Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Submarines => Topic started by: thegrimreaper on April 18, 2012, 08:51:49 am
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Build of my Sheerline Trafalgar Class sub is now progressing well. I am about 70% done on the WTC which I have again constructed myself and probably about 50% through the build of the hull, my first question is what motor size should I be looking at I know Mr Sheerline had revamped the sub so it runs on a 12 volt stick of batteries along the bottom of the hull, I have a 7.2 volt motor and was wondering if that could be used along with a 7.2 battery and make the difference in weight up with lead along the length of the keel. The motor would be direct drive much like the Akula from Sheerline. Only thinking of using this motor as it is lying around and I am not going to use it for anything in the foreseeable future.
Regards Mark.
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You haven't mentioned the type of motor or its RPM.
The propulsor on the Trafalgar has a coarse pitch and lots of blade area, so you're going to be needing low RPM, and plenty of torque to swing it around, I would estimate somewhere between 2-3000RPM. Doubtful your motor meets that criteria without gear reduction. I would say the motor /gearbox combination you have in the Vanguard would be closer to what you need, although the propulsor is somewhat different.
I think the Sheerline boats use a 12 volt Speed 400 (385) type motor geared down about 6:1, Chris could confirm or deny that. Having watched a few Sheerline Trafalgars in action, they always look a little slow to me- I would prefer a bit more performance, as these boats are no slouch in real life. Officially their submerged speed is listed as 32knots, but the real figures are always classified.
The Trafalgars I have looked at do not have any pre-swirl stators moulded into the shroud like the Vanguard has. The exception to this is Ramesh's version, Steve Reichmuth built a new shroud with stators on. This provides the counter torque that prevents the boat leaning/twisting over when under way. So if you go for higher power, perhaps this could become an issue.
If running lower voltage motors, will your water pump make good pressure on lower volts? I've found geared pumps tend to drop off a bit when you run them on lower voltage, so you might want to test that out for yourself. Also the the tank will take longer to fill/empty.
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Hi Mark,
The Traf, Runs on Mfa 385 with a 5.1 reduction.
Or you could use an electronize 365 with http://www.puffinmodels.com/product.php?prod=1508 /On 6.1 ratio
With that setup the motor should pull hardly any amps, therby giving longer run time.
regards
adam
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Sorry about that Andy I rushed the question because I am in work Just had a look at the MFA web site may as well stick with their motors and gearbox combo and sort out a 12 volt battery from the component shop forgot about the water pump needing 12 volts (ddooohhh).
thanks for the link batfish puffinmodels bit expensive just for a gear box but thanks anyway
regards Mark.
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Well you have the motor from the Vanguard, so you have the opportunity to do a little testing with that first, or you can go with the smaller MFA motor and gearbox Adam suggested, which operates at about 1000RPM lower than the one you have in the Vanguard,
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I am going to go for the small MFA that Adam suggested only because I think the Vanguard is over powered hence me having to alter the throw of the throttle. or even maybe fit the same combo that is in the Vanguard to increase the speed a bit so as to get a bit more performance out of her as you stated Andy they can look a bit slow as a model where as in real life the Trafalgar is the sports car of the sub world. As to the power roll encountered when hitting full power I think that is just the case of learning not to go from full stop to all ahead in one swift movment but to just take it easy.
Mark.
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What sort of top speed were you getting out of the Vanguard then, only saw it meandering along in the video you posted.
I take it you know the formula for scale speed- take the full size speed and divide that by the square root of the boats scale. So in the case of your Trafalgar that is square root of 64= 8. 32 knots divided by 8 is 4 knots. But if we assume these boats can do a fair bit more than 32 knots, then we would look to perhaps 5 knots.
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Speed on the Vanguard was to fast so fast that the rudder became totaly unresponsive will be re ballancing the Vanguard on saturday ready for testing again on sunday will ensure the wife gets some decent video this time. Last time out the Vanguard was nearly on the plane %% well slight exageration but ...... Thanks for the working out of the scale speed Andy
Regards Mark.
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Unresponsive rudder- that's an interesting handling quirk. Usually as boats go faster the rudder becomes more sensitive, sometimes too much, and other issues creep in like too much sail induced roll. Perhaps the C.G needs moving back a little towards the middle of the boat.
