I acquired my Thrun, Version A in 2017 as part of Bob Thrun’s collection.
The Thrun, Version A is 63 mm. tall, 26 mm. wide, 6 mm. thick, and weighs 30 g.
Bob Thrun invented this ascender while researching semi-mechanical ascenders for his book Prusiking. In effect, he saw what others had done and realized that creating semi-mechanical ascender designs was almost too easy. He mentioned this one, which is arguably the simplest way to make a semi-mechanical version of the Prusik knot. I once asked him if he had ever made one, and he replied that he had. I found this in his collection, so I assume that this is the original Thrun Ascender.
The center hole reduces the ascender’s weight.
I made my Thrun, Version B in 2005.
Version B is 51 mm. tall, 20 mm. wide, 3 mm. thick, and weighs 6 g.
I made this Thrun Ascender from some hardware store aluminum. I based the dimensions on a Prusik knot tied with the accessory cord shown in the photo. Strength is not an issue - if it bends, it bends; if it breaks, I've still got a Prusik knot on rope.
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