Thread: Gears vs RPM vs size = speed??

Given : (little off topic math check)

RPM=7500 (loaded)
gear ratio = 16.6 : 1
Wheel diameter 1.5 inches

What is the calculated speed in the below units of measurements?

a. inches per second

b. MPH


Robot gearbox

The Square Root of (Total Shaft Horsepower / Weight ) x Constant = Speed
Speed Calculator

Heres how I figuerd it. I think its right bit maybe not. this is calculated on a gear reduction of 16.6:1

pi X 1.5 gives you 4.71 inches per rev. on the wheel

at a 1:1 ratio that would give you 35325 inches per minute @ 7500 rpm

divided by the ratio of 16.6 gives you 2128 inches per minute

which equates to 35.4 inches per second

which equates to 2.01 MPH.


35.4 inches per second with a 2.02 mph speed is my answer. Billy

Originally Posted by Billy

Heres how I figuerd it. I think its right bit maybe not. this is calculated on a gear reduction of 16.6:1

pi X 1.5 gives you 4.71 inches per rev. on the wheel

at a 1:1 ratio that would give you 35325 inches per minute @ 7500 rpm

divided by the ratio of 16.6 gives you 2128 inches per minute

which equates to 35.4 inches per second

which equates to 2.01 MPH.


35.4 inches per second with a 2.02 mph speed is my answer. Billy

These are the numbers I came up with also. Just checking.

I usually miss the ball park and end up swagging.

DANG...well think I'll just stick to the building and redoing instead of the designing....lol. Think I'll delete my post...thats embarrassing! lol

Cane Pole, thats the way I remember doing it too. I checked the numbers and thats what I came up with.....well rounding was a little different. I always use pi as 3.14159, cause I don't use a fancy calculator....just a simple one.

Isn't deleting your own embarrassing posts an abuse of your moderator powers? :D:D:D

did you see the numbers I came up with?? lol

I can do alot of stuff...but math is not one of them!!

Actually if I had the stuff laying in front of me I could figure out what I wanted to do with it or what needed to be done with it...I just use trial and error on paper...lol...instead of the easy smart way like you guys....lol.

And no...not abuse of power...just saving of face...lol...I would do it for you too!!

Trying to beat my own record. The robot in the video runs 32.4 inches per second. You get disqualified if you run off the track or fail to stop for the gate. The track is 1 foot wide and the turn radius (curves) are 6 inch radius.

Accuracy counts. I hope I can stay on the track at 2 mph. Speed kills.:D

This one (video) is front wheel steer. I am trying to build an articulated front wheel steer with an articulated body. Trying to overcome the mass effect some way when maneuvering thru the turns. Ain't easy. Sure is fun.

I'll say it again CP...if I only knew half of what's in your head.......lol