Learning how to build Lotus Seven replicas...together!
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PostPosted: September 26, 2017, 1:53 pm 
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Joined: March 30, 2011, 7:18 am
Posts: 1448
Location: central Arkansas
sbeckman7 wrote:
I'm not 100% sure which motorcycle engine would be a best fit for the car, but it's down to a handful

For a prototype, parts is parts. In some markets, if production is below a certain number, you don't have to worry about emission certification. In others, everything has to be certified... and that means the powertrain has to be certified for the type of vehicle it's used in. Something that meets emissions requirements in a motorcycle is non-compliant when installed in a car, *even if meets the emissions standards.*

Looking down the road, if you wind up having to have your chosen powertrain certified for automotive use, there's no need to limit yourself to motorcycles. You should also be looking at snowmobile or light utility applications. They generally have a wider torque curve than motorcycle engines, which makes them friendlier to operators, but they manual transmission versions usually have much beefier clutches, and automatic transmissions are available on some of them.

A word on horsepower: my daily driver is a small Suzuki Cultus sedan, sold in North America as the Geo Metro, Chevy Sprint, Pontiac Firefly, or Suzuki Swift. It's a four door sedan, seats five, and has 50 claimed hp from a lawnmower-simple three cylinder engine. It will also cruise comfortably at 80mph, and while acceleration won't startle anyone, "it drives like a car." The early US-market VW Beetles had 40hp, and even sports cars like the Triumph Spitfire made do with a bit over 60hp.

There's no great weight or fuel consumption penalty for two, or even three, times the power, but some insurance companies adjust rates with both absolute hp and power-to-weight ratio. I don't know of any market that taxes by hp any more, but in some places it played a factor in your annual registration costs. And the more powerful and faster the car is, the more attention you're going to have to give to brakes, tires, etc.

200hp in a 1200 pound car would be *quite* sporty. You might want to make a lesser engine "standard" to keep the insurance companies happy.

> 40" tall

Been there. Done that. Slammed my head against the roof every time it hit a bump. Laying the seat back "fighter pilot" style required sliding the seat squab forward, which would have been fine if I could operate the pedals with my knees.

Sometimes the drawing board or CAD station can be misleading. I strongly suggest you grab an old car seat and some plywood and mock up the seating position. The first Locost I built, I made a plywood mockup of the cockpit, mostly to make sure I could actually get in and out of such a car before building one, since I've had fairly major knee surgery. What I found out was that there was no way I was going to fit into a "book" car... and a Locost doesn't even have a roof to worry about.

Remember Jeremy Clarkson's comment about the Ford GT40. "The GT40 is forty inches tall. And I'm not."

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