If
the bobbin is not properly closed, the bobbin can open and let
the rope escape, resulting in an air rappel. I lost a long-time
caving friend recently because of this. He was exceptionally skilled
but one small oversight proved fatal.
Look at the illustration and note that the seat carabiner can press against the safety gate - this makes me nervous as well. None of the safety gates are particularly strong. Since bobbins are popular among the rebelay crowd, there are many opportunities to overlook whether the side plate is closed, whether the safety is engaged, and whether the carabiner is resting against then gate or not.
Finally, be sure to use the safety carabiner on the trailing line. Many people fail to do so.
Be careful to ensure that the bobbin is closed with the safety catch engaged before trusting your weight to the device.
[ Top | version B | Version C | version D | Version E | Return to Bobbins ]
I acquired this descender from Speleoshoppe in 1979.
The two side plates are made of 32 by 3.3 mm. aluminum. The upper end of each side plate is bent inwards in a quarter circle so that when the bobbin is in use the side plates keep the rope on the top bollard. The lower ends of the side plates are bent to converge at the attachment point, which consists of a 14 mm. beveled hole in each side plate. One side plate pivots to allow threading the rope. The bollards are turned aluminum with a milled slot to keep them from rotating on the fixed side plate. The bollards are drilled and tapped then bolted to the fixed side plate with 7 mm. A2 bolts. Shoulder nuts lock the bollards in place and also retain the pivoting side plate. The pivoting side plate pivots on the lower shoulder nut and has a slot to allow clearing the upper nut. 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 side plate.
The pivoting side plate 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 marked "THIEL" and "A2".
The attachment point on the pivoting side plate is beveled on the inside, rather than the outside. This is an obvious oversight in manufacturing, since the beveling serves no purpose there. Otherwise, the bobbin is fairly well made. The threaded bollards provide a much stronger mounting than if they had been just bolted on through a cylindrical hole with bolt and nut. Since only about one half of each bollard is exposed to the rope, the bollards wear unevenly. Most bobbins are designed to allow reversing the bollards, effectively doubling the life of the descender. The lower bollard is symmetrical and requires no modification to allow reversing. The upper bollard could have been left asymmetrical, but Petzl provided a second threaded mounting hole to allow reversing the upper bollard.
This is the simplest bobbin in my collection, and although
I don't use it as often as others, it probably is also the best
for those who prefer simplicity. There is really nothing extra
on this bobbin, and also very little to fail. Even if the user
were foolish enough to rig in backwards, the closed attachment
hole on the pivoting side plate would almost certainly prevent
the bobbin from opening. After doing the research for this article,
I'm tempted to make this my primary bobbin in the future (except
for rebelay pitches) - assuming I ever use a bobbin again.
[ Top | version A | Version C | version D | Version E | Return to Bobbins ]
I acquired this descender from Speleoshoppe in 1979 at the same time as Version A.
It differs from Version A by having a quick-attachment feature. The attachment point on the fixed side plate is enlarged to a 23 mm. high by 13 mm. wide hole located 3 mm. off center. A similar hole on the pivoting side plate has been cut open on the narrow side, so the side plate resembles a hook. The opening of the hook is covered by a spring loaded, stamped steel, sheet metal guard which is roll riveted to the side plate.
The markings are identical to Version A's.
The quick attach feature allows the user to keep the descender
attached to the seat maillon while rigging into or derigging from
the main line. This is a nice feature, but usually I find that
the limited clearances provided may the task more hassle than
it is worth. In addition, the guard tends to get fouled with mud,
thus defeating the closing action of the safety spring. Corrosion
is also a problem, which is why mine won't function. The roll
rivet is installed incorrectly, with the relatively smooth rivet
head on the outside and the sharp, poorly formed roll crimp on
the inside next to the rope path. Furthermore, the attachment
point is not beveled. In general, I find the idea of a quick attach
feature very desirable, but the execution of the idea could be
substantially improved on both this descender and many others.
[ Top | version A | Version B | version D | Version E | Return to Bobbins ]
I obtained this descender from J. E. Weinel Inc. around 1987.
The major difference between this and the preceding design is the inclusion of a third auxiliary rod and modification of the side plates to accommodate the third rod . A reduced diameter end of the steel rod passes through the upper end of the fixed side plate. A steel washer is then placed over the outside end of the rod and the end formed into a round rivet head. The opposite end of the rod has a flange to engage the pivoting side plate. The side plates are cut out of 3 mm. aluminum and red anodized. The upper end of the side plates are offset to place the auxiliary bollard closer to the "up" side of the main rope. The pivoting side plate is notched to clear the auxiliary bollard as well as the upper main bollard nut. The pivoting side plate has a quick attack feature similar to Version B's. None of the attachment points are beveled.
The pivoting side plate is stamped with an illustration of how to rig the bobbin, the Petzl logo, and "FRANCE." The bollard bolt heads are marked with"A2."
The auxiliary bollard works very well for keeping the rope
on the upper main bollard without binding, but is less satisfactory
when used as part of the braking system. The rod is too small
to function well as a third braking surface, has no means to insure
that the rope stays on the rod reliably, and is located where
it forces the rope into an inconvenient position. This last point
is particularly noticeable if the trailing rope passes through
a maillon clipped to the seat maillon as indicated in the Petzl
instructions and required for safety. In this case it requires
too many contortions to switch from the two bollard mode to the
three bollard mode.
[ Top | version A | Version B | version C | Version E | Return to Bobbins ]
I acquired this descender in 1990.
This bobbin is almost identical to Version D, except for two changes. The first and significant change is that the fixed side plate is stamped to provide two reinforcing ribs on the lower portion. The second, of no real importance, is that the rivet holding the gate is installed with the head on the inner side of the side plate.
The pivoting side plate is stamped with an illustration of how to rig the bobbin, the Petzl logo, and "FRANCE." The bollard bolt heads are marked with "IN-IV" and "A2-70."
The reinforcing should add some rigidity. I would have extended it further, not because doing so was necessary, but because it could be advantageous and could be done for essentially no cost.
[ Top | version A | Version B | version C | Version D | Return to Bobbins ]
I acquired this descender from Inner Mountain Outfitters in 2006.
Version E differs from Version D in the clip-in area of the front plate. The lower portion of the plate widens to 42 mm. overall and 17.6 mm. at the spine of the attachment hook. The gate is now plastic. It pivots on a steel rivet, and a spring set in a deep slot closes the gate. With the gate closed, the opening is only 15.8 mm. high. The gate has a widened flat spot on the outside that is clearly designed to provide a convenient place for one's thumb to act to open the gate.
The pivoting side plate is stamped with an illustration of how to rig the bobbin, the Petzl logo, and "FRANCE." The fixed plate is also stamped with an illustration of how to rig the bobbin. This diagram is reversed from the one on the pivoting side plate since one is looking from the other side. The fixed plate is also screened with "06031FE9591." The bollard bolt heads are marked with "PETZL" and "A2-80." The Petzl logo is molded into the gate.
Petzl switched to a plastic gate on their on their stop bobbin by 1997, but I didn't see one on a standard bobbin until 2006. I can't think of any reason for the delay other than the time needed to sell the existing inventory of the earlier design. This gate design greatly reduces the risk of having the seat carabiner force the gate open. It also eliminates the corrosion problem that I've had with the metal gates on some of my other Petzl bobbins. Curiously, the hook does not have the reinforcing sound on their stop bobbin, version E.
[ Top | Version A | version B | Version C | version D | Version E ]
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©2007, Gary D. Storrick