adapted through gearboxes to drive the prop shafts. Nuclear submarines use steam turbines, again through gearboxes, driven by steam being produced by the reactor heating water.
To answer your question about why not have a slow running turbine. The power band of a turbine doesn't start until it reaches a high RPM. Very similar to an F1 racing car, imagine one running at 3k, you could most probably overtake it with a Reliant Robin (nothing against them by the way), but put at over 15k and the power band kicks in, you have great power at your fingertips, that is why they have so many gears, it allows them to stay within the power band being produced by the engine without slowing it down.
So basically, what is being discussed is, run the turbine at fast speed to get to its ideal power band, then reduce that speed with the aid of a gearbox to a speed that can be used with a standard prop drive. The main problem is keeping the turbine running at high speed requires large amounts of steam (remember we don't have unlimited heat sources as in a nuclear sub), so generating that steam, and getting rid of the heat in producing that steam is the main issue.
I do hope that this explains it ok.
John
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Hi John!
I think you are getting slightly confused here.
Now THAT is highly likely! :D
But what I mean is (and should have explained better) the RN of the early 20th century ditched triple expansion steam engines for a whole raft of reasons, adopting steam turbines with great rapidity, while the modelling steam fraternity have tended to stick with, at best, century-old technology.
Full sized steam turbines run around the hundreds of rpm's - handy for direct drive propellors or for low gearing. I can see that model steam turbines might well have to run at tens of thousands of rpm for scale and efficiency reasons, making them fairly impractical (short bearing life, massive gearing required) for models.
Please correct me if my assumptions are wrong - would I be right in thinking that (slow rev) reciprocating engines are powered mainly by the pressure of the steam created, while (high rev) turbines run mainly on the kinetic energy of the steam? If that's the case, is there not some engineering middle ground possible that could result in a "few thousand" rpm steam plant more suitable for model boat use? Something that doesn't result in wear and friction along the lines of the reciprocating engine, and avoids the high rev wear amd large steam loss of small turbines?
Andy
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No correction John, just a simplification for Andy, If you run a low voltage motor and grip the shaft you can
relatively easily stop the rotation? add a few gears and watch yer fingers
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Hello, good to hear things moving along, I'm in a different time zone here (Minnesota USA). It does seem any turbine worth its salt is high rpm. In order to accomplish a reasonably useful one for model purposes (large model maybe) I'd like to reduce the rpm too, even if it means there's a lot of potential power lost. Many of the turbines have the first gear reduction within which I'd also like to omit for simplicity, if it doesn't result in more problems.
To get maximum torque and lowest rpm I'd want the largest rotor possible (I think), which I'm assuming would be around 4" dia. It could potentially go as large as 6" if the casing and other geometry can be kept within the space. It seems I could burn gas to provide 10000 btu's per hour (4 horsepower of heat), maybe that could convert to 1 horsepower of steam (25% efficient), then if the turbine was 25% efficient I'd get 1/4 horsepower. Overall that is 6% efficiency. Maybe I could burn 20000 btu.
The props are rated around 4000 rpm, 70 ft-lbs per second per shaft is about 1/4 hp, I'm not sure exactly how the prop works out but I get about 2 ft lbs of torque on the shafts. Direct drive on a 4" diameter turbine would require 4 ft lbs, or 12 lbs force tangential on the rotor (that is 70 ft lbs per second).
If the steam speed through the nozzle is close to the rotor speed 840 in/sec and the weight of steam (1 hp) going through in one second is 34.5/3600 = 0.01 lbs then the power is 1/2 hp. If the steam speed going in is 1150 in/sec or 133% the speed of the rotor then power in is 1 hp.
By volume the rotor has to carry 13.7 cu in of steam through the rotor per second, divide by 840 in/s gives 0.016 sq in crossection effectively (or 0.2 cu in per one rev), that's only .008 cu in per bucket with 24 buckets. And the nozzle diameter is 0.025 in if there are 24 nozzles. So how many psi is required to force the 34.5 lbs per hours of steam through 24 - 0.025 in dia nozzles?
If there is one thing I know the above calculations are all bull, but I don't like to read so I'm guessing, can someone spare me and correct it? Another problem might be the finite number of buckets and space between them when the steam gets cut off (maybe it will hum :angel:)
Go for it... Cap
density is .00007 lbs/ci then .5pv^2 is 3556 in-lbs/s or 296 ftlbs/s, 1/2 horsepower
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Hi Cap,
I noticed a chap had put this up on paddleducks, so I stole it and transferred it here.
To me, he has made the gearing too complicated, as stated before, a simple but good quality worm would do the initial stepdown gearing, then to a simple fwd/rev gearbox.
http://www.youtube.com/watch?v=irp004zw8pQ
The Jensen turbine looks to be a basic pocket type, but I think the exhaust is a bit haphazard in this design. I think it has been designed for the 'toy' market.
You are going a bit over the top with the theory bumph, most of us on here are the suck it and see brigade.
It is a shame that you are not a bit closer as I could most probably knock you up a prototype in a couple of days, but anyone in the UK within striking distance of where I live is quite willing to take up the offer to develop one, on the understanding it costs me nothing other than my time to produce, and I would "be in on the act" if it went commercial.
In fact I have nothing special on next week, so I just might knock up a basic prototype.
John
John
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OOOOH Bogstandard, wash your mouth out with battery acid! You can hardly count the likes of Prof Chaddock
with the suck it and see brigade! The clip you have picked up illustrates exactly the need for speed and efficiency
of turbines in that:-
1 You can hear the turbine slowing DESPITE the high gear reduction.
2 The overhung rotor is more difficult to balance - reduced RPM
3 Open EXHAUST - If sealed can be COMPOUNDED.
To name but three, - in the other clips on the same vids, some of which Capricorn have been made in the land
of the free ;D the one in which shows the making of an electric generator to power a 'Flash light' bulb, not
only does it not immediately work with the as designed input system (OK thats what we're about here) BUT
even by blasting it with high PRESSURE compressed air, you can still hear the rotor STALLING.
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John,
That's great your offering to build a prototype, I'd be happy to consider purchasing one. Being from another region entirely, and not having heard the term bumph, I had to look it up "Extra periphery crap, surplus to requirements.", extraordinarily accurate. 20 years ago I might have had a clue what I was doing, now I just guess. I'll look at the video later (takes time). Thanks for all the input (all) it's very helpful, and an actual working turbine engine would be more than helpful. Cap
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Circlip, I'll have to listen more closely and digest. What might be a reasonable low rpm? 15000?
Got started, you see I can just start screwing one bit on at a time and soon I'll be screwing the prop on the end.
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You didn't say you were making a GAS turbine!
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GAS turbine! English joke. Just to throw another hat in the ring (Rickenbaker) American joke, the really high
speed bearings are LIQUID or GAS!
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The droll, dry English humor alive and well? I don't know what you mean, whose Rickenbaker? The propane is for the boiler silly. Although one of my great grandparents was from England, Norwich area I think, the rest were Irish and Scotch Irish, so I can't be expected to trust you all ;), heh, heh. A gas turbine would be a little more direct wouldn't it? Cap
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Hope I didn't offend anyone :o. Just to show you I'm not all full of hot air see photo (it's helium, not hot air). It's my other 10 foot long model. A 1:80 scale airship, 10 feet long, 20" diameter, that photo is old, had to crop it quite a bit to fit in the 256k max postable size here. It's got the flaps, servo's, motors on now, all it needs is a lightweight reciever and gasbags. Current weight is 175 grams, add gas bags and battery, it's be close to neutral bouyancy (I hope). Cap
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Based on my previous experience of pocket edge turbines (not a lot of it), I have drawn up a very basic sketch of a small turbine that should work well, and would give a compact design of about 50mm OA diameter and length.
I am just finishing off an engine at the moment, so maybe next week I might be able to knock one up for running on air.
My boiler has now finally given up the ghost, and I have no way of 'steaming' one, but if air trials show it works well, I can knock one up out of materials for running on steam, then I would require the assistance of someone with a boiler. Unless someone wishes to donate a brand new 3 1/2" vertical boiler with all the goodies attached ;)
The nozzles will be a converging design, starting at 3mm and ending up at 1.5mm, and by using a basic steam speed control (my own totally sealed unit), proportional fwd/rev should be obtainable.
Tangential exhausts will help to 'scrape' the steam off the rotor and hopefully reduce the pressure build up in the chamber.
John
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Capricorn, shame on you. >>:-( (Eddie) Rickenbaker was one of your countrymen who came over to France in the
Great War, (WW 1 ) to beat the German Air Force for us. His emblem on the side of his Nieuport was a top hat
inside a circle. I am sure I have seen the construction and operation of a simple and muti-stage turbine similar to
the bogstandard one on one of your sites overthere, will try to find it.
