Trebuchet
This is a trebuchet I built. It's actually the second one I built; the first one is 3/4 this size. It is made primarily of pine, since it was what I happened to have on hand. The top brackets of the A-frames are white oak, as is the throwing arm. The axle is made of a 3/4" red oak dowel. I would have used white oak again, because it's both stronger and prettier, but they don't carry white oak dowels most places. As for the dimensions, the base is 14 1/2" x 20". The two A-frames are 26" high overall, with the top brackets being 4" high. All the frame members are 1" thick and 1 1/2" wide. To make these, just get 2x8 or whatever seems most suitable, and rip pieces 1" wide on the tablesaw. The throwing arm is 31 1/2" long overall, the long arm being 24 1/4", and the short arm, measured from the centre point of each pivot, is 5 1/2". The arm tapers from 1 1/4" x 2" at the bottom down to 15/16" x 5/8" at the top. To achieve this taper, there are jigs you can use with a tablesaw, but I don't have one. I simly laid out the lines and used a drawknife for most of it, finishing and taking it down to the lines with a handplane.
The counterweight box is made with a simple frame of 1 1/2" x 1/2" members joined together with 1/4" dowels, then covered over with 1/8" thick strips placed vertically. You can get the idea of how it's put together in the bottom picture.
Pretty much everything on this is done by hand, the exceptions being ripping the frame members on the tablesaw and drilling the dowel holes. NB: when drilling the holes in the throwing arm for the axle and the counterweight box, do so BEFORE tapering the arm. That way it is easier to make sure you drill straight. Use a drill press if you have one. Of course, it's not really necessary to taper the throwing arm, but I think it looks much nicer that way.
Click the thumbnails to see the full images.
Here is a sequence of it firing.It can throw a golf ball about 100 feet. I only got one try throwing the golf ball, though, because I only had one, and 100 feet down from the trebuchet there is a bit of a swamp right now, as the snow melts and the ground is still frozen. Maybe I'le find it in the summer, after it's dried up down there.
This is the firing apparatus. I have pulled the strings aside to give an unobstructed view. I made this out of a couple of 10d nails.
Here is a joint between a crossmember and an A-frame member. It is a half lap joint with a dowel to reinforce it. I think it's probably a bit of overkill, but it looks cool.
And here is what's in the counterweight box. It's about 11 1/2 pounds of stones.
