Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Steam => Topic started by: belli on May 12, 2020, 07:06:41 pm
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I did manage to find a Choupette kit about four months ago, the plans arrived today! The engine drawn in the plans is quite detailed and I guess drawn from a real engine, 3/8" bore and 5/8" stroke, twin cylinder. Boiler is 3" diameter and 4" long (high), does anybody have any details what the boiler engine combo on the plans was? I think this would be a nice size engine to build.
First day back at work yesterday, I made enquiries with one of our suppliers for Cu tubing. I am able to source 2" x 0.047" wall (52mmx1.2mm in old money) tubing and 3" x 0.067" (76x1.7mm) wall for the bigger. Do you think I can use these for boilers? I've poked around for boiler designs but none have really grabbed me, anybody have something nice like the one on the Choupette? It looks like a horizontal boiler that was turned vertical.
Crap, gotta answer all these question before I can post....
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Bonjour belli,
Is that this Choupette you refer to ? https://www.youtube.com/watch?v=BGl2mnb5dC8 (https://www.youtube.com/watch?v=BGl2mnb5dC8) and https://www.youtube.com/watch?v=yertSsjcFQM (https://www.youtube.com/watch?v=yertSsjcFQM) ?
A boiler of 52 mm is nothing, the one I have is even not enough powerfulfor 2 x 0,5 cm3 machines :
https://www.youtube.com/watch?v=o6k7qQFPZUU (https://www.youtube.com/watch?v=o6k7qQFPZUU) and https://www.youtube.com/watch?v=OFuptbMf4aw (https://www.youtube.com/watch?v=OFuptbMf4aw) She has 5 minutes of autonomy.
A wall of 1,7 mm is sufficient, my 100 mm JMC boilers have walls of 1,5 mm and are tested at 10 Bar (150 PSI), example: https://youtu.be/NOcpmwRUadU (https://youtu.be/NOcpmwRUadU)
76 mm, especally if it is an outside diameter does not leave a lot of room to the water, to be used with a small machine (2 cm3 max).
This 80 x 120 mm gives about 15 minutes of autonomy without whistle : https://youtu.be/F4n25B1pJzY (https://youtu.be/F4n25B1pJzY)
And, depending of its conception, a vertical boiler can contain less that an horizontal of same height/length and has an impact on the gravity center of the boat
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Bonjour Raphaël (or is it Bonsoir?)
Merci pour votre conseil. J'ai commencé seulement il y a 6 semaines avec les bateaux à vapeur et j'e n'ai aucune expérience. J'ai 5 mètres de tuyau de 50mm qui actuellement ne me servent à rien.
J'ai contruit un moteur de votre ami Bourdillat, le guignol convient très bien à mon côté autistique. Je ne suis pas sur si il est un bon candidat pour un bateau. Jusqu'à présent j'ai fait deux Paddleducks (Twin), un Paddle Duck (simple), le Bourdillat, un SEL (je ne sais pas pourquoi car on peut les acheter pour 3 fois rien?), un PM Research #2AM.Maintenant je suis occupé avec deux cylindres oscillateurs et avec un cylindre oscillateur twin que j'aurai du probablement construire en premier.
| | Merci,
Bellisimo
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belli.... we are always to post in English here on MBM, so have copied this for you......regards Derek
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translated text.....
Thank you for your advice. I only started 6 weeks ago with the steamboats and I have no experience. I have 5 meters of 50mm pipe that currently serve me no good. I built an engine of your friend Bourdillat, the guignol suits my autistic side very well. I'm not sure if he's a good candidate for a boat. So far I've done two Paddleducks (Twin), a Paddle Duck (simple), the Bourdillat, an SEL (I don't know why because you can buy them for 3 times nothing?), a PM Research #2AM. Now I'm busy with two oscillator cylinders and with a twin oscillator cylinder that I probably had to build first
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Bonjour Bellisimo,
The JPB steam machine has no reverse, it could be convenient for a speed boat. Sorry for your 5 meters of 50 mm pipe, but they can be useful only for gas tanks and oil separators.
As you seem to be a good machinist, why wouldn't you buy a smaller pièce of copper tube with a larger diameter to build your boiler, depending of course of your choice (horizontal or vertical) ?
