I started making my Bat Climber about two decades ago, but did not finish it until 2004.
Jack Speece described the Bat Climber
in 1968 (Shippensburg Grotto Newsletter, v. 3, 3),
and Bob Thrun devoted a few sentences to them in his book Prusiking.
I eye-balled my Version from the drawing in Bob's book, but instead
of putting a straight toothed cam surface, I used a smooth circular
one - for no other reason than I haven't gotten around to milling
teeth. Jack & Bob note that the Bat climber has no advantage
over a single-cam climber like the later Gibbs.
Mine, frankly, is a lemon, but part of the reason is the cam angle
that I used. Since the two cams rotate independently, the original
Bat Climbers had a safety pin on each side to keep one cam from
closing before the other. I didn't put a safety catch on mine,
and it is practically impossible to get the cams to close simultaneously.
Interestingly, this is why mine actually hold - the sharp nose
at the bottom of the first cam to close digs into the rope, providing
enough friction to get the ascender to hod. Maybe if I sharpen
this nose, it will cut the rope in two, and you won't have to
put up with any more of my bad jokes.
At some time I might make a more faithful copy of the original to see how it works, but until then, I'll leave this one in the collection box.