# Reliability

How reliable is the 5:3 external gear ratio for the drivetrain? It is a 4 wheeled base and all four wheels are directly driven by high strength 393 motors. The robot weighs about 20 pounds

Why not switch out the motors to high speed?

5:3 = 1.66666:1

In my opinion, it could be reliable, if you are not using mecanum wheels.

Already have tried doing that. For some reason the 5:3 ratio has more torque than the high speed motors. We tried 2 parallel situations : one with high speed motors and one with high torque motors and 5:3 external gear ratio. The 5:3 gear ratio definitely has more torque.

We are using all 4 omni wheels

If the 5:3 has more torque, how much slower was it in a speed test vs high speed drive?

Thats the thing which actually surprised us… It was also faster

Well define “more torque.”

In a pushing battle it might win because of traction. The gears on the 5:3 are heavier so would help slightly in a pushing battle.

Were the robots the same weight?

Also there is a tolerance on motors that means some motors have slightly more power than others so I would find it more likely you had a slightly better motor on the 5:3 and a slightly worse motor in high speed.

You cannot have your cake and eat it too. What you gain in speed to must lose in torque or vice versa. You can however maximize both by making your system more efficient. With this in mind, the more moving parts you have on your drive train the more loss you have in the system; thus I would think direct drive high speed would be more efficient than adding an entire extra chain system. make sure in your testing you place both systems under the same circumstances.

This is very true. Sometimes people get confused by an increase in non-conservative forces (e.g. friction) and cite it as a decrease in torque. To eliminate this confusion, it is imperative to use (essentially) identical test conditions.

//Andrew

Thank y’all… We finally figured out a way to get around this. I appreciate all of your comments