Which would be better for a solar car large wheels or small wheels? Disregard mass of the wheels. I need to know because my school’s Solar Bike Club is building a solar car to compete and the question was posed to me.
Depends on your drive train gear ratio, and whether you’re going for range or speed. Consider, though, that you’ll most likely be on side roads with fairly rough surfaces, your suspension will probably be pretty light, you’ll want low rolling friction, and you’ll probably be looking at bicycle wheels.
Meanwhile, there have been a number of solar car projects and races/tours in recent years, and a good Web search will do you wonders. There might even be some design and construction tips out there.
Good luck, and let us know how it works out.
Thanks Elvis, the race is performed over about 2 and a half hours with 33 laps to be completed on a two mile track. Our sponsor was thinking about using motorcycle wheels or wheelchair wheels or something smaller.
What you really want to do is minimise rolling resistance. Bicycle wheels off a racing bike with the tyres pumped up as hard as you can get away with would be a better solution than motorcycle. I don’t know squat about wheelchair wheels though.
Everything I read on the subject agree that larger wheels have less rolling resistance. This is especially true for rough surfaces; the difference diminishes for smoother surfaces. However, if you make it too large, weight and wind resistance will increase. The ideal size depends on the road surface - on very smooth surfaces, very large wheels are not worth the weight, but on rough roads they probably are worth it. I think it also depends on vehicle size - on larger vehicles, the impact of the added weight and wind resistance is smaller.
I agree that road bike (bicycle) tires are probably the best choice. Think about it - bicycles are designed to get the most out of a very limited power source, while motorcycles can (and do) compensate for inefficient tires and drivetrain by using a more powerful engine.
Most road tires are designed to be pumped to 100psi or so, which is already pretty high. You can’t visibly deform it if you press the tire with your finger. I would use the correct pressure and not risk going higher. If your vehicle is very heavy (like twice the weight of an adult), you might want to select a tire designed for tandem bikes. The most common tire sizes for bikes are 26" and 700C. The 700C is more popular for road bikes, but you can find good road tires for either size. If you decide on a smaller tire, 20" (406mm) and 16" (305mm and 349mm) sizes are also common. If you have trouble finding those smaller tires and wheels, try a shop that carries BMX bikes or recumbent bikes. My favourite source for small tires is Hostel Shoppe, which specializes in recumbent bikes and accepts on-line orders.
You might want to study some commercial high-performance tricycle designs for ideas. The most well known companies are Greenspeed, ICE and AVD. In fact, Greenspeed has built solar racers in the past, and they also sell frames and parts that may be useful for your project. They’re in Australia, but they have a lot of experience with overseas orders, and I hear the are a good company to deal with.