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Hello Raphael,
Copper tubing is not so easy to get, the supplier is only willing to sell full lengths. As you say, it will not go to waste. I have also 38mm and 44mm that will be used for gas tanks and other smaller steam/gas vessels.
I also got a length of 76mm tube that will used for the first two boilers, one horizontal and one vertical. Probably 3" dia and about 4" long. I will finish the small oscillators first as I am great at starting things but not finishing them...
I did draw the 'Puffin' in CAD last night so that the parts can be laser cut, should be a quick simple build for a small oscillator with a 50mm dia. boiler... :embarrassed:
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Bonjour Bellisimo,
I will follow with a great interest your progress, thank you in advance to sgare with us ok2
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A little bit of progress from the weekend.
I bought a plank of wood from the local hardware, I am not sure what it is and it didn't say on the label either. It has a fine straight grain that I thought looked quite scale and so I cut some strips on the table saw and planked the the deck. When placed side by side there was almost no distinction between them and so I used a black Koki pen and ran that along each edge first. The results are not bad but the wood has a fairly light colour. I then decided to do some experiments....
The three patches are plain, no finish, then a 'Teak' varnish (it looks like runny poop in the tin) but it is still not dark enuf for my liking. The last is just plain sanding sealer. I wish I had used black paint along the edge of the strips to make a bit more definition.
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For the caulking lines I use thin black card glued between each plank
This company sell many sizes of copper tubing although postage maybe a problem . if you are quick import duties may not be a problem. They will sell by the inch sorry 25.4mm
http://www.m-machine-metals.co.uk/metals_database.html (http://www.m-machine-metals.co.uk/metals_database.html)
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Thanks Frazer,
I bought a piece of Mahogany at the lumber yard, it was reasonably clean compared to some of the rough sawn planks they had. Pushed it through the saw to make some planks and stuck them down with black paper 0.02mm (about 0.001" thick) in between. I will see if I can find some thicker stuff for experimenting. It is quite distinct even with the darker wood and one coat of sanding sealer, makes me want to strip all the planks off and start again... {:-{
You can make out my hurried sanding marks in the photo but less so in reality.
I had a look at M Machines Metals and just for interests sake offer the following figures:
From the UK (shipping would have been a couple of bucks?) the 3" x 16 swg is offered at GBP 2.52/in. The copper tubing I sourced through the company from one of our suppliers worked out at GBP 0.69 per inch (delivered). Granted its a lot of tubing but I'm a gonna build a lotta boilers...
Cheers.
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The card works well although its a bit of a fiddle
It looks like youve a few hulls on the go so a few boilers will come in very handy
keep well
cheers
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I stuck the card to the edges with a little bit of glue stick first. The brand I have is UHU but I'm sure it's the same for all the others out there.
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For caulking I use electricians black tape. Lay have a half dozen planks on edge and press the tape on then turn over and cut between each plank and you get planks with self stuck plastic on one edge. The plastic is black all the way through.
It works well and can be scrapped to finish with a Stanley knife blade along with the deck. Joggling is also not as hard as it looks but the margin plank needs to be twice the width of the deck plank as half gets cut away anyway.
Cheers
Geoff
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So, my goal for today was to better cut the strips (cut the strips better?). I made a few modifications to my little table saw, added a finger board to push against the fence, another to push the job down and a bracket to hold the fence steady at the rear. I will make some mods to this, it really needs a finger board to hold the material behind the blade too. Tomorrow I will make a new finger board that is longer and can be adjusted behind the blade. Will see if I can find some 1/8" MDF.
I will also stop by the shops on the way into work and see if I can find some slightly thicker card for the caulking.
Geoff, thanks for the idea. I will give it a try but the strips I cut are not uniform in thickness and so I hit them with the belt sander after planking. I know, gotta be careful.....I wonder if the tape would clog the belt?
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The CAD files for Rose are finished, hope to start cutting tomorrow. If they look OK I'll post them here.
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A little inspiration for you - Choupette (https://vimeo.com/22777437) :-))
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Here's a little progress on 'Rose'. The parts seem to fit together well, I cut the bottom from card just to check the fit and it was not bad! Considering it was computer generated...I made an assembly jig to hold everything straight while the bottom is built. The formers have a little tape on them and this is glued to the jig. When they need to be removed it is an easy task to pull the tape off. The design is interlocking to some degree and the laser scribes a line where the bottom meets the keel. In hindsight I should have made a template and then I could have scribed the line on both sides.
