Trebuchet of the large variety (a work in progress), 4.28.07 update

Step 4 Main support: design and construction

What I call the "main support" is the vertical piece that goes in the center of the base; it will hold the treb's axle. Each of the two supports is designed to break down into three components. When the pieces are bolted together, the main support is about 15' 6" tall. Cool.

I needed 18 8' 2x6's for these; you can get fewer boards if you buy 10' lumber but the costs were actually about the same and using 8' pieces gives a lot more scrap (useful later). Here's the cutlist for both of the main supports:

(cut this many 8' 2x6's) at (into these measured parts for each 8' 2x6)
2 at 4', 2' 5 1/2" (thus cut one 8' piece into 4' and 2' 5 1/2" pieces and then repeat with the other 8' piece)
2 at 4', 2'
2 at 4'
2 at 5' 4"
4 at 6' 8"
4 at 4' 4"
2 at 6' 1 1/2"

The SketchUp file will be most helpful in construction--the same techniques that were employed in the base construction were used here (16" overlaps, nails, glue, music). Once your pieces are made, align them and drill holes for the bolts to come.

I actually held off assembling the very top pieces (blue) of the main support. The axle will pass through this part and I wasn't sure of how to drill the axle hole such that the axle is level. This'll be posted in the questions section and mulled over. A response and my course of action will eventually go here.

As stated earlier, save your scrap! There's going to be a lot of extra wood and future pieces of the trebuchet will make good use of them.