# Need advice on conversion: Looking at RWD



## John (Sep 11, 2007)

A lot of manufacturers produce an AWD version of some of their vehicles. These could be a source of some of the RWD parts you need. I think Toyota made a GT4 version of the Celica. Parts are likely to be hard to find and expensive though. Unless you’re contemplating direct drive you'll still have a lot of trouble getting a gearbox to fit and I'm not sure how strong the RWD bits are as they are essentially supplementary to a FWD car. I think it would be a lot easier to start with a RWD car if that is what you want like a 3 series BMW coupe perhaps.


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## Devon Hynes (Dec 7, 2007)

It will be quite expensive, you'd need to build supports for not only the motor in the rear end but also a diff and axils, unless you wanted to go with 2 motors (one per rear wheel) but you will be looking at ALLOT of manual fab work.

Suspension will need to be redesigned, your car was designed to have the wieght of the motor ad transmition in the front end and a light rear end.

But one thing I'd like to say is that ANYthing is possible. I'm still in the learning stages of my future EV, but I do have quite a bit of experience working on cars. Anything can be done if you have the time/money/and most emportant patientence.


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## Brendonbosy (Dec 13, 2007)

It sounds like the consensus I'm getting around here is that if I want RWD, direct drive would be the easiest (probably only) way to go. How does it work exactly? Are there 2 motors directed mounted in the wheel like a hub motor for an E-bike? Or is there one motor mounted mid-way between the two wheels, feeding power to each of them equally? Also, what are the advantages and disadvantages of direct drive?


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## John (Sep 11, 2007)

I'll tell you what I've gathered from what I've read. With direct drive you will need power and lots of it. Something like a Zilla 2k controller and dual motor setup along with batteries that can produce the goods like AGM's. The motors should probably be fitted with external blowers for cooling. You will no longer have a reverse gear and so must reverse the motor to perform this function (add a reversing contactor). You can also put in twice as many batteries and parallel/series switch your dual motors (add in four more contactors). The disadvantages are you have considerably increased the cost of your various components and increased the electrical complexity. The disadvantage of high performance is poor range. For the sake of battery life AGM's shouldn't be discharged bellow about 50% DOD so their usable energy density is poor compared to flooded batteries they also don't self balance during charging and so require external balancing circuits. They can produce very high discharge currents and without degrading charge recovery as much as flooded batteries and of course are sealed and so can be mounted in any orientation and inside the passenger compartment. The advantage of direct drive is besides not having to change gears and mechanically simplifying the setup by dispensing with the gearbox is the performance. Acceleration isn’t interrupted by changing gears and driving the vehicle is simplified. There is also no chance of over revving the motor by applying power when the drive is in neutral.
For the dual motor set up I can think of two configurations I think would work. You could adopt a diff less setup like what the Tango T600 uses. With each motor driving one of the rear wheels through a reduction box. This would be difficult as it would require sourcing suitable reduction boxes and making custom drive shafts to connect to the wheels not to mention difficulties making things fit into the available spaces. You could also couple two motors inline connected to a conventional tail shaft driving a differential.


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## Brendonbosy (Dec 13, 2007)

Hmm, it sounds like this is going to be just as much a pain as trying to run a drive shaft from the front. I've read a couple articles like this one:
http://www.cafeelectric.com/blog/?cat=3
Overheating and inefficiency climbing hills seems to be a real problem. As for just simply buying a RWD car, I would prefer not to. Most of the RWD cars that I like (Lexus SC400, Toyota Supra, or BMW 3-series coupe) are a bit out of my price range. I could get an old 92' SC400 for cheap, but the other problem is that its a real heavy weight at 3650 lbs. Until high-density Lithium sulfur batteries come out, converting that would be very difficult and expensive. My Corolla right now is a nice lightweight at just 2400 lbs.

I guess I'll try and post one last question at this in my desperate attempt for RWD before I give up. Is it possible to just mount a motor in between the two rear wheels with a gearbox attached? (pretty much a FWD setup, but on the rear wheels)


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## Mr. Sharkey (Jul 26, 2007)

Anything is possible given enough time, money and fabrication skills. You are trying to work up a plan to convert one of your "favorite" automotive platforms, but from this side of the monitor, it looks like you need to find a new favorite car, one that lends itself to the drive systems that are available and affordable.

I think we had this discussion in another thread here. Part of your new way of thinking to exist in the EV conversion world is to shed you preconceptions as to what you will want, like and ~really need~ in the way of a car to haul yourself over the pavement. Until the "Big Battery Breakthrough" (all of which is pie-in-the-sky at this point in time IMO), you are going to be faced with the reality that big, heavy, luxurious asphalt mansions aren't going to make very practical conversion candidates.

My advice (again) is to find some econobox with a little flair, something you wouldn't be embarrassed seen driving, and convert that as your first EV. Doesn't matter if it's RWD, FWD or AWD (although one platform may have advantages over the other for you), just get out there and do it. Leave your driver's ego by the door and realize that some sacrifices will be necessary until we all live in that parallel universe where batteries self charge and drive motors have output equivalent to ICE powerhouses.


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## Brendonbosy (Dec 13, 2007)

I'm not looking for a car to get me from A to B. If that were so, I would just leave the slow, clumsy gas engine in my Corolla). I'm looking for some muscle in my car. Keeping my car on gas power wouldn't work for that for the following reasons:

1) An engine swap is VERY difficult if the engine is not part of the same family/design.

2) Because an engine is big and requires a lot of venting/cooling, it would be abolsutely impossible to mount it in the rear for RWD. Running a driveshaft from the front would mean I would have to change the chassis, VERY EXPENSIVE and practically impossible.

3) Because of the reasons listed in #2, my car would be restricted to FWD. FWD is a very poor format for performance. Unless you got a lot of weight hanging over the front, acceleration can suffer from torque steer, loss of traction, and resistence in turning.

Basically I've opted for EV power due to its simplicity, ease of maintenance, efficiency, power potential, and ability for modification. I like the car I have right now. Personally I think some of the best car designs were from the late 90s. I don't care much for the new car designs today, and I don't want to drive some old boxy slow junk. I want my car to tell the drivers behind me "don't even try to pass him".


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