# Rack and pinion distance Help

I need to find the distance of one rotation of a pinion in a rack and pinion setup. I need a formula because I’m programming it and I can change the distance i need easily.

So if i have a rack (movable) with a pinion (stationary) in my hands i need to know how far the rack moves with one rotation of the pinion. What do i need to measure in order to know. (example teeth #, teeth length, ect.)

I would expect that distance to be the circumference of the pinion. If you need complete precision, and want to avoid any math errors, mount it in its final configuration and simply measure.

I’m interested to know where you got the rack. I don’t recall us having one from this or previous KOPs, and our team isn’t very familiar with where to buy such things.

Calculate the circumference based on the pinion gear’s pitch diameter.

``````            circumference = Pi * pitch diameter
``````

You’ll need to know the diametral pitch of the pinion gear your using along with the number of teeth.

``````              pitch diameter = (# of teeth) / (diametral pitch)
``````

So …

``             circumference = Pi * (# of teeth) / (diametral pitch)``

Thank you very much Mr. Sparks This ended a very long discussion with my brother, also I can finish programming.

As for your question beiju I have no idea where my team is getting them I’m not involved in that but I would say your best bet would be Andy Mark (http://www.andymark.com/searchresults.asp?cat=212) quick search.

McMaster Carr is a great place to get a lot of these things. For racks and pinions: http://www.mcmaster.com/#gears/=amxsji