I'm beginning to see how these boats can take days and days to put together. I'll post the CAD files here in a day or two when I am a little further along and more confident I have it right.
Thanks Aeronut, I am still some way away on the Choupette. I have decided to do the deck over with mahogany but only after I give it a go on Rose first. In one of you videos I see your Record Imp vice, I have one given to me too many years ago to remember, I still have it and still use it almost daily.
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Rose is a nice little build
What do you think of the table saw in the pic Proxxon ?. I currently use a slitting saw in the mill not very good for the mill but cannot justify a Byrnes .
cheers
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I like my little Proxxon, I really wanted a Dremel but they are hard to find. It has cut many wing spars and leading edges, mostly spruce/bass/balsa (up to about 3/8"x1/4"). It can slice up 1/8 ply and maybe 1/4" if you go easy (lite ply or poplar play) but not birch ply. I never run it for very long periods as it has no cooling for the motor to speak of. The blades are quite pricey but I think it is worth buying a spare, maybe a rip saw blade when you purchase the machine. Trouble is I don't know of another kind of saw like it.
I also have the smaller one (KS 230) which was a local on-line second hand goods site, paid about $50 for it. That is a toy and I wouldn't recommend it.
I would really like to get the thicknesser for making the planking strips but alas...
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Thanks, i had wondered about them. I tend to use Birch ply the most although its usually 1/16
I keep looking at my electric plane to make a thicknesser from it.Just not sure how to do the anti kick back fingers at the moment.Although when I had the use of a planer/thicknesser I found that when making 1/16 planks they would chip out or shatter often so maybe a waste of time?
Before the next build I need to get set up for wood again
cheers
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I bought a drum sander ( https://www.grizzly.com/products/Grizzly-10-1-HP-Drum-Sander/G0716 ) kinda machine, was about $200 then. What I have is not a Grizzly, it is far worse but I'm hoping it will do the job intended for it. It is stored in a friends garage and as he is high risk I probably won't get to fetch it for a few months... :o
The Proxxon is sat on a contractors saw which does the heavy lifting. I like my Rockwell tools and would sell my mother for a Unisaw but alas...
The birch ply that I bought is really quite soft, the 1/8" you could roll into a tube, it's nothing like the birch ply I thought I was buying (probably why it was cheap). Apparently this is 'normal' birch ply, has about the same color as the first deck planking and sands quite easily.
I am busy with the new steam plant and keep making mistakes, I think the steam port on the cylinder (drilling) is too close to the edge (1/16") and might not seal properly. I will finish the engine exactly like is and if it doesn't run nice, will put it on the shelf with all the rest. The two singles you see behind were the first 'double'. I was dum and drilled the holes for the ports thru the frame, when I drilled the hole for the pivot pin it broke through both. Not wanting to throw them in the dustbin I bored out the pivot hole and pressed a bush in. This has effectively sealed off the drillings but the engine can only be single acting now. Two new frames were made with a shorter con-rod so that the spacing of the ports could be made larger and then they won't break through on the pivot hole.
I have made two cylinders at 8mm bore and want to make two at 9mm, I can mix and match the parts between them to compare how they will run. The base needs to be shorten at the output end to provide more clearance for the prop shaft.
And now a question, I have thought about fitting the deck to the hull. If I add the stringers at the deck joint, glue the sides on (which is how i think it is done) and the deck doesn't match, what then? Do I make the deck over size and fit it later, knock some of the sides off? If I fit the deck and then run the stringers then I can place them that they line up perfectly but I guess the deck has to run over the sides as you don't want the sides poking through if the deck it too small?? Clear as mud?
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Thanks for the info,
My preference would be fit the deck and cover the joint with a rubbing strip thats if Im understanding you correctly
Iv made the same mistake with the port drilling in the past guess we live and learn
JP Duval ? has on his site some nice wobbler drawings.I scaled his marine engine down for my Basil Harleys Victoria buil
3/8 bore 1/2 inch stroke
I will see if I can find a link
This site has some good steam info although youve probably seen it
steam and steam models (http://www.vapeuretmodelesavapeur.com/accueil/index.html)
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The engine did start off life as the Basil Harley Double Oscillator for Victoria. I drew most of it for fun as it seemed a nice size and complete but did not pay attention to where the ports were drilled...
