We had a one-wheel bike trailer made by Mongoose for E before he could ride a 2-wheeler, around two years ago. Even then he liked mountain biking, so we took it onto rough gravel paths and other unpaved adventures. It may not have been designed for that, but still I was shocked one day to find that the critical linkage between his bike and mine had broken and bent and was on the verge of total failure. (Such failure would have made him crash badly, like ejecting the front wheel of a conventional bike.) Not only that, but the second linkage we had (for a different adult bike) was broken the same way.
I set about building a replacement, and making it as strong as possible. I also decided this would be a first milling project that E could help on. The banner photo above is from this milling. In the photo below, the original part is on the left and the new on the right.
While building this was fun, and it worked perfectly, it was a bit foolish to make it before contacting the manufacturer and asking for a repair. Also, at the time of creating this part I somehow imagined it a long-term investment, but E outgrew it within a year.
If you want a metallurgy puzzle, why didn't the original part fail catastrophically? The shape looks horribly weak, but finding two copies in the same state before failure suggests it's rather stable. My guess is the steel inner surfaces work-hardened, making them stiffer and stronger? Also note the manufacturer's weld to the steel pipe is in the worst possible place.
I set about building a replacement, and making it as strong as possible. I also decided this would be a first milling project that E could help on. The banner photo above is from this milling. In the photo below, the original part is on the left and the new on the right.
While building this was fun, and it worked perfectly, it was a bit foolish to make it before contacting the manufacturer and asking for a repair. Also, at the time of creating this part I somehow imagined it a long-term investment, but E outgrew it within a year.
If you want a metallurgy puzzle, why didn't the original part fail catastrophically? The shape looks horribly weak, but finding two copies in the same state before failure suggests it's rather stable. My guess is the steel inner surfaces work-hardened, making them stiffer and stronger? Also note the manufacturer's weld to the steel pipe is in the worst possible place.
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