Towards loco wheels

As the workshop project rounds up, I will soon have no reason to hold off on starting work on 622.  The first major stumbling block is of course wheels.  If I can’t make those, then I may as well abandon the project; and by that, I don’t just mean the engine, I mean Pembroke itself.

Well that got needlessly dark fast.

I’ve been thinking about how to make the wheels for months, as I had already found I couldn’t source all the sizes I need, even in P4.

Model Railway Journal is a great source of inspiration for locomotive builders, and one of the ideas I have stowed away is to build the wheels from solid, but only fret out a few of the spokes.  The rest are added later, and I’m thinking of casting them in place.  By turning everything in one operation, the axle hole will definitely be straight and centred.

I’m planning to use split axles on this model, following some ideas from Andy W,  over at the Scalefour Forum.  With the axles and wheels one electrical unit, I can make the wheels and tyres out of a single piece of metal, with an interference or soldered fit to the axle.  This departs from tradition in that most model locomotives have separate tyres (why?).

In the end, there are several non-traditional ideas here, and I would appreciate your feedback as to whether you think they are good or not:

  • Turn the tyres and axle holes in one operation on the same piece of metal.
  • Use a minimum number of metal spokes and cast the rest in resin.
  • Employ an over-length axle to aid with quartering.


11 thoughts on “Towards loco wheels

  1. Very interesting ideas; I like them. Especially cutting through the thinking about separate wheel and tread. My only suggestion at this early stage of the design relates to the “cut in place” and the “cast, add-on” spokes. Was thinking the spokes and counter weight need not be cast in place, but a cast part that is later glued into place. Low stress on that joint, so not seeing the benefit of “cast in place”. That thought lead to another: recess the outer face of the wheel tread, and the “cut in place” spokes, etc, so all of them can be faced with a “circular and spoked” casting (which is stronger to remove from a mold). That also eliminates the need to machine appealing profiles on the outer face of the “cut in place” spokes. Recess them, face them flat and layer on the casting. Thinking 3d tech to create your masters. The casting over “cut in place spokes” would, of course, have much less depth than the spokes that are entirely cast.

    Hope that is not too obscurely phrased.

    1. Thanks Rob. I thought about a face for all the spokes being glued in place, but it makes for a more complex part – one that couldn’t be cast in an open-face mold, and the thicknesses will be difficult to 3D print. Either way, the machined part needs to exactly match the cast part, and that’s when I arrived at casting in place!

  2. Hi Rene,
    This all looks really fascinating work, I wish you all the very best. I do like your thoughts in your sketch! Although I have very little experience myself, I wonder if you have seen this article on the site of my former club:
    Sadly, we lost Sid Stubbs a few years ago but Dave Booth is still with us and happily still modelling away, both decent Gentlemen whose work I could never hope to match but greatly admire.
    Cheers, John.

  3. Very interested to see how you approach this Rene. As an “armchair steam p87″er, I’ve been mentally struggling with the same issues….. A small cnc lathe seems the best solution, says the engineer. My wallet disagrees.

  4. Rene,
    If you make the wheels and tires in one piece, how will you insulate one wheel from the other? Even if you do, you will still have to insulate the wheel from the side rods (assuming they are conductive). For this alone, I think insulating the tire still has merit.
    Don Ball

    1. Hi Don, I actually plan to use two half-axles, similar to typical Diesel engines. This way, with the tender trucks also picking up, albeit one side each, I get six axle pickup, which should be pretty reliable. Cheers, Rene

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