Model Boat Mayhem
Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: Jeremy on November 23, 2011, 11:38:12 am
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I would appreciate advice on a brushless motor for my Dumas Chris Craft 19" racer (28" long). I fitted a 2881KV water cooled in-runner with a Seaking 60 amp ESC and 8.4V NiMh battery to my Bluebird and it goes fine. It looks as though I made a mistake in opting for the same set-up for the Chris Craft which has a submerged drive as against the surface drive of Bluebird which planes over the water. The motor on the Chris Craft sometimes stops in mid lake >:-o which I am told may be due to overheating. The advice so far has been to reduce the prop size (current 35mm diameter, 30 degree pitch) and the battery to 7.2V. However, I am told that a lower power motor would be the best solution, particularly as the Chris Craft is not normally run at full throttle. Ideally I would like an in-runner motor, around 1800-2100kV for batteries of 7.2-8.4V to fit the same 380/400 motor mount and of apprximately the same dimensions (45mm long, 32mm diameter). Does anyone know of a motor that would fit that spec? The higher powered motor could then go in my Slo-mo-shun which I want to upgrade from its current Graupner Speed 600 Race 7.2V unit.
Jeremy
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i reckon this will fit the bill for ya:
http://www.hobbyking.com/hobbyking/store/__17725__XK2845_B_2000kv_Brushless_Inrunner.html
you can still use that other motor just put a 30 to 32mm diameter prop on it. where did you get the prop you have from?
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Motor looks the right size - thanks :-). But would it not need to be watercooled (as is the Seaking 60 amp ESC currently installed)? My props are all Graupner plastic from Cornwall Model Boats. I have 25mm and 32.5mm diameter examples on order from them and will try them with the existing motor first. If that doesn't work, I'll go with the Turnigy.
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i dont think heat issues will be a problem especially on 7.2 and 8.4 nimh. ill see what else there is.
where did you get the motor from that you currently have??
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I got the combo BL5 from Prestwich model boats.
www.prestwich.ndirect.co.uk/brushless.htm
It works fine on Bluebird (would go even faster with Lipos) and I bought the same combo for the Chris Craft without maybe giving it sufficient thought. As I have watercooling installed in the boat, I might try to find a water cooling jacket that fits the Turnigy. If you come across an alternative motor that is water cooled, that would be even better.
(http://s8.postimage.org/5lk4fblj5/20111117_3a.jpg) (http://postimage.org/image/5lk4fblj5/)
(http://s12.postimage.org/l7eb1plrt/20110724_50small.jpg) (http://postimage.org/image/l7eb1plrt/)
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the cooling jacket on the motor you have will fit on the new turnigy one. with the smaller 32.5mm prop though i very much doubt it will create enough heat to warrant a cooling jacket.
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Except that it is not removable.. :((!
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heres one btw its exactly the same. they are removable because there push fit and sometimes epoxied on:
http://www.ebay.co.uk/itm/RC-Boat-Aluminium-28mm-380-Motor-Water-Cooling-Jacket-/220778484560?pt=UK_ToysGames_RadioControlled_JN&hash=item33676c5350
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There is nothing wrong with the prestwich set up you just need the correct prop and make shore you have water colling working correctly as the speed controller MUST have good water cooling as they reduce the heat sinks on them now and fit water cooling plates that are not very good without water passing through them, try contacting Prestwich and ask what prop they recommend as they are selling it as a combo, or just go a lot smaller and work your way up plastic props are so cheap these days,underproping will not hurt it it will just rev and go slower, you should always start small with props and work up.
Mike have you used the turnigy motor in a boat ? what prop did you use? have you any pictures of the set up?
Peter
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not that motor no i just found him one that suits the criteria he wanted. its essentially the same motor, just lower kv. Seaking, Turnigy, FlySky, hobbywing, eurgle, Imax and some others are all the same chinese company. I have a 2845 brushless motor though not the turnigy one a seaking one.
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not that motor no i just found him one that suits the criteria he wanted. its essentially the same motor, just lower kv. Seaking, Turnigy, FlySky, hobbywing, eurgle, Imax and some others are all the same chinese company. I have a 2845 brushless motor though not the turnigy one a seaking one.
there all from the same factory? same spec ? not what I have seen of them
Peter
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OBVIOUSLY JEREMY THE TURNIGY WILL NOT SUFFICE SO DONT BUY IT
HS93 IF YOU FIND A BETTER CHOICE FOR THE KV AND SIZE HES ASKED FOR THEM BY ALL MEANS PUT IT UP.
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Calm down, Calm down, I only asked if you had tried it, no where did I say it would not be suitable.and I queried your statement that they are all the same, as I have had motors from most of the company's named by you and found the build quality varied.
