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Cam failure discussion 24-Apr-2015 At 12:17:42 PM jezza

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On 24/04/2015 Macciza wrote:
>Cant agree Patto - look at the equations at the end of the standard cam
>models for parallel vs flared cracks. As the flare approaches the cam angle
>more friction is require to hold it . Where do you get the 2x figure from?
>Are you suggesting that deformation is the main reason cams fail in flared
>cracks?

What? Look at the maths again. Under normal cams, flared cracks there's an equation that shows cam angle required for a given friction coefficient. Doesn't depend on flare angle.

Flare angle has a powerful effect on compressive forces on the cam though. That actually makes sense to me intuitively at last. If it's buried on the back of a downward facing flared crack and you fall on it, that cam is going to get stressed all right. It's going to have to work harder so as not to unwind.

I'm pretty sure Patto meant 1/2 x, not 2x. As the flare angle approaches the camming angle, the outward force produced by the cam approaches infinity (according to the maths in the attachment).