[theBootJr]

I am thinking about building an electric doodlebug. A doodlebug is a homemade tractor that is now used in pulling competitions at some fairs in New England. They are normally build from an old truck with a heavy duty rear end and 2 transmissions for an incredibly low gear ratio. They pull a weighted sled on concrete. The Doodlebug has to weigh less than 4,000 lbs and good machines can pull well over 30,000 lbs.

Most of the ones run at my town fair they are powered by an inline 6. Recently someone built one powered by a small diesel engine and they have been winning every year. This made me think that an electric doodlebug would be even better due to the torque available. I figure a large forklift motor would be perfect for this build. Is this a crazy idea or is there some merit to it?

 

[Electric Land Cruiser]

Perfect application. You need tons of power and torque for a short time period. 6 cylinder gas or a small diesel I'm thinking 300+ft-lbs or something like that? Is that your competition?

 

[theBootJr]

I think they make less torque than that because they aren't even running at a high RPM. I'm hoping to find a deal on a motor at a local shop. Is there anything i should be looking for?

 

[Electric Land Cruiser]

You should probably try to find a motor with a similar RPM range to a gas engine to keep gearing and everything about in the same ballpark. Either pick a motor and then match the battery voltage to it, or pick the battery first and match the motor to the voltage.

 

[Duncan]

I think they make less torque than that because they aren't even running at a high RPM. I'm hoping to find a deal on a motor at a local shop. Is there anything i should be looking for?

Read the thread on choosing a forklift motor - its long but you can skim through a lot of it
I would be looking for an 11 inch diameter motor - it will weigh about 100 kg
Finding a motor!
Find out who repairs forklifts in your area and go and VISIT with cash in pocket - speak to the workshop guys - you want the one they have been keeping "just in case"
You want a DC motor - recent forklift motors are AC and not what you need

Voltage - you can seriously overvolt and overcurrent those motors
Mine is a Hitachi motor rated at 10 kw - 48 volts and 208 amps
So I feed it 340 volts and 1200 amps
Voltage is needed to get the speed up - amps = torque