I will make one new frame as per his drawing for the single oscillator as I have a lot of free time at the moment. {:-{ I have since discovered that this engine design is spread right across the web and there is at least one very well drawn example (also French, can't remember where) that I abandoned my drawing attempt. I do like re-drawing them to preserve the designs. I have done many airplane designs, some are on the 'other' groups.
I started drawing Victoria too as it looks like a nice size and fairly simple but came to the conclusion that you really needed the vac form hull. It would be possible to make your own hull but I don't have that amount of energy.
I have seen so many websites now but nothing really gets you learning more than doing. If I have a whole bunch of shelf queens when I am done, I will be fine with that. These engine are currently numbers seven through nine from when lock-down started. While we have technically returned to work, there really isn't much going on.
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The hull for Victoria is reasonably easy to do .What ever you do dont buy the vac formed hull from the UK supplier its junk and thats been polite about it.I sent it back and built plank on frame using 1/16 ply
The other problem from memory with the vac formed hull is its about 25mm shorter than the drawings and even at its original size things are a tight fit.If I was doing it again I would build it at least 1/2 as big again
I used the Duval engine as Basils simply has to much soldering involved and with my luck one of the passage ways would get blocked.
For a single single acting engine I pinched the little loco Crackers engine design with a few mods it punches above its weight and has an inbuilt trunk guide that makes a big difference to the engines life span
James Senfit also used the trunk guide idea on his Bijou and Thimble engines .I built his Thimble engine at 2/3 size 2mm bore and stroke its about the size of a match head
On simple wobblers K&N brass tube makes very good cylinders as its very true and it saves a bit of machining as well as a lot of weight around the pivot a point often overlooked although Im guilty on my last engine
When making wobblers I like to use a simple jig to drill the port face holes its just more accurate for me at least
I built a couple of Cracker T locos to try some ideas out for burners using a straight through flue and Im happy with the results so this is the way I may build River Princess boiler sort of suck it and see.
The last model plane I built was a Bowden free flight design with a AM 2.5 diesel all old school
Its always better to cut metal although I often doubt my sanity over dumb mistakes but thats what I get for sticking to fag packet drawings
Iv not done that dirty four lettered word for sometime %) thank god
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Hey,
Found the Victoria drawings, they were from NZ. I don't know why I thought he was French...
http://www.vapeuretmodelesavapeur.com/telechargements4/ensemble-marin-oscillant.pdf (http://www.vapeuretmodelesavapeur.com/telechargements4/ensemble-marin-oscillant.pdf)
I arrived at the same conclusion as you regarding the soldering, I just don't trust myself not to ruin a good set of parts with my poor soldering skills. The little double is all screwed together, seems safer that way. I should be able to continue with it tomorrow.
I have the Cracker plans on standby...
I have used the K&S tubing before, I bought a pack of K&S oddments, longest piece was about 3" and lots of different sizes. The single acting cylinder will be made with a piece about 3/8" bore. I've wondered how the mass of the oscillating cylinder would affect performance, in theory it wouldn't as all the energy taken to accelerate the mass should be returned on the deceleration. Haven't reached a conclusion in my head.
"Thimble engine at 2/3 size 2mm bore and stroke its about the size of a match head", that's insane! I think about 6mm would be the smallest practical size I could manage, smaller than that would hurt my fingers. As for drilling the ports, all the sizes are done with CAD and the mill has a DRO. I can put the holes exactly where they shouldn't be...
My goal for tomorrow is to source some acid for pickling the copper as I want to start with the boiler construction. I can gethydrochloric very easily and I can get battery acid (sulphuric diluted) fairly easily. I am looking for citric but have only found small containers at the food mart used for baking (about 4 oz. for a $1). I might just buy a bunch of those and get on with it. I cut two pieces of 3" tubing, one is about 3.5" and the other about 4.5". I'll start with those and see from there, I'll post a sketch here and perhaps you could offer some suggestions. 2mm?? :o
Cheers,
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belli......You will find Citric Acid at more competitive price/quantity from Home Brew stores O0 ..... Derek
[You may need to increase the concentration above the recommended value]
https://nationalhomebrew.com.au/wine/national-home-brew-citric-acid-100g (https://nationalhomebrew.com.au/wine/national-home-brew-citric-acid-100g)
'For acid bathing of copper and ceramic saddles, dissolve 5g in one litre of cold water and soak for 24 hours'
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When I made my first boiler I ordered a kilo of citric acid. Got a funny look off the postman.
