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Old 08-19-2010, 07:42 PM   #78
sbrownn
SlowMo
 
Joined: Oct 2006
Oddometer: 457
Sprocket crack

Quote:
Originally Posted by lennie
I have just spoken to my original machinist who drilled the locating hole and he has informed me he drilled then reamed the hole with a 3mm ream.

Makes sense as there is the chance that the 3 mm drill can drill undersize.

He has suggested a 3.05 mm hole so that after case hardening that the pin is still a push fit.

I have also discussed the current issue with the crack from the pin to the cam locating hole and he explained that the hole is at the end of the crack and it will not travel any further.

Makes sense as when a windscreen or plastic screen cracks you drill a hole at the end to stop the crack going any further.

If anyone wants to check this guy out visit www.epicycle.com.au. His name is Pete Smith and he used to run the Ducati Dealer Team in Australia race team in the 1990s.

Thanks for the feedback and input too.
Seems like the problem wouldn't be so much the crack spreading as the reduction in the amount of material that is resisting the load on the sprocket. I am assuming that it is only the amount of material between the pin hole and the outside edge of the sprocket that is maintaining its integrity as the crack runs all of the way to the center hole? A crack in a windscreen isn't very comparable to a crack in a sprocket as the loading is completely different.

Your sprockets completely eliminated hot weather pinging under load as well.
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