Failed Steering yokes?
A friend has sent me a recent Technical Bulletin from the CRMC issued 29/4/2022. It contains in part some disturbing comments on the “failure of steering yokes”. It reads in part
“Failure of Safety Critical Parts….Norton Steering Yokes: Video evidence of a crash shows that a rider entered the long left hand Dibeni Bend lost control of his machine and that the steering yokes then failed resulting in a crash. Luckily the rider was unscathed, but the bike suffered damage. The machine in question was a Norton and we have had reports of similar incidents with Nortons.”
That last sentence is alarming, and from the bulletin it is not clear what this failure consists of. I’ve looked on the CRMC website but cannot find this or other TB’s, so this information may be restricted to registered CRMC members.
Even under racing stress, I cannot see how this failure might occur. Thought or comments anyone?
PS CMRC posted this bulletin on Facebook apparently. Whatever that is;-)
I suppose everything will…
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Still at a loss to comprehend this
I'm still struggling to picture what this failure actually amounts to: distorting? Actually fracturing and breaking up, to cause the loss of control mentioned? Coming loose at the clamps/top nuts??
If indeed it is not an isolated incident as stated, perhaps in the interest of our safety at large the Club could make a formal request to CMRC for more details, and give us all some sort of Bulletin?
On a vaguely similar line, I seem to recall a comment many moons ago where a club member had a fork slider snap in half like a carrot whilst riding, and thankfully was able to bring the bike to a safe halt. Subsequent examination of the break showed that much of the surface evidenced the typical ally "rust" gunge, with only a small amount displaying a fresh,clean break. This meant he had unknowingly been riding with a cracked slider for quite some time, and I think FairSpares (as was then) examined their s/h sliders and found some had similar hairline faults only discovered by crack detection. Scary.....
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steering yokes
I bought a Bsa B50 with crash damage, the previous owner told me that he had been riding along a straight road when he crashed, the forks had alloy yokes the bottom yoke ( forged I think ) was bent but intact the top one was in several pieces and was a cast item, both being genuine Bsa parts I note that the alloy yokes were only fitted to the 250 and 500 singles the 500 and 650 twins had steel yokes.
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I suppose everything will break given time and abuse. Front-end crashes and subsequent straightening can't help. But I can think of anything that would single out Norton in this regard.
Do you know to which Norton this applies? And are they talking about original parts or after-market light alloy parts. No slight intended to Andy Molnar but cast magnesium? https://www.tga.co.uk/products/bottom-yoke-and-stem-7quot-centres/