Pushing a sub onto the plane is down as riding 'on the step'. Doubtful they do this on a bomber boat, but here's a neat pic of a Valiant class doing just that!
(http://s12.postimage.org/t8kpvcwft/valiant.jpg) (http://postimage.org/image/t8kpvcwft/)
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Mark , Andy,
You could always use robbe brushless motor for 212 as its 100kv i,e 100rpm per volt,
So 12v 1200rpm.
Electronize 365 motor is rated to 15v rpm wise with 6.1 reduction should be 1200rpm.
Regards
Adam
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Thanks for the info on that Adam but I will be steering clear of brushless on the Trafalgar only because I have already got a speed controller for her that has got to be used on a brushed motor hopefully when I get the motor I will not have the interference problems I had with the Vanguard which has now been solved but what a headache that was. I do have a question for Andy though only as the guy seems to know a lot, Andy I need to source some bellows from somewhere the only ones I have found are a supplier on e-bay from Warrington, they work ok on the Vanguard but they are a bit small being about half the size of the ones I have on the Akula, I know I could ask Chris at Sheerline but I don't want to keep bothering the guy especially as I didn't get the kit from the man.
Regards Mark.
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MFA 385 runs at 11000RPM, which at 5:1 gearing gives 2100RPM unloaded. The low noise 385 is rated at 7000RPM, which would give 1400RPM geared down 5:1. But 1200RPM sounds so slow.
For bigger models I think the Robbe bellows are nice, well moulded, they concertina well and have plenty of free movement, you should be familiar with them as you built a U47. Cornwall models sell them, I'm sure there are others too.
http://tinyurl.com/br5lkeo
SHG bellows were seen as the gold standard for many years, but unless they've improved the tooling I'd give them a miss, because the ones I received weren't as well moulded as some earlier examples I'd seen.
Graupner bellows, and some examples from China tend to be a lot smaller. Some people prefer to use glands, either based on nitrile o-rings, or silicone tubing. Six of one, half dozen of the other.
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Thanks for that Andy will order some from cornwall models when I get home later. as to the rudder problem on the Vanguard I don't know what causes it all I know is the faster she go`s the less responsive she is to the rudder, slow her down and the rudder starts to bite but she need about a quarter of a mile to turn I have managed to increase the throw of the servo by about 5 Degs and I am at the moment working on extending the lower rudder with a piece of perspex which should work as I have seen it done on other subs I don't want to get into fitting a pump and tube system which was originally mentioned in my Vanguard thread as I don't think it would work that well.
will have to suck it and see on sunday if we get a bit of nice weather am on jollydays next week so plenty of time to sort out the Vanguard and get some serious building done on the Trafalgar.
Regards Mark.
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Where have you positioned the centre of gravity on the boat.
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C of G is in the center of the Vanguard and which is in the center of the ballast tank the boat sits nice and level in the water when on the surface but needs ballancing for submerged running as she tends to submerge tail first.
Regards Mark
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It's not too far forward then.
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If anything Andy she may be a bit light on the water but thats not a bad thing all that I do is pump some water in to her that gets the impeler and shroud under and gets the towed sonar point just touching the water. Its then just a case of a little bit of throttle to get her moving, if you hit the throttle to quick though you do get torque roll and a lot of cavitation from the impeler for not much of an increase in speed, thats why I ajusted the throw of the throttle full power is just to much for her but at about half throttle she looks good, Sunday will be my big test with her, hopefully I will get her all the way under instead of keeping the sail well above the water.
Regards Mark.
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There isn't much you can do about ventilation (this is what is happening here, not cavitation) on a spindle stern, the shrouded prop helps a bit, but with the prop so close to the surface, you just have to keep the speed down to stop the prop sucking down air until you dive the boat.
Submarines that were designed to spend most of their time on the surface e.g. most boats of the two world wars, had their props mounted low and tucked underneath the hull to avoid these problems.
If the boat is a little tender, then you can add foam high up but below the waterline, and lead in the bottom to increase the metacentric height, but it will make the boat heavier.
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Live and learn I always thought that ventilation/cavitation were one and the same the production of air bubbles from the blade tips, thanks for clearing that up. thanks again for all the tips Andy would realy be strugeling without your help.
