2 Brushed motors in series will....

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Papa   1 kW

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2 Brushed motors in series will....

Post by Papa » Nov 02 2008 1:12am

.... I assume, see half the total supply voltage, and likewise the RPM on both will be halved.
That said,... Even though the RPM is halved at each motor, my TOTAL useable torque (because two motors are driving) should be approx double - even though each motor is seeing only half the supply voltage. In other words; My vehicle speed will be half, but in exchange, shouldn't I see greater torque? Any enlightenment would be greatly appreciated.
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Kurt   10 kW

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Re: 2 Brushed motors in series will....

Post by Kurt » Nov 02 2008 2:44am

My old ebike used dual brushed/geared motors but only the one speed controller.I ran them both at 48v but becuse the speed controller had a 30A limit they shared the load so both could pull a max of 15A.speed was about the same but the motors were under less stress as they only need to suck 1/2 the Amps to give me the same power.

kurt.

cerewa   100 W

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Re: 2 Brushed motors in series will....

Post by cerewa » Nov 02 2008 8:30am

Papa, you've got it right. Two in series will get all the amps and half the voltage. So you should expect twice the torque.

The only way to know for sure if it'll work well is to try it, though.

If you want to, you could also try halving the voltage of your battery (for example if it's four 12v SLA's at 48v, set it up as two parallel and two series). Then you could either run one motor (if that gives enough torque) or two motors in parallel.

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rkosiorek   1 MW

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Re: 2 Brushed motors in series will....

Post by rkosiorek » Nov 02 2008 2:59pm

After reading about the Kill-A-Cycle doing this with their brushed motors i decided to try it on my EV-Warrior. it uses 2 450W brushed Bosch motors in a friction drive against the rear wheel.

in series you get a lot more torque for acceleration but lower RPM. in parallel you get less torque but higher RPM. the limiting factor on the bike was the friction roller. the contact area was too small to carry the full torque and the roller would slip and skip against the tire.

to limit some of this slip i modified the drive so that the motors would drive a toothed belt like a caterpillar or tank tread. the belt would then drive the tire. by virtue of the larger contact patch i hoped that i would eliminate the slip. when it worked the traction drive worked well but it had some severe reliability issues.

i discontinued these experiments after i discovered the reliability and simplicity of direct drive hub motors.

rick
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dogman dan   100 GW

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Re: 2 Brushed motors in series will....

Post by dogman dan » Nov 02 2008 5:20pm

RLT has a similar setup with dual brushed motors. He may be able to save you some experimenting.

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