Wheel Specification

[andrew jukes]

I am interested in Golden Age Models' forthcoming Silver Jubilee train and, partly as a result of comments I made about their P4 wheels on earlier coaches and partly because of wanting reassurance that the Silver Jubilee wheels would be better, I seem to be in the position of specifying the dimensions of the new wheels.

The flange profile must obviously be as specified in the Digest and this is almost exactly as shown in the Exactoscale wheel drawing, as supplied to the producers of the Exactoscale rims. A pdf of these two drawings is attached. The 'almost' relates to the way in which the blending of the radii on the gauge face of the flange is achieved, and is not significant.

The questions are:

1. What wheel width should I specify? Exactoscale use 1.67mm (= 5" on the prototype). The P4 standard requires 1.85mm minimum, but only 1.67mm of this is the running surface. I am inclined to tell Golden Age to follow the Exactoscale drawing but thought I ought to see if there were any strong objections.

2. What back to back to specify? Although I would favour something a little wider (17.82mm), I will tell Golden Age to set their wheelsets to 17.75mm and will supply an Exactoscale 17.75mm back-to-back gauge for checking purposes. Any comments?

Regards

Andrew Jukes

[Russ Elliott]

Andrew - below is an older forum diagram I'm sure you'll remember for the limiting case with a 1.67 wide tyre and a P4 BBmin setting. At your BB of 17.8, and a tyre width of say 1.8, the minimum tyre to rail contact overlap is getting up to about 0.9, which is at least the full railhead width. I don't think I'd want to go much below that for tractive wheels, although I can't explain my unease about a lower value with much objectivity. For coach wheels in bogies however (is that the context here?), wheelsets will never be far off perpendicular to the track, I can't see much problem in going down to a TW of 1.7.



I'm all agog as to what Golden Age's reaction will be to the wheel drawings (!), but I think my first priority would be to discuss wheel suspension.