Peter
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the build quality is varied but so is the price you pay for them. ive read somewhere that there all linked somehow, i cant remeber where though. its just funny how the hobbywing seaking 180 esc is the same as the turnigy 180 esc and its funny how all these escs can all be set up from the same programming card. From what i gather Turnigy is hobbyking's renamed range of hobbywing parts.
I will withdraw the statement then that their all the same chinese company, because i have no proof.
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Hi Mad Mike
I've gone for the motor and cooling jacket you recommended and I'll transfer the BL5 combo to my Slo-mo-shun - an upgrade from the Graupner Speed Race 7.2V unit which does not really provide enough power whilst getting extremely hot. Thanks for your advice. :-))
Jeremy
(http://s8.postimage.org/w0ivfvl5d/20110224_3.jpg) (http://postimage.org/image/w0ivfvl5d/)
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tell me how it goes when you done :-))
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Will do, Mike but it will be a few weeks before I get the parts, particularly the cooling jacket. Hopefully, I will get a chance to check out the new set-up in January.
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Hi Mike
The motor and cooling jacket have both arrived, earlier than expected :-). However, I cannot get the cooling jacket onto the motor >:-o. It obviously has to fit tightly because the motor casing forms the inner wall of the cooling jacket. There are O rings at both ends and a spare set is included. Advice on how to put this on would be much appreciated. There must be a way!
Jeremy
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while ive been offline ive been thinking and heres what i would do. Put the o rings on the jacket then using get this BUTTER to slide the the cooling jacket onto the motor. When its on flush the water jacket threw with hot water and a little fairy liquid. :-))
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dont use WD40 as it can ruin the rubber seals, just try a bit of fairly Liquid to get it on then it will wipe off and wash out of the jacket.
Peter
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there is a product called rubber grease (no sniggering please) available down here in most engineering supplies places, designed for just that sort of thing.
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theres a product called vaseline here does the same job :-))
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Except that Vaseline attacks rubber seals ........... %)
Use Silicone based grease :-))
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lol seals bein attacked by tubs of vaseline %%
i still reckon butter will do it. Not much point buying a tub of grease for 1 small job.
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I too am a great fan of vaseline for many modelling jobs but I have used rubbergrease on the piston tanks of my sub and it works a treat and only seems to come in small tubes similar to superglue which is good because I tend to lose it inbetween uses.
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lol seals bein attacked by tubs of vaseline %%
Vaseline is Petroleum Jelly. Petroleum Jelly rots rubber.....
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yeah i weighed that up. we use to use it to put rubber radiator hoses on. probably not a good idea. The hot water melted it fast though so didnt cause any problems.
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Depends on what rubber it is.
Nitrile rubber isn't damaged by Vaseline. Neoprene and silicone is however. Silicone rubber is also damaged by silicone grease, although that is about the only rubber that is damaged by that grease.
If you don't know what rubber the seals are made of, the safest lubricant to use is animal or vegetable fat. So a thin smear of butter, marge, lard or cooking oil will not damage the seals. Even just smear of saliva or water will probably be sufficient to get the seals to slide on.
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Thanks to all for the great advice but, unfortunately, still no go :((. Take the O rings out and the jacket slides on easily. Put them in and, seen from the inside, the motor just buts up against the O rings and no amount of pushing or twisting get is over them. I found this film on U-tube which shows the procedure with a finned motor.
http://www.youtube.com/watch?v=dB8iey86mL8
However, the Turigny is a smooth cased motor with no fins. Has anyone fitted a water jacket to one of these and can point out the jacket which they fitted? It may just be that the one I got on ebay will never fit. The alternative would be to fit the jacket without O rings and seal both end with epoxy resin. Would this work?
I could run the motor without cooling. Its spec is at the link below. I would run it on the Chris Craft with a 7.2V battery, a 60 amp Turigny ESC and a 30mm prop.
http://www.hobbyking.com/hobbyking/store/__17725__XK2845_B_2000kv_Brushless_Inrunner.html
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If your struggling with the o rings then epoxying will work, as long as you make a good seal. I found when epoxying some nipples to my cooling jacket that they dont form a brilliant bond, but as long as the motor isnt bashed about too much it will stay in place. it might help to rough the surfaces a bit. Its a shame really because the cooling jacket should fit that motor. {:-{
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Thanks to all for the great advice but, unfortunately, still no go :((. Take the O rings out and the jacket slides on easily. Put them in and, seen from the inside, the motor just buts up against the O rings and no amount of pushing or twisting get is over them. I found this film on U-tube which shows the procedure with a finned motor.
http://www.youtube.com/watch?v=dB8iey86mL8
However, the Turigny is a smooth cased motor with no fins. Has anyone fitted a water jacket to one of these and can point out the jacket which they fitted? It may just be that the one I got on ebay will never fit. The alternative would be to fit the jacket without O rings and seal both end with epoxy resin. Would this work?
