Technical details
I acquired this descender from the manufacturer in the mid-1970s, probably about 1976. The device is covered by U.S. Patents 3678543, 3695397, and 3757901.
There are three models of Hobbs Hook illustrated in the brochure that accompanied the one that I bought. I have one of the standard models, consisting of three pieces. The main body is an aluminum and is 195 mm. long, 76 mm. wide, and 16 mm. thick. It is roughly pentagonal, with parallel sides and a pointed bottom. The upper two-thirds has an irregular cutout opening to the side of the device. Below this is a 44 mm. wide by 38 mm. high rounded rectangular hole. Finally, a 12.7 mm. hole at the bottom provides an attachment point. Two pips on the side are used to limit the motion of the optional brake bar described below. Two dimples in the device serve as wear monitor points. The entire frame is well-rounded except for the tie-in hole, which is beveled. A hole in the top of the frame extends down the open side and across the side opening. A 116 mm. long, 7.9 mm. diameter aluminum spring-ball pin fits into this hole and acts as a safety to keep the rope in the device. A hole in the side of the short leg of the frame lets the pin balls expand to lock the pin in place, provided the pin is turned properly. A hole in the top of this pin accepts a 25 mm. wire ring that serves as a finger hold for removing the pin. My pin is marked "AVDEL 52133" which is undoubtedly a part number. The third piece is the optional brake bar assembly. In top view it is oval with a 17.5 by 79 mm. hole sized so that the bar can slide over the top of the main frame. Its outside dimensions are 93 mm. wide and 31 mm. thick. It is 21. 5 mm. high for most of its width, with extensions at the top and bottom of one end increasing the total height to 55 mm. These extensions are large enough to bridge the opening in the side of the main frame. The brake bar is stamped (with ink 3 707516 and "Brake Bar". The main frame weighs 288 g, the pin and ring 19 g., and the bar 87 g, for a total of 394 g.
There are at least two other variations to the Hobbs Hook. The fire-fighting model appears identical except the inward-sloping (45°) portion of the frame is eliminated. The rope locking model is similar to the fire-fighting model, but adds two springs that fit over the frame and force the brake bar upwards. I have not tried either of these models.
The Hobbs Hook can be used in several ways. The factory literature recommends three principal configurations: a wrap, a brake bar configuration, and a double rope configuration reminiscent of the the Longhorn.
The
wrap configuration allows incrementally variable friction. I prefer
to use two wraps. The wrap direction is not important for kernmantle
ropes. On laid ropes, the wrap should be made in the same direction
as the rope (i.e., right-hand for right-hand ropes) so that the
device does not tend to unravel the rope. It is possible to add
or delete wraps on rappel, but it is difficult to do so and I
do not recommend attempting it. Like most wrap devices, the Hobbs
Hook in the wrap configuration introduces considerable spin on
free drops. The rappel can be tied off by passing a bight of the
trailing line through the rectangular hole and over the lower
horn.
The
brake bar configuration avoids the spin of the wrap configuration,
but requires an additional piece of equipment. The tall side of
the brake bar should be on the open side of the device so that
it spans the opening. Friction can be enhanced by passing a bight
through the rectangular hole, clipping a spare carabiner through
the bight, and arranging the carabiner as a second brake bar.
The brake bar arrangement can not be locked off in the same manner
as the wrap configuration because the brake bar spans the opening.
I've found that the device can be locked off by looping the trailing
line over the top of the device; however, this method is not as
secure as the lock-off used for the wrap. An alternate is to pass
a bight through the rectangular hole and tie it off in any of
a number of ways. This method can be secure, but is invariably
cumbersome.
The
double rope configuration has less spin than the wrap configuration,
yet does not require the brake bar. Note that the bight is placed
around the long side of the frame rather than the short horn.
This increases security and leaves the short horn available for
tying off.
There are many variations to the three configurations recommended by the manufacturer, none of which seem to offer any substantial advantages.
The Hobbs hook is well made. There are no sharp edges and all edges are well-rounded, except for the beveled attachment hole. The pin is long enough that there does not seem to be any tendency for it to back out, even if it is not turned to allow the balls to engage properly. In any case, the pin does not support any load, nor does it touch the rope. The pin is almost optional in the wrap and brake bar configurations, except when negotiation the pit lip. The wear monitor points are located in a position where the rope does not usually run over them, so they do not function as well as they could. They also seem to be to deep for my taste, and I would retire a Hobbs Hook long before the wear marks indicated that I needed to.
The manufacturer warns the user not to use the device with polypropylene rope or other ropes having a low melting point. Bry-Dan recommends 11 mm. to 16 mm. nylon rope, but notes that the device will work with 6.4 to 19 mm. rope.
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©2007, Gary D. Storrick