Sad part is we broke the thing the night we were setting up.
Does not help the throwing arm was put on backwards. The main part of the arm split right down the middle. This was a precursor to what was to following.
So in the morning we fix things and had it up and running. Worked great for the first 10-20 flings. Not much distance on our water balloon but it did work and people were having fun. Then disaster struck.
We broker the trebuchet again. Almost identical break to the prior time. A split right down the middle of the main part of the throwing arm. The shorter stabilizers in the front were not effected.
In the end it looks like the bolts used to hold things together were the real culprits. Each of them was causing alternating forces on the main part of the arm. Even though this was not all that big the arm had enough mass to cause a lot of force. Thus the first bolt was working to keep it from going forward. The other bolt was working with the forces caused by the front section and heading in the other direction. Thus the ultimate result of the 2x4 splitting.
I'm not so sure that multiple bolts on each side would solve the problem. You might stave off the issues but your still dealing with a lot of torque and forces being applied. I also ran into signs of cracking/splitting in one of the corners of the base.
That I guess is the risk of thinning a 1 1/2 inch board down to 3/4 inch. Just shows how much force is applied even by a young kid.
One person suggested in the future to have some type of metal band around this questionable section. This would hold the wood together but ultimately does not solve the issue of the split.
It looks like most regular trebuchets have one solid piece for the throwing arm. Since we want this to be rather portable and have it fit in the trunk of a car like the Ford Focus it is kind of hard to go this route.
Some even suggested have the main part of the arm extend all the way to the front. Not sure on this as well.
What is interesting to note is the fact that most of the regular trebuchet designs all work around one axle with next to no support.
But, how do you make this work so that two persons have to jointly pull down on the bar that is acting like the counter weight. Since there is a good ratio on the height of the axle, to the lengths of the parts of the throwing arm, etc it's make it hard to have anything that works for smaller kids.
So maybe in the end you have to have some kind of adjustable arm or attachment to the arm so accommodate smaller/shorter people.
I did find a good version with full instructions on the web for a trebuchet that flings tennis balls and the like. It's smaller and does not appear to have anything over 60 inches long.
It is worth taking a look at.
Ripcords Tennis Ball Trebuchet
Buaidh - NO - Bas
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