Way back in 2010 I was playing with the idea of designing a Lotus 7, but my the goals for the Locost were very different. At that time I wanted to make a chain driven lotus with a motorcycle engine. I loved the idea of a lightweight sports car, I wasn't alone either. Someone had build the Lotus 7 I was dreaming of building. Click here to see an awesome 900lb chain driven R1 powered Lotus. Just looking at the Lotus Mike did below makes me want to build a second lotus, one powered by a motocycle. Maybe in the future.
The engineer in me loves the car in the image above. Yet the owner very clearly states it doesn't make a good street car. Motorcycle engines have very little low end torque so they need to be revved very high to extract the maximum performance out of the engine. This works great on a race track, but isn't ideal on the streets. Having to rev an engine to 7,000 rpm before the engine develops power and having a power band from 7,000 to 10,000 rpm sounds really great but wouldn't be fun on the streets.
Even today's newest motorcycle engines lack low end torque compared to a modern day 4 cylinder car engine. Here is an example of a 2016 R1 dyno'ed by Cycle World. Notice the lack of power and torque until 8,000 rpm. Then consider how much a 2016 R1 engine in good condition would cost.
Also Motorcycle engines lack a reverse gear, so some clever engineering is needed if you want to back up a motorcycle powered car. Typically motorcycle powered cars use either and electric starter motor or a reversing gearbox. Both options add complexity and cost. My ideal Locost 7 build has changed a lot since 2010, but the drive to build a sports car has always been there, lurking in the back of my head.
One thing that made the locost project so much easier was in 2012 David Flavell posted the miata uprights online. They were in a Step file. This allowed me to use them in SolidWorks, my CAD software of choice. This made my decision infinitely easier to use a miata as a donnor car. Uprights are one of the centerpieces of the suspension design. Without even buying a miata I could start on the design of the suspension.
Click on Image to be taking to Grabcad and download the files
Click on Image to be taking to Grabcad and download the files