[Land-speed] Trans Tail-shaft

3 liter saltfever at comcast.net
Tue Jun 26 21:38:17 MDT 2007


Otto: Can rollers really take the abuse in the tail shaft? Have you actually
seen them in there? At 8,000-9,000 rpm of the 2" diameter yoke can you
imagine the speed of the little rollers? Can they get enough lube? It might
work for an 8 second drag race but how about 2-3 minutes of LSR? 

 

Am I doing my math right? At 8,000 rpm the circumference on a 2" diameter
yoke is traveling 4,188 ft/min which is marginally acceptable. But the tiny
1/8" rollers have to go 16 times faster. (The ratio of the circumferences
between 1/8" and 2" diameters is 16:1)  So 16 x 4,188 ft/min is 67,000
ft/min. for the rollers. Yikes!! Or put another way, the tiny rollers
pressing against a 2" diameter object spinning 8,000 rpm have to travel 16
times faster.  8,000 rpm x 16 = 128,000 rpm for the rollers.  Holly cow!!
Can they really do that? That is an incredible rpm.  -Elon


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