Relationship between gear pitch and diameter

[seanwitte]

Thanks for the information. I want to add a castor coupled to an encoder to measure distance. The castor I'm looking at is a 6cm omni wheel. Since the castor is so small I have to gear it down before the encoder, at a ratio of 3:1, so that the shaft speed at the encoder is less the 300 RPM max for the part. I was planning on using a 24 tooth gear on the castor shaft and a 72 tooth gear on the encoder. The finest pitch I saw was 48, so they would be roughly 0.5" and 1.5" diameter each. Is this a resonable plan or is there a better way to do it? The shaft on the castor would be 1/4" and the gear on the encoder would be mounted directly to the shaft on a locking hub.

[Rosiebotboss]

There is an excellent section on the Standard Drive Products website regarding gear and drive components and the engineering behind them. Follow the link.......... http://www.sdp-si.com/D190/D190cat.htm