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Why should the headtube deal with that force to the full extent, it would be more likely that the cup main section which is sticking out of the heattube and has quite thin walls would be stretched, too.
But even if that were to happen in a normal headset the only effects would be that the whole fork would move minutely upwards as the (effectively) conical crown race moves upwards relative to the cup (because the ring of bearings in the lower race would have expanded slightly) and that the top cup-cone interface would loosen minutely. It wouldn't act to loosen either cup from the headtube, which is the risk in your design.
ffm-
It wouldn't act to loosen either cup from the headtube, which is the risk in your design.
We'll see. I get your point, but I could also imagine that it will only loosen after many thousands of km, or not at all, that's why I need to run this test.
Also because..
If you were going to all this trouble, could you swap out the head tube?
.."all this trouble" is actually just 20 minutes of lathe work, compared to the massive surgery of swapping the head tube.
jetski
I get your point. But:
Why should the headtube deal with that force to the full extent, it would be more likely that the cup main section which is sticking out of the heattube and has quite thin walls would be stretched, too.
In the end, there is no way getting around trying it I guess ;)
At least nothing can go horribly wrong, i.e. there's no danger involved if the external cups should gradually go loose.
Of course brazing them to the headtube would be better but then I can't take them off anymore if I have another idea and also I would have to make them out of steel instead of aluminium which takes much more time and effort on the lathe, and theres the extra effort of brazing involved.
Just making two cups out of aluminium would be super easy and fast.