How do tricams work? What's the physics behind tricams in active mode?

Eric Moss wrote:

What color was it?  I nearly pulled a grey camalot and replaced with a pink tricam that held solid.  It was a vertical crack.

The smallest of the camalot juniors.  The rope for behind the trigger when I fell pulling the trigger and breaking the trigger.

dave custer wrote:

If it's a log spiral, the shear force does not change with crack width.

My recollection is that (according to Malcom Daly) the angle is not constant.   If I recall correctly, it is higher for tighter placements (but I could have it backwards).

In any event, I was taught to err towards less-tight placements ("half-cammed"), in order to facilitate removal.

Mark Pilate wrote:

Clint, that’s pretty much a nonsense statement.

Climbing “safely” involves setting good pro and traveling light.   Most commonly a few Tricams are carried and used to supplement a std rack to allow for a more optimal (safer) placement that an SLCD cam would provide or just couldn’t provide.  

For example, in this pic, the ONLY pro that would work is a tricam (And it was bomber) Not any cam, no nuts, not a pin, ball nut, big bro, tape knot... whatever.   Not theory, fact.  

If you truly want to be “safer”, add a couple Tricams to your rack.  

Because the crack is flaring outwards? Isn't the tricam here relying on a similar force vector between the stinger rails and rock as regular cams, which also suck in flares?  What about a Totem here? 

K Go wrote:

Because the crack is flaring outwards? Isn't the tricam here relying on a similar force vector between the stinger rails and rock as regular cams, which also suck in flares?  What about a Totem here? 

No no no.

No way could you protect that shallow, flaring, horizontal with a cam, you know better than that!

A tricam won't stick in a perfectly smooth flare either, but if there's a divot for the fulcrum to sit in, it will work.

I should hire Sam as my lawyer.  He’s been spot on lately.

In that particular flare, any cam squirts out with minimal pull.  The force vector on the Tricam is perfect.  It does have a small divot for the Fulcrum point and the force is directed inwards.  

Mark Pilate wrote:

I should hire Sam as my lawyer.  He’s been spot on lately.

If the cam don't fit, you must acquit!

Eric Moss wrote:

What color was it?  I nearly pulled a grey camalot and replaced with a pink tricam that held solid.  It was a vertical crack.

What does “nearly pulled“ mean? Gear holding seems pretty binary to me.

csproul wrote:

What does “nearly pulled“ mean? Gear holding seems pretty binary to me.

Slipped about an inch and nearly came out of the crack, just under bodyweight.