# Autox / Time Trial Mazda RX7 Tube Chassis Conversion



## brian_ (Feb 7, 2017)

An FD with a "solid rear axle" and tube frame presumably means that the only things related to the production car are the shape of the body and the use of a rotary engine. If varying that much from stock you could consider a drive unit (motor and transaxle) from a production EV mounted at the rear with an independent suspension. The R32 Skyline with a Tesla drive unit and suspension, described in this forum, would be an example of this approach.

If you retain the live beam axle the motor needs to be in place of the transmission (possible if you get the motor selection and operating voltage right), or in place of the engine. If you can shift without a clutch - which should be practical with the dog ring box - and you use a hollow-shaft motor and no clutch - you might be able to mount the motor back against the gearbox (instead of in front of a bellhousing), leaving more room for battery in the original engine space.

With a tube frame you have more flexibility in battery location than when working with a stock body. A battery box between a rear drive unit and the driver's seat, or two boxes flanking the propeller shaft (if keeping the beam axle), or in the passenger space (if you don't need to carry a passenger) are all possibilities to consider.


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## brian_ (Feb 7, 2017)

s1mpsons said:


> ... with a Jerico 4 speed dog ring gear H pattern trans.
> ...
> I am imagining a scenario where I reuse the rear axle, driveshaft and jerico and get a bell-housing adapter for the front motor. At the moment 1st gear and second gear are very tall - literally too tall to have an NA rotary be even drivable on an autocross.
> 
> Any thoughts?


Gearing issues will depend on your motor selection, but whatever you choose it will likely produce peak power at a substantially lower speed than the Mazda Rotary, so those lower gears might be appropriate.

This discussion was a good excuse to look into Jerico transmissions. I assume that you have a WC4. Their ratio chart shows a broad selection of ratios, and you can change them buy buying (or trading for) different gear sets.


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## Batterypoweredtoad (Feb 5, 2008)

How much do you want to spend and how much are you willing to learn? What is your fabrication ability? What is the required range?


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