I could run the motor without cooling. Its spec is at the link below. I would run it on the Chris Craft with a 7.2V battery, a 60 amp Turigny ESC and a 30mm prop.
http://www.hobbyking.com/hobbyking/store/__17725__XK2845_B_2000kv_Brushless_Inrunner.html
Jeremy,
Does the water jacket have enough meat on it to machine grooves to take the rings, if so send it up to me and I will machine grooves at each end for you.
George.
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George
Kind offer :-)) but the O rings are already located in grooves at either end. The jacket is just too small (by a tad) for a 28mm diameter motor. Not a great expense on ebay and I'll put it down to experience. I'll go to Astec and make sure I get something that fits.
Jeremy
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it turns out a few people having the same problem {:-{
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Can't you just run some mastic around each end- bit less permanent than epoxy, and should remain watertight provided you're thorough.
You could use silicone or acrylic mastic.
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I have just received a Leopard cooling jacket from Astec - fits perfectly :-)). I would definitely suggest avoiding the one I first purchased off ebay. It does not do what it says on the tin.
http://www.ebay.co.uk/itm/RC-Boat-Aluminium-28mm-380-Motor-Water-Cooling-Jacket-/220778484560?pt=UK_ToysGames_RadioControlled_JN&hash=item33676c5350
Thanks to all for your advice
Jeremy
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apart from that little flop have you got the new motor installed.
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No so simple :((! With the Leopard jacket in place, the diameter is too big for the 360 size bracket. I could turn the bracket round, except that it is firmly epoxied to the butterfly keel at the bottom of the hull. Wrench it out and I could destry the boat. I will try the ebay jacket sealed with mastic and see if that will do the job.
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lol thats just bad luck
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Mastic did not do the job! :((. Motor runs fine but the jacket leaks. I'm wondering whether heating up the jacket might cause it to expand enough to allow it to be fitted with its O rings. I'll have a go and see. Someone must have fitted one of these. Prestwich Model Boats sell a motor with exactly the same jacket already fitted. I will ask Dave Marles about it. He may know the secret!
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try this pete its a long shot though. put the motor in the freezer to make it shrink. put the seals in the jacket and put the jacket in boiling hot water, stick it on the hob in a saucepan.
DONT FOR HEAVENS SAKE BURN YOUR HANDS use gloves or something and put a big o butter on the freezing cold motor and try pushing the jacket on. makes sure your get all the old silicone off first.
have you got any pics?
Btw it seems like this jacket is a bit tight so maybe you could loosen it up a bit with a file. if you have one of course.
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How about smaller diameter (cross section) O'rings they should be available from local bearing shops or similar,
Nick
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Hi Nick
Very close to the solution! Before I read your posting, I paired down the O rings in situ using a dremel sanding drum and then, using butter and a fair amount of force, I was able to get the jacket on :-)). It will never come off now. Anyway, all's well that ends well and many thanks for the various suggestions along the way. Mad Mike suggested earlier that several others have encountered the same problem. I hope this helps.
Jeremy
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next time we get someone asking how to put a cooling jacket on a motor you will be the man :-))
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Just to let you know that the Turnigy 2845 2000Kv motor, 25mm prop and a 7.2V battery gives the boat a great turn of speed :-)). It is almost silent in operation and the battery seems to last forever. When I next get down to the lake with a camera, I will post some photos and hopefully a video. The modified O rings clearly work to seal the water jacket - not a trace of water inside the boat. Thanks to all for your advice :-).
Jeremy
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Link to U-tube video:
http://www.youtube.com/watch?v=cLd2vhbfe9w
She goes well :-)
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You mentioned prop diameters and a pitch of around 30' - and some have mentioned smaller diameters. Are you only using X type racing props and not shallower pitch more scale like propellers?
As I remember in the Graupner range of props there were several classification dependent on pitch and blade shape. There were three blade scale type props with shallow pitch, 2 blade 'racing props' with a high pitch and then really high pitch carbon fibre ones for surface drives - I think the designations may have been P, X and S but don't quote me...
A change to a shallower pitch prop but similar diameter with a higher revving motor might keep a decent speed, drop the current draw and run it cooler.
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Prop is Graupner sub-surface drive racing prop 32.5mm diameter. It seems to be well suited to the set-up. Motor runs cool and almost silent.