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Now it is time to start cutting the buttresses
for the axle supports. To make things simple I used all 30
and 60 degree angles. This kept the buttress beams shorter
without sacrificing their ability to add lateral support. |
Here are the buttresses for one of the
supports. Three more and they will be all done. These were
all made from 8' long 2"x6" beams. All I did was
cut angles into each end of the beam. This saves the extra
cutting of shortening the beams. |
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Next it was time to cut the holes in the main supports for
the axle to sit. The main supports were the only pieces that
I used other than a 2"x6". I used 2"x10"x10'
for these since they will be supporting the entire load and
all of the forces of the swinging bucket and beam. I have
both pieces clamped together so that I can make sure that
the holes are in the same place on both pieces |
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Now that one hole is finished I can test fit a bushing.
Looks like a perfect fit. |
You may be asking what I am doing here
(Gee Buzz, what are you doing there?) Glad you asked, I
am adding a 2"x6" perpendicular to the 2"x10"
to add to the crossectional area. This will act like an
I-Beam and give the supports the same amount of rigidity
as a beam that is 10"x7"! There is another reason
which will soon become clear. |
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And here we have it. This piece has been glued and screwed
and I could stand in the middle of it and not get any deflection.
Now, let's put it up on the base and see what it looks like... |
Wow! Look at how tall that thing is!
It is strange how things don't look very big when laying
down on the ground but when you stand them up on end they
are enormous! The two CO2 tanks are sitting on opposite
corners because the base is a little warped due to crappy
choice of wood (which later was changed) and due to the
fact that I had not one single level surface to build upon. |
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This is how the two buttresses that run inline with the
base were supposed to go. Unfortunately, I forgot about the
I-Beam configuration on the other side. If this trebuchet
were not meant to be disassembled then it would not a big
deal. |
There we go, a little change to the cut
angle and problem solved. |
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Here is the other reason for the little I-Beam thing
on the main support. Because this whole trebuchet needs
to be able to be broken down I need a way to be able to
remove the side buttresses while still have it structurally
sound when in place. Each buttress is held in place with
a 1/2" bolt with fender washers at each end. The fender
washers distribute the load of the head of the bolt and
the nut from crushing into the wood when tightened to 50
foot pounds. So, the entire support structure is held in
place with only 14 bolts (7 per side, one for the support,
and two for each buttress).
One the lever arm and bucket are removed the rest of the
trebuchet can be broken down in 10 minutes! |
Here is one of the supports standing
on its own. |
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