Drivetrain Help

[Joe Johnson]

To a rough order of magnitude, the following is a good rule of thumb that I tell folks often:

A good starting point for gear ratio for the drill motors is shown below:

(Diameter of your wheels measured in inches) * 10 = Ratio from the armature of the motor to the wheels

For example: Given an 8 inch wheel, you need an 80:1 ratio from the armature to the wheel. Given a 2 inch wheel you need to have a 20:1 ratio.

Note that the drill transmissions have a ratio of ~20 in "HI" and ~64 in "LO"

Again, this is only a rule of thumb but it is a pretty good one as a starting point. It seems to balance pushing torque and top speed pretty well.

You need to really do the math if you want to use some motor other than the drill motor as a drive, but that is beyond the scope of this note.

Hope this helps. Others please comment.

Joe J.

P.S. Generally speaking it is better to run the transmission in "HI" and provide an additional ratio via chain or by some other means. Essentially, the main benefit is reduce side loading on the drill mounting points & drill shaft. Again, this is not a hard and fast rule, but it is a good place to start -- moving away only when there is good thought and valid reasons behind the move. JJ