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bell adults vert 2.0 multisport helmet 2Twenty MIPS Bike - Acid Green NWT - Loungefly Backpack Size:2 10pk teen use hand adjustments
NWT - Loungefly Backpack with Disney Cats
co m /us 39
teen use
Size:2 10pk
Calculations Variables R = 13" = .330 m r = 1.5" = .0381 m speed = 10 mph W = mass of bike + mass of wheels + mass of rider = 15 kg + 2 kg = 75 kg = 92 kg µ r (coefficient of rolling friction: rubber & dry asphalt) = .05 µ k ( coefficient of friction: rubber & rubber) = 1.16 T = torque on wheel t = torque on friction drive P = power of friction drive Figuring out RPMs 2Rπ = 81.68 in = 8.666 2rπ 9.42 in 10 mi x (5,280 ft/mi x 12 in/ft) in x 1 rev = 7,757 rev x hr = 129 rpm (wheel) x 8.666 = 1120 rpm (friction drive) hr mi 81.68 in hr 60 min so the motor must be rated at twice that, or 2,240 rpm , without taking friction into account Torque required to turn the wheel F f = µ r x Fn F f = (.05)(92kg/2)(9.81m/s2) = 22.56 N T = R x F f T = (.330 m)(22.56 N) = 7.44 Nm Power needed by friction drive to produce the torque to turn the wheel t = r x F f 7.44 Nm = (.0381 m)Ff Ff = 195.28 N account for friction: Ff2 = Ff1 x µ k Ff2 = (195.28 N)(1.16) = 226.52 N t = (.0381 m)(226.52 N) = 8.63 Nm Power = Torque x Velocity x Conversion Factor P = t x v x c P = (8.63 Nm)(1,120 rpm)(.1047) = 1,011.99 Watts so the motor should be rated at 1.5 to 2 times that, or about 2,000 Watts Results: Final Results:
hand adjustments
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