Electric Motor Torque and Gear Ratio

by Sean
(Spokane, WA)



I am wondering what the torque I can expect out of a generic forklift motor would be.

I just acquired a Ford Ranger that I'm going to convert. I was thinking about refurbishing a couple old forklift motors. The transmission fell out of the truck, so I thought I would hook up the motors more or less directly to the rear wheels, no rear diff or anything. I'm worried that by bypassing the rear diff which has probably around a 3.73 to 4.1 ratio.

Since a lot of people run their cars in third gear which is about direct drive, they still get the gearing advantage of the rear differential, multiplying their torque four fold. The question is would two refurbished forklift motors be able to get the 3000 pound vehicle off the line without any mechanical advantage from gearing?

Hi, Sean -
I took your question to Steve Clunn from Green Shed Conversions in FL.

He said:

"The lower the RPM the higher the torque is going to have to be. You are starting off with a marginal motor to begin with (the forklift motor) and then not wanting to give them a 5:1 ratio, which would come about from the transmission and the rear diff.

The general trend is to have higher RPM Motor so they can be smaller in size and have a gear box that has a 8 or 10:1 ratio.

Going the other way is going to require a much bigger motor and, since these motors are going to making torque instead of RPM, they are going to heating quite a bit. Everything can be a trade off. What do we gain by not having a proper gear ratio?

Back to your question.

Off the top of my head, the two motors, if they are 80lbs each... would work with a 6:1 ratio. you would need 4 motors of the same size to give the same performance with a 3:1 ratio, so probably 12 motors would be needed for the same performance with a 1:1 ratio.

You will also need a controller that can run all 12 motors in series."

Steve mentioned that they sometimes have used Netgain motors for sale that would work for an electric car conversion.

Hope this helps!

Lynne


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