[nimblemotors]

By design exercise, do you mean you are not going to actually build a car?

Originally Posted by akumabito

Just as a design exercise, I would like to design a single-seater commuter vehicle. I would like to keep it relatively simple, so it would be in the realm of the home builder. In essence a 'green' version of the Locost home-built sportscars. (Because I am new here, I can not yet post links to websites. If you are curious, search for Locost Builders in Google) Obviously, the design would be geared entirely towards fuel efficiency rather than performance.

What I had in mind was a single seater, three wheeled vehicle. Two wheels at the front, one at the rear. The easiest way to build it would be by using the engine and swingarm from a light motorcycle. The body of the machine would be teardrop shapedfiberglass, with a clear canopy.

I would really like some input on a few design choises I have to make.

Starting with the engine. The whole vehicle would be as light as possible, aiming for under 300kgs (660lbs) including fuel, excluding the driver. Since it will be designed as a commuter vehicle, and part of my commute includes a highway I can not avoid, it has to be able to cruise at 100kph or 60mph. For the engines, I am looking at these options: 125cc, 4spd semi-auto / 250cc, 5spd manual clutch / 250cc CVT -power output for all these engines would be in the 10 to 20Hp range, with the smaller displacement engine being on the lower side of that figure. Of these engines, which would be preferable? I'm thinking the 125 could reach the best fuel economy, but I am worried the weight might be a little too much for the little motor to pull.

Next are the tires. Most low-rolling resistance tires are for 14 or 15 inch wheels. Would smaller wheels be even more efficient? For example, the classic Mini uses 145/80R10, pretty much the smallest tires a street-legal vehicle could run. Would these be preferable over the larger LRR tires I wonder?

There is much more, but I will try not to bore you guys with an enormous wall of text and instead take this design process step by step.

Any input would be greatly appreciated!.