Here is the email conversation between Selcuk and myself, note his comments that he seemed aware of the problem? Or is that just me? Anyway the fact that the bearings could not be pressed out when brand new, but can after riding suggests that somehow the bearing degrades or the delrin stretched leading to the bearing movement.
Other wise i thought he handles the situation well... FIRST EMAIL:
Hi there Selcuk.
I was racing on the weekend when the mount bolt you made for Geoff Searle snapped, the entire derailleur got caught in the wheel and then went around and cracked the chain stay on my bike. Is there a reason why it would have done this? AS you can imagine im a little annoyed but when you try products like these (as brilliantly as i thought i had been built) you have to expect failures of some sorts. So im curious why it would have done it, it wasnt over tightened, it was correctly built, everything had been fine for the two or three months i had been riding it. One theory i had may have been that the chain had hopped off the jockey wheel (one of yours) jammed inbetween the cage and jockey and caused it to snap the bolt... Ive noticed that when i had hopped off and checked out the problem, the jockey wheel had slid off the bearing over the bearing cap and the chain was wedged in the now created gap. The bearing cap could have been the issue as it doesnt stop the bearing from sliding sideways, so an option to fix it might be to increase the diametre of the cap to cover the sides of the jockey wheel body and then prevent sliding. When my new jockeys arrive ill build some bigger caps for them to try reduce the chaince of it happening again.
What do you think?
Tayler ReedFIRST REPLY:
I am very sorry that this has happened to you.
Before I make a further comment pls send me your drivetrain set up.
Crank .Compact or regular? Brand?
chain: Brand and type.
Casette: Smallest and biggest cog teeth figures.
FD and RD: brand & type.
Thanks for your input.
I run a stronglight fusion 2 crank, 53 - 39 with SRAM Red chain, 11 - 23 SRAM Red cassette. Super record front derailleur and a SRAM Red rear derailleur. Strange combination but it works great.
I emailed you mainly because i was curious to why you think it could have happened?
Thanks for the info.
I check with QC and will revert. Can be tomorrow.
Thanks for your patience.
That fine, thanks Selcuk.THIRD REPLY:
Making some tests with some pulleys from the lots we have sent Geoff and you.
Not quite sure but assume it is a pulley braekdown rather than a bolt failure.
Machine will run during weekend and I will revert on Monday.
Thanks for patience.
Thats fine. I think it may have been because the pulley, with enough force, can slip over the bearing and them jam onto the cage plates. Thats what my theory is. Let me know what you find outFOURTH REPLY:
Your case is much of importance to us because we are manufacturing Delrin pulleys for other applications where much greater forces are applied than within a bicycles RD.And where NO caps at all are used .
But due to some troubles in the past we have worked out a manufacturing method hand in hand with DuPont end of 2010 where we have solved the problem.
The Delrin wheels are heated up to a certain temperature in a special liquid .
Then they are taken out and have to cleaned very good and very quickly because the bearings are pressed in using some two component industrial bond .
The pulleys are then taken into an air cooled chamber where the Delrin shriks around the bearings outer race.
Nothing new that we have found out during weekend tests but we think that we may keep an eye on the structure of the industrial bond after longer storage times.
Nevertheless I am very sad of what has happened to your RD .
I am suggesting to check the bearings lateral strength of your new pulleys just by trying to push them out by your thumbs force. You should not be able to push them out of their slots.
Despite belief if they should come out pls use a strong bond (3M Scotch Weld PR 100) to glue them back.
Before doing this please take care that the original bond left overs are cleaned on the outer race of the bearings as well as in the Delrin wheels slot.
Please use a very tiny amount of bond to reglue them because otherwise you will glue your bearings by pressing the overdose out to the other side which will press through the seal into the balls of the bearing.
Let me know about your findigs.
So this is where i left the conversation, mainly because i read theemail then promptly forgot to reply... Damn you memory...