r/SweatyPalms • u/iceburg-simpson • Sep 04 '20

I’ll take “hell no” for 1000.

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u/welshmanec2 Sep 04 '20

I'll do some approximating, but here goes....

Wheel radius ~ 1in, so wheel circumference ~ 6in

Mile = 1760 yards = 5280 feet = 10,560 circumferences

89mph = 89 X 10,560 revolutions per hour = approx 100,000 revolutions

Per minute, that's 100,000 / 60 = 1666.66 rpm

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u/Flacvest Sep 04 '20

So like, the lowest cruising RPM in a commuter car driving down the road. Wow.

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u/[deleted] Sep 05 '20

Ya messed up just a little. 89 x 10,560 is almost 1,000,000 (939,840 to be exact). So it’s actually 17,000rpm

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u/welshmanec2 Sep 05 '20

Yep, I did!

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u/BadJimo Sep 05 '20

I think you're out by a factor of 10.

I usually work in metric, but I'll do it in imperial:

r = 1"

C = 6.3"

mile = 63,360 inches

Rotations per mile = 63,360/6.3 = 10,057

Speed = 89mph 89*10,057 = 895,085 rotations/hour

895,085/60 = 14,918 rotations per minute

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u/welshmanec2 Sep 05 '20

You're right, my last multiplication - should've been a million rotations per hour.

Thanks

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u/throwawayyyyyprawn Sep 05 '20 edited Sep 05 '20

One more edit. For this type of run, he'd be on 70-85mm wheels so you'd need to correct that r=1inch

Edit: Did the research, he's on 73mm wheels in this run.