Ian
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Isn't tintrnet wonderfull? Just Googled model steam turbines and it came up with a couple of interesting links:-
www.archive.org/details/modelsteamturbin00harrrich copy of harrisons book to download, - cheaper than
nearly $90 Canadian to buy original copy. Other site was www.indianarog.com
Ian
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Lost my whole post, got to write it over.
John, I wasn't able to open the larger version of your drawings (true back of the paper napkin sketch, the best kind). Does it have the fingernail type buckets like the other one? 50mm sounds a bit small, but you've made them before, is that a prototype or do you thing it can steam a 10 ft long 100 lbs destroyer at 8-12 knots? I thought you all held out on metric, we still have the imperial units here, eventhough just about everything is metric (from China etc).
Circlip, Forgive me, I thought the name sounded familiar, did Eddie shoot down any zeppelins? The internet is great, I had some time at work today for a bit, the connection is much faster there and found many many turbines, boilers etc, some very strange ones, quite the assortment. Thanks for the links, I'll look.
Check out the tiny steam (compressed air) engines on this one, one fits on the fellows finger nail:
http://www.powerhousemuseum.com/collection/database/?irn=214818
Cap I'm working a bit on boiler design I'll send over a sketch sometime
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Wrong website, although that one is interesting, the small fingernail sized one was on a machinist web site, the machinest is from India or something and make everything on a huge old lathe. I'll try to refind the website but here's the photo of it.
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Try here, half way down the page.
http://www.prismz.com/minipower/
John
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Steve, Have you seen anything related to that turbine, the picture looks a hundered years old. I recall now the Indian machinest, Iqbal Ahmed, pretty niffty 4 cyl gas engine.
http://www.craftsmanshipmuseum.com/Ahmed.htm
I'm still struggling with what to make the hull out of, it would be a huge project itself. Scaleshipyard. makes a 1/48 scale fletcher hull around 7 feet long. I don't know how well it holds up to heat, but it sure would simplify building this project. It's a bit small though, and the weight drops a lot, down to 40 lbs rather than 100.
I've done a bit of plaster casting, it appears that plaster might make a decent liner for the burner/boiler, heavy though.
Cap
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Hope you're all still around! Have done some adding and weight is more of an issue than I had expected, not too surprising I guess. The plaster liner adds a lot of weight. Had to shink a few items down a bit, dropped one propane tank and one motor, and it won't be carrying a car battery. Still in preliminary stages but I now have a better idea of the weight issures.
Also had to make the decision to make the hull out of wood, did not want to but it's more likely for me to build, and it's light in comparison. I'll cover it with fiberglass. All the wood will have to be sealed up and probably encased in some sort of resin.
So is what type of vertical boiler are we looking at for your turbine John? What are the goodies?
Cap
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Hi Cap,
When a post starts to get sidetracked away from the main original subject I tend to ignore it for a time until it gets back on track.
Unfortunately another main project has reared its ugly head in the workshop, so for about another two weeks that will now be taking priority. So when this post is on about steam turbines again rather than how small a chaps engines are, I will pick it up again.
John
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There are some interesting video on www.youtube.com if you do a search for steam turbine ..... O0
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Only two small observations Capricorn, It doesn't matter whether you are using 'Normal' or Flash steam, why
are you determined to use a vertical boiler? and why are you thinking of using PLASTER as an insulant?
With a HORIZONTAL boiler the CofG is lowered, and the modern insulators, EXCLUDING Asbestos are akin to
what NASA keeps chucking into space - CERAMICS, - no not porcelain's but ceramic papers, about 3mm SORRY
1/8th of an inch thick, so you can multi layer.
Ian
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Sorry John, didn't mean to get off the subject. I'll try to draw a version of your engine and see how close I come, then you can look at it and tell me if it's close. Cap
Thanks First Sea Lord I'll take a look on another computer this one is not good for viewing videos, I know there are a lot out there. I'm just trying to zero in on a good turbine engine, so it'll take some time, but sounds like John is quite the engine builder, what's the point in torturing myself if I can get one from him?
Ian, I think the one I'm planning is a horizontal boiler, John wants a vertical boiler. I'll look into the ceramic paper, it sounds expensive. But now that you mention it, with weight being a bigger issue than I thought it's probably worth looking at other material. I just figured I'm going to try to throw as much flame as I can in to it and I'd like for it not to glow orange. Plus the plaster casting is simple and buildable for me, but I'll look some more. Thanks Cap
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Cap,
If you read my post about the boiler, I was in fact joking. My boiler is now defunkt, and I jokingly asked if anyone was willing to give me a new one.
You should be considering if at all possible a horizontal, maybe with a ceramic burner, these are a lot more efficient. A flash boiler would be ideal but I have no idea who is producing them. There is one drawback with a flash boiler in that it has to have a pump to supply water. The way they work is unlike a normal boiler which is basically a tank full of hot water being kept hot by the burner to produce steam, a flash boiler only has a small amount injected which instantly turns to superheated high pressure steam, and is usually in sync with the engine so when the engine speeds up so does the flow of water. A good example is if you have a pan full of water on the stove and you are waiting for it to boil - a normal boiler, if there is no water in the pan and you dribble a little bit in slowly, instant continuous steam - flash boiler.
As I said in my previous post I am just designing and making a new type of air operated engine, so it will be a couple of weeks until I can concentrate on something else.
John
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I see, I thought maybe you wanted to get a boiler for a turbine engine. I'm slightly familiar with the flash boilers, understand the principle, and was thinking about it but it seemed a bit tough to make. In any case I always intended for it to be horizontal. I'll also look at ceramic burners too, I've seen a few but obviously aren't very familiar with them. Hope your other engine goes well. Cap
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Have made some progress on hull. How's that turbine engine coming John? Just kidding, it would be great if you had time but I'll plod along and get something in there eventually. Cap
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A bit more progress. Still hoping to use a steam turbine, but it's tempting to go ahead with some scooter motors.
(http://i262.photobucket.com/albums/ii92/capricornzzz/IMG_0474.jpg)
(http://i262.photobucket.com/albums/ii92/capricornzzz/IMG_0471.jpg)
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Capricorn, Hi
I was just gathering information to pass to you on RCGroups and here you be!
Strong suggestion - don't go for heavy insulation, in fact don't worry too much about it! There are a lot of balsa steamboats with sinple light insulation.
You can use litho plate - bend up a U shaped piece long enough to cover the boiler/burner - you can make it the chassis for the whole sream plant so that it lifts out for lighting, service, cursing at.
Plumbers use carbon cloth for insulation when soldering pipes close to wood or combustibles - this is abourt 1/8 thich and light and flexible - line the hull with one
My favourite (we have a u in Favourite here) is aluminium (we have an i in aluminium too) cooking foil - lay 3 or 4 layers together, put it in place and crimp the edges -
viola! lightweight insulation
andrew
still going to look in the loft! ;D
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Thanks Andrew! Those are great tips, I guess I should figure that out when I see the boilers with real wood slats around them, thats a great tip. I'm glad you reminded me, earlier in this string cvabishop mentioned an article, it was in modelboats uk 2007, and he copied it and emailed it to me, I'd nearly forgot about it. If that's the one you can postpone your trip to the loft, or I can email it to you as well if you're not sure or want to see it anyway.
I take it you work with live steam, I really have to take some time and look at others work, I imagine you've got some I'll look for them too.
Pops directed me here a while back and I've gotten a lot of good input, advice etc, I haven't done much regarding the turbine for a while though, must get back at it, the time for it is approaching.
Cap (Joe Cain)
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Joe,
Yes, cheerful (but irreverant) bunch on this forum
The magazine I am remembering will be Model Boats of about (guess) late 70s or early 80s - I'll see if it comes when I call.
andrew
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Thanks again Andrew,
Any ideas on the turbine itself? I was encouraged by Johns design (Bogstandard) above, he sketched what he thought would do the job, and he has some experience with them he said. I'm afraid he was ill though and I'm not sure he'll be able to build it.
Anyway, I took his design and put it on cad, with my own guesses on some of it. I like that it has reverse built in, and I think I'm understanding more how it works. I'm not sure I'm going to be able to make it, I have a small lathe now, but not a milling machine for the rotor buckets, plus many of the sizes are just guesses. Anyway here it is:
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I thought I could edit the post but don't seem to be able to.
Please delete the last pdf, jbturbine.pdf and use this one:
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Cap,
I've not been following this thread but find your plans to build a turbine along with your 1/35 DD build over at RCG impressive. O0
Am looking forward to watching this one. Will a Turbina build be next?
