[modeleng] Re: Steel Wheels
- From: "Phill Smith" <steam@xxxxxxxxxxxxxx>
- To: <modeleng@xxxxxxxxxxxxx>
- Date: Fri, 18 Nov 2005 21:59:28 +0800
Barry,
Do it with the "thou per inch" interference fit, and shrink them on.
The best way to do this accurately (and so they can't come of through
continual cornering) is to put a small step on the inside of the rim, with a
matching inner bore in the tyre. When running, the forces of the engine
going around a curve are trying to push the tyre of the rim towards the
frame. To counter this, the shoulder is normally made around 80 - 100 thou
(2 - 2.5mm) wide and 20 - 40 thou in step. There is no need for this step to
be a press fit, but I make it so anyway. It is also under the flange so it
can't be seen..... But the best bit is that it acts as a stop for the tyre
when it is dropped on, which locates it square, and at the correct position.
Oh........ One other thing. Don't be tempted to increase the interference
fit, as the stresses may be increased enough that the rolling stresses
(compressive stress) may permanently stretch the tyre so that it comes
loose...... I have seen a loco have this problem.
Cheers,
Phill.
----- Original Message -----
From: "Barrie Purslow" <bpduo@xxxxxxxxxxxxx>
To: "Model Engineering List" <modeleng@xxxxxxxxxxxxx>
Sent: Friday, November 18, 2005 1:48 AM
Subject: [modeleng] Steel Wheels
> I have just acquired, at great expense, a piece of steel tube 8" I.D. and
3/4ins. wall thickness. I am about to start machining it to produce six
steel tyres which I intend to shrink onto three pairs of existing, cast iron
wheel sets (after machining off the current treads). The plan is to make the
tyres with one thou per inch of interference, expand them with heat then
shrink them onto the wheels.
> Before I pluck up courage to do this job does anyone have any advice to
offer?
>
> Barrie
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