Front	Rear

Technical Details

I acquired my Micro Rappel Device from Gearshop.com in 2000.

The New England Micro Rappel Device is forged from steel alloy (4160?) and then given a a black oxide finish. Mine is 92 mm tall, 52 mm. wide, and 10 mm. thick. The rope hole is 23 mm. high and 23 mm. wide. The top center thickness is 9 mm. The shaft length and width are 34 mm. and 32 mm., respectively. The auxiliary hole is 18.2 mm. high and 15.6 mm. wide. The eye measures 18 mm. by 16 mm. The ears are 6.5 and 5.7 mm. long. My New England Micro Rappel Device weighs 150 g.

One side is stamped with "81337-X11-1-4160-1."

Comments

The New England Micro Rappel Device is a "micro" size figure eight with ears. that is intended for emergency use only. It is a small device that is easily carried, and it is designed to work on 3 mm. or 5 mm. cord.

The left-hand figure shows how the device is rigged for 3 mm "rope." The extra turns are important for generating enough friction. Typical 3 mm. cord has a breaking strength of only about 1.8 kN (400 lb.) which provides essentially no margin of safety, especially if a knot is used for securing the upper end of the line. In my mind, 3 mm. is string, not rope, and I wouldn't rappel on it without a belay. Don't be surprised if a string breaks if you test it with full body weight.

The right-hand figure shows how the device is rigged for 5 mm "rope." Thicker cord naturally provides more friction (the contact angles are larger - remember the snubbing formula) so the wrap used for 3 mm. is not needed. The safety situation is slightly better when 5 mm. cord is used: the breaking strength for 5 mm. cord is typically about 5 kN (1100 lb). This doesn't provide a large safety margin either. Given a choice, I’d set a 9 mm. rope and a device that could handle it on my windowsill - which is exactly what I did for three months in late 2000 when I was living on the ninth floor of a Czech hotel.

Rigged for 3 mm. String

Rigged for 5 mm. Cord

The figures suggest an interesting question: exactly where do you clip in? The eye is too narrow to accept two full size locking carabiners. The answer is to clip one carabiner into the lower hole, and below the red cord shown in the figure.

The New England Micro Rappel Device is protected by U.S. Patent 6,095,282.

New England Ropes used to include a Micro Rappel Device with their Micro Rappel System. That system consisted of a small belt pack, a belt that could expand into a seat harness, two locking carabiners, 26 m. of 5 mm. "rope," a descender, instructions, and a bunch of warnings undoubtedly written by lawyers. I was able to acquire a Micro Rappel System on eBay in 2007, but the newer kits no longer contain a Micro Rappel Device (they include an SMC Personal Escape 8 instead). The instructions that came with my Micro Rappel System describe rigging the SMC Personal Escape 8 but still show the Micro Rappel Device on the cover photo.