pic: Dual FisherPrice Gearbox

[artdutra04]

Since it sounds like you are really concerned about weight, you can also just open up the FP transmission from the KOP and use the plastic gears from those for the first few reductions in your transmission.

Another way to lose weight is to use Lexan instead of aluminum for your sideplates. Just note that you won't able to swiss cheese Lexan as much as the aluminum; you'll have to make the ribs a little wider.

You also won't ever get 327 rpm out of your transmission unless you're running the motors at above 12v. Even without having the transmission connected to anything, the few percent losses of torque at each gear reduction will mean your motors won't be running at free load.

Originally Posted by vivek16

I looked and it says that their bushings have a surface speed of about 197 fpm. (197*12)/(3/8*.5*pi)=6397 rpms

I picked the ultra low friction bushings from igus. Please correct me if I did my math wrong.

Check your math; the circumference of a circle is π*d.

With a 3/8" diameter shaft, the maximum rpm that I would run those plastic bearings with is 1003 rpm. 197.0 ft/min * 12.00 in/ft = 2364 in/min. 0.375 in * π = 1.178 in. 2364 in/min / 1.178 = 2006 rpm. Divide that in half to factor in a 2x safety margin, and you get 1003 rpm.