- #1
LDC1972
- 65
- 0
Homework Statement
This is a final hurdle of a long question designing a simple gear train. That is done but now am not sure of my calculations for power in / out and torque in and out, so hopefully someone can help?
OK - I have 4 spur gears inline, Gear A = 100 rpm 80 Teeth (input motor - unknown power?)
Gear B = 160 rpm 50 Teeth (idler)
Gear C = 160 rpm 50 Teeth (idler)
Gear D = 400 rpm 20 Teeth (output against a load of 200 Nm)
And ALL shafts carry a frictional resistance of 5 Nm
1/ What is the input power at shaft 1 (gear A)?
2/ What is the efficiency percentage?
Homework Equations
P = TW
T = P/W
T1 x W1 = P input
The Attempt at a Solution
I have done the following:
(TA x WA) - (TB x WB) - (TC - WC) - (TD - WD) = ZERO
And TA x WA = Power input
Convert the rpm to rad s:
Gear A = 100 rpm = 10.47197551 rad s
Gears B and C = 160 rpm = 16.75516082 rad s
Gear D = 400 rpm = 41.88790205 rad s
Input Power (Pi) = (TB x WB) + (TC x WC) + (TD + WD)
= (5 Nm x 16.75516082 rad s) + (5 Nm x 16.75516082 rad s) + (5 Nm + 200
Nm x 41.88790205 rad s)
Input Power = 8.755 Kw
Torque in = Input power / WA = 836 Nm
Torque out = 205 Nm
Power out = TW = 205 Nm x 41.88790205 rad s) = 8.587 Kw
Efficiency = Output power / Input power = 98 %
Does this look correctly tackled? Any advice very welcome!
I like the 205 Nm out as the gear ratio is 1 : 4 and the output is 1/4 input, which makes sense?
Last edited: