UKC

As in the title, pretty simple. Do you guys think this would work? If so, why? If not why not?

http://www.facebook.com/photo.php?fbid=382388128484576&set=a.1502006183...

Jamie

In reply to JamieLewin: you try it first and let us know how you get on!

In reply to JamieLewin:

I believe it would depend on whether the primary loading is taken by the cam or by the nut. If the former it would exert a turning moment upwards where the cam meets the nut thus forcing the nut upwards and making the arrangement fal.

If the loading comes onto the nut first then that would tend to tighten up the arrangement, making it work.

In reply to JamieLewin: be interesting to see a drop test done on that. Im not convinced how stable it would be but I suppose if there's nothing else available..

In reply to JamieLewin:

I think the Camalot (if loaded first) might exert a greater lateral force on the Rockcentric (or whatever it is) than it is designed for.

In reply to JamieLewin:

I think you are suicidal! The problem is to do with the metals being of a similar hardness and so the cam having little to no purchase against the nut.

Cams work (in part) because of the metal deforming against the rock under load. If you have a cam against a similarly hard material then that deformation doesn't happen in the same way and the lobe has less purchase.

Have a read of the sliding nuts paragraphs here: http://needlesports.com/NeedleSports/nutsmuseum/camsstory.htm for some basic understanding of friction coefficients.

Also the cam is a force multiplier and will exert force on the side of the nut in a perpendicular axis. Nuts are not intended to be loaded like this and would [very] possibly be crushed on the flank. If you load the setup with 10Kn and the cam has a camming angle of 13.5% then I think I am right in saying that the force multiplication would be 7.4:1 and that means 74Kn pressing on the side of the nut.

Let us know how it works out if you try it, but don't do it with yourself on the loaded end, as I said... that would be suicidal.

In reply to JamieLewin: If you loaded the nut surely it would just close the cam and pull through.

In reply to JamieLewin:
If you draw a line from the hypothetical pivot of the cam along the camming angle towards the hex it looks like it would contact the rock under the point where the hex does. This suggests to me that if the cam was loaded it would roll the nut around clockwise and the cam would pop out.
if you could guarantee that both bits would be loaded simultaneously then it may work.

In reply to Trangia:

If you loaded the nut first it would just compress the cam lobes and slip through. Looking at the picture if you just pulled the nut downwards with your hand it looks like it would slip out.

I think you'd have a better chance if you were loading the cam. If the nut was flat sided I agree that the cam would rotate it out of possition because as the cam compressed and moved downwards the flat side of the nut would rotate past vertical and the force generated by the cam would be pushing at an upwards angle on the nut.

With the nut having a concave surface though you would have a better chance, although if the cam moved down enough it might do as you suggest. I don't think it would be as likely to rotate upwards though as the force would not be applied upwards until it passed to the outer edge of the concave surface. I.e. the force would be applied at 90 degrees to the point of contact of the concave surface, which if the cam didn't drop too low would be horizontal, in theory! In practice I think the pieces would move, they would both have to stay in pretty much the exact same position for it to work. All you would need would be for the force generated to overcome the friction enough to move the nut half an inch down or the cam to compress into the rock too much and the whole thing may fall to pieces.

Cool placement but I wouldn't want to lob onto it!

Ben

In reply to aretherenoneleft:

... and if you loaded the cam the nut has room to rotate so would do so and the cam would slip out the bottom.

Nice idea though!

Might actually work better with the nut turned side on, but would then depend very much on how the two contacted each other

In reply to EZ:


Just like to point out this is purely a hypothetical question. I sat and wondered whether it would work for a while. Just thought I'd see what you guys thought too.

Jamie

In reply to JamieLewin:

Probably not.

If you load the nut it'll rip. If you load the cam it'll likely slip immediately down the nut or roll the nut until it slips down the now significantly more flared placement. With the nut upside down you might just persuade it to hold but then in a real fall the cam would probably just crush the nut anyway.

As John said, nut end-on to the cam is probably the best bet at making those two bits play together but it'd be a bodyweight placement.
jk

In reply to JamieLewin: The cam would turn and where normally it's face would be up against immovable rock which would allow the cam to exert pressure, you have it on something which can easily pivot. I am up for having a go at anything sensible.

That is not even in the same country as sensible.

You might as well not bother placing it.

In reply to JamieLewin: That my friend, is fookin bomber! crack on...

In reply to EZ:


A vertical load L will result in a horizontal load of L/tan(theta). And the vertical load in a cam is split between the two sides, so, for a 10kN total load, I'd expect each side of the cam to exert 5/tan(13.5) = 20.8kN. i.e. the multiplier is a factor of 4.16.

I'd agree with your opening statement, though; the cam is unlikey to get a purchase on the nut, and will thus slip out.

<I should say that I'm going on EZ's description of the setup, which sounds like a nut and cam inserted into a crack together, our corporate firewall blocks Facebook...>

In reply to JamieLewin:

i think they already invented something that would make this arrangement obsolete...........i think they're called - Bigger Cams!

In reply to JamieLewin: honestly, i would give it it a go, looking at angles it should load up OK, loading cam obviously, but would possibly work better with the rocentric upside down as john said

In reply to JamieLewin: Literally did this a couple of days ago(as a silly add on to a belay), I tried weighting it and the bugger held! who knew?

In reply to JamieLewin:

Looks like the kind of thing MacGyver woud use! Except instead of a hex he'd use a toilet roll tube. Oh and instead of a cam he'd use a pinecone :-P

In reply to JamieLewin:

Would you clip both, both but equalised or just the cam? I'd be tempted to equalise to stop the hex rolling out and I would extend the hell out of it to stop the cam walking. Even so, I'd rate the chance of this holding a decent fall at about 20-30%