Chuck
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Hi Chuck,
It's pretty much the same thing, I have gotten a lot of input on the steam turbine part of it here. I hadn't done much on the turbine or steam plant for a while, nothing more than talk, but will need to start some time. I probably should have started with the turbinia, more appropriate for the first step I suppose.
I'm getting some input on the turbine design by John, so I'll be revising it some more. Cap
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Upped the size to 40-50mm range. Second of many iterations.
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Check out this crazy idea (see pdf). To be able to make it this one is mostly a bunch of discs rings and holes. The steam goes in one side where the holes are smaller, as it flows through progressively larger holes it is thrust back and forth through the stators and rotors, much like a regular marine turbine, but using angled holes rather than blades. Again doubtful success, first the holes are straight, not curved like the blades, and being so they have to be more oblique. But if more holes were used so it's almost like all that is left are blades maybe it would work a bit. Comments?
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Hi, Capricorn
Declaration of interest -I'm and engineer who has worked with steam turbines since I was 17, (but none smaller than 60 MW - about the size of a small house with boiler).
Small turbines have snags that can be hard to overcome - especially leakages, sealing etc.
Look how long it has taken for gas turbines to get small and efficient. They have benefited from the work done on car turbochargers, and steam turbines should be able to as well!
Pre-forgive a short lecture.
Probably worth getting the basics in.
There are two ways to get the energy out of steam (or any other gas):
Reaction and Impulse (to be difficult some turbines use a bit of both)
Reaction basically reverse the direction of the fluid (steam) and the turbine wheel picks up the energy - the turbines with "U" shaped notches or buckets are pure reaction machines
Impulse - usually airfoil blades, and they act as rotating wings in the steam flow. All big generator steamers are of this type - lots and lots of rows of rotor blades (getting larger as the steam pressure drops) with fixed stator blades between them to reverse the flow.
Lecture over - you can come out now
Thoughts on the "johnsturbine"
- nice, neat and makeable
- good idea to have a reverse feature - since the reverse is not required for high power the "pockets" can be cut in the side of the forward wheel
-Will need a high reduction to the prop - I wonder if the turbine could drive a electrical generator and then the prop could be electrically driven?
Thoughts on the crazy idea
-good crazy idea! I have no access to machining but I do have a friend with YAG laser - hence lots of identical holes are simple
-it works by reversing the flow - it is mainly a reaction machine - the holes don't have to be curved
-worth a try!
All these turbines and ideas can be tried with commpressed air - I think you have said this previously.
Model boat steam is hot, but not very hot.
Materials like bakelite, silicone rubber are perfectly happy at these temperatures
How about moulding the "body" of the johnsturbine in a silicone potting material - possibly with side plates holding the bearings
for a trial - make 1 rotor (in aluminium?) on 1/4 inch shaft with ballraces
Hold it together as a sandwich with a ring of bolts
see how it goes!
Reduction gearing - possibly an epicyclic gearbox with large reduction - about 50:1 (guess)
I have lots of dead electric drills - this is what they wear on the front
It might not be efficient , but it might work!
To begin with - we should not be seeking elegance or efficiency - we need first to get the thing to overcome its internal friction, then to deliver a little power to the shaft, then more and better power
How goes the hull?
andrew
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Hi Andrew,
The single rotor phase has already been proven.
http://www.youtube.com/v/wImhE-zNTgk&rel=1
During the first runnings the bearings were preloaded to prevent runaway past the safe bearing speed of 45k and to slow it down faster so that three runs could be got in in about 2+ minutes, without having to wait too long for the rundown.
One the second vid, the generator load keeps it from running away, but still reaches a very good stable RPM.
http://www.youtube.com/v/KW6V7JWbQwk&rel=1
The turbine shown has a 60mm diameter all brass rotor, with a 6mm thru shaft. The triple rotor one should have a 40 to 50mm diam rotors, again out of brass but with 5mm shafting.
I understand where you are coming from by using the pockets in the side of the rotor for reversing, but I designed this for actually running in reverse at fairly high speed as well, and it is rather difficult to get the jet totally concentrated and contained within a specific channel when impingeing onto the side of the rotor, hence my design for a separate reverse running rotor.
In fact the main rotor would be made in one piece, with 18 pockets (20 degree spacing) either side of the machined wall, but the pockets between the two sides would have an offset of 10 degrees between them to allow an even smoother running rotor, in effect having 36 pockets at 10. deg apart.
This engine, with a gear down of 15 to 1 should give a very good output for say a four or five inch prop. But the gearing comes later and needs to be proven after the engine is fine tuned. But I have a special inifinitely variable gearbox that will sort that out in no time, to give the best results for power output.
John
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John,
Forgive me, I had probably not read your posts sufficiently carefully and had not realised how far you have got
Thanks for the information and references - I will study with interest
Certainly I was not trying to teach you to suck eggs.
Since I am an engineer without machining capability I tend to imagine kitchen table solutions to devices, and this was the line I was thinking down.
Capricorn has a lovely hull, there - and the desire to turbine it!
Anything I can do to help, I will
I came across this, today
http://www.john-tom.com/ElmersEngines/12_turbine.pdf
best regards,
andrew
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Andrew,
No need to apologise at all, in fact it is nice to get a bit of conflicting input sometimes, makes you think down different routes.
I studied the Elmers turbine a couple of years ago, and it is rather basic, with a lot of hand finishing required, plus the shape of the blades wasn't very helpful at getting rid of the exhaust at high speed.
John
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Thanks John and Andrew, all this is greatly helpful to me. You are both so experienced in turbines and steam, along with everyone else I think I'll be able to do this.
The john-tom stuff is great, I was heading that way (on paper) for a while with a disc and holes drilled in it around the outer edge, but didn't take the final step of machining off the edges of the holes to form the cups, that looks like something I might be able to build. Will keep it in stuck away on hard drive, hopefully easier to find then in loft but not for certain.
The sketch with the plates with holes that I posted here is interesting but I have some reservations about it (probably doesn't work, certainly not how shown).
I'm going to try one more experiment with the computer fans. Here's a movie of the first:
http://s262.photobucket.com/albums/ii92/capricornzzz/?action=view¤t=MVI_0565.flv (http://s262.photobucket.com/albums/ii92/capricornzzz/?action=view¤t=MVI_0565.flv)
This time I'm going to use the thin 60mm fans with 11 blades and see if I can make a regular turbine alternating rotors and stators, mostly just for experimental sake. The main problem (besides the blade spacing) is that when I flip them the airfoil shape of the stators will be somewhat backward, which I assume, theoretically and practically nullifys them, but I guess I've got to experience it myself until I'm satisfied.
Here's a more developed idea which is certainly farther than my experiment would likely go. Originally I got pushed to the small ones to get higher rpm and ran the steam in tangentially. But I was really impressed how much torque this 60mm fan blade had under the compressed air, I just have to find some way of utilizing the wind off the first blade on more blades.
In any case I think the one with the fingernail buckets is the likely one to go farther, so I certainly haven't abandonded it just taking frequent detours :P.
Thanks again for input, and don't take any of the sketches to seriously they are always at best half finished (for instance it occured to me, like John said to offset the buckets (or nozzles) on the double forward rotors to provide more constant pressure on it)
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In the fan turbine you might require some fixed vanes in between to straighten out the flow before it hits the second set of blades. As the pressure is coming off the first set it would be very turbulent and going all over the place.
John
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Hull progress good, all but the very tip of the bow is done:
http://i262.photobucket.com/albums/ii92/capricornzzz/thIMG_0599.jpg
Plenty of room (I think), and should have 70 to 100 lbs payload (minus hull), but some of that may need to be bottom ballast.
John, I'm not sure if you are referring to the fanturbine on the movie or the drawing, I've got so many versions going it doesn't help. I assume the drawing, there I should have been more clear, the (red) fan blades would be fixed, although they look free, I didn't show the connecting piece, but it would be something like what the fans use, maybe four struts, each fixed fan blade hub would have a ball bearing so they stay centered on the shaft and probably thrust bearings between each fan. The shaft would have one flat side and the rotor fans would key onto that and then via all the thrust bearings the whole thing would be held together from the ends (didn't show that either). The taper I'd as soon skip, likely to destroy the blades for one plus make the thing a lot more work to build, it's just that they always seem to have the taper for expansion.
I've been prodigously drawing different turbines, check out the latest one, an impulse turbine again I think but with four small nozzles and two stators and two out rotors to try to pick up a bit more energy from the exhaust. Splits the jet like a pelton wheel type (or whatever they are called).
This time no color variation, but the center one and the two outer ones turn, the other two would be fixed somehow. It's just so hard for me to anticipate how sharp the curves should be etc, no idea if it would even turn.
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The probs with how you have it is, where do you get rid of the exhaust?
In basic format this rotor would be open to atmosphere, but in your situation, not a very good idea.
