I actually work in NDT too and I’m a materials scientist, that’s why I’ve got access to all the measurement tools I’m using. There’s not really any need to go as far as dye penetrant here or any microscopy, because the extent of the cracks can be seen with the naked eye. I’ve actually spotted another more significant crack at the other end of the crank arm which basically writes it off. I can open that one up by flexing the crank arm, so I’m not going to be risking riding on it.
Yeah, this is basically where I’ve arrived, too. There would be a small risk of breaking it if I tried to straighten it but now I can see it’ll almost certainly break if I ride on it. Like you say, it’s not worth the risk on a component which is so rare it’s a museum piece. Plus, realistically, there’s the issue that I use all my bikes properly and I don’t want want a big failure and the associated loss of teeth etc.
Trust me, I don’t want to break anything on this. I’ve already sacrificed the crank bolts and sheared that screw - that’s already a couple too many things for me!
What a find. If it were mine I would disassemble it and put the frame and fork in a bath of phosphoric acid (ph down for pool for aquariums in the states, dilute a quart in enough water to cover the frame with jugs and buckets of ballast water so the frame is covered) the other steel parts I would soak in Evapo Rust as it only takes away rust.
I don’t know about the alloy parts, perhaps cleaning and buffing like old motorcycle cases. I use a cotton wheel and buffing compound. The alloy will be shiny but the pits will still be there. I would take a rag with gloves and coat all cleaned and de rusted steel with Ospho, a fantastic dichromate and phosphoric acid rub on primer. Don’t get it on the threads. Photograph and measure the location of the decals and color. I use a piece of lath to mark the decal location. I would replace the spokes, but make sure first they’re not odd ball. One of my old bikes had butted spokes with different gauges at each end. I had to use j bend washers on the replacement spokes. It will look fantastic just cleaned up without even a respray. Such a beauty. Slow patience will remove the corrosion. Here in the States hot rodders coat cleaned up rusty parts with a penetrating oil called Gibbs. I’ve used it and stuff doesn’t continue to rust. It’s very pricy. I think it’s only automatic transmission fluid mixed with a foaming penetrant. It didn’t lift or fade any of the old decals or paint. The phosphoric acid will lift any paint that has even minor rust under it so you might not have much old paint to remove. I rubbed on the Gibbs with a rag. The coat is thin and after it dries you can’t tell it was put on. The seat must be carefully cleaned as it might just disintegrate if it’s soaked in anything like polypropylene glycol, which museums sometimes use to preserve leather. After cleaning I usually use a very slow drying marine clear flexible epoxy on the whole saddle top, filling and penetrating into leather cracks. I fill and reinforce around the rivets, top and bottom. This stuff is unforgiving and must be mixed at exactly 2:1 or it won’t dry. I use bottle caps for measuring the amount to rub into the saddle leather. Mix for at leas five minutes. It takes two days to dry. If I’m happy with the fill and epoxy reinforcement I next melt canning wax in an old tray and submerge the whole saddle in it, letting it soak in but being careful not to burn the leather. This causes wax hardening so it really won’t move to fit your sit bones. I’ve done this many times and it usually works. If the saddle leather is real rotten it just breaks apart but yours looks like a candidate. Wax hardened saddle.
