I built a Razor GFD with a 24v 750w motor for my son. It was a little faster and had lots of torque.
I want to build a Razor GFD that will go double the speed. I'm willing to replace motor, controller and thumb throttle. I would prefer a 24v solution vs. 36v and adding a third battery mostly due to space constraints on the Drifter. However, if a 36v is far superior I'm sure I can figure out how to package it.
What's the best and simplest solution to double speed.
To start off we have modification kits available for the Ground Force Drifter with motors up to 48 Volts and 1800 Watts on this page:
The Ground Force Drifter's original motor is only 250 Watts so a 750 watt motor should be just powerful enough to double its speed.
To double the speed and keep the battery pack at 24 Volts the gear ratio would need to be increased. This could be done by installing a motor sprocket with twice as many teeth than are on it now, or by installing an axle sprocket with half as many teeth than are on it now. I ran some gear ratio calculations to show the increase in speed with these different sprocket configurations.
Unfortunately we can not get 22 teeth motor sprockets or 16 teeth Ground Force Drifter Axle sprockets. However we do carry a 16 tooth sprocket for #25 chain with a 1/2" bore that could be drilled or machined out to have the same size inner diameter as original 32 tooth Ground Force Drifter sprocket. If I remember correctly the Drifter's original axle sprocket has a 17mm ID bore but I might be wrong so please measure it before drilling out a new sprocket to replace it.
This 16 tooth sprocket is our item # SPR-2516B which is available on this page: http://www.electricscooterparts.com/sprockets25chain-motor.html
If the battery pack was increased from 24 Volts to 36 Volts the top speed would not be doubled and would only be around 19 or 20 MPH according to my calculations. Running a 24 volt motor on 36 Volts would also be more risky than running it on 24 Volts because depending on how hard it is used it may run hotter than normal which could possibly damage it. Here are my calculations for running the motor on 36 Volts.
I based all of these calculation on a 2500 RPM motor. If your motor has a higher or lower RPM then the calculations would need to be slightly adjusted for the difference in RPM.
Here are links to the calculators I used.
Top Speed Gear Ratio Calculator: https://www.electricscooterparts.com/motorwheelgearratio.html
Motor Overvoltage RPM Calculator: https://www.electricscooterparts.com/motor-overvoltage-rpm-calculator.html
I think that installing a custom bored 16 tooth sprocket on the rear axle would be the best and simplest solution to double the speed.
With the 32 tooth axle sprocket replaced by a 16 tooth axle sprocket the acceleration and torque would be significantly reduced at least by 50%. If you do not need a 25 MPH top speed and still want good acceleration an torque then maybe a less drastic gear ratio change would be better, such as changing to a 20 or 24 tooth axle sprocket instead of a 16 tooth.
Regarding the motor, controller and throttle question how many Volts and Watts do you want to increase the power to?
Please let me know if you have any questions.
We also have modification kits for the Razor Ground Force Drifter with motors up to 1800 Watts which can be found on this page:
Yes the THR-38 thumb throttle woks with the SPD-361000 controller. THR-38 comes with a 3 wire connector that plugs right into the SPD-361000 controller so it is plug and play. The THR-38 throttle's wire terminals would just need to be pushed into the included connector before it is plugged into the controller.
The Ground Force Drifter's brake lever switch has a 2 wire male connector, and the SPD-361000 has a 2 wire male connector, so they are not plug and play. The brake lever switch's male connector would need to be changed over to a female connector in order for it to plug into the controller. We could also make an adapter that would allow the GFD brake connector to plug into the SPD-361000 controller brake connector for $3.95 if you do not want to put a different connector on the brake lever.
The SPD-361000 has the best cooling of our 1000 watt 36 Volt controllers because it is the largest one available. However it does require a heavy duty switch such as our SWT-156 or SWT-700, or a power contactor such as our RLY-36150 to turn it on and off. The SPD-CT660B9 could be turned on and off with the Ground Force Drifter's original power switch.
If you have any further questions please do not hesitate to ask.