Friday, April 2, 2010

Bicycle Chain Wear Test From Wippermann

Wippermann is a German bicycle chain maker. Their stainless steel chain Connex 10sx tops a list of chains in their on-going wear test to 1% elongation (click on above). If you'd look, the wear life variation is huge between the top and bottom of the list. I also believe theirs is the only stainless chain in the list so you can go "hmm?" to that.

The testing is being performed on a rig with a 52-tooth front ring and a 17-tooth rear cog, with an applied chain tension of 300 N. The test phases feature the following phases :

- An in-line 5 hour run with original lubrication.
- A offset test to both left and right side for 5 min at 50 Hz and then 10 hours at 100 Hz after independent applications of water, oil and sand to the chain.
- An inline 15 hour test at 100 Hz with above mentioned pollutants, which is then repeated every 15 hours after cleaning until chains show a 1% change (or 8mm increase from DIN specified length of 800.10 mm). This change happens due to wear of pins against the roller.

The following video put together by Cantitoe Road shows the test protocol. A text description of the phases can be found here.

What I'm hoping they'd add into the bevy of substances to soil the chain is de-icing salt used commonly in wintry regions. Some salt water spray would be appropriate. The chains could then be stressed to twice its recommended working load and then inspected for cracks or changes in cross-section.

Salt could be one of the prime culprits in the recent case of Shimano 6700 chain failures. We were all left guessing in that post and some of us even declared it a materials issue. Well, the news is that of the affected parties sent in his chain for hardness testing to a third party facility and the tests didn't point to a materials related defect. Puzzling eh?

But the people who work in marine environments know the almost invisible, catastrophic failures on loaded chains, whether they are galvanized or stainless. Microscopic cracks develop and grow within and sooner or later, you may have yourself a broken product.

I was also hoping that multiple sprocket combination could be utilized in this test, as opposed to just one fixed combination of 52/17T. I have written recently about chordal action in tiny sprocket sizes, those lesser than 17 T.

In that post, I calculated the variation in chain speeds of a 52/11 and a 52/12 combination and wondered about the long term effects this would have on sprocket wear. Dan Connelly asked me whether I had any data with me to back this issue. At that time, I replied that I had none.

It would be interesting to see whether the theory agrees with practice.

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