Jerry.
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I used to buy Scalecleen by the stone from the States its a form of citric acid and works far better. Check the spelling not my strong point.
No luxury digi thingy ma bobs this end just a ciggy paper and count the turns :} .I used to make a living fixing tool makers oops moments and they always blame the machine but the fault codes never lie %)
cheers
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This is a small wobbler I made for a 12inch Puffer.
Its still waiting for the hull
Have you seen Les Propers Youtube he has some nice small boats and steam plants
https://www.youtube.com/watch?v=9rcorLIJVdU
https://www.youtube.com/watch?v=EURne7s7u-8
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I mailed Leslie to get a copy of his book but regrettably wasn't able to. I do like his little boats but they might be a trifle small for me, shaping the hulls would also be a bit time consuming and quite difficult to get symmetrical if you were impatient like me. I think if vac-formed or molded hulls were available, that would be better for me.
I also have the building of Clyde puffer on the list, they were really what I found first and the French Mini-Vap 50's. I have the Boxer Clyde Puffer in CAD, ready for laserin' but haven't got to it. It might make a suitable hull for a simple steam plant as it could be built in a few hours if you had all the material to hand. There is a nice read here: https://www.modelboats.co.uk/news/article/puffin/525 of a fellow that did exactly that. It wouldn't take long to put something like that together.
I did buy JohnTom's Clyde Puffer in CAD and was terribly disappointed. I work with CAD a lot and what I received really was of no value. Taking some images that you have found on-line, feeding them thru a photo to CAD converter really doesn't cut the mustard.
Regrettably things at work are starting to tick upwards, I will be busy for the next two weeks but will endeavour to spent a little time finishing off some engines and making a start on some boilers. My favourite non-ferrous supplier will be re-opening on Monday, they do allow me to go and pick through the off-cuts. You still pay 'full' price but at least I can get smaller pieces. The flywheels of these three engines were machined from 11/2" hex bar as that is what I had....
Keep building Frazer, more photos and sketches please.
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There is some drawings on the net for a Clyde Puffer named Vital Spark I think this is what Les based his boat on
Good luck with the engines
cheers
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OK, today's haul:
Ten pints (about 5l) of battery acid, $9.
Plastic bucket (I'll be careful) with a lid, $2.50.
Silicon O-rings, 6x1mm (8mmOD) $1.72/100.
Silicon O-rings, 9x1.5mm (12mmOD) $2.00/100.
They couldn't find the 3x1mm... All other sizes are available, minimum order is $15 per size (about 700 O-rings), six weeks delivery.
623, 624 and 625 Bearings $0.55 each.
Most of the designs I have seen for small steam engines recommend O-rings but offer no suggestion of sizes, Frazer?
Now, back to the salt mine <:(
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Most of my engines are Imperial the smaller have a 0.070 cross section the larger .103
Silicone O rings are for static applications from memory but they are what I use and just bung a new one in when needed
Groove sizes on this site not the cheapest but I dont want several hundred
With O rings fitted you will need a lubricator as they dont like to run just on wet steam
The 3mm are they for the piston rod seal if so just make a standard packing gland and use ptfe tape it will make little difference
https://www.glrkennions.co.uk/silicone-o-rings.html (https://www.glrkennions.co.uk/silicone-o-rings.html)
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Those sections are much heavier than I thought, 1.7mm - > 2.6mm My thinking was that on such small pistons, 8-10mm, 2mm section would be simply too large. I'll call tomorrow and see what they have.
Correct, the 3mm was for the piston rod, never thought to try PTFE tape. I do have some graphited/grease/yarn kinda packing, quite large, about 1/4" diameter, was going to try pull it to pieces and make a seal from that. I did also buy some 1/8" square graphited yarn for the Stuart 10 pistons.
I try to machine the pistons to fit the bore but never quite seem to manage a good fit. Tried lapping with polishing compound, making a new piston, trying again, etc. They just never seem quite right. Maybe the fits are good but I just don't know what a good fit is. I'm hoping with the O-ring I can machine the piston slightly under size and the O-ring will provide the fit. Most of my bores are honed with a Sunnen machine at a friends place but the smaller hones are missing their stones. I guess I'll get some stones ordered soon.
