DIY Electric Motor Mount

by Ben N on May 9, 2018

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Recently, I’ve been posting to YouTube some video instructions that I made about how I converted a 1996 Geo Metro to electric.

A viewer asked about how the electric motor was mounted – whether it simply bolted to the transmission, or if it was additionally supported in some other way.

Great question!

The motor IS supported! In the original design of the car, the engine and transmission are bolted together and there are three mounts that connect them to the frame (OK, unibody) of the car. One mount is on the transmission, going between the transmission and firewall. The second mount is on the far driver’s side of the transmission. The third mount connects the engine to the passenger side of the engine bay.

Because the transmission was reused for this project, it simply went back in place (after the electric motor was attached to it,) and re-used the two stock mounts.

The third mount went to the engine, so it would have to be modified to instead help support the large electric motor.

DSC_0035When working on this, I was at a friend’s house. (Tom G. You might remember him from some Electric Dodge Neon Videos we made…) One advantage of working at Tom’s house was that he had both an arc welder and a plasma-cutter. We also commonly had a group of friends coming over to work on robots and electric cars. (These groups and projects eventually lead to the founding of the Milwaukee MakerSpace.)

Having access to both tools and mentors went a long way towards me learning how to weld and otherwise gain confidence and experience working on projects.

So, when it came time to build the motor mount, I had the privilege of having a few friends help me.

First, we already had the transmission with electric motor in place, but the weight of the motor would twist the transmission a bit on its mounts. Adding a third point of contact would support the weight of the motor and keep the entire unit from being twisted. We put a jack under the motor and raised it until a short spirit level set on top of the motor indicated it was nice and level. After that we could take measurements between the mounting point on the frame and the position of the motor. A custom mounting bracket would need to be built to that custom size and shape.

DSC_0014Fortunately, we had a few tools at our disposal. For one thing, the electric motor had several bolt holes on its back end. I was also far-sighted enough to keep the bracket which originally mounted that end in the forklift from which I originally salvaged the motor. On a motor WITHOUT bolt holes on the back end, a mount can be custom built using either a cradle design supporting from below, or a ring mount that clamps around the motor.

I also found that simply placing a piece of paper over the end of the dirty/greasy/rusty motor and rubbing against it was an easy way to transfer perfect measurements of the motor and locations of the bolt holes.

DSC_0009Having the greasy paper template and measurements from in the car, I set to work free-handing a shape somewhat like a capital letter “Q”. The middle of the motor stuck out further than the plane of the mounting bolts, so I would have to cut out the center of the motor mount to allow for that. The large bushing that connects to the car was offset from the motor, so the “tail of the Q” sweeps from the motor to that point.

DSC_0066After making a tagboard template and testing it in the car, we set to work cutting the steel. We used the plasma-cutter to cut out the general shape from a piece of 1/8″ steel. We also cut the center and drilled out the bolt holes. The metal was rusty, so we made sure to first grid down a spot for the ground clamp. Likewise, we had to clean up some rust before welding the steel-surrounded rubber bushing that would mount the bracket to the frame of the car.

Once the cutting and welding was done, a coat of Rustoleum Rusty Metal Primer covered the entire “Q” with a pasty protective coating.

DSC_0069We slid the bracket into the car, drove in the bolt that held the bushing in place, jacked up the motor, and ran in two large bolts connecting the motor to the bracket.

The motor and transmission were now held properly in place with three points of contact, and in the correct position, exactly like the original engine and transmission combo.

 

For more about this DIY Electric Car Conversion project (originally built in 2008) please check out this YouTube playlist!

Until next time, stay charged-up!
-Ben

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