A terrible confession: I have used my CAMP SOLO 2 ascenders with 6mm tech cord (3800 lbs) simply girth-hitched through the bottom carabiner hole. The hole is 16mm diameter, and is through 4mm aluminum; the hole has been polished to have rounded edges. That 4mm puts a severe bending radius on the cord. Therefore, strength reduction is expected; but how much? Some sources suggest more than 50% reduction when the radius ratio (rope to bend) is less than 1.

I didn’t want to place my ascenders in harm’s way, so I made a quick analog from sheet metal, for a pull test. Since I planned to use 5 mm cord (vs. 6mm) in the test, I made the holes 13 mm in diameter (a ½” drill bit, with some rounding out), in 3.2mm (1/8”) sheet aluminum.; the pictures below show the actual ascender and the analog.

I put a steel carabiner through one hole in the sheet metal, and tied figure-8-on-bights to each end of a 2m length of 10.2 mm dynamic gym rope. One loop of the 10.2mm went over the carabiner, and the other on the tow hook of my Jeep. I tied loop in 5 mm Maxim polyester ( 1124 lbs bs). I joined the ends with a double fisherman, and girth-hitched the 5mm cord through the second hole. The other end of the cord was attached to a 3-ton crane scale, and the cranes scale was attached to a rigid steel post in the ground.

Then I drove the jeep as slowly as I could, and snapped the Maxim loop. I took a video of the crane scale display; the highest recorded force was 939 lbs. The graph of force versus time is below.

Note that the time one hears the “snap” on the video is well before the registered peak force, and the time from 0 force to the recording of the peak force is only 4 seconds. A serious problem is that the crane scale has a time constant of at least 1 second, so there is a substantial lag. From my comparisons of break tests with the jeep pull, versus those where force is supplied by a come-along, the jeep-pull method tends to underestimate peak force by about 10% (when both are read by the crane scale).

A girth-hitched loop, where the bending radius is not severe, breaks at about 85% of the strength of a loop; and the loop should break at about 2x the mbs of the single cord. 939/(2x1124) is just 0.42, or 42% of the raw strength of a loop. But for the 2x3800 lb cord, if proportional, we would get 3192 lbs. Any activity that puts 3192 lb on a single ascender is likely to be catastrophic., and the breaking of the cord is not your biggest issue. With the newer linescale 3, and much more rapid sampling, goes to 1096 lb bs in analog, thus breaking at 49% of raw loop strength, or 3705 lbs projected to break the girth hitch on the real ascender.