Thanks,
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I also unpick a strand from 1/4 packing either works OK for me
A thou clearance on the piston is my target for steam engines Hot air engines are a different matter on these I have made some external laps to size the pistons
Dont make the ring grooves undersize as it will become a problem as the engine goes over BDC or TDC it will bind a wee bit of wiggle room is better
The more important thing is the piston is concentric to the piston rod as is the bottom cover and packing gland .This is why I use the glue chuck as my kit is simply not accurate enough to just use a collet
Probably telling my Granny how to suck eggs
cheers
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belli.....3 x 1 o-rings
3 x 1 o-rings ...[9-020 or 6-018] are non preferred sizes and may be available in 70 Shore NBR which is not suitable for our modest steam pressures
[/size]2.9 X 1.78 [1-006] is probably the closest generally available in FPM or Silicon to suit a 3 diameter shaft Silicone is listed as ~~ 70 Shore A and is recommended as for static applications FPM [Viton] is listed as ~~75 Shore A so is more suited to dynamic [piston or rod gland] applicationsAs frazer notes...picking smaller strands of graphited cotton yarn [J Walker Packings] is absolutely suitable :-)) for both piston and gland, although may need a little preload to attain the first steam pressurization
Derek
[/font]
[/size]Derek
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Progress but slowly....
I am building at approximately the rate that I can source the bits I need. The fire bricks arrived today, I can now build a mini hearth for welding the boilers together.
Here's a photo of the first two flanges, they came out better than the second two :o . The first form I made was too shallow and as the flanges were rolled over they extended past the end, I screwed a piece of scrap to the back of it to complete the flange so that I could check the size. Once happy I turned a new form that was much longer and just .2mm smaller and this gave me a very good fit. I have attached a photo of the fit, it presses in easily with my fingers but do you think the solder will still flow or does there need to be a bit of clearance?
The new form is held in the soft-jaws, allows me to remove it and replace without loosing dimension. When parting off the flanges I could do all four and they were exactly the same. Tool was CBN and it cut the copper very nicely.
I am also curious what the 'black' is on the commercial boilers (Cheddar, et al), is it paint or some chemical process? Should I make little feet and solder them to the boiler or how are they mounted?
One boiler is about 4" long and the other is about 5" long, both are 3" diameter. I will run a 7/8" fire tube through the lower half with about six 5/16" cross tubes. Does this sound like a good idea? I hope to make a gas burner for it.
There has been some progress on the engines, I will make new standards for the double acting cylinders and keep these two for some simple single acting ones.
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The black is just VHT paint
The fit I tend to go for is about 2 thou clearance or a very easy slide fit. I like to use a couple of rivets or copper rod to keep the end caps located when soldering. It stops them from moving just as the solder melts and saves a shed load of swearing
Iv just flanged my plates as well and the gas tank plates . I dont have the luxury of soft jaws so tend to friction turn them
If you look on Cupalloys web site in the Model Engineering section is a very good write up about silver soldering and its wicking properties
You may struggle with that blow lamp for hard soldering read silver soldering in the UK
On my other boilers the feet are held by the banding for the lagging
Remember a copper tube under external pressure will take a lot less pressure to collapse it compared to the same pipe under internal pressure. There is a big difference
On a 3inch boiler I would use a larger flue around 1 1/4
I have been experimenting with flues using a home made calotherme simply a tin the flues fit into and measure the temp rise in a given time and gas used and Im finding the plain flue no tubes with a poker type burner uses less gas heats the water quicker and the exhaust temp is 100 degrees C lower than the water tubed one although this is just experimental at the moment .Im using wet back deign as in the flue turn 90 degrees within the boiler shell
Keep well cheers
frazer
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The gas torch in photo is used to light the larger one.... It has a click starter.
The bigger torch I have is still a bit small I think, the front 'nozzle' is about 1" in diameter, heats the flanges to red in about one minute. Most of my tools are sourced at porn shops and I haven't seen a larger one yet, to buy new is quite pricey. I'll figure something out.
