pic: Planitary Transmission

[Alex.Norton]

I know that the ND motor won't allow much variation but it is some and it does add to the output force so I think i could gear this a little higher if I wanted to.

I would be gearing the output shaft directly to a set of 6 inch wheels since the reduction through the trans is high. Meaning if the robot was pushing an object with 200 pounds (something that I have seen FIRST bots do) it would produce 34 Nm of torque on the output shaft. There is a reduction to the ND motor of 3.67:1 which means that everything at stall there would be 9.2 Nm of torque on the ND motor which is less than the motors stall torque. As said by many people this is not an optimal solution but it is the easiest thing to machine.

A major part of the box was that it was easy to machine and assemble. All the parts can be made on a small CNC mill with limited skill or on a small lathe. These two things make a worm gear hard for a more powerful motor. In any case the output rpm of the ND motor is 84 rpm and with a reduction of 3.67 the change in output speed of the output shaft is ~45 rpm which translates to a speed difference of 1.18 ft/s so it varies from 7.55 ft/s to 8.73 ft/s which isn't a big difference but...

I will post a pic of the planetary showing the inner workings and a pic of a chassis that it could work with.

Thanks for all the compliments.
Alex