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In December 2006, Ken Kramer delivered a second Motorized Ascending Device. James Wells made this M.A.D. using blueprints obtained from Nevin Davis in the early 1970s. James donated the MAD to my collection via other cavers, and it took a while for it to arrive at my house, passing from one caver to another over many months. Until it arrived, I did not know that a second M.A.D. existed.
When
Ken and I opened the box containing Wells' M.A.D., we noticed
that it was not complete. Most of the work had been finished,
but the throttle assembly had not been attached. Nevin's original
MAD had a motor-cycle grip throttle, but he later replaced it
with a smaller and lighter handgrip. James had parts for a grip
throttle, so I decided to use them to complete his M.A.D. I used
my lathe to make a mounting post to attach a motorcycle grip throttle
and a kill switch to the right side of the M.A.D. I also milled
a bracket for attaching the other end of the throttle cable to
the engine. You can see this bracket just above the yellow fuel
cap in the photo.
Ken and I found a broken gear in the parts that came with this
M.A.D., and also found a box and receipt for a replacement part.
We assume that James had started the engine on his M.A.D., and
that it had failed. For this reason, I have not tried to restart
the engine.
This M.A.D. is 315 mm. tall, 455 mm. wide, 285 mm. thick, and weighs 10800 g. Since this MAD followed Nevin's blueprints, there are many similarities, but some differences as well. I decided to describe Wells' M.A.D. using photographs of the two versions sitting side by side.
The rear view shows what the user sees. The most apparent difference is the motorcycle handgrip sticking out from the right side of Wells' M.A.D. James included a copy of Nevin's blueprint for the M.A.D., as well as a number of photographs. Some of these showed the original motorcycle grip design, which differed from my design completion in several ways. Nevin's original design had a second handlebar sticking out on the left, but I did not include this when I finished Wells' ascender.
Here we see the right side of the two ascenders. As you can see, Nevin removed some excess material from the cover plate to lighten the ascender. James' version is about 400 g heavier than Nevin's, part of which is due to using a different engine and a larger fuel tank. Such a small weight difference is not important. Another difference is that Nevin put bushings on his cover plate to help support the two gear shaft bearings. I did not bother adding these when I completed the Wells M.A.D.
The large hole on the right side of Nevin's ascender is where he located his handlebars.
Here are the two ascenders with the cover plates removed. Wells' still has Dykem from the layout process; I haven't taken time to remove it. As expected, the internal working of the two are similar.
This shows the front view of the two ascenders. (The views are not quite equivalent because James' M.A.D. has a larger, rectangular gas tank that holds his M.A.D. in a more upright position than Nevin's). From this angle, you can see why I chose not to add a left-hand handlebar to Wells' M.A.D. - sitting in front of the engine, it would have had to stick out very far to the side.
James and Nevin used different brand engines, but they are both small, integral clutch models. James' uses a much larger fuel tank than Nevin's. When comparing the photos, remember that the rectangular gas tank holds James' M.A.D. in a more upright position than Nevin's.
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