Technology Single versus Dual Axle
Black Diamond holds a patent on the dual axle
design. Dual axles
permit cams to have a more usable range (with the exception of the new link cam). Range is the difference between the minimum safe cam width and the maximum safe cam width.
Omega Pacific holds a patent on the link cam design. Link cams use a single axle
design but each lobe has multiple parts allowing it to have the largest range on the market. The disadvantage with the link cam is that it is heavier than most other cams. OP counters this argument by stating that you will carry less gear due to the increased cam range the link cams provide.
Offset cams use a similar design to single axle
cams, but one of the sets of the lobes is smaller than the other. Offset cams are used in flaring cracks.
"Offet Cams are specialized pieces designed to fit in pin scars primarily for aid climbing.
Cams placed in flaring cracks are far more susceptible to pulling out than placements in parallel-sided cracks. Climbers using Offset Cams should be very experienced in the art of cam placements and thoroughly understand the limitations of cams placed in flaring cracks." - Metolius
Most cams come with flexible stems. Flexible stems are excellent for horizontal placements. Rigid stems (placed in a horizontal placement) create leverage, increasing forces on the rock and gear. Rigid stemmed cams are cheaper.
Forged friends (below, right) come with 'Gunks tie-off holes' allowing you to make safe horizontal placements.
Bring two nut tools to help get jammed cams out. A lot of cams 'walk' into cracks and their owners do not know how to get them out (and occasionally they are not coming out). The problem is often simply fixed with two nut tools though.
The cam has walked into a crack deep enough so that if you pull the trigger, the lobes will not be contracted.
If you are on lead (and you can't trust your partner to split the booty) make sure you have good pro
above you because you will be using both hands. Ask your belayer to take (your climb is still clean in my book if you are stopping to get out a nice shiny cam). Bring some thin accessory cord (a one foot loop works great). Wrap the accessory cord around the trigger and connect this to your harness
(you may need to extend the cord with a Quickdraw). Lightly lean back so that the trigger is constantly engaged hands free. Grab both nut tools, one per hand. Place the end of both nut tools on either lobe (of one set of lobes; I normally start with the deeper set). Use the crack to gain some leverage and squeeze the lobes together (make sure you are weighting the trigger just enough to keep it open, but not enough to hold the cam in place). The cam will likely pop a few millimeters forward (after playing with it). Switch to the other set and creep them forward. Continue this cycle until the trigger will contract the lobes.
If the cam has been there for a little while it is likely that many people have messed with it. A major concern is spring damage so inspect it yourself. If the trigger wire snapped you can use the tactic above, but place the accessory cord directly on the cam (not on the trigger). Replace the wires yourself (not expensive) and you have a great new cam. If a cam has been exposed to the elements (UV rays, rain, etc.) for an extended period of time you may want to replace the webbing.