pic: 2010 window motor winch

[rsisk]

I have to agree with Tom about the great explanation from Joe, but, show some mercy on a software guy and explain the formula use to calculate the 54W below.

TIA

If you are trying to lift a 120lbs motor 3ft in 10 seconds -- that means you need 54 Watts. If you only have 40Watts (the best you can do with 2 window motors at 12V) then you are not going to do that much work (lifting the robot that high) in that amount of time... ...no matter how you gear things...

[sanddrag]

Originally Posted by rsisk

I have to agree with Tom about the great explanation from Joe, but, show some mercy on a software guy and explain the formula use to calculate the 54W below.

TIA

I'll take a shot at it. Work = Force*Distance. Power=Work/Time. So, say we are trying to lift 120lb to a height of 3 feet. Then you need to do 360lbf-ft work to it. To do this in 10 seconds, you need 36lbf-ft/sec of power. There are 550lbf-ft/sec in one Horsepower. There are 746 Watts in one horsepower. So, you need about 49 Watts to make this pull. If you consider the force required to accelerate the robot from zero to loaded-line-pull speed, and inefficiencies and whatnot, more power will be required.

[Vikesrock]

Originally Posted by rsisk

I have to agree with Tom about the great explanation from Joe, but, show some mercy on a software guy and explain the formula use to calculate the 54W below.

TIA

Here's one way I came up with 54W:


120lbf * 3ft = 488 J (Work = Force*Distance, there's a conversion factor from lbf-ft to J in here as well. Google Calculator did this conversion for me)
488J/ 10s = 48.8W (Power = Work/Time)
48.8W / .9 = 54 W (Gearbox efficiency)

From what I remember reading here and erring on the side of caution I would use 80% as the gearbox efficiency yielding 61W of power necessary.

Also be careful using 120lb as a weight. A full 120lb robot this year could end up at over 150lb after adding battery and bumpers. Using 150lb and 80% efficiency you need about 76W of power to complete the lift in that time.

[the man]

But you have to account for the bumpers and batt