David Heacock's 1985 Avanti EV Conversion (In Process)
An Advanced DC 9 inch motor was decided upon to drive the Avanti since some of the reference material available indicated it would be adequate for an EV up to 5000 pounds. Since one of my goals was to keep the total weight of the finished vehicle to 4000 pounds or less it seemed reasonable to used this motor. The major concern was how to connect the motor to the Harley transmission. A friend of my brother, who had his own motorcycle and machine shop in the Los Angeles area, was contacted to discuss possible ways to connect the motor, through the Harley primary, to the Harley transmission. The final design was a taper lock connector. This type of connector has been used on other EVs and seemed to be a solid way to connect the motor to the sprocket within the Harley primary. The following pictures show the finished taper lock that slides over the motor shaft. In the first picture of the assembled unit, the narrow end slides over the motor shaft. The second picture shows the sprocket with the hub, which has six split sections.
The completed taper lock unit is mated to the Harley sprocket and as the three mounting bolts are tightened and the two sections are drawn together, the taper lock tightens down over the motor shaft. The following pictures show the taper lock adapter installed over the motor shaft with the first picture showing the motor shaft before the taper lock and sprocket were installed and the second picture with the sprocket installed. As it turned out I later had to remove the taper lock because I needed to seal an oil leak coming from the primary case. This proved to be a fairly straight forward process where I simply loosened the three bolts and then tapped on each of them until the rear hub separated from the front sleeve, thus releasing the grip on the motor shaft.
The next step was to provide a mounting system to support the motor, primary and the Harley transmission. Again, the shop in Los Angeles came to the rescue and designed and built the necessary mounts made out of aluminum to limit weight. The following pictures show the mounts supporting the drive train.
At this point I have to say the shop did an outstanding job providing the completed system, which as far as I know, had not been previously developed.
It was now time to mount the drive train to the Avanti frame after the modifications to install the Corvette rear end were completed. I again turned to my local shop where a platform was made to support the drive train and allow for tensioning of the drive chain from the transmission to the rear end. A special adapter for connecting a sprocket to the Corvette rear end was made by another friend of my brother. It is always nice to have a brother who has the connections to build the necessary components. The following picture shows the mounting platform for the motor, primary and transmission. Notice the hinge on the left side of the platform and the large adjusting nuts on the right side of the platform used to tension the drive chain.
The following pictures show the sprocket adapter for connecting the sprocket to the rear end and the completed connection.
The completed drive train was then installed on the modified Avanti frame as shown in the following pictures. A test run was made while the Avanti frame was still at the shop by hooking a 12 volt battery to the motor and to everyone's relief, the wheels turned as planned. After filling the Corvette rear end, the Harley primary and the Harley transmission with oil additional test runs were made for brief periods of time.
Update 3/7/2012
It has been a long time since I have updated the information on this site. After the electrical components had been installed and the drive train finished it was time to drive the Avanti under electric power. On the first drives around the block it was obvious there was a lot of noise coming from the motor and drive train. However, a friend suggested placing the transmission in neutral and spinning the motor to see how much each source was contributing to the noise spectrum. As it turned out most of the noise seemed to be coming from the motor. Another lesson learned, placing the motor in the back seat was probably not a good idea but then the noise was expected and I had plans to build covers for the drive train.
After driving the Avanti for only a few miles it was discovered that under a given amount of torque some very strange and loud noise was coming from the drive train. As it turned out, after backing out of the garage one day, I could not get the car back in the garage without a noise that sounded like something was being torn apart. Since my driveway has a slight incline I placed the transmission in 1st gear but the noise continued. So my neighbor and his son came over and watched the drive train while I tried to move the car up the driveway. As it turns out, the chain was actually being pulled over the sprocket teeth. After pushing the car back into the garage it was discovered the Corvette rear end had just enough upward movement at the sprocket adaptor and the electric motor had plenty of torque to simply lift the rear end and then pull the chain over the sprocket teeth.
After talking with a number of people it was decided the rear end adaptor would be modified so that it had a shaft coming out the front which would then be inserted in a pillow block. The only problem was that modification of the frame had placed a frame cross piece just in front of sprocket. After making a number of measurements and obtaining a pillow block and a modified rear end adaptor, the Avanti was taken to the shop that had installed the Corvette rear end. Here they installed the new aircraft grade aluminum sprocket adaptor and the pillow block. The following picture shows the rear end adaptor, the sprocket and the pillow block
Back on the road again after several months, the problem with the chain jumping the sprocket teeth seemed to be solved as I could drive up my driveway with no problem. The Avanti was then driven and tested at greater distances and speeds. However, there did seem to be some slight noise coming from the drive train and upon inspection, nothing was found. Then one day driving around several blocks with a friend in the car, the loud thrashing noise came back under light acceleration. I got out and found the chain was somewhat lose which seemed a little strange but I figured maybe the chain was stretching some as it was new, thus causing the chain / sprocket problem.
After getting the car back in the garage I started to tighten the chain and upon closer inspection I discovered the new shaft on the adaptor had broken. After spending many hours just getting the parts out I took the following pictures of the broken shaft and the mounting plate for the pillow block. What appears to have happened is that the bolt heads mounting the sprocket to the adaptor were contacting the pillow block mounting plate and the constant stress finally caused the shaft to snap. The first picture was taken under the car with the broken shaft still in place. The last picture shows the wear pattern caused by the bolt heads hitting the mounting plate.
Back to the drawing boards, it was decided an improved adaptor shaft, made out of stainless steel with the proper radius where the shaft meets the rear end adaptor, would be built and installed. The following pictures show the new shaft mounted in the adaptor and the problems with getting it back in the car without removing the rear end. Again, the problem was the frame cross member. A much better design would have been to build a much thicker shaft with two pillow blocks but that would have required major work on the frame cross member.
Thus far with this arrangement the Avanti has now been driven over 270 miles at speeds up to 43 mph.