Any chance, once the ideal position has been found, of drilling through the web and pinning the eccentric? Hopefully, a small pin will not shear, nor the hole weaken the web too much

Ideally, how about finding the ideal position, scribing across web and eccentric, separating, applying anaerobic sealant, and reassembling with the marks aligned?

Howard

Hallo David. Can I ask again about the size of the loco. What gauge is it?…..ie what is the distance between the wheel treads. I did offer some advice on fixing a return crank for a 6-coupled loco a short while back. That was a Gauge 1 (45 mm track) loco though, which is a completely different kettle of fish as regards the size of crankpins etc than say a 5inch gauge as there is only a tiny amount of mating surfaces. So the fix will be different.

As regards the repositioning of the crankpin I can only offer my commiserations. It seems to me that there are few options other than going back to square one and ensuring all the crankpins are properly aligned and the wheels accurately quartered. But, if the loco is of small gauge you might get away with…..and it makes me wince to say it………..leaving the centre coupling rod bearing snug on the crankpin and take a tiny amount of material from one or both of the coupling rod end bearing surfaces. Even if this goes horribly wrong you can rebush the coupling rod bearings to get back to where you started.

The above quick fix has worked for me in the past with no observable problems in running.There are far better qualified and more knowledgeable than I on this forum who might assist you further.

Mick

As a non loco man, without any first hand knowledge, the problem with all locos seems to be having the crankpins truly at right angle to each other, at the same radius, and the coupling rod centres exactly the same as the axle box centres. When everything coincides, superb, when there is a slight discrepancy; problems.

And that ignores the effects of expansion as things warm up!

In UK the Great Western Railway used optical alignment and worked to close tolerances. The horn guides were ground on both sides of the frames at the same setting.Their locos were quiet and efficient. Unlike some other railway's locos, it was very tare to hear one "clank" as it moved, even in wartime. One GWR man is reputed to have said "We scrap at the sizes where others assemble"

Hope that you get everything sorted out and have a really potent loco.

Howard

I think that I might have used an appropriate Loctite grade (say 638) to fix the insert which I am pretty sure would obviate silver soldering. If the wheel is cast iron you may well have a lot of trouble silver soldering it.

Mick