Your comments on the boiler are interesting, I thought that the cross tubes would slow the flow of the heat and transfer more of it into the water. Maybe I'll try the 4" boiler without the cross tubes, I can get some 1 1/8" tubing, maybe make the fire tube out of that then. The next size up I have is 1 1/2" which I was going to use for the gas tank.
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In the UK the gas tank would need to be tested to 400psi from memory so you would need to calc the right gauge of pipe. Although that may not be the case in the USA I would ask around before going ahead it may save a bit of time
Im not convinced myself over my finding and need to try and have a word with a couple of guys who know there onions better than me
My thinking is that the poker burner gives a greater heating surface for the flue and the air velocity through the flue is lower but this is getting far above my knowledge or capabilities .
I think Malcolm Beek did a center flue design a few years back that was in one of the model boat mags. I will have a look tomorrow during my playtime in the shop
The problem with flued boilers for simple steam plants is the lack of water capacity=run time . That why Iv been playing with T style boilers. The top of the T gives or acts like a large steam dome and allows for more water space in the main tube
You can see the idea in this wee videos
https://youtu.be/zfPa4YFEPsw (https://youtu.be/zfPa4YFEPsw)
https://www.youtube.com/watch?v=sW6PKkHYcaQ (https://www.youtube.com/watch?v=sW6PKkHYcaQ)
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I have looked at Peter Arnots and Malcolms boilers they both used a 28mm dia flue with cross tubes
cheers
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Just to chip in and I'm a novice with boiler building but I do build my own oscillating engines. I know model practice differs from full size practice but the water cross tubes (and any fire tubes) are there to increase the surface area of the heating surface for the flame to reach and should allow for faster heat up time and increased steam production.
I've also looked at Peter Arnot's boiler designs and like the fact the fire tube bends upwards at 90 degrees internally so is surrounded on all sides by water. Having said this the Cheddar Puffin boiler version 1 uses return fire tubes in the upper half whereas the version 2 is like the Arnot boiler design. The Cheddar version 2 also uses a ceramic burner and holds 40% more water due to the internal design but is no bigger than the version 1 and it produces steam very well.
Very interested to see how your tests work out.
Cheers
Geoff
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Hi Geoff, the Arnot boiler works very well I built it for my River Queen
The flue burner Im using is an inverted radiant style . I agree with what you say about cross tubes but for some reason when Im testing these flues I seem to get better results with an inverted radiant burner in a plain flue .No idea why or if Im working this out correctly
cheers
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Frazer, when you say inverted 'radiant style' and 'poker', do you mean that the burner is a long, rectangular 'pan' with a ceramic element or mesh along its length? Inverted, do you place this upside down? Forgive my dumness...
I did buy some orifices (orifi ?) (jets?) yesterday, they were a buck a pair. I lied when I said that I had 28mm tubing but I did get some today, was a full length (18'), bent a bit in the middle, paid $20 which seemed fair.
Here's a picture of the Arnot boiler for those not familiar.
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The burner is a poker type. just a length of KS tube with several cuts half way through across it. Then it is wrapped in a fine mesh
The cross cuts need to be finer than the gauge of the tube or they dont burn well or at least the ones Iv made dont
The burner sits at the top of the flue with the slots facing down
I make my own gas jets and tune them to the burner when its in the flue. Starting with a 0.4mm hole that is closed down to .15mm (number 3 jet)using Colin Binnies idea except I have made a punch that is guided.These holes are then opened up using a tapered broach
The broaches are easily made from sewing needles or the likes of Cousins clock and watch part suppliers sell them
The flue is very close to the bottom of the main barrel about 2mm clearance
The Arnot boiler is a good steamer and powers my River Queen 7/16 x 1/2 inch V twin easily
The design Im looking at is 2/1/2 dia with a plain 22mm flue using a 1/2 inch poker burner with a wrapper of fine mesh eccentric to the main tube a bit like a cowboy wagon cover
Im looking at using a large steam dome to allow more water in the main barrel
Just not sure at the moment if to go with this idea or not. For simple boats I prefer simple pot boilers meths fired very toy like but when I do a mock up it looks ungainly in the hull too tall
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Quick calc (3" boiler, 1/16" wall): a 28mm flue takes up 6% of the water space (less volume) but adds 27% more heating area.
