[ScotD]

My project is a small reverse trike for 1 person for highway travel, probably using a 125 to 250 cc engine and weighing between 300 and 500 lbs, cruising typically at 55mph, and getting over 125mpg I expect. I’d like to get maximum mpg, though if there would be no more than a few mpg difference I'd probably go with narrow body (front wheels outside) as it would be a little easier to build and take less material.

The narrow body would result in less area. The front wheels would have small fenders close to the tires and probably something like moon disks to reduce drag. Drag coefficient would be worse due to some exposed front suspension as well as front wheels. Example is the HyperRocket, though it’s bigger and more toward sport-car.

The alternative is to make the body wide enough in the front to cover the front wheels and suspension – width would need to be enough to accommodate wheels turned and height enough to accommodate suspension travel, though just behind my head (roll bar and body tapering behind) would remain the highest part of the body at about 30 inches off the ground. There’s no need for more than 24 inches width to accommodate my body. Example is the California Commuter, though it’s lower, lighter and probably a little better aerodynamics than mine will be.

I plan to keep the front wheels small – possibly 10 to 12 inch scooter wheels with 3 inch tires, so maybe 15 to 18 inches high and around 3 inches wide.

Any thoughts about which approach would provide the least drag and how big the difference might be will be appreciated.

Thanks,
Scot