Please help me calculate gear ratio/speed (image)

Lynxmotion Rovers, Sumo, and Tracked
1

Hello,

I am trying to calculate the gear ratio of a bot I am working on. For some reason I cannot wrap my head around it.

Basically I have an outer wheel, and inside that, a smaller wheel attached to a motor. I am trying to choose the correct speed/torque motor for this application.

The image below has the dimensions, as well as my required speed. I know weight plays into the selection of torque, but for now, I just need to figure the RPMs.

I would like to get a grasp on doing this so that I can modify the design, or desired speed and be able to re-calc it myself, so if anyone could walk me through it that’d be great!

Thanks!

img.photobucket.com/albums/v146/ … Ration.jpg

2

Not a guru at all, but the RPM of the 6.25" diameter and 4.50" part are the same. The ratio for the 1.25" diameter and 4.50" diameter parts is 3.6:1 or in other words the 1.25" diameter part will need to rotate 3.6 times for every single rotation of the wheel. So using our wheel calculator I get an RPM of 268.79 on the 6.25" diameter wheel for 5 mile/hour. This would need to be multiplied by 3.6 for the 1.25" diameter part RPM, or 967.64 RPM… I think. 8)

3

Thanks!

Is this wheel calculator posted somewhere?

4

'Course it is: lynxmotion.com/ViewPage.aspx … wheelspeed :smiley:

5

Thanks!