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Ground force drifter needing torque after larger wheels

Hello, I’ve installed four 8 inch pneumatic wheels on the Ground force drifter.  I’ve also installed the Currie 750watt motor.  Running on stock controller, 2 12v 10Ahr batteries, the drifter is very slow to get going.  In grass I need to give my son a push start.  Did I kill off all the torque by installing the bigger wheels?  I’ve read that I could increase the axle sprocket to gain torque back.  That may be a difficult task.  I’ve also temporary added another 12v battery up to 36v  to see if that helps the low end torque.  That really didn’t help out much.  I’m still running stock controller, would up grading the controller give me the torque back.  Which controller would you recommend upgrading to?  I’d like to stay at 24v now, then up the voltage to 36v down the road. The Currie motor can run both 24-36v.  I’d like to find a controller that can do both voltages as well to avoid buying another controller in the future.  I found a Kelly controller that could do both, but not much instructions on making the connections. The Kelly controller KDS36100E the specs seem a little high. 100A 1 minute, 60 A continuous, I don’t know if that would burn up the Currie motor, the motor is speced at 30A 750 W.  There’s a lower controller 50A for 1 minute, 30 amps continuous. 

It seems like there are several possibilities to solve my issue. 

What are my best options moving forward?  Any help would appreciated  

The larger diameter rear wheels increased the gear ratio to a point where the motor can no longer produce enough low RPM power for a normal rate of acceleration. The original controller is for a 250 Watt motor so upgrading from the stock controller should help with the acceleration.

I ran a gear ratio calculation and found the new top speed with the 750 Watt motor and 8 inch wheels is 21.33 MPH. A 750 Watt motor is suitable for this top speed. However, this top speed is approaching the power limits of the motor so it would probably not have fast acceleration or be able to climb steep hills with the current gear ratio.



The 750 Watt Currie motor has a 30 Amp continuous power rating so using it with a controller that has a 30 Amp current limit would be the safest combination. The motor can be run at more than 30 Amps intermittently though, so a controller with more than a 30 Amp current limit could be used to provide more current for acceleration and short distance hill climbing.

We carry a speed controller that is easy to install which runs on 24-36 Volts and has a 50 Amp current limit. It is our item # SPD-241000D. Here is a photo of it.


Please let us know if you have any questions.

Thanks for the information.  Looking thru the available controllers I’ve found the SPD-601000A.  According to the specs, this controller also run between 24 and 36V.  What’s the difference between SPD-60100A and SPD241000D?  Could I safely run my Currie 750 with the DPD-601000A?  According to the specs, both seem to have a current limiting features. I would only need a 3 wire thumb throttle and a relay switch or heavy duty switch. 


Can your 24V relay RLY-24150 run on a supply voltage of 36 volts as well as 24v? The specs say rated voltage 24v and maximum voltage 36v.


On a side note,  If I end up wanting to increase the wheel sprocket to help low end torque,  I’ve found the 47 tooth sprocket item SPR-2547.  I see it would drop my top speed to 14.5mph, but then I could but to 36v to get my speed back if I wanted to.  Would the 47 tooth give me noticeable low end torque or really not worth the trouble?  I think the OD of the 55 tooth is physically too big. I think OD to the 47 tooth would fit without hitting the frame of the drifter.  If I remember correctly the diameter of the drifter axle is 30mm.  the ID of the 47 sprocket 1-1/8 is slightly smaller in diameter than the axle.  Can your machine shop increase the ID of the sprocket to fit the drifter axle?  I could bolt or weld it to the flat side of the original sprocket and slide it over a bit or adjust the motor for alignment purposes.



SPD-601000A has a factory current limiting specification of 30 Amps, however, we have had customers report that it can output significantly more than 30 Amps and one customer got a reading of 45 Amps from it when riding uphill on 48 Volts. Between the SPD-600100A and SPD-241000D, I would choose the SPD-241000D because it has a larger and better-designed heatsink so it should run cooler.

As far as safely running the motor is concerned since the motor has a 30 Amp continuous duty rating a controller with a 30 Amp current limit would be safest to use with it, however, a controller with a higher current limit could safely supply more temporary current to the motor for faster acceleration and short distance steep hill climbing. With a controller that has a current rating that is over 30 Amps, the rider would need to make sure under high demand conditions to not continuously supply the motor with over 30 Amps otherwise the motor could overheat.

Increasing the rear axle sprocket size to 47 teeth should provide a significant increase in torque because it would allow the motor to spool up to speed faster and the motor makes more power the faster it is spinning. 

The Ground Force Drifter's rear axle should have a 20mm diameter so the 47 tooth sprocket with 1-1/8" ID will fit over it.


Please let us know if you have any questions.

Thanks for all the helpful information.  couple last questions, can I use the heavy duty motor reversing switch you sell SWT-715 with my currie 750w motor.  the motor is reversible however I just need to locate a reversing switch that will handle the current.  specs says rated for motors 2200 watts and under.

will your 24 volt 150amp power contactor RLY-24150 operate coil voltage up to 36 volts if I decided to upgrade the supply voltage to 36volts?  Trying to avoid buying 2 if I don't need to.  the specs say rated coil 24v max coil voltage 36v...  If i upgrade to 36v, could I just tap off the 24v from the 2 of the 3 12 volt batteries to energize the coil to trip the contacts.  How would that work?

Yes, our reverse switch item # SWT-715 is compatible and will work great with a 750 Watt motor.

Our 24 Volt 150 Amp power contactor item # RLY-24150 has a maximum coil Voltage rating of 36 Volts, however a 36 Volt battery pack recharges to 41 Volts which is higher than the power contactor's maximum coil Voltage rating so we do not recommend using RLY-24150 with a 36 Volt battery pack.

Although not as robust as our 150 Amp power contactors, we do carry 24 Volt and 36 Volt 60 Amp power relays such as item # RLY-2460 and RLY-3660 which cost significantly less than our power contactors so it would be more cost effective to switch over from a 24 Volt to 36 Volts if using them.

Please let us know if you have any questions.

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