How to size spindles for solar car

Question

I'm working with a group of high school students to design and build a solar vehicle for a regional competition. The entire vehicle will weigh about 600 lbs, with the weight distributed to 4 high-pressure bicycle tires on custom hubs and rims. For various reasons, the team has decided to use spindle axles, attached at one end, at each corner of a frame, and we're trying to work out the required diameters. The track is a straight 'drag strip', quite flat, so shock loading is not a worry. I'd appreciate any advice on sizing the spindle diameters. I've noticed that trailer spindles are about 1 inch diameter for a 1000 lb rating, but that's my only reference point. Paul Mathews

Brian Whatcott · Accepted Answer

I used half inch bolts as rear stub axles on a recumbant tricycle. They were sized this big to fit the wheel bearings.

If I run a check on a 0.4 inch round stub axle, 6 inches long, loaded

100 lb at 1.2 inches from the fixed end and 100 lb at the free end, I find the bending stress is 14.2 ksi which is conservative I find 17.4 ksi for a 3/8 round axle. and 29.4 ksi for a 5/16 in round axle.

Choose between 3/8 in and 0.4 inch round for preference.

Brian Whatcott Altus OK

How to size spindles for solar car

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