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Drum
(#1268)

 

Front View Rear View
Front View Rear View
 
Side View Open for Rigging
Side View Open for Rigging

Technical Details

I acquired my Drum from Julian Turner in 2010.

My Drum is 157 mm. tall, 106 mm. wide, 72 mm. thick, and weighs 699 g.

The drum consists of two 6.4 mm. aluminum plates, a bronze drum, a guide arm assembly, and some miscellaneous parts. A 5/16 inch (8 mm.) bolt holds the plates and drum together.

The plates have different shapes. The front plate has a canted, 45 mm. radius, semicircular arc at the top and a 73 mm. by 30 mm. lower extension. There are seven 12 mm. holes spaced around the edge of the arc, but these serve no functions other than cosmetic and lightening the device. Inside the arc of large holes are two smaller holes. The right-hand hole holds a 6.4 mm. steel pin that fits into a corresponding hole in the drum. This keeps the drum from rotating with respect to the front plate. The left-hand hole is empty. There is a corresponding hole in the drum, but the two holes do not align. The lower portion of the front plate has two bends to allow contact with corresponding arms on the rear plate. There is a 14.3 mm. hole for attachment near the distal end of the arm. A triangular block attached (with two countersunk screws) to the inside of the arm acts as another rope guide.

The rear plate has a canted, 45 mm. radius, 270° arc at the top and a 73 mm. by 30 mm. lower extension. There are nine 12 mm. holes spaced around the edge of the arc, but six of these serve no functions other than cosmetic and lightening the device. The remaining three holes have bronze bushings with 8 mm. holes in them. The pin on the guide arm engages these holes. The lower portion of the front plate has two bends to allow contact with corresponding arms on the front plate. There is a 14.3 mm. hole for attachment near the distal end of the arm.

The spool is a single piece of 58 mm. diameter, 26 mm. long bronze. There is a bronze rope guide brazed to the top, near the rear, that extends from the top to the 2 o’clock position. There is a 12 mm. high, 9 mm. diameter steel guide pin inserted near the front at the 10 o’clock position.

An 85 mm. long, 22 mm. wide, 6.4 mm. thick guide arm sits in front of the front plate. This arm pivots on the central bolt, and a knurled knob screws into the arm. A smooth extension on the knob assembly engages one of the three bushing holes, keeping the arm fixed on descent. The three hole provide three friction options. The distal end of the arm holds a stainless steel rope guide assembly made from a short length of 16 mm. bar welded to a bent 3.2 mm. plate. A countersunk Allen cap screw holds this assembly to the plate.

There are no markings on this device.

Comments

I was bidding on some other items on eBay, when the seller, Julian Turner, asked if I was interested in this device. In his words,

I was a member of a Caving Group in my home town of Plymouth years ago when we pioneered what we now call SRT single rope technique down mine shafts. SRT first started with Jumars in the USA but we developed a descender of which there is only one in the world I know because I drew the plans for it and my friend made it. I have used it a few times on long drops and it is the smoothest descent and heats up least on the descent. The ’’Drum’’ as I called it is made of 2 alloy sides with an adjustable arm for rates of descent and the drum being made from phosphor bronze with directional mouldings. I will email you the photos of this unique device. We did trial a wood descender for use on wire ropes but it jumped too much on the descents and we chickened out! If you are interested let me know.

Naturally, I was interested, and we worked out a mutually agreeable deal.

The drum has some relatively complex machining for a homemade device, but the design is clever and the end product compact.

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