My Bumblebee Electric, upgrading from DC to AC Options

[palmer_md]

Hello all,

I'm a long time lurker here, and I've posted a few times, but I'm starting this thread to discuss the upgrade I'm doing to my 74 bumblebee LE.

I converted the car to electric drive starting in 1995. I purchased the car in 1994 with the intention of putting in a chevy v8 or something, but after looking at what that would take I opted to put in an electric drive train. The car was sitting in a field with weeds all around and no interior, engine, transmission or anything. It took a few years to just get the car restored before I could put in the electric drive. I got the car on the road as an electric in 1997. It has been a fantastic car for commuting and it is a lot of fun to drive, but with all the lead in the car it was a bit heavy.

I decided last year that I was going to upgrade the car to lithium power which will remove about 700lbs of battery and give me more power and more range at the same time. I purchased a gearbox (BorgWarner 31-03) that is the same as a Tesla Roadster, and I got a Siemens induction motor and inverter that will give me almost as much power as the Roadster. I should end up with a little less weight than the Roadster which should allow me to have similar performance numbers...assuming I can get enough grip from the tires.

In order to fit this motor and gearbox under the hood, I'm going to have to remove the firewall between the trunk and the motor bay. The gearbox sits between the axles (obviously) and the motor will sit above it (hence the space time conflict with the firewall). This is not a problem since I've seen posts with this firewall and trunk floor removed and then triangulating by putting a bar between the strut towers and then two more from the towers down to the rear trans cross bar in the trunk. This part of the build is all pretty clear in my mind. The connection between the strut towers works perfect as an upper mounting point for the motor and gearbox. Existing motor and trans mounting locations work for the lower support.

The area where I have a question is with regard to the gearbox location. In order to put the gearbox and electric motor in the car, it installs like a transverse motor in a FWD vehicle. The gearbox is mounted slightly to the driver side of the vehicle and the motor is to the passenger side. So instead of the existing 901 getting installed exactly in the center between the two wheels, I'll have to mount the eGearDrive about 5" toward the driver side of the car comparatively, and then I'll have to put in an intermediate half shaft on the passenger side to allow for the articulating portion of the axles to both be equal length (about 5" shorter than stock). Anyhow, this is my question, and one that I thought I'd ask for help here first before heading to a drive shaft shop to get opinions. Will the suspension work well with 5" shorter drive axles. It means probably steeper angles as the suspension articulates, but I think it should work. I just don't have any experience in this area and I'm going to have to get some help with this decision before I start cutting the trunk apart to install all of it. If it does not look like it is going to work I'll have to come up with a plan "B".

I'll post some pictures in a later post, but I wanted to get the question about the drive shafts out there since I need that answered.

Thanks,
Michael

[palmer_md]

Yesterday I removed the motor and transmission. I still have much more to remove before I do a mini restoration on the engine compartment and give it a quick coat of new paint.

Started work on the temporary support between the rear strut towers. I'll have to figure exactly where to place the permanent support once I test fit the new motor and gearbox.

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.palm-motors.com-12389-1386547648.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.palm-motors.com-12389-1386547648.2.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.palm-motors.com-12389-1386547649.3.jpg)

[barefoot]

Yesterday I removed the motor and transmission. I still have much more to remove before I do a mini restoration on the engine compartment and give it a quick coat of new paint.

Started work on the temporary support between the rear strut towers. I'll have to figure exactly where to place the permanent support once I test fit the new motor and gearbox.

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.palm-motors.com-12389-1386547648.1.jpg)

Wow, neat projects. I'm curious re the use of the gearbox, do you use all gears, and how are shifts accomplished ??

[palmer_md]

Wow, neat projects. I'm curious re the use of the gearbox, do you use all gears, and how are shifts accomplished ??

I am thinking of doing one of these conversions on the near future. What's the Avwrage cost on parts?

With the DC conversion, the max RPM is about 5000, so shifting is not unlike the stock motor. The DC system had much less power and torque than the motor I'm installing now, so the transmission was necessary. Actually the car ran very much like a stock 914. It was quite a bit heavier but I had about the same horsepower and a bit more torque than the stock motor, but it (torque curve) was flat from 0rpm to 3000 or 4000 where it began to taper off. The new motor has much more torque and is capable of 10,000 rpm, so I can get away with a single speed gearbox. I'd prefer 2 speed, but the single speed gearbox that Tesla used in the Roadster is very efficient and robust, so I am going to be using this same gearbox. Downside is that I'll be limited to 95mph at 10,000 rpm.

As far as conversion costs, the cost varies wildly. If you purchase old forklift equipment used and install used batteries, I've heard of people doing it for under $3000, I've also heard of conversions over $50,000 in components. I'm going to be in the $25,000 ballpark, and my first conversion on this car was in the $10-$15k range. (neither include vehicle restoration costs...which I'm discovering more every day as I remove parts...no surprise to anyone here I'm sure)

Discussion of conversions and cost should be moved to the linked thread above. PM me if you post there, and I'll join the conversation over in that thread. I'd like to keep this thread about my conversion specifically.