Cam Lobes and Teeth

[AlpineMonkey]

I wish that once I bought a piece of gear it would be good for the rest of my life, but I know that isn't the case, of course.

 

Today I was unloading my pack and checking out some of my cams. On some of them the teeth or almost completly gone. Do the teeth make that much difference? Is it bad to use a cam with no teeth? Some of my cams have almost no teeth and are only 4 yrs old, where as I have climbed with older folks who still use about 20 yr old cams, wich have been re-slung. Does anyone know anything about cam teeth, any comments? Of course a manufator would say, "retire the cam." It seems that it would be incredibly easy to take a small grinder and put some notches right back in.

[Peter_Puget]

Teeth have essentially no impact on holding power.

[AlpineMonkey]

Awsome, thats what I wanted to hear.

[Doug]

I tend to agree with Peter. However I would caution you about grinding some new teeth in the cams. Depending on the alloy, the grinding may cause cracking internally in the plate or forging thus degrading its integrity.

 

[111]

if you must, hand file them, no power grinding

[G-spotter]

Dentures.

[archenemy]

I have cams that have no teeth left and I use them regularly (still). I get a little sketchy about using small ones in a spot I may take a fall, but that is it. I always regain my trust in them when I aid with them and they hold fine.

[selkirk]

Ever notice that the new small Zero cam's, or the Splitter Gear cam's from a couple of years ago, come from the factory without teeth?

 

As I understand it teeth mostly make people feel warm and fuzzy, and I guess could concievable make them sit better around crystals, but the holding power has nothing to do with the teeth.

[fern]

hold power does relate to the cam still being "cam-shaped" - i.e logarithmic spiral of a particular angle. If the teeth are ground off more in some areas than others, or if the cams have flat-spots then the force geometry has changed, and the holding strength has changed. That is theory. Is YOUR cam still "strong enough" in practice? I dunno. For me, I look at my small cams with a critical eye for flat spots and wear that has changed the lobe shape. Usually this wear is related to the thing getting stuck and being wiggled a bunch at one position of retraction. Anything bigger than orange metolius I worry more about spring strength than cam shape and even then I don't worry too much.

[Dannible]

I read somewhere that cams with more defined teeth (like WC or metolious) hold better in wet or icy cracks. Anyone know anything about that?

[hafilax]

I think the grooves are there to encourage the cam to hook up on features in the rock in order to initiate pressing against the sides (increasing friction) in parallel sided cracks. You tend to see them more with the harder alloy aluminum. I think the idea is that if friction is pretty low to begin with that the cam will just pop out before it can start squeezing out which is what holds it in place.

 

The smaller cams usually have a relatively soft alloy and no grooves since the margin of error with those pieces is small and adding grooves would be detrimental. The soft alloy deforms more easily around the features sort of making it's own grooves. They also are more likely to flat-spot.

 

For wet or icy cracks I guess the theory would be to increase the pressure exerted by the cam lobe by reducing the cam contact area which would fracture the ice or displace the water. Metolius made fat cams for a while with the opposite goal for use in rock that may fracture under high pressure like sandstone.

 

If your cams are really that worn I'd be worried about the logarithmic spiral profile as mentioned by fern.

 

Friction is actually much more complex than the theory presented in most elementary physics courses and boarders on being wrong in most cases. Deformation and 'hooking up' are actually very important to determining the friction force.

[sobo]

Craig,

I agree with the manufacturer. Retire the cams.

You can just give them to me and I'll make sure they get back to the manufacturer.