I really like my cams, and as I've explained before, they allow me to climb rocks without having someone else go up and place bolts.
A cam works by having at least two and up to four spring-loaded, rounded metal lobes(1) that oppose each other. The spring allows the lobes to be pulled in, by a trigger bar(3), making the cam head more narrow. Then the lobes are placed in a crack in the rock, they expand, and hold tight. A stem(2), either single or U-shaped, extends from the axle running between the lobes. The rope is clipped to this stem by a carabiner(4), often attached to a nylon sling(5).
When a climber falls, force is applied which pulls on the stem causing the lobes to expand even further. This outward pressure is transferred to the rock, and combined with friction in a good placement, the cam holds in place.
The rounded lobes are actually curved in a logarithmic spiral. This is important because it allows the outward pressure caused by the expanding lobes to always have the same angle. If the lobes were just circular round, the angle of the outward pressure would change depending on how far engaged the lobes were when placed in the rock. I'll go ahead and steal an illustration to help me explain this part.
(There are a lot of people who have explained this a lot better than I can.)
Here's a nice diagram that Metolius provides:
Anyway, this blog started out as a post about my first time falling on trad gear. Thing is, since I started this blog, I've fallen on the gear more than once, and the excitement and luster of trad virginity has slightly faded. Only slightly though. It's turning into trad love. I fell on the yellow TCU (Metolius "three-cam unit") on a climb called "Extreme Unction" in the most beautiful canyon in the Wasatch.That's Jerad getting ready to go up second and clean all my fancy cams up.
I fell again on a yellow TCU in the San Rafael Swell on a climb called "Anchors from Hell".
The picture doesn't do the climb any justice at all. The climb is a finger crack in a tight dihedral with scary moves up at the top. I actually fell just a little bit off the ground, but it was still nice to have the gear hold me off the deck.
I'm going to take the liberty of linking a photo that Adam (friend) took of Alex climbing on "Old Bushmill's" crack. I was actually able to climb this crack cleanly and didn't have to test any of the gear that I placed. (It would have held fine)
This crack is in a really wide dihedral and goes from rattly fingers up to big hands in size.
I climbed it twice before I felt like I was ready to lead it, and by then, it was the end of the day. I was sure shaky, and almost slipped out of the crack in a few places. It was exhilarating to get up there and clip the anchors. I almost hated to be lowered back down to the horizontal world. If anyone ever gets a chance to climb something like this, don't let it go. Crack climbing is dangerous and painful and so so rewarding.
Climb safe out there.
Price
Excerpt from Rexburg, August 1996
10 years ago