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I acquired this descender from SAR in March, 2006 when it first became available.
The front and rear plates and the handle plate are stamped from 4.2 mm. aluminum, cut and formed to shape, and anodized. The top portion of the plates are 20 mm. apart, but the lower portions bend until they nearly touch, which they may under load. The rear plate has 14.5 mm. wide by 29.5 mm. high irregular eye. 12.5 mm diameter pin fixed near the top of the rear side plate, and forms the axle for the pivoting side plate. A second, 11.5 mm. pin attached to the rear plate (34 mm. below the first pin) supports the control lever and the lower bollard. The pins are pressed into conical bushings on the outsides of the plates, then planished to secure them in recesses cut into the bushings.
The pivoting side plate has a spring-loaded, stamped, steel gate that allows one to rig the bobbin without unclipping from the seat harness.
The lower bollard is a 44.2 mm. diameter, 15 mm. thick aluminum disk with a 27 mm. long flat surface on the bottom and a 2 mm. deep U-shaped groove around the remainder of its perimeter. It pivots on the lower pin, with the pivot axis offset 12.5 mm. from the disc's center. The handle pivots on the same post as the lower bollard, fitting between the bollard and the rear plate. The handle portion is covered with a plastic grip for comfort. Friction from the main rope's passage tends to turn the lower bollard towards the upper pin, but a pin in the rear of the bollard engages a slot in the handle, limiting the bollards travel. The upper end of the handle plate has an 11 mm. diameter, 14.7 mm. long post pressed into it. Serrations on the pressed section keep the post from rotating. With the handle in the lowest position, the gap between the post and the upper bollard is 7.2 mm.
The front of the device is screened with "SCARAB", the SAR logo, "Ø 10,5-12,5", a small circle with a dot inside, an icon consisting of book with the letter ""i," "prEN12841-C", "CE-0120," a diagram showing how to rig the SCARAB, and "ID No 05-0064" (which is the serial number).
Normally, the load on the rope would cause the bollard to lift the lever until the blower bollard pinches the rope against the upper bollard, thus locking the rope and ideally arresting the descent. The rappeller uses the handle to keep the autostop feature disengaged. If the rappeller squeezes the lever too far, the post on the handle moves to squeeze the rope against the upper pin, slowing or stopping the descent. I found that it took a good grip to move the handle enough to allow my descent. This could become tiring on long drops. I had a similar observation for the Single Rope Technique Stop Bobbins, and the cause was the same in both cases: squeezing the handle actually lifts the user. Of the two, the Scarab was more comfortable.
The
upper extension on the control arm provides a convenient place
to hang bights for locking off, as the pictures at right show.
The stamped gate is well-made, but I would like to see a more pronounced outward bend so that my thumb wouldn't slide off it so easily when I try to open it.
The book icon makes sense, apparently SAR doesn't think that
reading is dangerous and
chose a more sensible icon than some others have.
A small projection on the rear side of the handle looked like an appropriate point for another one of the conical bushings. I suspected that this was the design intent but mine somehow missed getting one during manufacture. I wrote to Dave Allport, and he confirmed my suspicion. Here are relevant excerpts from his note:
Thanks for the photo and I think I know what's happened and can not understand how it got through the inspection/packing. It looks as though it has not been riveted over and into the chamfered recess in the washer.
The shaft is slightly knurled to grip the sides of the hole then riveted over the washer. If you wish to do the riveting there would be no problem as all that needs doing is to place the brake bobbin onto a flat metal surface with the rivet facing up and then planish around the edge of the rivet with a flat faced hammer to form a slight dome so it fills the chamfered dish in the rivet. On the other hand if you don't feel you can or should do this I have no problems in sending you another.
It seems this was a "one time only" oversight so
I wouldn't hold it against the Scarab.
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Before fix |
Normal Scarab |
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I acquired this descender from SAR in January, 2007. Dave Allport gave me this one as a replacement for Version A. This particular Scarab was manufactured in November, 2006.
Version B is essentially identical to Version A. I found the following differences.
It was very nice of Dave to send me a replacement Scarab, and I thank him for it. He also included a few washers so that I could use one to repair my original one.
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©2007, Gary D. Storrick