I like the idea of the poker heater, simple to build and I think I can see why the cross tubes would be of no real benefit especially if the poker were the length of the flue. The hot air velocity would also be less (I think). The steam dome idea would also allow a little more water in the boiler but the benefit might no be that great unless the water sloshes around a lot, rough seas....
My 5" piece of tube I cut has a dent in the end, I tried to tap it out over a former, used a small ball pein from the inside without too much success. I could see the light when the end cap was pressed in how it would open the gap next to the dent. Drawing the tube I am sure has work hardened it and I didn't really want to knock 1" off the tube. I decided to try annealing it, my torch is definitely too small! No amount of waiting would bring the end of the tube to red hot, granted I didn't pack bricks around it but simply kept the flame in one place. Really need a bigger torch, horror of horrors, I might have to buy new >>:-(
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I have had a bit of a rethink on the boiler and as an experimental one it will be 54mmOD with a 22mm flue about 125mm long. This with the radiant burner giving about 0,2KW will allow the engine to run at a constant 500rpm assuming the boiler will deliver 2456ml of steam per min
Well thats the theory just need to order the materials and see what develops the 2.5 inch drum and plates can be kept for another adventure.
The velocity through the flue is a lot lower with the radiant burner than the normal torch style also as the velocity is lower the heat has longer to be absorbed by the flue. The plain flue does not generate turbulence like a tubed flue this also increase the velocity of the gases. This is for small flued boilers . A radiant burner is more efficient and uses less gas and due to the better time lag for heat absorption the exhaust temp is lower in my test about 100c to 170c also when i test temp along a flue it is constant give or take a wee bit
Another benefit using the radiant because it is using less gas I have not had a problem with the flame lowering due to the gas tank chilling or freezing
Thats about as well as I can explain what is going on in the plain flue as far as I know . I have done some testing on flue diameter to burner dia just need to check my maths for a rough ratio
I have taken a couple of pics of one of these burners operating in the flue if its of any interest
Many thanks to Sandy SCS steam for clearing up a few points my muddled brain was struggling with
cheers
frazer
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Ok, finally things are kinda back to normal (the new normal??).
I have wanted a simple to build hull for an SEL type steam plant and stumbled onto the Bowman Snipe type boats. There is a thread on the other forum describing the construction but no dimensions. I did ponder this...
I made some forms from laminated pine and cut them in a curvy shape. I laminated three layers of 1/8" birch with some glue that said 'waterproof' on the front and 'water resistant' in the little writing. I didn't worry too much as I thought that if this boat ever did make it to the water and got so water logged that the glue joints separated...
There was a lot of 'spring back' of the laminated sides, probably around 3/8". I glued the mold back together and cut a more curvier curve and for the second attempt used just two layers of ply, this result was much better but I think the front section where it is more curvy should have been curvier still but it is very close.
I also did get me some Gorilla's for the second glue up, coulda gotten Gators but the Gorillas were cheaper. I used a mist spray bottle to slightly wet the wood before clamping and I think the joints will be sound. Now to get the bottom glued in and I'll be off to a good start.
This will be a rudder only build and with a simple spirits fired boiler using one of my SEL type reproductions. I'll glue a deck on, strip plank it with the mahogany, white hull and I think it will look OK.
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I have the dimensions for the Jenkins Bowman boats including Snipe .Eagle, Peggy , Peter Pan, and a few others just shout up if you need any sizes
Also for Stuart Turners Henley although that may take a bit of finding
The later Jenkins boats were cut from the solid like Russian dolls
keep well
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Cheers Frazer but this one is 'Bowmanesque' (spell checker says this word doesn't exist...). I made it 26" as that seemed a good size, about 4.5" beam. I made the 3/8" sides thinking that there would be lots of meat for sanding, rounding the corners and such but in hindsight I guess it's only ever going to be a fairly elementary boat.
Oh, haven't seen your build in a while. :-)
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The build is coming on if a little slowly :} Seats are all in decking done boiler and burner made just on with the fittings then a steam test
The original boats of that era had about 3/16 to 1/4 timbers
Tony Bird has a couple of videos of his recreation and shows a simple bending technique
Basil Harley did a write up and a set of drawings for the later Luton Bowman he named Celia May
Keep an eye on youre builds weight as they are not the most stable of designs
https://youtu.be/ZkjxqZwaDV8 (https://youtu.be/ZkjxqZwaDV8)