Isen workshop: adventures in batch production (or not...)

So next near total disaster reared it's head this weekend. @oxygendebt messaged me, 'hi bikes great cranks dont fit y u ruin my weekend 4?' (I'm paraphrasing/making it up but you get the idea). Turned out that his record UT cranks with P2M power meter was fouling the chainstay at the inner ring. Obviously suboptimal.

If I build a Talbot, I'll chuck chainset, brakes, wheels etc in whilst building just to check everything clears. Building 35 bikes at once that isn't viable, so we spent a long time working our the static drawings, and making sure everything cleared, which it did. Until friday.

Having picked up the frame, the issue seemded to have been 2 fold, one easily solved, one useful for the next batch, but nothing doing for these.

1. The chainstays have a lot of dimples, chainset dimples, 650b dimples etc. It seems that the person dimpling has done it by turns rather than actual depth, so there is some variation in the depth. But not a lot.
   
2. This is the one that caught us out. It seems that there is a difference between some stays between the beginning of the tapering of the stays, where we have worked on the assumption it was the same. This means the 'wide bit' has been a bit further further forward on some of them. Should be an easy thing to build a check into the process, but caught us off guard this time.
   
   

Luckily it is an easy fix, and needs a number of things to have gone wrong for it to be an issue. To double check this doesnt happen again I am going to build a dummy chainring to mount flat to bb shell to check clearances going forward.

#csb