[GreenKeys] [External] Nylon and fiber gears

[Jones, Douglas W]

On Aug 20, 2019, at 8:50 AM, John, W9DDD wrote:

> Question, are all nylon gears white?  I have a gear that is dark colored that at first glance appears to be fiber.  However, it has a metal center and really looks more like a plastic than fiber.

There are plenty of black plastic gears.  Delrin, an excellent plastic for making gears, is black.

> Which leads to another question, mixing nylon fiber and steel.  I'd assume it's not a good idea to mix.

The converse is true.  It is a good idea to mix.  As far back as the 19th century, they knew that brass or leather gears (soft) running on iron (hard) led to both quieter operation and less wear.  I don't think it matters which gear in a pair is the soft one, so long as you aren't near any stress limits.  I've seen very small diameter steel pinions driving large diameter nylon gears, and I've seen small brass pinions driving large steel gears.

To bring this into GreenKeys land, on the Teletype model 33, the motor has a steel pinion on the end of the shaft, and it drives a nylon gear that drives the timing belt.  On my model 33, the plastic gears are white nylon.

		Doug Jones
		jones at cs.uiowa.edu