[modeleng] Gear wear

  • From: "alanjstepney" <alan@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
  • To: <modeleng@xxxxxxxxxxxxx>
  • Date: Wed, 11 Aug 2004 13:22:44 +0100

As I am sure many of you have discovered, once friends and neighbours learn
that you know which end of a screwdriver to hold, along comes a steady
stream of "could you just look at this" type jobs.
Yesterday I had a hedge trimmer passed to me, as, "it only made a noise and
didnt cut".

It is a Black & Decker, with their usual arrangement of a spiral gear formed
into the armature shaft, running on to a larger nylon gear wheel.

The gear on the armature is worn down almost to the root of the teeth.
The nylon gear appears unworn.

I checked, and the shaft is VERY hard, and yet has worn far mroe than the
nylon.
I have seen this happen before.

Logically the nylon, being softer, would wear faster, but the reverse is the
case.

Any explanations anyone?

alan@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

www.alanstepney.info
Model Engineering, Steam Engine, and Railway technical pages.


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