Trebuchet progress

[johnridley]

More than half done I'd say. The frame is complete, except I was short a 2x6. The throwing arm is done, other than trimming the release end.
Still to do:
Buy/make U bolts to hold the axle onto the top beam.
Cut the center out of the main beam (leaving just the axle)
Build the weight box
Figure out position of winch and pulleys and mount them.
Build the release mechanism, and mount hooks for safety restraint ropes
Get some rope and make the sling (this may wait until we're on site).
Get some more bowling balls.

It occurs to me that after firing, the top of the arm is going to be 16 feet off the ground, and we'll have to get a cable on it to pull it down. L says just use a long stick to loop the cable over the end. That will probably work fine; a 12 foot stick in someone's hand should be tall enough.

I've received word that the local bowling alley has literally "a barn full" of old bowling balls, and we can probably get as many as we want.

Comments

[madtechie2718.livejournal.com]

Hey, John - since you are 'The Man' with respect to woodworking.....

I've just been watching Terry's DVD of last year - the hybrid lox/wood engine might just fly, with a little luck.

Since I can't bring (without some very tedious airport explanations...) stuff across, do you have the kit to bring along a couple of offcuts of timber - maybe 2 or 3 inches square, a 12 to 15 inches long with a 0.5 to 1.0 inch hole drilled lengthwise?

I think I have devised a way to make such a beast actually fly...

[johnridley.livejournal.com]

Sure, though I'll probably have to hand-laminate 2x4s to get that. Anything over 1.5 inches thick, the only way I've seen generally available is in deck timbers (4x4, 4x6, etc) and those are always treated. The treatment probably is at least somewhat fire-retardant, and even if not, probably not a great thing to breathe after burning. There's a general caution to NOT burn the stuff. In general that's because burning will leave a pile of toxic ash, but I'm pretty sure you'd have toxic fumes as well.

Anyway, I have a raft of short 2x4 pieces. I used up pretty much all my wood glue laminating this throwing arm, I'll go get some more tomorrow. I think glued-together 2x4s should be good. It would be easy for me to gouge a groove down the middle of them as well so that there would be a hole down the middle of the finished piece. What diameter hole do you want, assuming the piece of wood will be 3" x 3.5" outside? 1/2"?

[madtechie2718.livejournal.com]

Let's try for one of 0.5" and the other at 1.0" hole.

I can think of reasons why each size is both good and bad - justification for experimentation....

But whatever happens, it should be fun!

We are arriving sometime after noon on Wednesday, so should have time to build the seesaw launching mechanism.