[Bicycle Bob]

Originally Posted by elhigh

I've fantasized about building an ultralightweight city car.

The structure I have in mind is something like the original Velorex, a skin stretched over a frame. But to make it stronger, I would impregnate the skin after installation to make it rigid and bond it to the frame, so it would contribute meaningfully to the vehicle's overall rigidity and crashworthiness.

My ultimate goal would be to build the lightest car possible. I think you could have a fully enclosed chassis that didn't weigh much more than a hundred kilos. Add on the glass, passenger accommodations, suspension subframes, engine cradle and everything else, and it should be possible to have a small, roadworthy car that will comfortably seat two abreast that doesn't weigh more than 500 kilos.

I think. I'm not an engineer. But this car wouldn't be intended for long trips, so it needn't have tremendous cargo capacity or even a very large fuel tank. If it could reliably deliver 50 mpg from a small diesel drivetrain, a 5-gallon fuel tank would be 250 miles of range. That's almost as much as I can consistently get out of my Forester, which is ostensibly a "real" car with "real" range (and a heck of a lot more than it would get if I only drove it in the city). If you're going to take a long trip, scoot out to the rental place with your little city runabout, pick up a real car and scoot back.

In my head, the concept is part Isetta, part Edison2 VLC, part Mercedes Boxfish concept and part wicker basket.

It is good to see another serious lightweight enthusiast here. For an easy but thorough grasp of the engineering involved, I heartily recommend J.E. Gordon's "Structures." His chapter on how to approach light weight design is without peer. Most of the specialized automotive information you also need is beautifully presented for the amateur in Fred Puhn's "How to make your car handle."