Philip Hall wrote: I have found on occasion that if an axle, being too short, is not inserted all the way into a wheel the wheel is more likely to wobble, but this has been in extreme cases.
Touche Philip (don't know how to do an " E acute" accent!). The pair of wheels has a wobble with max BB of about 17.85 and minimum about 17.65. When I was pushing the pair together on the GW jig they slid together surprisingly easily. Maybe because I was using Araldite having filed a small groove all the way round near the ends. The BB gauge was difficult to remove and I found the B2B was around 17.25. So I tapped the axle end (wheel supported on the vice), aiming for max 17.75, and I thought I'd got that. Not for the first time mysteriously the reading seems different now that they are fully cured. Anyway I'm going to go with them and if I get problems I'll know the cause.
Dave Holt wrote:I find it a bit odd when people shy away from setting things down on paper and then find that parts of the rods or valve gear go clunk. Surely, it's so much easier to make any necessary alterations before assembly than having to try to disassemble delicate parts in order to modify them? Each to his (her) own.
I'm sure you're right Dave but I find the idea too daunting. I do wonder whether I'd have foreseen all the fouling issues I have had with the Crab if I'd drawn it. Today reassembling the chassis with the new centre pair of wheels I found I had some new fouling with just connecting and coupling rods attached, arising from the thicker bosses. The front coupling rod was fouling the bottom of the motion bracket, though only when the crank was at the forward position, on a curve such that the centre wheel was deflected outwards. The issue is that the motion bracket has a little too much "meat", though it may be prototypically correct. A few strokes of the file sorted it. I just don't think I'd be able to work out what these dimensions would be from looking at it on the flat in the fret. Most of the issues I had were like this, quite minor. I think I take the kit maker on at least some trust. There have not been many issues with the valve gear. It would be interesting to know what particular problems there are to look out for in future, maybe worth a different topic? - you have mentioned a couple like expansion link outside the connecting rod.
Dave Franks wrote:Just finished a lovely wee P4 loco for someone yesterday so piccies soon.
Look forward to that Dave!