Repair cast iron wheels?

This topic has 10 replies, 7 voices, and was last updated 19 April 2016 at 11:12 by Perko7.

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21 March 2016 at 22:27 #231113
Perko7
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@perko7
Hi, just turning up some 5-inch gauge wheel castings and found several small (grain of rice) to medium (baked beans) sized holes inside the castings. Most are in the centre where the axle hole will be bored but some extend outside this area. There still seems to be sufficient good metal for the wheels to be firm on the axles. Can these be filled in with something (plastic metal or similar) to restore a full surface or should i order replacements?
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21 March 2016 at 22:27 #8064
Perko7
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@perko7
21 March 2016 at 22:36 #231114
julian atkins
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@julianatkins58923
Hi Geoff,

It rather depends what the wheels are for. If they were castings for a 5"g steam loco I would send them back as reject castings.

Cheers,

Julian
21 March 2016 at 22:37 #231115
Emgee
Participant
@emgee
Geoff

Depends on the terms of sale when you bought them, if you were told they were seconds then I would think you have no claim. If you purchased them from a recognised supplier as good castings then I would think you are likely to get replacements for the faulty parts. Contact your supplier.

Emgee
22 March 2016 at 05:39 #231126
Paul Lousick
Participant
@paullousick59116
Hi Jeoff,

As stated above, have the castings replaced.

If, as you have said, there is "sufficient good metal for the wheels", the holes could be filled with with something like Loctite Fixmaster steel putty which is a steel reinforced, two-part epoxy which can be machined, drilled and tapped.

Paul.
22 March 2016 at 06:38 #231130
Perko7
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@perko7
Thanks heaps for the advice, have contacted the supplier and awaiting his response. They were supposedly 'good quality' castings so should be no reason for him to not replace. A pain though with the time already wasted machining them and now having to wait for replacements.

Cheers.
14 April 2016 at 07:17 #234555
Perko7
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@perko7
An update:

No joy as yet from the supplier, so i've pressed on with the castings as supplied.

Reasonable success, managed to machine off the dodgy bits and patch the holes with metal putty while keeping within the AALS minimum diameter/width requirements.

One requirement not evident so far in the published standards is tolerances – what is the accepted tolerance for wheel back to back for 5inch gauge?

What about for differences in wheel diameter? So far i've got about 0.2mm difference in tread diameter across the whole set of 6, so should i be trimming those at the upper end to more closely match those at the bottom end? How close would i need to go for a rod-coupled diesel shunter?

Thanks in advance.

Geoff P.
14 April 2016 at 09:30 #234569
IanT
Participant
@iant
Hi Geoff,

My wheels are half your size (I model in Gauge 3) but I don't worry too much about tolerances to be honest. I just try to get them as near the given dimension (in my case G3S standards) as possible. What I do 'do' however is always use a mandrel turned in-situ thus ensuring that all my wheels can be turned to the same diameter (as far as possible) by locking the various slides not in use and putting the same cut on each wheel. For my larger wheels I use a small faceplate with a replaceable nose/mandrel piece that is effectively a consumable and can be turned and die cut to ensure everything is running true. This is of course left in place until all work is completed.

So my advice (if you really want to make adjustments) would be to take a similar approach in terms of mounting your wheels (which you may already be doing of course), fit your "smallest" wheel, touch your tool to this and take the lightest of cuts, lock up and then take the same cut over all the rest of your wheels.

In my view it's much more important to get your wheels the same sizes than to worry too much about tolerances. Also, yours are only 8 thou out (smallest to largest?) and in your scale I'm not sure that's really a problem. But then this is simply my take and others here may (probably will) disagree.

Regards,

IanT
14 April 2016 at 09:36 #234573
Neil Wyatt
Moderator
@neilwyatt
I recall reading somewhere of significantly bigger differences in diameter (proportionately) on full size engines.

Neil
14 April 2016 at 20:05 #234629
John Purdy
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@johnpurdy78347
Geoff

What I do to get all the wheels the same is to machine them as Ian says, then mount them on their axles, quartering if required. I then mount them in the lathe between centres and starting with the smallest one at the tail stock end I set the top slide to the cone angle and using the top slide take a light skim to just clean up the tread, lock the cross slide and saddle. Then reverse the set and do the same with the other of the pair. Then do each set in turn. This way all your wheels will end up the same size an concentric with the axle.

John Purdy
19 April 2016 at 11:12 #235247
Perko7
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@perko7
Thanks Ian and John, that's pretty much what i've been told in other forums as well, so i've turned them all on a mandrel to within 0.5mm of finished size and will make any final adjustments once they are pressed on the axles. Cheers.
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