Mazda truck EV conversion 3

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Clutch or no Clutch

Should the electric motor be connected directly to the transmission, or should the electric motor be connected to the clutch? Here are some of the factors to consider.

  • Clutch has a flywheel embedded in it. It is a very heavy metal disk. In an Internal Combustion Engine (ICE) vehicle, it functions as a mechanical capacitor smoothing out power from the pistons. When the vehicle stops at the red light, the ICE engine will idle and continue to spin, so the clutch is needed to separate the engine from the wheels. In electric vehicles we can cut the power off completely at the red light and stop the electric motor, so no need to have clutch. Remember that the clutch and the flywheel are together. If the clutch is included, the electric motor has to speed up the flywheel every time it starts to spin.
  • Clutch is also used while changing gears. If the electric motor has enough torque and speed range, only single gear (second gear?) could be used. But it would still be useful to change gears while climbing hills.
  • Finally the problem of coupling the electric motor to the clutch OR the transmission. The picture below shows the type of part needed to connect to the clutch. You have to remember that there is no off the shelf part that will fit that shape nor the splined shaft for the transmission. In either case the part must be machined in a machine shop.

pix from 2008mazdaEV100_5282.jpg.

I ended up not using the clutch except for one crucial part of the clutch, the splined portion that connected to the transmission. Pictures below show the clutch after I took it apart. I would definitely include the clutch the next time around.

pix from 2008mazdaEV100_5288.jpg.

The bearing at the center of the clutch guides the tip of the splined shaft of the transmission.

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The two pictures above show the two sides of the clutch: one side is connected to the engine, the other side is connected to the transmission. The clutch disk goes in between these two sides.

pix from 2008mazdaEV100_5292.jpg.

I took apart the clutch disk. The four springs you see in this picture absorbs the coupling shocks whenever we change the gear and lift the clutch pedal. Look at the part at the upper right hand side of the picture. It fits to the splined shaft of the transmission.

pix from 2008mazdaEV100_5293.jpg.

The side view of the part that fits to the splined shaft. I tried to shave off the outside, but it was hardened steel and would not budge. Gave up on the idea.

pix from 2008mazdaEV100_5294.jpg.

Shaft Coupler

At this point there are three problems: coupling the shaft of the motor to the splined shaft of the transmission, the adaptor plate to mount the motor to the transmission bell housing, and the motor mounts to securely mount the electric motor to the body of the vehicle.

No amount of searching on the internet helped me with the first problem. Namely, a part that will fit 1 3/8 inch diameter keyed shaft on the motor side and the 1 inch splined shaft on the transmission side. The closest thing I found was a shaft coupler shown in the picture above rated for max torque of 6600 inch-pound at $110 each. It turned out that if the outside of the part from the clutch was shaved off, it would fit inside the shaft coupler exactly.

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Shaft coupler mounted onto the electric motor.

Adaptor plate

At this point I needed a machine shop. Most machine shops are geared towards bigger projects and will not deal with one time projects such as this one. However, I found one guy in Cornelius who was willing to work on this project, Joe Strasburg 503-693-8578. He was a very nice guy and certainly exceeded my expectations, highly recommended.

I bought a 3/8 inch thick aluminum plate and explained to him what I needed. He asked me to disconnect the transmission and bring it to his shop. You can see the resulting adaptor plate in the pictures below. He also was able to shave off the hardened steel part to fit into the shaft coupler. Another part he built was the two spacers between the adaptor plate and the motor face plate.

pix from 2008mazdaEVPreparing for motor mount

pix from 2008mazdaEVAdaptor plate mounted on the transmission

pix from 2008mazdaEVElectric motor with the shaft coupler and the two spacers on each side

pix from 2008mazdaEVLooking into the engine compartment without the transmission

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pix from 2008mazdaEVTransmission, adaptor plate, and the spacers installed

pix from 2008mazdaEVControl Box and the motor installed

pix from 2008mazdaEVPower comes from the cable connected to the external power source

pix from 2008mazdaEVController and the motor installed

The control box was still connected to the DC power source coming from the transformer. I lifted the rear wheels off the ground and did a test run. When the truck was in gear, the wheels started spinning.

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2 Responses to Mazda truck EV conversion 3

  1. Steve says:

    So how is the project going now? I am just starting to work on a similar project also with a 15Hp 3-phase AC motor that I’d like to put into a 1982 RX7.
    What has your experience been since completing the project? What’s it like to drive?

  2. Rex Ryan says:

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