[Andrew Remmers]

Are you sure you need a 1:27 ratio?

Because we have a 1:9 ratio on a 4 inch wheel powered by 2 separate motors and it shoots far over 10 feet I could only imagine how far that one goes, as for heat build up we are allowed to use a kind of lubricant on the gears so that will eliminate some of your problem. Try to zip tie the rubber on the wheels onto the wheel thats what we did and there is no problems with it. For shielding the system you could shield half of the wheel depending on your design and amount of materials available.

just my .2 cents

Andrew