Tractor Work Resumes

by Ben N on June 6, 2021

After a long hiatus, I’m working on the Electric Tractor Conversion again.
This past year was a bad one, with COVID, a couple of deaths in the family, and other issues.

One of the most difficult for working on the tractor was probably the fact that I was cut off from my typical resources for working on such a project. For example, I don’t have my own lathe or mill. I typically would use such equipment at a cooperative workshop, like the Milwaukee Makerspace, but that was essentially shut down for a year.

Likewise, I’m always trying to learn, and that usually means meeting up in-person with friends who are more skilled than I am in welding, machining, electronics, whatever it is that I need some advice or direction on while working on a project.

10.5″ diameter drive motor from a Nissan brand forklift.

I’ve decided that the best approach for the tractor is simply to use forklift parts. Forklifts are very common electric vehicles and the components are based on simple 36 and 48V DC battery systems. A tractor and a forklift also both have similar speeds, duty cycles, and expected levels of abuse.

Drive motor, test fit in approximate location.


I pulled the 10.5″ diameter series-wound motor from my “wheelie Tractor”. That motor is pretty much the maximum size which will fit in the tractor, both in terms of diameter to the faceplate of the transmission AND length, if I want to have enough room for a hydraulic pump. I originally bought this motor at a rummage sale, pulling it from a scrapped forklift the seller had, and used it in my Electric Geo Metro.

Forklift pump and motor.

Likewise, I located an electric motor and hydraulic pump from a forklift. After a little searching, I figured out that it’s considered a 6 gallon per minute pump. The electric motor spun fine when powered by my dumb multi-volt battery charger, and I was able to test it for proper rotation. After that, I tried running fluid through the pump to actually measure the flow rate. (I used water, knowing I’d make a mess, and the cleaned out and oiled the pump afterwards.)

At 24V, this pump CRANKS!

At 12VDC, the pump ran about like the flow from a garden hose, pumping 5 or 6 gallons a minute. When I tried running the pump at 24V, it really WAS twice as powerful… At least for about 10 seconds, before I blew the fuse on the battery charger. This was with an unrestricted output. At this point, I don’t know exactly how the pump will perform when it is instead pushing a hydraulic cylinder. I would imagine that the pump would slow down considerably. If needed, I COULD always add a speed controller for the pump.

Using my engine hoist, I was able to move the drive motor over to the tractor and roughly position it next to the transmission. It looks like a good fit. Of course, EXACTLY how far the motor will be spaced away depends on the hub which will connect the motor to the flywheel, as the flywheel needs to be in the same location as it was when mounted on the engine.

I was also able to wrestle the hydraulic pump and motor into approximate position. (I slid a stool under the tractor as a stand for it.) That motor might still be able to be mounted a little lower. That would allow for a nice rectangular area ABOVE the drive motor and pump for the battery pack. There’s only a small amount of space between the two motors and between the pump motor and the radiator. As long as I don’t have to move the drive motor out too much, I think it should be just about a perfect fit!

I’ve also been thinking about the machining that’s required for the motor mounting plate, the motor shaft to flywheel, and even how to connect the hydraulic pump to the tractor.

The tractor originally used hard lines all the way from the hydraulic reservoir to the engine-mounted hydraulic pump. I need a way to connect hoses from the new pump to the body of the hydraulic reservoir. I think the best approach is to machine a piece that matches the end flange on the hard-lines. It’s a relatively simple shape – just 3 bolt-holes and a hole for each of the send and return lines. That could easily be made with a mill and a drill-press. Alternatively, I could just CUT the hard lines, but I would still need to do at least a little machining to the ends of the pipes to adapt them. Since I’d have to do some machining anyways, I’d rather not damage the original hard lines and sell them to somebody else who is trying to keep their classic tractor running.

Flange end of the hydraulic hard lines which bolts to the tractor hydraulic reservoir.

I also spoke on the phone last night with a friend of the family. A few months ago, he was in the hospital with a life-threatening case of COVID. Now, he’s back out and doing well. As a semi-retired machinist, he has a lifetime of experience designing and machining custom parts. He offered to let me use his mill and give any tips and training I might need. I also consulted with him on creating custom splines, so that I could make a component which would properly slide onto the splined shaft of the drive motor. He told me that he has access to an EDM at his shop and that would be an ideal way to cut precision splines.

I feel like the ball is finally rolling again on the tractor conversion. I’m glad folks are getting vaccinated, and that we can “get back to normal” again, or at least something like it!

Until next time, stay charged up!
-Ben Nelson


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