How accurate can frame geometry be (angles, length)?

My regular off the shelf 40 dollar digital protractor has the accuracy of ±0.2° so I wouldn’t even know if I managed to hit ±0.1°. 0.5 is something I am happy with in my own builds and this is in terms of achieving the technical spec - in reality it might still ride like shit, no matter how accurate my miters were :smiley:

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Has anyone worked with steel and titanium and has a sense for which material distorts less (which then should allow for higher accuracy)?

And thanks to everyone for all of your input!

Steel is less distortion. I am always amazed at how much titanium contracts during welding.

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Do you have any knowledge if that is related to elongation Daniel?..or amount of heat and size of fillet. Trying to think of the mechanics there.

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Welding and brazing melt metal, which collapses any built up heating expansion pressure, then cools to a smaller size, which makes warpage an inevitable fact of welding and brazing. Rigidly fixturing something doesn’t prevent warpage but isolates it to the weld area. Most steel is compliant enough that it’ll mostly yield if it can’t move.

Titanium is where warping gets complicated. Titanium’s coefficient of expansion is lower than steel, so warpage over its full welding process temperature range is actually lower. Good luck convincing anyone who’s welded it though! Its yield strength is extremely high, so it can’t yield like steel as it cools. Instead, it winds up stored warp deflection in unexpected places to release as a fun surprise when it comes out of the fixture.

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@Daniel_Y is that a total tolerance or a ± number?

It was +/- tolerance

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[quote=“Homo_Birota, post:5, topic:3019”]
± 1mm of front center length is equal to ±0.1° of head tube angle (at least at the HTA range I’m looking at).
[/quote]gg

I know this is thread necromancy, but this popped into my head last week and I felt compelled to reply.

Above is an incorrect assumption that I missed at the time;

my head tube angle might be “out” by half a degree and I wouldn’t care as much as getting that front centre where I want it. I wouldn’t even measure the head tube angle after welding;

/rantover

I won’t name names, but I repaired a very popular production brand frame a couple years ago, and when I put it in the jig the head tube angle was 3 degrees steeper than the brand website’s geo advertised :grimacing: and if I recall, BB drop was quite far off what was advertised as well.

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