2 brushed motors in series, one esc - RC Groups
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May 16, 2012, 10:18 PM
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mikeythev's Avatar

2 brushed motors in series, one esc

Hello everyone. I was hoping for some input. I received a mostly-built Dumas Coast Guard Lifeboat kit with two old honkey can motors. I thought about upgrading to brushless but don't want to mess with that right now. Has anyone run these off of one brushed ESC? The motors spin in opposite directions, and would be connected in series to keep their voltage close to 6V. I was considering this ESC from Horizon.

The motors make a heck of a lot of noise, and I thought it would be fun to keep it noisy. If anyone has upgraded this boat with 2 BL motors and 2 BL ESCs, please let me know. Any input would be great.


ps. I'm usually hanging out in the plane section, but I love rc sailboats. Now I'm venturing into new waters. Literally!
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May 16, 2012, 10:46 PM
CG Bob's Avatar
That ESC will do the job. There is no real need to upgrade that boat to brushless power; the full size USCG 44' MLB had a max speed of 14 knots (16 mph or 26 kph). The full size boat normally cruised at a speed of 8 - 10 knots (9.2 - 11.5 mph or 14.8 - 18.5 kph).

I'm using a Futaba MC 210CB ESC in a 30" PT boat model with two counter rotating motors.
May 17, 2012, 06:09 AM
Registered User
A motor being noisy is not usually a good sign for long life. A few drops of oil on the bearings might get them both working properly.
With motors wired in series, it is vital that both are set up mechanically identically. If one is marginally more heavily loaded than the other, the voltage across it will drop, and the voltage across the other will increase, so the relative powers will change with a corresponding differential steering effect. If one motor fails disconnected, both stop, if it fails shorted or stalled, the other gets all the available voltage.
May 17, 2012, 08:50 AM
Sport R/C Flyer/Sailer/Driver
Agreed with above. Seris wired motors can pose many headaches if one motor start working than the other due to a draggy propshaft, gunk in a prop, unmatched motors, etc.

Parallel wired motors avoid all of those issues and ensures each motor gets the same voltage. And as above, if one motor stops then the other motor will keep going to get the boat back to shore.
May 18, 2012, 01:06 PM
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mikeythev's Avatar
Thanks for the input. The noisy part comes from the half a dozen gears that mesh noisly. I couldn't say that the motors are noisy.

I see the point about parallel vs series. I was wondering if two motors in parallel will blow that ESC out. I would assume that each stock motor for that boat wouldn't pull more than 20A each, totalling 40 amps. However, that would make for some short runs.

Maybe a brushless upgrade with two motors and a direct drive would be a better option.
May 20, 2012, 06:08 AM
Registered User
Best way to find out is to measure with your trusty multi meter. Saves a lot of guessing.
May 20, 2012, 01:19 PM
Registered User
there are also some relatively cheap ESC's that are made to run twin motors...

infact theres a slightly different proboat ESC that will do it... it's stock in the PT109 and the 47' coast guard lifeboat ... 2 battery inputs, 2 motor outputs, and water cool

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