I acquired this descender from Rocksport in Somerset, U.K. in 1981.
As in the single rope bobbin Version A, there is a fixed and a pivoting sideplate made of 32 by 3.3 mm. aluminum. The upper end of the fixed sideplate is bent inwards in a quarter circle, while the upper end of the pivoting sideplate is bent into an 11.4 mm. I.D. inverted U-shaped channel. The end of the sideplate is cut so that when closed, approximately 2/3 of the width of the sideplate is in contact with the upper bobbin,. The remainder is cut away to allow clearance for opening the bobbin. When the bobbin is in use the sideplates keep the rope on the top bollard, and the end of the top sideplate keeps the rope from jumping between the two grooves in the top bollard. The lower ends of the sideplates are bent to converge at the attachment point, which consists of a 13 mm. hole in each sideplate. These holes are beveled on both sides. The bollards are turned aluminum with a milled slot to keep them from rotating on the fixed sideplate. The lower bollard has a single wide rope groove, while the upper bollard has independent grooves for the two ropes. The bollards are bolted to the fixed sideplate with 7 mm. A2 bolts. The pivoting sideplate pivots on the lower bolt and has a slot to allow clearing the upper hole. The lower U-groove bollard is mounted through a hole in its center, but the upper V-groove bollard uses an off-centered arrangement to allow a smaller clearance slot in the upper sideplate.
The pivoting sideplate is stamped "PETZL", and "FRANCE". The bolt heads are marked "UV" and "A2".
This bobbin is substantially larger than its single rope equivalent,
and so one may be inclined to choose the smaller version on
weight considerations alone. The disadvantage of this choice is
that single rope bobbins effectively can not be used on double
rope rappels, and hence can not be relied on when conditions are
not known with absolute certainty in advance. My experience suggests
that one will eventually encounter situations where a double rope
rappel is needed. Single rope bobbin users will not be able to
deal with these situations unless they have a second rappel device
available. This is a strong argument against using bobbins as
opposed to other devices. Double rope bobbins do not have this
disadvantage, and can be used on single ropes as well.
I obtained this descender at the same time as Version A.
This Version Differs from Version A in two ways. First, it has a quick-attachment feature similar to that on the single rope Petzl bobbin Version B. Second, the lower bollard has a U-groove for each rope rather than a large common one. The bolts are about 1 mm. too short to completely extend through the nuts.
The pivoting sideplate is stamped with an icon illustrating how the descender is threaded, but anyone who needs this assistance shouldn't be using a bobbin anyhow. It is also stamped "PETZL", "MAXI 1500 KG", and "FRANCE". The bolt heads are unmarked.
All of the comments on the single rope Version B quick
attachment feature apply here as well. The lower bollard design
is substantially different than that of double rope Version A,
but I find very little difference in the performance characteristics
of the two, since they are both too fast for my taste. Lighter
cavers might notice a difference. When a double rope bobbin is
rigged for extra friction during a single rope rappel, the two
groove design has the advantage of keeping the rope paths separated
on the lower bollard, where the directions of rope motion may
be opposite.
[ Top | Version A | version B ]
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©2007, Gary D. Storrick