Posted by Chris Case [108.247.147.90] on Wednesday, December 02, 2015 at 12:30:18 :
In Reply to: Re: design posted by jay massy [75.48.5.203] on Wednesday, December 02, 2015 at 11:58:08 :
Tires on road have a coefficient of friction of about .7,. That means for every 2,000 pounds on the tire, there is only 1400 pounds of friction. The tire being 36" tall, the lever arm is 1 1/2 feet long. Hub diameter of 4" means a 2" arm. So 9 times the force on the 'pinch' surface. 9 times 1400 = 12,600 pounds. Welds filler @ 50,000lbs/insq tensile strength means 1/4 bead 1" long. Safety factor of 5x means weld it all the way around.
Bolt pinch maths is beyond my shop math, but a guess- I've heard that a head bolt exerts 70,000 pounds of squish. Steel on steel has only half the friction of rubber on pavement. So 35,000# to resist 12,600 pounds of torque. Not bad, but what if the bolts loosen? I guess I would put a few inches of tacks on, including tacking the bolts to prevent loosening.
Caveat: I'm only a machinist, mechanic, and thinker. NOT a mechanical engineer.
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