[modeleng] Re: Gear wear
- From: "Terry Lane" <tel@xxxxxxxxxxx>
- To: <modeleng@xxxxxxxxxxxxx>
- Date: Wed, 11 Aug 2004 22:34:02 +1000
Well AJ, that is just one o' them things that defies apparent logic.
Actually, the answer is usually quite simple - the softer material 'picks
up' grit and other hard stuff which embeds in it's surface making it, in
effect, a sort of lap or hone.
You only have to look at some of the old line shafting that ran in shearing
sheds & other places in this country - these shafts were often carried in
wooden (red gum for preference) bearings & I've seen 1 1/2" steel shafting
pretty much worn thru' while the wooden bearing was hardly touched.
> 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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