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I acquired this descender from Repetto Sport in Genova, Italy in 1982.
The Tracson incorporates features of both an eccentric cam ascender and a bobbin. The device consists of a number of parts mounted on a roughly trapezoidal 3.9 mm. thick red anodized aluminum back plate. A 15 mm. hole is drilled in the lower left corner of the back plate, then the corner is bent inwards at a 90° angle. This hole is the main attachment point. The upper left corner is also bent in slightly to serve as a rope guide for the upper bollard. A second 15 mm. attachment hole is cut in the upper right, then the right side of the plate is bent around 180° to form a channel for mounting a cam.
The upper bollard and an irregular shaped rope guide is attached near the upper left corner of the back plate with a 8 mm. bolt, nut, and washer. A 5 mm. steel pin through the back plate keeps the bollard from rotating and a second pin keeps the rope guide from turning.
Below this is the lower bollard assembly. A 9.5 mm. bolt and shoulder nut secure the bollard and a pivoting cover plate assembly, as well as a flat steel spring in the outside of the back plate A 5 mm. steel pin through the back plate keeps the bollard from rotating. The cover plate is an irregular hexagonal 3 mm. aluminum plate which keeps the rope from slipping off the lower bollard. It has a spring loaded latch which engages a post riveted to the back plate below the lower bollard. Also present on the cover plate are an 8 mm. pin provided as a finger grip and a very small pin with no obvious function.
The cam assembly consists of a steel cam, cam spring, and cam pivot. The cam is very similar to a Jumar cam, with a (3)(4.3)6 conical tooth pattern. The tooth axes are perpendicular to the cam face. Above the cam is the cam actuator, a two piece cog pinned to its own pivot. On the outside of the back plate a lever is pinned to this pivot, so it actuates the cog. A spring keeps the lever in the raised position, where it does not interact with the cam. A third pin through the back plate channel prevents cog over-rotation. The lever can be rotated downwards, thus opening the cam. An Allen setscrew in the lever handle can engage a hole in the flat spring, thus locking the cam open. A piece of foam is placed between the flat spring and the back plate, but its function is not immediately apparent. The cam itself acts against the rope, with the lower bollard acting as the anvil. The lower bollard has a flat area machined into the rope travel surface to improve its performance in this function.
The Tracson bears no markings other than a sticker giving the name of the device and some information on the manufacturer.
Denis Motte invented the Tracon and applied for a patent in April 1978. He received French Patent #2,422,587 the following year.
This device is an attempt to make an ascender and descender out of one piece of equipment, and the result is needlessly complicated. I count no less than 37 parts to this device, and I may have missed a few. The idea of a combination ascender-descender is appealing, but since the functional requirements for the two types of device are so different, attempts to devise a combined apparatus have been mostly unsuccessful. The Tracson is designed to be used as a bobbin and as a chest ascender in the Frog system. It fails to achieve an advantage over, say, a Petzl Stop bobbin and a Petzl Croll ascender used in the same manner.
When I first tested the device, I found that the rappel characteristics were much like other bobbins. Fearing rope damage from the sudden closure of the toothed cam, I stopped before engaging the autostop feature. When I tried to disengage the cam under load by using the lever, the lever pivot bent and the lever would no longer engage the hole in the flat spring. The applied force did not seem excessive, but damage resulted anyhow. I managed to repair the device, then I tried using it as an ascender and the cam pivot bent again. At the 1989 N.S.S. Convention, Alex Sproul told me that when he tried his Tracson, he experienced the same failures I did with mine. Either we both have lemons or the material in the cam pivot is inadequate. I no longer use the Tracson for fear of destroying my collection’s copy.
Although I find this device fascinating, I cannot recommend it for caving use.
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[ Top | Version B | Return to Bobbins ]
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| Front View | Rear View |
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| Front View: Open for Rigging | Rear View: Open for Rigging |
I acquired my S.A.R.L. Voynett Tracson, Version B in 2017 as part of Bob Thrun’s collection.
My S.A.R.L. Voynett Tracson, Version B is 192 mm. tall, 107 mm. wide, 50 mm. thick, and weighs 589 g.
The pivoting cover plate on this version is anodized.
The Version B handle casting has some small differences where it connects to the cam actuator. The end of the actuator now has two flats, and the handle casting hole is pressed onto the actuator. The pin connection has been eliminated.
The Tracson bears no markings other than a sticker giving the name of the device and some information on the manufacturer.
Because of the problems that I had with Version A and Alex Sproul had with his, I decided not to test the new design to see if the changes to the cam actuator and handle work any better than they did for Version A.
The Tracson was originally intended for climbing the masts of sailboats.
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