Editor's Note: CR4 would like to thank Bill for contributing
this story and sharing a photograph, schematic, and YouTube video. Thanks,
Bill!
Trebuchet 1: A Simple
Design
Here's the first trebuchet (left), cocked and ready to toss an egg! My brother
(foreground right) and my nephew (foreground left) own a machine shop. This
trebuchet took the three of us an afternoon to build. I got to their shop at 1
PM, and we all left there around 5 PM. We needed this trebuchet for a contest
the next morning.
As you can see, the design is pretty simple. We used a 2 1/2" piece of
PVC pipe (split lengthwise) for the trough, a fiberglass rod for the arm, and
chunks of scrap metal for the counter weight. The axle was made with hardened
dowel-pins stuck in the end of a piece of PVC, complete with Delrin bushings
press-fit into holes in the plywood frame (which I built while the other two
were finishing up jobs for their customers). We all made parts of the rest.
Trebuchet 2: Our First FAT
I've posted a video on YouTube of our first floating arm trebuchet (FAT). It
shows the thing slinging a golf ball (which you can't see more than a glimpse
of). If you watch closely - and enough times - while looking at different parts
of the whole, you can see the principle behind the floating arm treb. Click here to watch the video.
Trebuchet 3: An Improved Floating Arm
Trebuchet
 I just so happen to be in the construction phase of an improved floating arm
trebuchet. The principle behind this device is that the counter weight moves
only vertically as the arm's axis moves along a horizontal rail on wheels. After
going through much analytical geometry, etc., etc., I finally settled on the
design above. The drawing does not show the complexity, but if you use your
imagination, you may get a better idea of why I piddled with this for over a
year before starting to build one.
The improved version I'm working on uses a pair of
elliptical ramps and an escapement mechanism to allow the weight to be dropped
from a much higher position. The lower part of the elliptical ramp flips out of
the way of the wheels which roll down it (actually, there's two wheels and two
ramps, but you only get to see one side from a side view). The purpose for the
ramp is so that the weight can be raised as high as is practical to provide a
smooth transition from vertical motion to horizontal motion of the axis of the
trebuchet arm.
Steve Melito - The Y Files
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Re: Three Trebuchets