If all goes well and I recover to clear my backlog, in about a month or so I could make a prototype, but had a look at my stock this morning and the largest rotor I can make is about 35mm, 5mm of that would be the seperation wall. The cost of prototyping a larger one would be rather expensive. But the smaller one would prove the motor and give some figures for expected power output.
John
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John, That would be great if you build a prototype, do you have bearings and everything? How much do you think a larger one would cost? The boat has two propellers, and although I was thinking one large turbine, it may be more effective to use two since they are smaller. (Can you make two that turn in opposite directions? :D !)
What's the special infinitely variable gearbox? That sounds intriguing.
Andrew, since you work with the bladed turbines I was wondering how much the airfoil shape does for them, obviously it's important, but if the stator blades have the airfoil reversed how much affect would it have do you think?
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Gentlemen,
I have just posted a turbines in practice brain dump on
http://www.rcgroups.com/forums/showthread.php?t=816710&page=3
I will (mercifully) not subject you to it here.
John, I have viewed the turbines running, beautiful workmanship and sweet balance!
Capricorn, we are studying at the feet of a master!
Having seen and heard them I have become quite motivated to learn more and experiment a bit
Capricorn has started with computer fans - and is, I think, mainly using them as a quality set of bearings carrying a regular set of blade tips (this is good!)
I saw another video using my preferred basis - a Computer hard drive motor. These have quality bearings and machining, a generator in the middle (if required) and need only the addition of the blading to commence turning!
Also I have several (I rewind brushless motors for model planes and boats)
andrew
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Gents,
I think you are missing a very important point here.
STEAM. It is 'orrible stuff when working with it, and introducing it to bearings and fine wiring soon shows how nasty it can be. Even fairly high quality stainless bearings that I use suffer, I reckon between 30 to 40 hours running and it would be time to change them. That is why I went for a modular system where a bearing change could be done in less than an hour. The way 'toy' turbines work is by venting to atmosphere on the opposite side to the support bearing. In large engines they have power to spare and so they can afford to lose a bit of efficiency by introducing complicated sealing galleries to protect the bearings.
In this type of engine we can't do things like that, so we have to attempt to channel the steam where we want it to go, even though we haven't extracted all the power out of it, maybe a small secondary turbine could be run off the exhaust, but that is getting ahead of ourselves.
With regards to building two, running in opposite directions, no problems. But the first stage is to see if the small prototype has the properties to give what we want.
With regards to the variable gearbox, here is a picture of it with the rotor and generator from my turbine. By twiddling the little knob on the side of it you can go from 1 to 1, to 1 to 500, on the run. I have only ever seen one at this size, and I've got it.
http://i202.photobucket.com/albums/aa102/bogstandard_photos/3turbinerotorfinished.jpg
John
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That's a dandy looking turbine John. The gearbox, it must not be gears I take it, it wouldn't really be infinitely adjustable then would it? Or maybe it has some sort of diffential in it, have you peeked inside? Or is it secret?
I understand what you say about the steam being hard on the device, it must be simple to for my use too, changable bearings certainly shouldn't be a problem. In my case they wouldn't probaby have a lot of run time anyway, unless I rent a slip for it which isn't likely.
I did plan on running fairly large pipe or pipes from the exhaust back out the funnel, maybe through a condensor, just because it would be fun to build a water cooled condensor on it too, if there is room and can take the extra weight. How big of exhaust pipes do you think it would need to be low pressure enough?
I'm going to need to think about the boiler or boilers again, with the tubines relatively small, I could put in two relatively large boilers (if needed), the two compartments are roughly 7" high x 11" wide x 17" long, with some room into the above deck room, each with it's own funnel (convienient for sure). But I sort of planned on one boiler in the front room using the front funnel, and the back funnel would be for the steam exhaust, so if I used two boilers the stacks would have to be shared between steam exhaust and heat exhaust from the burners, I suppose a simple divider would keep them from spilling steam down into the burners. There is also a pipe with a downturned funnel on the end, much smaller, I'm sure you know what I'm referring too (if not see picture of fletcher, on the back of each main funnel are the little ones), I'm not sure what they were for, maybe diesel generator exhaust? I had thought they were the steam relief valve outlets which is what I was going to use them for.
Andrew, thanks for the info on turbines, I never was quite sure about the difference between impulse and reaction, so that clarifys it for me. The computer fan "turbine" that I made was basically an impulse turbine with the tangential flow onto the tips of the blades. (I actually gutted the wiring and had to use my own larger bearings but I saved all the fan bearings for later use in something).
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Bother - Just lost the post for the second time
Sketch of my trial turbine attached - might get it cut in the next couple of evenings
Where are are you in the New World, Capricorn?
andrew
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Andrew,
That looks good, how do you cut the buckets in? Wondering what you will use for the housing too (polycarbonate it looks like). Can you seal it so steam doesn't get into the electric motor? What is the motor rpm listed for?
I live in Minnetonka Minnesota, just west of Minneapolis. It's been the dead of winter here for a month now after a warm early winter, seems like a pattern now, but finally starting to warm up. Ice out of the lakes is usually in April.
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Hi Andrew,
Looks a very good design, and should work well.
Be very careful on initial trials as the bearings might be designed for high precision and smooth running, and designed for hard drive rotational speeds (somewhere between 7 - 10K). These types of turbines will, if made correctly will reach over 300K. On my inititial trials I preloaded mine to keep it about 40K max. Bearings have a bad habit of actually exploding, so as much safety precautions as possible.
I can't believe what some people get up to on utube, they take such unecessary risks.
Good luck with it.
John
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Good Morning, (and it is)
Did the earth move for you, in Crewe, John?
Our house is a gravity structure (110 year old lime mortar) so I need to have a look for any movement
Thanks for the observations and advice - I know that steam is searching and fairly evil - in all honesty I am aiming to use this motor chassis and a sacrificial proving gadget, and if the bearings croak, they croak.
Safety will be taken seriously - my 12 year old will be assisting me and I aim to show him that "everything is possible, bounded only by safety and society"
It will be tried on air to begin with - a little kinder and more controllable
Couple of pics attached of the victim motor - sorry about the focus - my camera needs good "Verticals" to pull a good focus and clearly didnt find any. The buckets are only freehand penned at the moment.
It works very well as a motor - I have brushless controllers for my planes, and since there are 3 wires it was not too difficult to fiigure the connections - it spins well on 6V, very well on 7.2V and wonderfully well on 12V.
Cutting the buckets? I have no machine tools or dividing head so I will use the best kit I have - drill stand and dremel with either a home-made end mill or (more likely) diamond burrs - I have a cutting plan in my head but can't describe it - I will take pics as I go.
andrew
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Capricorn - the trial setup will use an aluminium plate as the motor end plate (with a hole for the wires to emerge)
The main "block" will be a high quality plywood (safety and availability) and the open end cover will be Perspex or (most likely) polycarbonate
When I see how it goes I will either continue with electrical generation or revert to high-geared mechanical drive
Thinks - the motor running as generator will produce 3-phase AC, and I (probably) want single phase DC so I need to hatch a rectification scheme that gets to where I want.
An alternative might be to feed the raw output straight into a similar 3-phase motor!
andrew
andrew
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Andrew, Where are you located? Did you have an earthquake?
That looks like a pretty nice motor, I haven't got any of those. A turbine electric drive would be a slick drive system. Been pressed for time the last couple days but am eager to hear how it goes. It's good to have the generator part of it, easy to put load on the turbine.
Joe
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Joe,
I'm in the midlands of the UK - about an hour north of London - yes we had a 5.3 Richter earthquake last night, centred deep in the boonies of Lincolnshire about 60 miles away. I will check my chimneys tonight!
BFO - it had never ocurred to me that I can load the turbine (to prevent excess of rpm) with a resistor in the electrical circuit.
Thanks for that.
andrew
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I take it earthquakes are rare there? We are pretty safe here, the nearest major fault being in Missouri, which has the potential of being serious because it's inactive for long periods of time and therefore hadn't been viewed as a threat at least until recently.
Hope turbine test goes well, how tight of a tolerance is there between the rotor and the housing, that's something I'm curious about, I see that as a potential difficulty if I build one from scratch.
Joe
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Joe,
Lots of tremors - few earthquakes. The nearest plate edge is in mid-atlantic but they still can and do happen
Pic of the intended cuts attached. Didn't happen last night - I stripped a Seagate drive with my son. The motor is sweet, but uses the case as housing, - this might be a GOOD thing if the concept works as it would be a built in support and housing!
Clearances with impulse turbines should not be critical, and they are using velocity, not pressure, to spin the rotor. There needs to be enough clearance for the steam leaving the buckets to have a free way out and not interfere with the jet.