Regards Mark
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Cavitation is caused by pressure drop over the propeller blades, resulting in the water literally boiling, forming bubbles which ping against the blades. Cavitation can result from too much blade angle or very high speed. This isn't going to be an issue with the prop on the Vanguard- it's slow revving and the angles of attack of blades is quite shallow.
Ventilation or aeration, is dragging air from above the waters surface, usually as a result of the prop being too near the waters edge, or not having anything above it e.g. like a spindle stern submarine.
On a lot of submarines, you'll see when running on the surface the commanders trim them stern down to get the prop as low in the water as possible. For instance I've noticed the new Astute class is often trimmed lower at the stern, Russian Typhoon class do this (Ramesh replicated this with his Typhoon). On the old Holland classes (Edwardian submarines) this was taken to extreme, and the difference between surface and submerged trim was radically different.
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I have got that motor/gearbox in by trafalgar. It's an Eden but with piston tanks and I find it under powered for my boat, I am looking at replacing it with a MFA geared 500 sized motor.
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Maybe combo Mark used in the Vanguard, or possibly the 6:1 spur geared motor (non-planetary) as if the Prop shop propulsor is anything like the earlier version supplied with the Vanguard, it'll have a lot of pitch (I calculated about 125mm pitch on the Vanguard), so you may want to drop the revs a little.
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Mark,
If your needing an eco500 motor and 5.1 gearbox give me a shout, both r brand new never been used.
Adam
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At the moment guys the Vanguard is how do you say Bugg**d its ripped the drive shaft to pieces inside the WTC I need to source a solid drive shaft 6mm to 4mm if anyone has a supplier I would be grateful will not be bothering with them silicone flexible ones thats what has destroyed itself, I dont know why everything is in line when running their is very little vibration from the motor or the propshaft and nothing has come loose the only thing I can think of is that the item was a couple of years old but had been kept in an ait tight comtainer so .................?????
Regards Mark
Batfish can I take a rain check on that motor for a couple of days mate ??
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Have a look on your other post, Mark...
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What's wrong with the usual Raboesch or Huco style Hardy Spicer coupling? Easy to mix and match the shaft sizes, about a fiver from the local hobby store, and should easily take the strain. Also Prop Shop do some nice couplings, but you might have to wait a week or two, you know what Simon is like.....
http://www.cornwallmodelboats.co.uk/acatalog/raboesch-couplings.html
http://prop-shop.co.uk/index.php?id=26§ion=services&sub_section=products&product_type=26
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Huco style coupling I have already got two of them in situ on the out side of the WTC didnt realy want to put another one inside thats why I used the silcone type flexible inside. I think I am going to have to move the motor a bit further back to get another Huco coupling in. I know I will get there eventualy <*<
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Just had a quick word with Nigel, he'll knock you up a solid joint if you want one, Mark.
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Okay. It doesn't mater that much really how many you have, the main thing is to insure they're well aligned to prevent noise.
You can get Oldham couplings, they are very robust and allow for a little misalignment. A solid coupling will also work fine providing there is no misalignment.
http://www.rpmechatronics.co.uk/shop/products.php?2910&cPath=27_38_194
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Why not do as I (and an awful lot of people) do...fix everything in position with a solid coupling, once all is set and glue hardened off, replace the solid coupling with a Huco or similar...job done.
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Motor and seal in end cap are dead centre true I have just moved the motor back and cant get the tube back together so its back to the drawing board the Huco coupling in the wtc is to big for the purpose Andy the link you put up is a great thing but 10 days lead time. I will go to Steve Webbs in the morning and see if he has anything maybe use a tamiya dog bone on it that would be smaller.
Rich Thanks, if I cant get sorted tomorrow I will defo give you a shout
Quick question if I took the gearbox off the motor what differance would it make to powering the sub ??
Regards Mark
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It'll just bog down, get hot and draw a load of current. The gearbox is there to reduce RPM and importantly increase torque, so you can drive that 2.3" propulsor nice and easy.
You can get motors that deliver 2500-3000RPM without reduction, but they tend to be bigger, heavier, and are quite difficult to source, definitely not the kind of thing you will find at your local model shop.
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Chears for that Andy will have to source a differant motor for the vanguard over the next few days cant be bothered with altering the tube now thanks again Andy
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Why do you need a different motor? You won't find anything significantly more compact other than a 385 geared motor, which may be powerful enough seeing as you found the 500 a bit lively. You can get Oldham couplings from other places too you know.
