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Author Topic: Returning to boats after 25 years WHICH BRUSHED MOTOR advice  (Read 2410 times)

Ultrarep

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Returning to boats after 25 years WHICH BRUSHED MOTOR advice
« on: December 05, 2015, 11:56:44 am »

hi guys
Well after a long Break from RC modelling of about 25 years both time and funds are more readily available to pick up the hobbie I loved so much.


Problem is someone seems to have moved the goal posts not just a bit, but quite a lot.


I was and hopefully still am a competant builder and capable user having run cars(early tamyas (like the roughrider) and several boats (MFA Spearfish was the last), aswell as many planes and helis (still in the loft)


The time and opportunity has presented its self to get back into boats as I have bought a 36inch all wood Rivarama ready for RC but also or mainly (i still cant be honest with myself on this) coz it just looks fab!


The last time i used electric with boats and cars the only real option was the Mabuchi RS540 and battery choice was limited to a NiCad pack that would last 4mins and take a month to charge, not to mention speed controlers you needed oven gloves to adjust.


I want to set the boat up with a full true twin motor arrangement with twin stick throttles for manouvering and a semi scale speed most of the time.  However i do want to have a bit up my sleeve should things get a bit competitive when the friends all pile back in (and they will) so that i have a bit if a surprise ready.


So any help with motor choice etc and anything else would be gratefully recieved


I have looked at the moror tables and want good speed available but not for much of the time and a good duration on the battery.  I have sort of come down on the speed 600 range but your views on these or others in a similar size and type of boat would be appreciated



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inertia

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Re: Returning to boats after 25 years WHICH BRUSHED MOTOR advice
« Reply #1 on: December 05, 2015, 12:23:19 pm »

Why do you insist on brushed motors? This sort of model just cries out for high power and low weight, and the very restricted space to fit what are quite large motors (because of the open cockpit) makes the smaller brushless type even more sensible. They are certainly more efficient, which means that the precious energy stored in your batteries will last that much longer. Using a modern fast charger you can recharge a 2600maH LiPo pack from flat in little more than ten minutes.
It's not a Black Art any more, and they need be no more expensive than a pair of Speed 600 motors and matching ESCs. As an example, a pair of these motors http://www.componentshop.co.uk/lc2826-17t-1050kv-leopard-outrunner-brushless-motor.html coupled with these speed controllers http://www.componentshop.co.uk/30a-waterproof-brushless-motor-speed-controller-esc.html would do the job very nicely for a shade under £100. I've excluded the cost of the batteries as that would be identical for either set-up. If you search the Chinese websites you can find similar items for a lot less. I was very much against brushless motors for all sorts of irrational reasons but, having tried one successfully, I'm now a convert - certainly as far as performance models are concerned.
Dave M
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Ultrarep

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Re: Returning to boats after 25 years WHICH BRUSHED MOTOR advice
« Reply #2 on: December 05, 2015, 01:00:02 pm »

Hi Thanks for the quick reply


Wow i thought brushless was all too expensive and also far too buzzy but you make a good case here.  Can I ask if these are controlable at low speeds? as i think I have read they are not as slow running as brushed but if thats wrong or not that noticeable in use then I may look at these again.  Just another level of complexity to get my head around now, but thanks.


Is an out runner better than an inrunner ?
Also is it better to have a higher Kv and just not use it to the max


Any further advice would be usefull on these things as you have now wetted my appetite and the speed monster is stiring
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inertia

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Re: Returning to boats after 25 years WHICH BRUSHED MOTOR advice
« Reply #3 on: December 05, 2015, 01:45:40 pm »

There is a whole noticeboard about brushless motors etc on this very forum. You'll find far more on there than I can put in one post, but to answer your queries very briefly:
1. Low-speed control is much better than it used to be, even with sensorless motors. That said, you are building a Riva speedboat - not a tug.
2. Outrunners have more torque and don't run at such loony speeds as inrunners, so they tend to be the preferred option for our scale model boats. 'Fast electrics' are a law unto themselves.
3. A brushless motor will always run at the "calculated" speed i.e. Volts x kv when the full voltage is applied. It will just take more current to do so the more you load it up (with a larger prop), but you have a proportional ESC anyway. Just don't push the throttle stick so far, or reduce the travel on that channel (if you have a computer radio). If you find it's much too fast then reduce the number of cells in the pack.
BTW you don't have to use LiPo batteries if you don't want to; NiMH cells are fine, but don't even think about SLA bricks.
Here's a short video which Martin D took of my little 1/16 scale (24") Huntsman at Wicksteed. There's some low-speed reversing round about 45-50 seconds in. The power train is as described in my previous post, using a 3S LiPo battery (11.1v) and 32mm 3-blade bronze prop. https://www.youtube.com/watch?v=uw1C8SfZPS4&feature=youtu.be
DM
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Ultrarep

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Re: Returning to boats after 25 years WHICH BRUSHED MOTOR advice
« Reply #4 on: December 05, 2015, 01:51:12 pm »

Great info and helps me a lot.


Many thanks for your sage advice.


Have already registered with the site you sent info on and have a packed wish list.





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inertia

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Re: Returning to boats after 25 years WHICH BRUSHED MOTOR advice
« Reply #5 on: December 05, 2015, 03:38:31 pm »

You're most welcome, but there are folk here with far more first-hand knowledge of brushless matters than I have. As regards Component Shop, that website should be on every boat modeller's list of Favourites (or Bookmarks if you use Firefox). They're really nice people, too.
DM
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Netleyned

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Re: Returning to boats after 25 years WHICH BRUSHED MOTOR advice
« Reply #6 on: December 05, 2015, 03:48:22 pm »

They're really nice people, too.
DM


Not bad looking either  :-))


Ned
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inertia

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Re: Returning to boats after 25 years WHICH BRUSHED MOTOR advice
« Reply #7 on: December 05, 2015, 03:52:43 pm »

Down, boy - DOWN!  :o
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