On clearance I would bow to John and people who have done it!
andrew
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Andrew,
It looks like you have it figured out, I was curious how you hold the motor while machining it. I don't imagine you have a dividing head, I'd like to have one but they are minimum $500 for a cheapo one (I think) so not likely, I bet John has one. I figure I can probably put something together for a specific spacing but may be just as well marking by hand with a protractor.
Anxious to hear the results. (Hope your chimney held up)
I've been idle no news to report on the turbines.
Joe
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Andrew,
Just a bit of info on how I do it.
I do use a rotary table, or a dividing head, just depends which one is handy.
I do it in one hit as set up like your 'x' picture. As shown in the first pic.
The nozzle is stepped down from 3.2mm (1/8" tube) inlet, to 1.5mm in steps, to increase the velocity of the either air or steam. You can see mine in the second pic.
The outer running clearance I set at 0.5mm (rotor diam of say 30mm, running in a chamber of 31mm diam). The tangential exhaust starts to strip the air or steam off at approx 90 degrees from the inlet nozzle impact point. You can just see the exhausts in the second pic.
John
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John, Like Andrew said, masterly work. Is that your original turbine or a new one? That rotor must be 60 or 70mm or so isn't it?
I should say I have 70mm propellers, opposite hand, three blade type D, that's about scale size but I'm nearly convinced they will be too small. I'm not really very experienced with boats enough to know, although I've done some investigating, what do you all think?. The ship is 10'6" long and should weigh somewhere between 100 and 125 lbs. I think the props (raboesch, I can't spell it), are rated at 4,000 rpm or something around there, I'm not opposed to exceeding that, but I imagine it's efficiency as well as vibration, possible damage to the props and maybe cavitation at some point.
I think I need to drop in the shafts and electric motors temporarily, get the weight up and test it before I'll know much, I'll work toward that. I've got to seal the inside of the hull and glass or cover the outside, hopefully I can do that before spring.
All the best. Joe
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I located the article I remembered on steam turbines in Model Boats - September 1985.
I suspect it is not as relevant now, but I have uploaded it to Photobucket
http://s222.photobucket.com/albums/dd159/andrewh_photo/plansscans/
The second half of the article was published in October 1985 - but I don't have that edition - wonder if anyone else has?
John - thanks for that picture - it tells several thousand words - I see the exhausts leaving and the general quality.
If I have been a good boy, and led a clean life, I might finish up soon with a little Colchester lathe which is being disposed of at work - this would open things up a bit for me, but the steam turbine might be behind the pair of 1/10 scale 20hp Fowler ploughing engines!
Joe, thats a lot of boat! I am not (ever) defeatist, but wonder if you have given some thought to a backup electric propulsion? You might want to have a way of returning her to the bank anyway if anything should go pear-shaped on the water!
Your props and thinking sound quite sensible, but at this size I think you would be amazed how efficient the hull and props are (compared with smaller boats)
I have been following a build of a STAGGERING Yamato about twice as big, I think (sorry, havn't got the link to it here) The builder is using 4 DC motors off a pump assembly that must be available in the US - I'll post the link when I find it, if that would hepl give you assurance about the props'revs/etc.
andrew
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Andrew, Thanks for finding the article! I haven't read it yet but will.
I have planned to have auxiluary electric motors, I'm not sure exactly how I'll get them connected in. Now that you mention it if I figured out how I want to mount them now that could be a permanent installation, the only thing is I'm not sure that the aux motors will be adequate for testing the max speed etc. ??? The aux motors I'll probably use for that are surplus motors from allelectronics (pretty nice for $3.50 ea), see photo. I thought scooter motors for testing the hull, bigger, high powered ones.
I'll look for the the huge yamato, I find the big ones fascinating, thought I was nuts at first until I saw some really big ones, have you seen the Arizona that is about 40' long a fella is building in his backyard? There are some aircraft carriers that the pilot rides inside, driven by a small outboard motor. Here on MBM Martin was starting a 1:35 scale Hood, but I haven't seen much on it for a while.
I tend to agree on your propeller opinion, I haven't given up hope on the small props, just haven't got the know how to be sure they'll do it.
Thanks for all the input, great help. Joe
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Andrew,
I read the article, still very valid I think, it confirms the high rpm recommendation. I keep hoping to get by dropping the rpm but keep hearing it's not the point on turbines so it's good to hear again. 1,000 rps is up there, (hopefully half that works), fortunately these days halfway decent gears are relatively cheap, just have to remember to get spares. etc. Hope you and your son get chance to test turbine soon, am waiting to hear, and John you must get busy again, help excersize you arm.
Joe
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1/96 Yamato build
Interesting not only in the speed, precision and compotent home-engineering of the whole thing, but it might help with drive train, power ideas
http://www.wmunderway.8m.com/cgi/yabb/YaBB.cgi?board=BuildB;action=display;num=1200112206;start=15
Fwiw - I see that new hard disc drive use fluid bearings - It will be interesting to see if these are any use to us!
I havn't cut pockets yet, but have the device fitted to a backplate - its a start!
andrew
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Andrew,
The new hard drives are now running at 10k rather than 7.2k. Don't believe all you hear about bearings and hard drives.
I used to be on the ground floor making protos of the damned things, and I can tell you now, they might sound all singing all dancing, but they will be the cheapest thing that they can get hold of to keep the price down, they have most probably done away with the balls completely and stuck in a chamber of oil, and called it some super duper thingymajig name to make it sound great, designed to run so many hours and then fail, just enough to get them thru the warranty period.
Caps,
I have had a total rethink on the turbine and have designed one in my head that puts all rotors together as one unit, I thought that seperate units would cause a balancing problem at such high speed. But it does mean that machining tolerances will have to be fairly tight (about 0.002" rotor to case clearance) also the exhausts will start to scrape much earlier (about 45 deg after inlet). Easier to make, more compact and only two bearings, both on the outside, so will have a better chance of keeping cool.
Your props will hopefully need about 400 to 500 rpm top wack, so a gear ratio of say 100 to 1 reduction would be the most that would be required. Need to see the speed output by the turbine before that is needed.
I have already geared up the making on a model engine site that I use, it will be after I have finished my latest project, and should take about a week if my health holds up. Then we should see if it comes up to expectations. The difficult bit will be making the throttle/reverse unit for it, but again the idea is locked in my brain at the moment, but it should work. As you know, I make on the run, piccies are for those who don't know what they want to do.
John
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Interesting that you've rethought it. Am anxious to see it but I assume I won't see any piccie's for a while. I read the article from Andrew by Terry Burnett, his sounds like a successful turbine but a bit beyond my means to construct, also chapter 12 on turbines and centifugal pumps, that turbine I might be able to make, and I can make it big enough too.
Will have to look into the fluid bearings, I imagine John is correct about their being as cheap as possible but they must rack up the revolutions by the time their life is over (be it with little load on them). Interesting you mentioned Seagate hard drives, they put them together here in the twin cities and one of my coworkers was there last week to review their roof for another bridge crane. They have rather intense security, he couldn't bring anything but a pad of paper and pencil inside (so not likely to come out with secrets or anything else :'().
John, when you say top wack do you mean max rpm's? I wouldn't think 400 or 500 rpms would be enough, I'd like a bow wave up to the deck if possible, but that's probably only 7 to 10 knots actual speed, which isn't slow but I was expecting to run those props pretty hard.
Cap
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Cap,
As far as I can remember, Rabo props are a built up design (rather than cast) and had a fair pitch on them. On the full sized ship they were most probably only turning just over 100 rpm. I don't think my calcs are far out for the size and speed required. but easy enough to rectify if wrong. My Clyde puffer weighed about 120lbs in the water, that was pushed along fairly rapid by a Rabo 4" prop running at 150rpm., and that was a bluff bowed hull with a lot of displacement, unlike yours which will be a lot sleeker in the water. The probs with running larger built up props at high speed, the blades tend to flex or come off.
If I can get this new design running somewhere between 35 & 40k (loaded) in forwards and about 25k in reverse and still have a good power output I will be more than pleased. Just depends how much pressure will be needed to get there. Won't know until it is tried, but going by what I have noticed with my larger version, I hope that it will be below 40 PSI, just depends on the volume then, whether a normal boiler can keep up with it.
John
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John, You remember correctly, they are not cast. I put one on a shaft with the 12v motor, and if I remember correctly (which I may not) it ran around 3,000 rpm with no load, at 7.2v it runs 2,200 rpm and it doesn't make a noise (obviously those figures have nothing to do with the prop). I ran it in the tub with 7.2v and it moved a heck of a lot of water around (that's not a very precise description of the prop performance either). At least in my case I likely won't be steaming it around a lot, but I sure wouldn't want the blades to flex off.
I don't know but I think one way or another I'll be able to get enough steam for it, like I said I have what seems to me to be a lot of room if needed.
I hope your arm is doing better John, do you know yet if it's going to be better than before?
Cap
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Cap,
I thought I would let you know that I have made a tentative start on the proto on an engine build site, here are a couple of pics, the first shows a quickie sketch of what the engine should look like and the second is a pic of the raw materials.
(http://i202.photobucket.com/albums/aa102/bogstandard_photos/3Roturbinitialsketch.jpg)
(http://i202.photobucket.com/albums/aa102/bogstandard_photos/3Roturbscrapbits.jpg)
This proto engine will be about 3" long x 2" high x 2 1/2" wide (excluding shaft length)
I hope to make a start on the rotor tomorrow.
My arm by the way is right back to square one, so now working again with one and a bit arms.
I will keep you posted on the progress.
John
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I'm sorry to hear about your arm, wish it had turned out better, but you've still got your mind and that's more important as you get older.
Great that you've got the materials, looks substantial, but I imagine a lot of it ends up as shavings. That's your special valve on the side and the exhaust on top it looks like.
I've ordered some epoxy coating for the inside, paint essentially, hope it's not too stinky, I've used 5 minute epoxy, it's strong smelling but not too bad in small quantities. We'll see what this is like. Then decide what goes on the outside regular fiberglass cloth and epoxy or paper or just paint? I think it will crack on the plank joint without reinforcing. Hopefully I can get it ready for a putt around the lake come late April when the ice goes out around here (usually, it's been a cold late winter here though).
Andrew, have you made progress on the turbine? Cap
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To totally seal your plank on frame hull, the best solution is to glass tissue the whole of the outside, when dry, pour glass resin on the inside and slosh it about so that everywhere is covered. Doing it that way, the hull ends up as a totally bonded and sealed unit. When it is all dry, fill and flat the outside. The underside of the deck also needs the same resin treatment. People tend to forget that and wonder after a while why all the planking is lifting and the deck warping, especially with the damp atmosphere caused by steam.
John
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Cap,
I would suggest (humbly) a one-word mod to John's suggestion for the outside of the hull, and that would be cloth rather than tissue. Both will finish up doing the same job but you will curse less with the right cloth!
My favourite for a hull is twill-weave cloth (this is what the females in your life will descride as bias-cut) Goes/drapes round curves better than mat/tissue or plain weave cloth.
My favourite resin is epoxy (though I dislike the chemical) - probably since a friend gave me 3 US galls of the stuff! 5-min epoxy is the worst (imho) for smell and function. Slow cure versions and the 2-part paints are much less objectionable.
John,
Nice sketch of the turbine concept - I see what you mean about the bearings held in cartridges outside.
With a shaft each side it could drive paddlewheels on each end.
<<straight face>>
Are paddle wheels Ok at 50 to 70,000 rpm?#
I have several steam boats with non-self-starting oscillators, and often want an electric drive to motor them back to the bank if the engine stops. Adding another prop and shaft is easy, but not what I really want.
My solution (though I have not done it yet) is a friction drive 385 motor swung into contact with the flywheel by another servo (I have spare channels)
How many shafts would your DD have in real life, Joe? 2? or More?
Presumably it would be possible to use a heli clutch or similar to clutch in an electric drive to the existing props (actually since heli clutches are centrifugal it might be a better idea to clutch in the steam turbine drive)
There are beautiful cousins of roller bearings called sprag clutches which grip in one direction but are completely free in the other - I don'y know how small they are made but I wonder if they would help.
No progress on the trial turbine - I'm rigging my Brig now
Sorry to hear about your arm, John. From your sketch you are a right-hander, hope this isn't the one with the problems.
andrew
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Well thank you both, I got some input on RCgroups too, it's much the same, I haven't used paper or cloth so it will be interesting. We'll see how many yards I need, probably cost a small fortune, the epoxy for the inside is 25$ a qt, plus the hardener.
Great point John on the bottom of the deck, I may have forgotten that too, total seal is what I'm shooting for, dolphinite in all the screw holes too.
The destroyer is a Fletcher (at 1/35 scale), I haven't done like many and picked a specific named boat, for one thing it isn't an accurate copy of the hull, it's squared off on the bottom, doesn't have the secondary keels etc so I'll probably leave it at "destroyer". It has two props, apparently on the real ones they prop shafts weren't symetric, one was tipped up more and offset maybe? Not sure why, although I read it, I doubt I'll do that.
A clutch of some sort is what I'd probably look at first, Pops is building 1/48 scale Fletcher (clayt.com) and he used the same type of contact wheel that you mention above Andrew, for his anchor chain winch, I'd probably think about that type as well. I'll look at the heli's and roller type.
Cap
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Cap
For when you get back from work
http://www.renold.com/Products/SpragClutchFreewheels/Sprag_Clutch_Index.asp
My brig is here under scale sail (for the adventurous) and on RC groups (brig Volante)
andrew
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Andrew,
What you call a sprag clutch, we call a one way bearing. I have been using them for years and have many in my stock of bearings. The main problem with them is when in the 'freewheel' mode, they don't like the shaft spinning inside them going too fast.
There is a fairly easy way of having an emergency motor, and it only comes into contact with the gear on the shaft when it is energised.
When the motor is spun, the idler gear is thrown over to come into contact with the drive gear on the shaft and the action of the electric motor shaft still turning keeps it in contact with the propshaft gear and so drives it. When the prop shaft is turning, it automatically throws the idler gear out of engagement. You do have to make sure the electric motor is turning the right way and is on the correct side of the shaft. This is a system used by ic engine boats to restart the motor in the middle of the lake, but it will work for an emergency return to the bank.
(http://i202.photobucket.com/albums/aa102/bogstandard_photos/startermotor.jpg)
John
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John,
Thanks for the sketch - I love your involutes - an automatic system with no drag when its disengaged
My cunning plan was similar, and used friction drive onto the flywheel
While trying to think of a controllable clutch, I realised that the tank drive systems must have servo-operated clutches - I know that Tamiya sell them as loose systems - must have a look for interest.
andrew
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Here is where the rotor is up to. It is made from PB1 and is to the stage of being ready to cut the pockets.
(http://i202.photobucket.com/albums/aa102/bogstandard_photos/3RotorTurbine13.jpg)
John
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Wow John, that looks great, really. I've got to find out about getting it from you when it's ready, I'll send you a secret message. That is assuming you'll be willing to give it up or make another (or two :D)
I appreciate the input from you guys on the clutch but haven't done much on it, was hoping the epoxy would arrive, but probably Monday. I've got to go back and read all the posts etc on finishing with fiberglass and epoxy etc, but John you mentioned finishing the outside first then the inside, I'm sure it makes sense, but do you think it would be a mistake to do the inside first? I was sort of hoping the coating on the inside would key the planks together so I could give it a good sanding on the outside. If I sand the outside now some planks are "free" from rib to rib and may not stay sanded down if you know what I mean. I could "sprinkle" a bunch of CA in it to key them I suppose. If the epoxy coating isn't too thin I don't think it will leak though, I haven't got very wide cracks or anything. Andrew, you seem to have some knowledge on this too what do you think.
Thanks, Cap
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After many hours, this is what the rotor looks like. It still requires balancing.
(http://i202.photobucket.com/albums/aa102/bogstandard_photos/3RotorTurbine17.jpg)
John
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Wow John that's a beaut. I love brass and anxious to see more. Cap
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If you like that, you will love this.
http://www.youtube.com/watch?v=YpcQ4JinhzI
John
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Great job John,
Now if we can just hook it up to a blender so we can make some margarita's! ;D
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John, I do love it. I don't know what to say, great work! One thing about it is it seems very safe, no blades or buckets to fly off, that is a highly desirable feature. I read about some other small turbines, if the prop came out of the water they would quickly accelerate, run too fast and disentigrate which included flying pieces. I trust the rotor on this one would have a difficult time leaving the housing even if the bearings somehow came apart.
I'm certainly interested in finding out what it can do in terms of power, rpm under load etc. Thanks very much for posting all the info on it etc. I'll be watching as you finish it up and test it. Cap
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The power will show itself when it gets a gearbox on it.
Just for interest, have a look at this
http://modelsteam.myfreeforum.org/about9874.html
John
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That is the mother of all model steam plants (that I've seen which is relatively limited), thanks for the link. I'm at a loss for words on that one too John, maybe if I paint the boiler blue it will look so good? I must ask the fellow some questions about it.
Will you run a generator off the gearbox, or a propeller or something, maybe a micro dynomometer?
I've hesitated on the finishing of the hull, but once I begin it shouldn't take more than a day or two (3 or 4), got a bit of snow here so it looks like winter again, but should melt soon.
Can't wait to see more! Cap
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Well I started with some epoxy on the interior of the hull first, nasty stuff, I have to either wait until it's warm outside and finish there or risk getting myself kicked out of the house along with my boat. (yes it leaked through the cracks, but not too bad) The smell sort of permeates the entire house, I have now read through some other threads on fiberglassing and I have a bit of experience with the resin. (some of the same issues with the smell, the spouse, and how to work around the cold temperatures outside)
I'm not really looking forward to trying to cover this large of a hull on my first try, in fact I'd prefer to just paint it but if I force myself to prepare everything it ought to go all right (right?).
Looking forward to what happens with your turbine too Andrew. Cap
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Well you lot!
I turn my back for seconds while I climb Welsh mountains (and take part in a Footy regatta) and you all advance by leaps and bounds ;D.
John, lovely work!
and thanks very much, too for your step by step build on the machining site. As I suspected you are a craftsman and you have a gift for describing it too.
Cap, good luck with the glassing - I have emailed you with suggested method and encouragement!
I feel like the lazy musketeer. Does it count that I have won my first yacht race?
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Congratulations on the race Andrew and thanks for the glassing tips, it adds a lot to what was very limited knowledge on that subject.
Not a lot of progress on my part really, I slathered on a bit of polyester resin (as you pointed out, I had assumed it was epoxy), nearly asphyxiating the entire family, and have abstained for now :angel:.
I've been "thinking" about the propshafts and motors since I will be putting them in relatively soon. I'm looking into the centrifugal clutches for the motors, I guess that's the same as the sprag clutch that you guys mention above, just have to see what rpms they all operate at etc. Cap
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Cap,
Why are you considering clutches?
John
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John,
These clutchs would be on the electric motors, see sketch. When the motors are off the clutch bells would be turned by the propeller shaft, but the motor itself would be still, when the motors are on the weights in the clutches would engage the bell and turn the shafts.
They cause a bit of drag since the belts and bells turn but at least the motor armatures would not have to be turned by the turbines.
I'm looking at the gas powered RC car clutches, although I may have to go with lighter springs so they will engage at lower motor rpm's and make sure they work forward or reverse, I believe they essentially work in only one direction on the cars but will/should work in reverse as well.
Let me know what you think. These are somewhat similar to sprag clutch I think. Main issue I see is they may not be in use much but turn a lot and so bearing/lubrication might be a problem, especially if the propshaft rpm is high. Cap
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Well, I realize now the electric motors won't be able to turn the turbine gears even if the gear ratio is "only" 20:1. If I want to run electric with the turbines off or out of steam, I'll have to disengage the turbines from the driveline somewhere, in which case I might as well make it a transmission shift, maybe three position: turbines, free/neutral, electric. The shifting would take place with the boat pretty much standing still and the turbines and motors turned off. I guess that's what happens when I try to concentrate on one part while ignoring another, but at least I didn't order any parts, it's usually a couple hours or a day after I press the confirm order button that I have the revelation.
It seems worm gears would be handy for the turbine gearing, but unfortunately it results in perpendicular shafts and thrust on the fastest spinning shaft, neither desired. A double worm gear would put the shafts parallel again but what's the point then? The advantage of the worm gear is the large gear ratio with just the single gear engagement.
Any mechanics out there got ideas? How about gears turning 30K rpm (+-10K), am I going to be able to find gears for those rev's that don't cost a fortune? Cap
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Cap,
I wouldn't do anything yet until I have managed to get the engine coupled with the variable gearbox, then I will know roughly what to expect reduction wise. This weekend is my cutoff point, I am hoping to have all the steam control made by then. Only then can I get a tacho onto it.
I have a few people screaming down my ear at the moment.
John
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John, I'll not be getting any gears soon, probably not any clutches either. I was trying to figure out a way I might get the motors on temporarily in a way that might be able to remain permanent. Pops sent over a bunch of links to various mini clutches, wow, welcome to the world of clutches, I'll re post them here in case anyone else is interested.
http://www.tinyclutch.com/
http://www.autotronicsinc.com/
http://www.machinecomp.com/electro_magnetic_clutches_info.htm
http://www.wmberg.com/catalog/product.aspx
Pops (Clay) is building a similar boat, the O'Bannon, 1/48 scale, electric powered and with extraordinary detail and much more skill than I have. It will undoubtedly look more like the real mccoy, even the deck sheets are put on seperately and will have weld joints:
http://clayt.com/
Also Nico Ottevaere., the Nicholas, 1/48th scale too:
http://users.skynet.be/nico.ottevaere/
Nico's is just as extraordinary, particularly the gun director and turrets which I hope to emulate in some form. (There's several movies, one with turrets operating)
I've benifited much already via contact with these two fellas, and anticipate much more expecially if I trail behind a bit, which I'm doing well at so far.
Probably ought to stick to the steam plant, engines and drive on this string though, it's already 6 pages ::). Cap
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Well, I machined my first parts on the lathe, pretty simple ones, just a piece of tube with a tapered end. No need to worry about me overtaking you on the lathe John (or anyone else). They will be part of the shaft support just before the propellers.
Also have sketch for the shaft and stuffing tube, the oilers not shown yet, still pondering that. I had thought of a grease nipple and regular grease but I've seen several places that oil is better (including from Andrew). The center bearing adds a bit of difficulty to it, unless I figure the oil flows through between the shaft and bearing, or I add a small channel to let the oil around or I put in another oiling tube behind the center bearing the rear bearing wouldn't get much oil, probably the one that needs it the most. Any ideas on that please let me know. As usual I'll spend a few days trying to figure it out then check the forums, oh well, keeps me out of trouble.
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Its a very similar concept to turbines i used to sell many years ago. They arent manufactured anymore, but the company in question still shows upgrades for their machines on this website, not sure if it helps give you any ideas.
http://www.haywardtyler.com/uploaded_files/Steam%20Turbine%20Upgrades.pdf
Shaft sealing on these machines was using segmental carbon rings, about 4 or 5 sets to help breakdown the pressure, simple and not too much friction
Some form of water cooling to the bearings will help greatly.
Do you have any form of speed governor?
Most turbines are fitted with a speed governor and an over speed trip, that will shut off steam supply if the rotor goes into runaway mode :)
One customer bought enough spares to rebuild their rotor, bearings seals etc, and decided that for next shut down they would replace the spare parts in the valve mechanism. Wrong way round as it turned out, after rebuilding the turbine they restarted it without load and the controls valves, which hadnt been used for a week due rebuild had gummed up. Rated speed 3000RPM, speed seen on handheld tacho (before they ran for it) was 12,000. One bearing complete with part of the shaft was thrown in one direction and the other bearing complete with speed governor went the other way. These were about 20kg a piece and landed over 200m away.
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Albion,
That one is a little larger than the one I am building, but fairly similar in rotor design.
I am hoping that a centrifugal oil barrier will be enough to keep the steam away fron the bearings.
I am just making the control system for it. It will be fully proportional control for fwd/rev.
Hopefully running under full control tomorrow or the day after. Depends how cold the workshop gets.
Then I will be able to get a tacho on it to see what I have to work with.
John
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Albion, thanks for the info, that's a nifty looking machine, what are they typically used for? 3000-12000 rpm would be nice but I think we determined it would be tough to run that slow with the steam volume and overall size of the turbine? Too bad for the fellow who destroyed his, I imagine they are rather expensive, but lucky he wasn't killed by the sounds of it.
I'd have to defer to John on the governer, I do anticipate a safety mechanism of some sort, mainly in case a prop fell off or the gearbox or drivetrain failed somehow, otherwise I imagine if the props are kept in the water it would prevent over running.
If the steam pressure is limited to a certain maximum and the orifice or nozzle is limited to a given size there ought to be a limit to the rpm, just based on the flow rate but it would depend on the load, to limit the no load speed to a max rpm might limit the power with load considerably.
What would be the best type of governer do you think an electronic sensor or centrifugal weights, I seems an electronic sensor would be easier, but would have to withstand pretty intense environment. The drive for a centrifugal governer might be as liable to fail as the main drive system so would it be worth it?
Cap
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A bit more progress, have the stuffing tubes and bearings ready, along with the braces. Soldering the braces on the ends of the stuffing tube went much easier than expected. Not ideal strengthwise but the joints are good I think. Couldn't resist setting them in place, they aren't placed correctly in the photo, they'll be a bit lower, the diagonal braces will also go in slots rather than abut. I'm really hoping the props are big enough, I can maybe go to 90mm but no bigger. Cap
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Normally they are drives for pumps, compressors and sometimes generators, usually in a refinery environment.
i appreciate at this scale a governor could be problematic, and that a runaway is not quite so danerous either.
Also realise that you are still building it, but the big brother bascially uses small nozzles, typically three to direct the steam at the wheel (slightly offset from centre of the bucket). Also on the stator side are three similar stationary buckets. These cause the steam to bounce back from the wheel to the stator and back to the wheel in a corkscrew motion (hope thats clear). Might help with future improvements O0
Something else to experiment with is backpressure. Strangely turbines of this tpye (well full size ones anyway) work better with some back pressure in the exhaust casing.
It may also avoid too much steam condensing in the exhaust casing and forming a pool of water eventually causign drag on the wheel.
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Albion's contribution immediately reminded me of another possible existing device of about the right type and scale.
Has anyone got a turbopump from a V2? Don't everyone speak at once! ;D
They are extremely neat steam impulse turbines (the steam is generated by decomposing hydrogen peroxide) I played with them at school, (just after the last ice age)
Cap - I suggest that you don't want a governor (which keeps a set speed) but an overspeed preventer. All the turbines I have come across require at least 2 independant sytems to prevent overspeed safely.
[for fun - one of the big machines - 50,000 HP - would overspeed by 20% in 50 milliseconds if it lost the load at full power - so we had to detect and react (shut the main gas valve) in 20 ms to have a chance of catching it]
Stopping overspeed might be achieved by something like a helicopter clutch - a centrifugal shoe which is released by too much speed and bears on something stationary to limit the speed - its also a good idea to close the steam valve.
I look forward to seeing your control system, John
Great work, the builders
andrew
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Control system done, engine finished, ready for trials.
http://www.youtube.com/watch?v=1_Ey8v7fgig
John
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John, It is magnificent, I'm afraid my boat couldn't do it justice. I really like the little white knob, great touch. It's well beyond what I imagined. It will be very interesting to see what it does with a full head of steam eh? Hope you're able to catch up okay on your other work and not overstrain your hand.
Did you weight it? Just curious how much it weighs in at.
Been busy myself with my the prop shaft etc, just about ready to lock it in:
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Cap,
I actually managed to get this proto to give up a bit of info.
It actually ran at 16.5K rpm with very low pressure, so I estimate I am not far off at 30K rpm.
It definitely needs a lightweight rotor, the one in this is fairly heavy, but I estimated a 4 second switchover, which is about what I was getting. With a lighter weight, the switch over will be a lot faster and runup speed will be quicker as well. Aluminium would be ideal for the rotor, but wouldn't last very long, because the steam impingement on the rotor would just cut it to bits.
Also, it only needs two rotors rather than three, so it would be a lot smaller and lighter.
The little white knob by the way, is a glass marble, drilled and stuck on.
I now have to get back to my work load, I should have had four engines made two weeks ago, so this one now needs to go on the back burner for a bit. Plus I have to get a new compressor before any more test runs can be done.
John
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John,
Thanks for posting the video - sweet and smooth turbine, and the control system is effective and attractive, too.
Cap - the prop assemblies are also looking very good - are the mounting blocks going to stay square-ish? I'm not sure of your order of doing, but it might be a good idea to glass the basic hull before any of the drive gear is fitted - then you can recut the holes, fit propshafts, brackets etc and perhaps fit glass "collars" to help re-inforce and seal the area.
andrew
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John,
Thanks for the added info. 30k rpm is a lot, but you know I had an old dremel that was constant speed at 30k rpm and it had a brushed motor, and none of it ever wore out on me. I actually ended up frying it using it as a circuit tester of all the stupid things, lucky I didn't electrocute myself. We have 120 AC here typically, but for some circuits there is 240, like a well pump. I found some old wires sticking out of the wall in the garage and decide to make an outlet not knowing it was a 240 hook up, poof end of said dremmel.
So what's the best lightweight rotor material? How big of a difference do you think it makes? Is it just the time it takes to reverse direction and accelerate? I may be better off if mine doesn't accelerate too fast per what Andrew said in earlier post, 4 seconds is close to my reaction time so it might suit.
Andrew, I have since smoothed over the mounting blocks so they aren't dead square, I may try to turn a cone to fit on the end of each block, I wish I had chunks of brass around like John, I may able to find something suitable at the hardware store to modify. I did plan on glassing it without anything but the blocks on, even that I almost wished I'd left off but I think I had to.
I still hesitate to go forth with the glassing, but probably a good thing, usually I dive in without preparation, maybe I'm getting a bit smarter in that respect. One question; say it starts out horrible, I mix the epoxy wrong or something, can you pull the cloth off and wash the epoxy off with something if needed? It always makes me feel better if I know there is an escape.
Cap
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Cap,
Worry not, there are fixes for almost any of the possible errors known to mankind.
But preparation and planning - working the entire job through in your head, and having all the materials prepared is the key.
Work in small batches of resin - you don't have to do it in one mix
Cheat like mad (did I mention giving the cloth - the side next to the hull the lightest possible spray of spraymount so it doesnt want to squirm.
Warm the resin and hardener to very warm room temperature before you begin
start on detachable bits - convince yourself that the epoxy resin does cure reliably
You can't mix the epoxy wrong - well, you CAN, but you are the person who made that airship frame, and the Fletch hull in the first place - you won't
Each batch needs to mix for 2 minutes -
Be bloody bold and resolute.
andrew
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Cap,
The lightweight rotor is just not for runup and change over times, it is for stopping as well. The faster you can stop, the safer you are.
I have some lumps of titanium, but I think the machining would cost a fortune in blunted tooling. So I might just look at aluminium bronze or a thinner skimmed brass rotor. I think I could get a brass one down to about half the weight of the original, maybe even more, because of only using two drive areas instead of three.
John
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Andrew,
It was not worked out well in my head, and what I thought would happen with the rudder happened, but maybe I was mistaken initially. I mixed the epoxy just fine (2 minutes, lot's of bubbles but they went away), spread it on and put on the cloth, perfect so far. The problem was the three edges, I had thought I was supposed to fold the cloth over and overlap it, I didn't think that would work and it didn't, it frayed and wouldn't stay down, so I left them as flaps all the way around. Maybe that's the way it's supposed to be done, I hope, because that's the way it is. If I have to I'll carve another rudder.
Maybe it's not the right cloth, it frays easily, it's pretty fine almost like Oxford cloth. I could see doing the hull with it easy enough if it weren't for the blocks sticking up, also around the fantail I think it might bunch up, what do you do then? I sure wouldn't want to cut a slit and over lap it but at least it's lapped on a relatively flat surface rather than a 180 corner. And of course the bow is going to have to be slit so I'm not too excited about it.
We'll see tomorrow what it ends up like.
John, I see how the lighter rotor would be better as long as it's strong enough which I'm sure you'll acheive. Too bad the titanium is so tough to machine, it's probably expensive to. I know those milling cutters are expensive, even the cheap ones.
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Well the rudder turned out fine. The edges sanded right off and no frayed cloth sticking out anywhere. I'm glad I practiced on the rudder and got over it. Cap
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Hull is getting closer, it's fiberglassed, needs a bit of work yet but looks like it will be fine (to me).
Poor picture but, it's better than it looks:
(http://i262.photobucket.com/albums/ii92/capricornzzz/thImage002.jpg)
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A few more pictures, slow but sure progress. Will hopefully have in water by end of summer :P, I had hoped to by now but at current rate it's going to be a bit longer. Maybe within a month. Hope to test motors that I have with 75mm props, may need bigger motors and bigger props, we'll see.
(http://i262.photobucket.com/albums/ii92/capricornzzz/Image008.jpg)
(http://i262.photobucket.com/albums/ii92/capricornzzz/th_MVI_0758.jpg) (http://s262.photobucket.com/albums/ii92/capricornzzz/?action=view¤t=MVI_0758.flv)
(http://i262.photobucket.com/albums/ii92/capricornzzz/th_MVI_0757.jpg) (http://s262.photobucket.com/albums/ii92/capricornzzz/?action=view¤t=MVI_0757.flv)
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Hello all,
Ready for first test run, wish me luck.
Cap
(http://i262.photobucket.com/albums/ii92/capricornzzz/thImage001.jpg)
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Didn't realize the thing was THAT big! :o
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Hi Martin, it's actually too big, I'm going to need another boat to follow around, get away from shore. It's got a lot of room though. First voyage with electric motors went ok, just chose a poor location, not much room and too may hazards, I wasn't able to get it up to full speed but close I guess. Cap
(http://i262.photobucket.com/albums/ii92/capricornzzz/th_MVI_0978.jpg) (http://s262.photobucket.com/albums/ii92/capricornzzz/?action=view¤t=MVI_0978.flv)
(http://i262.photobucket.com/albums/ii92/capricornzzz/th_MVI_0982.jpg) (http://s262.photobucket.com/albums/ii92/capricornzzz/?action=view¤t=MVI_0982.flv)