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This looks good from Engel- http://www.engel-modellbau.eu/catalog/product_info.php?cPath=37_97&products_id=1833&osCsid=d7t9f6vnnt4hnm0s7k7k4n2si0
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Hi Mark,
Yeah no worries.
regarding your problems with vanguard, is the motor shaft alignment out?? do you have space for a seperate motor wtc as per Ramesh's Tireless build??
Also regarding couplings the std huco should be good for upto 3000rpm, Failing that if its internal ie within in wtc then perhaps mobile marine models coupling.
Dont know if andy has suggested but engel do a solid coupling, 3.17mm to 4mm or 4mm to 4mm,
if your looking at this route re coupling i should have a couple of engel couplings spare.
Might even have a lavayette motor mount and shaft seal going about........
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Mark needs 6mm to 4mm. 6mm is the output from the MFA gearbox.
Building a separate motor WTC would require a complete refit I think, and isn't really needed.
Huco couplings can be run above 3000 RPM, it greatly depends on the load you place on them.
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Mobile marine models, There couplings can do upto 8mm and there not that expensive. avaliable threaded or plain.
They also do shafts etc to order.
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Does nobody know a tame engineer? A swift visit, a donation of tea bags/milk and a bag of sugar....and a fiver or so in the guys pocket. Job done.
Find a friendly engineer, look after him, nuture him, buy him a bottle of scotch at Xmas....it'll be the best thing you ever did.
Rich
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found this little tinker in one of my box`s going to attempt to drill one side 6mm as it only 4mm as you can see it is tiny compared to the red Huco coupling hopefully it will work
thanks for all your help guys
Regards Mark
(http://s14.postimage.org/7d96pk2e5/DSCF2803.jpg) (http://postimage.org/image/7d96pk2e5/)
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Tricky business to accurately open out a coupling like that, chances are you'll wind-up with an off-centre hole and a coupling that runs eccentric causing vibration.
Might be tolerable as you're only doing low revs.
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didnt work not enough sidewall for the grub screw to tighten down so it looks like the Vanguard will be dumped in the shed as a project still underway to be finished when ever
Thanks to all for the help on this.
Regards Mark.
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Mark...send me a drawing of what you want, with measurements, and I'll send it off to Nigel for you.
Rich
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What are we talking here. A coupling 20-25mm long to accept a 6mm shaft at one end and 4mm shaft at the other?
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http://www.mobilemarinemodels.com/acatalog/Safety_Couplings.html
Come on mark its only £6
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Wasn't it something like that he had in there originally, that went bang?
Perhaps you could try replacing the tubing on the coupling you have. Polyurethane tubing is a pretty strong stuff, B & Q sell it, not sure if they'll have the right size for your coupling though.
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Gawden Bennett, you lot do make things difficult...links for this, links for that, complex measurements here and there....just use a piece of silicone tube to join the two ends together with a drop of superglue to hold everything together.
And before there's comments about the tube won't hold together, I've used silicone tube as couplings on fast electric boats, subs, tugs, etc...you name it, silicone tube will join it and hold together.
Proper job...
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Cheeky sod! Complex measurements indeed.
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Language, Timothy... ;D
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well reading that gave me a laugh anyway. I don't know what is wrong with British company's they all say they need money to keep the company going 4 company's that I contacted today reference couplings 2 said I would have to spend more than £20 to use my maestro card ??? the other 2 said they don't take maestro ffs what is this contry coming to when they can turn money down no wonder we are again in recession.................. Rant over
thanks Batfish but I have already destroyed one of them. So I did some Complex measuring which was difficult with the piece of string I use ready to pass over to Rich,when the wife said for FGS redesign the tekrak to incorporate a big red HUco coupling so .................. thats what I did all back together now with 3 Huco couplong one inside the WTC and 2 outside. Just got to wait for the sealant to go off and some nice British weather
Thanks guys for all the offers of help and all the help on here
Regards Mark
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Well done Mark...pleased you're sorted now. And well said Mark's wife!!
So we can all get some sleep now.... ;D
Rich
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dont know about sleep Rich I am in the process of building the Trafalgar so.............................watch this space
>>:-( >>:-( >>:-( :D :embarrassed:
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:embarrassed: