@mreynolds … I can think of other people who would be more likely to be voted “first choice to be launched” (you know, sort of like … voted off the island …)
1 Like
No one will even notice
This was after wasted entire day welding 50 pounds of bracing trying to fix gap clearance problem, only to make things worse
2 Likes
@John_Marlow Could you make a v2 with the only difference being increased distance between the cross pieces, 3 3/8" centers would be good
The current one appears to be on about 2 1/2" centers
Every other dimension looks great, the current one doesn’t let a ~7" diameter watermelon sit all the way in the pouch
We tested with both the 1.5" webbing and your 2" webbing sling, the 1.5" sling failed by ripping when we attempted 400 pounds of counterweight, the new sling could have worked but the ubolts holding the wire failed causing it to release early
2 Likes
We have a fully operational trebuchet, test fired it 3 times discovering that we need a much longer sling rope (meaning trough will have to extend between uprights). Mechanically everything worked great. The first fire with 300 pounds of weight didn’t release late enough, causing a high angle (similar to previous test)
Second test with 500 pounds of weight tore the sling, causing it to release really early. The third test the u bolts on sling cable came loose causing an ~85 degree release angle.
We will meet this saturday at noon to do final tweeks and pack everything up, next tests will be at sunday competition site during morning setup time.
Things to do on saturday:
- Switch to crimped on ferrules instead of U bolts to fasten sling cable
- Increase length of sling and trough (Make a few different lengths to swap out)
- Replace winch with next higher size (I made a mistake buying smallest one with only dynamic braking, I dont think it would be safe to attempt full lift with it, anyone want to buy a barely used 2000 pound atv winch?)
- Make some kind of net to catch sling end after release so it doesn’t flail around and get caught in arm as it rolls back
- Make and paint the signs that will go on outside of weights
3 Likes
You might be able just to shorten the cable on the winch to get you more pulling power. The more you wrap the cable the less it can pull. Unless you want to get another without the dynamic braking.
Will do.
Strange though. I could have sworn it was 3-1/2" when I made it. Gotta check out my building/folding process!
EDIT. Ahhh. Now I see the issue. You’re measuring along the inside of the curve (i.e., closest approach of the webbing). I measured along the outside.
1 Like
Are you saying you need multiple lengths of troughs? I would think that one super-long trough would work. It doesn’t seem that a trough that’s too long is a (functional) problem. But maybe I’m missing something.
I was going to suggest it’s possibly a conversion error between inches and the angstrom units you’re likely using for most of your work 
(totally a joke if not obvious, I love your tiny creations)
4 Likes
Meant to say just multiple lengths of premade sling cable, went back to edit to add that we also need a trough that extends through the uprights, probably about 10 feet long for the trough
1 Like
Save that pouch. I think that if I add another two outboard cross members it should likely hold the watermelon - at least as a spare sling.
1 Like
Have you looked to see if a chain come-a-long to load it? It may be cheaper than a winch.
V2 pouch is complete. I will bring it to DMS Saturday morning.
3 Likes
I have been thinking about how to do this. Do you have a particular plan/design in mind?
I have been watching and rewatching the videos. Obviously the net has to be someplace where the arm doesn’t have to pass through it.
If we put a net on the “legs”, would that work? (Yes, I know this may or may not be drawn on the back legs … I drew it here only for easier visibility. Obviously the net would have to be on the front legs!) A net would have to be a little slack so it absorbs some of the kinetic energy without tearing.
Sorry I have not read the last month worth of messages on here. I saw you guys loading it in the truck Tuesday night but then it was unloaded. Just a test or did something go wrong? I can provide a truck and trailer for game day. Let me know.
1 Like
I ordered a badmiton net, I was thinking of some scrap 2x4s clamped to the legs sticking up, which won’t look good but should work.
Could use bungie cord and hog nose rings to since it at intersections. It’s how they make them for cargo nets.
I have a large piece of “landscape fabric” we can use if you want to cancel the net.
I also have two of these heavy concrete footings. They will securely hold a 4x4. I know we aren’t supposed to stake anything into the field, so this might be an alternative. Do you want to use these?
No thanks, our legs will be stable enough as is (one of most impressive things in recent test video is the base staying absolutely stationary), and base will be sitting on some layers of OSB I will pick up Saturday morning
2 Likes