Big Wheels in 4mm?

In message , William Davies writes

There is nothing this size listed in the Mainly Trains catalog. The largest appears to be 32mm from Alan Gibson.

The real question is:- what are you building a model of? My guess would be something very early and something Mike Sharman might recognize...

Sharman Wheels only go to 7'9", BTW, and Romford's to 8ft.

Paul

You've got it. I'm looking at building one of the Pearson tanks in GWR ownership, possibly number 2002 unless I turn up better references on one of the others. Absolutely fascinating machinery. Still waiting for membership detais of the BGS at the moment, Cheers, Bill.

Unless it's freelance then it's got to be a Pearson express tank, that or a Stevens Crampton. They're the only engines with 9' wheels that I can think of (though 36mm would be close enough for the replacement Pearsons, too, with their 8'10" wheels).

*Interesting* prototypes, anyway :)

I would guess that reshaping a 7mm scale wheel would be unnecessarily tedious, but have you considered it as a last resort?

Ronnie

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You speak as if you have some experience casting wheels. I, for one, would like to hear about that. Seems to me that a useful wheel would need to be cast using hard, and therefore very high melting temperature, metals. I suppose the old time modellers did this all the time -- but for those of us that have never had to cast anything trickier than lead or resin, please explain.

-dave

Hi Dave, I've not cast anything of this nature, but resin casting in general is something I am quite happy with. I have a commercial grade resin in mind which has very similar properties to the plastic used in available wheelsets. I'm less confident about producing a perfectly circular pattern with 26 identical spokes, it's not something I've previously given much thought to doing. Cheers, Bill.

Thanks for describing the process. That's pretty close to what I'd envisaged, but it's always reassuring to hear from someone who's done it for real. When you did this, were your masters produced by fretting from a disc as described below? I was considering constructing individual spokes between a hub and tyre fixed in a jig to keep them concentric. This would be fore a master, the end product being cast into the tyre as you've described. Any thoughts?

I don't currently possess a lathe, but one's been on the shopping list for some time. I'll let the group know if this project ever gets off the ground, Cheers, Bill.

Hi Ronnie, I have looked at this, but the closest I can find has 16 spokes versus

26, not a good start, Alan Gibson has a 7' wheel in S scale that comes out at 33.3mm with 22 spokes, but it has a crank, so additional work there. If I go ahead, I'm getting resigned to making a pattern from scratch and casting. Cheers, Bill.

Nearly 30 years ago I was involved with producing masters, moulds and wheels for Scale7. The finished wheels had turned steel tyres that fitted into the silicone rubber mould. Acrylic resin liquid was then poured into the mould and acrylic resin powder added until it was all absorbed by the liquid. A piece of thin polythene sheet covered the mould and a large block of steel placed on the top to keep the resin undr presure while it set. The wheel was then carefully flipped outb of the mould and the back face very carefully faced off in the lathe and the central hole bored for the axle.

To make a concentric master you need access to a lathe. To turn the tyres you also need a lathe and to finish the wheels you also need a lathe. As you only need probably two wheels for the loco - four at most

- you could just as easily machine them from steel disks and fret out the spokes. Process described by Sid Stubbs in Model Railway News June and July 1959.

William Davies wrote:

I've done it both ways - we even had individual white metal spokes cast to make it faster to put the master together. No matter which way you do it, making the master is not a simple task.

William Davies wrote:

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