Welding frame rails / Rolling the Tractor

by Ben N on May 13, 2020

Converting this International Harvester 300 Utility tractor to electric has had a few challenges. One of them is that the engine is structural and connects the front axle (and everything connected to it) to the transmission.

I found a relatively quick and easy answer when I discovered that some other tractors have frame rails that bolt to the same transmission bell housing. I’d simply have to do some fabrication for the front end.

After cutting the rails, getting everything lined up, and making sure the sheet-metal (the “hood”) would go back on correctly, I ran into another issue; there’s barely any space between the rails and the front bolster. That bolster needs to swivel as the tractor goes over uneven ground.

Basically, I have a clearance issue between these two parts! But I also need to be able to keep working on the project. So, I decided I would finish the frame rails, by welding in place the mounts to the front axle.

The cut-offs from shortening the frame rails were sturdy pieces of metal that already had holes and slots in them. Two holes were close enough to lining up with those in the axle casting that I only needed to just ream them out with a drill.

With everything lined up – the tractor and frame rails, the front end (up on a pair of jacks for leveling) and the cut-offs bolted in place, I was ready to weld.

I made some rather ugly welds before having the welder adjusted. In the end, all the welds were solid – just not pretty. This should only be temporary, so I’m really not worried about it.

I raised the jacks a bit, removed the blocking under the tractor, and lowered the jacks. To my amazement, everything worked right. The tractor sat with its own weight on all four wheels.

After some clean-up, I wanted to see if I could actually ROLL the tractor. There’s a couple of reasons for that. One is just so that I could get it out of my garage if needed (such as for washing the thing off!) I also wanted to have a look at the transmission input shaft as the tractor rolls. That would tell me which direction the shaft spins, as well as give me a better sense of the gear ratios.

I put air in the tires. The second time I tried pushing the tractor, I also remembered to take off the parking brake!

Other than being heavy, the tractor rolled just fine!
Looking at the transmission input shaft, I could see that it spins clockwise. In first, it spun very fast. In fifth gear, it spin much slower. I also tried reverse. As expected, it spun even faster than in first gear.

One thing that I learned was that you CAN’T push the tractor in the opposite direction from what gear it’s in! It simply locks up. This must have something to do with the physical design of the gear system itself. But in a serious note, that means that I will want to make sure that I can NOT spin the electric motor backwards! Doing so would probably break the transmission! I’ll need to make sure to a software lockup to prevent accidental backwards spin.

Thunderstruck Motors VCU

I also got the Thunderstruck Vehicle Control Unit in the mail. This device should allow me to control the Nissan Leaf Inverter and Motor. I look forward to figuring out how it works and test-spinning the motor with it!

Until next time, stay charged up!
-Ben Nelson

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