Trebuchet

[Hayseed_Andrew]

Oh sorry, I though the concrete was for stregnth somewhere.

My bad.

How about the website, or do you have any good ones I should check out, because It's really pissing me off that mine wont fire yet

[paaiyan]

The link was bad.

I know the optimum arm ratio is 4:1 or 5:1

The counterweight:projectile weight ratio is about 100:1

The firing pin needs to be bent forward some, but not too far. If it's bent too far forward it won't fire, it'll just slam into the ground.

[Hayseed_Andrew]

Ya, the friend that I built it with has built ones before, (tabletop ones) and has had great success. The big one is just an enlargement of the small one, except for the weight which is less, so I think that's the problem. I'm still really proud of it though ahaha.

[paaiyan]

Yea we're gonna build this one and take it to the lake. Hopefully we'll get some good range. Probably be firing canteloupes.

[Hayseed_Andrew]

Awesome, post some pictures when you're done

[paaiyan]

That should jsut be a few days. We have to finish this before he leaves, I can't build it and transport it on my own.

[Hayseed_Andrew]

Mine fits exactly into the back of a truck, which was a complete accident.

[paaiyan]

Well I'm building mine so I'll be able to break it down. I'll label the pieces, put the bolts in a bag and assemble it on-site.

[Hayseed_Andrew]

Ya, I got that from earlier. Moving mine's a little difficult, so far we drag it with a tractor (I wouldnt reccomend that to anyone)

[paaiyan]

Hahaha. Yea I'm making mine as portable as possible. The concrete will just be bags, I'm not going to actually mix it. I'll just throw it in the counterweight box and bolt the lid on. That'll also make assenmbly easier, that way I don't have to haul up all 500 pounds at once.

[paaiyan]

Finally went and bought almost all the stuff. I still need to get some plywood, and concrete for the counterweight. I swear, the bolts nuts and washers to hold this thing toghether are more expensive than the wood, what kind of crap is that?

After looking around a bit, and not thinking that any of the 4x4's were going to be good enough for my throwing arm, I got a 12' 4x6 instead. That thing is massive, i have no doubts it could hold half a ton. My axle, however, is a 1 1/2" steel pipe at the moment, I haven't fugured out how much that will hold. The guy at Home Depot said he thought it could hold the 500 pounds I'm going to be using, but I'm not sure if I trust him.

[paaiyan]

Sweetness! I have a co-worker whos getting me 2 1/2" square steel tubing with 1/4" walls I can use as my axle. I'm just gonna drill the hole in my axle and jam the appropriate size pvc in it and that'll do great for an axle even though it's square.

[jimmy101]

Hayseed_Andrew: Don't you have the wheels thing backwards, or wrong?
Wheels are definitely used on swinging weight treb's.
Actually, I believe wheels help both kinds of trebs.

The only type of treb that doesn't benefit from wheels is a modern style that is designed to drop the weight straight down (I don't recall the name). None of the traditional styles are capable of dropping their weights straight down, the wheels help to minimize the amount of front to back movement the weight has on it's downward trajectory. Fixed and swinging counterweight treb's both benefit from wheels.

[chartreusesnot]

F.A.T is the name. Free arm treb i think... As far as I know, wheels are only useful on fixed counterweight trebs, and detract from the performance of swinging counterweight trebs.

[paaiyan]

Free-arm, floating arm. Whatever name you choose to give them. Mine's a hinged weight.And I'm building it so I can always add wheels later. But trust me, structural integrity isn't going to be much of an issue with this thing. Nothing is going to be made with anything smaller then a 4x4.

EDIT: Wheels woudl help a hinged-weight, just maybe not as much as a fixed-weight.