[modeleng] Re: Chain Sprockets

Clif,

Don't harden either - that's the way they are meant to be, so leave them 
like that. Yes, they will wear, and you will have to replace them, 
eventually. But if you harden the sprockets (because they are difficult to 
change later) then they will rip the chain apart, so it will not last long.

At our railway (Swanley New Barn Railway) our 10 HP 7.25" gauge diesels use 
1/2" duplex chain and we replace the chain much more often than the 
sprockets because it stretches. And some of our engines do in excess of 
1,000 miles per year. . . .

If you're still worried, then go to 3/8" pitch chain and sprockets, i.e. 
over engineer.

Peter
----- Original Message ----- 
From: "Clif Walker" <clif.gwr@xxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: 28 January 2009 17:35
Subject: [modeleng] Chain Sprockets


Hi All,
I am modifying one of my electric powered 5" gauge models from toothed belt 
drive to chain drive and have a puzzle which I thought that I would throw 
out for discussion.
The Chain Sprockets which are bought in items and seem to be made from very 
nice free cutting mild steel.

Should they be Case Hardened or left in their soft state?.

My thoughts go along the lines that if I case harden them will it wear the 
chain? and if I leave them soft will the chain wear the sprockets?
Bearing in mind that the chain can easily be changed, whilst the sprockets 
require major work to replace,it would seem the be best to harden the 
sprockets.

Also could a compromise be the thing, with only the small sprockets being 
hardened as the large sprockets have the load spead out more evenly.

The chain is 1/4" pitch, the small sprockets have 8 teeth and the large 
sprockets have 30 teeth.

I await with  Blowlamp and Kasenite poised.

Regards

Clif
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