I have now received the Darjeeling coach kits from Worsley Works. I no longer plan to light them (thanks, Brian Meldon for your important remark in my earlier post) but I do still need wheels!
The kit comes without instructions and I'm new to all this but even I have been able to identify the bogie frames. Sorry this photo is not sharp.
(https://forum.009society.com/proxy.php?request=http%3A%2F%2F1.bp.blogspot.com%2F-uhv7bHsKUQw%2FUmKmrmOEKXI%2FAAAAAAAAGJo%2F6XhEpWHF9ok%2Fs400%2F20131019_094857.jpg&hash=2a7957eabc367983e882b018a899527d373e340b)
If I buy from Worsley Works (see http://www.worsleyworks.co.uk/NG/NG_Wheels.htm (http://www.worsleyworks.co.uk/NG/NG_Wheels.htm)) which style and diameter would I want? I suppose I need the "Pin point 'top hat' bearings" too.
I'll be grateful for any help.
[I also wrote to Allen at Worsley Works and have got my answers: I should use 6mm diameter wheels. Apparently some of the drawing appear to show four holes (Worsley offers wheels with three holes) but others shows discs. Allen points out that they won't really be visible on the model anyway.]
Having seen several of these built up you really do not see much (if anything) of the wheels, so as long as they are the right size the number of holes (4, 3 or Zero) will not show. As to the right size I thought 6 mm would be about right, but having just checked David Churchill's drawings in Iron Sherpa 2 the diameter you want should be 5.2 mm for the later (and current) bogie stock.
Don't forget to get the "pin point 'top hat' bearings" too, and I'd suggest soldering these into their holes before folding up the bogies. It's probably going to be useful to get a 5-sided cutting broach to open the holes out slightly to take the bearings. Etched holes are usually made slightly undersize as it is much easier to cut the unwanted metal away than try to add metal to an over-size hole, and with that in mind take your time so that the bearings do not end up a sloppy fit in their holes.
Just realized to my horror I never posted my thanks here. My mother must be rolling in her grave.
I live in Libya so it's hard to get bits and bobs delivered but I've got the wheels and bearings now and am about to have a go.