problem statement
requirements and approach
current s.o.t.a.
initial designs
secondary designs
testing
final product

 

Current active frictional anchors for climbing come in 2 types: Expandable Tube Chocks and SLCDs. Here are some examples and a brief description of each type...

Expandable Tube Chock:

Only made by Trango, Trago Bros and BigBros are the only example of expandable tube chocks for climbing. They consist of two aluminum round tubes a spring and a locking ring. What makes this active climbing protection is sping loaded mechanism that is used to expand these devices inside a crack in a rockface. The chock is set by compressing the inner tube into the locked position, holding the chock inside the crack, pressing the spring release button so the chock expands, and then tightening down the locking screw.

This design is not very effective for a number of reasons, but the most important is that his has no way of generating the necessary normal force against the crack wall to induce a significant supporting fricitional force.

This concept is described in more detail in the initial and secondary designs pages.

Trango Big Bro

 

Spring Loaded Camming Devices (SLCDs):

By far the most popular active protection device on the market, SLCDs have an excellent reputation for they're reliability and ease of use.

Some examples include:

  • Wired Bliss Camming Units
  • Wild Country Technical Friends
  • HB Flexi-Fit
  • Black Diamond Camalots

All of these and other SLCD designs vary in certain details, such as trigger shape and handle type (wire vs. rigid) but they all share at least one common feature: The Logarithmic Camming Lobe.

The effect of this is described in detail on the secondary design page, but basically it ensures that no matter what position the cam-lobes themselves are in (i.e. how big the crack is) they always transmit the force of the fall at a constant angle from the axel. This ensures enough force normal (at 90 degrees) to the crack wall to generate the friction force required to hold the device in place.

How a SLCD sits is placed inside a crack

SLCDs have an advantage over other anchors such as hexes, nuts, and pitons because they are easy place and remove, requiring only one hand to operate. However, there is one major flaw in the design of SLCDs, an effect called walking.

Definition: Walking...

Walking is the gradual movement of an SLCD back into the crack in which it has been placed. Caused by vibrations of the handle due to the passage of rope through end of the anchor, this behavior happens, particulary in Four Cam Units, when one pair of cams holds against the crack wall, while the other pair slides backwards into the crack.

This can be hard to visualize if you haven't seen it before, so we have a small video clip demonstrating how this works. To see this behavior in action click here (663k). We appologize in advance for the poor video quality and bad "acting."

Walking is one of the main design issue we tried to address with our initial design attempt.