I have an old driveshaft cover that I found on the road that's about 3 inches in diameter. Pipe not bar. I dunno if I'd use it as the lever arm, But I did think about using it as the outer tubing and finding some big 3 inch barrings to fit the inner tubing into.
1 inch solid bar will be fine if you build it right and get the forces on it in shear. I've had over 500 pounds on my HCW with 1 inch bar. My 10 foot whipper has a 1 inch bar, and drops 400 pounds, and generates way more energy then a HCW. Your beam ratio is too low, and do not use a 4x4 for the arm. A single 2x6, tapered, and built out at the axles will work.
Yeah, i only intend to launch 1lb-ish objects, I’ve been using https://virtualtrebuchet.com for early modeling and getting a rough estimate of distances. I’ll play around with a 5/1 ratio in sketches like you said, i checked out your build and its just about what I intend to make, though, (if all goes to plan) mine is going to be a bit larger and have the fulcrum at 8ft off the ground. I might just be paranoid but i feel like a 2x6 just is too thin, its a whole lotta weight going real fast. Any reason why a 2x6 would be better than a 4x6?
The weight of the arm matters. Lighter is faster. My 15 foot whipper threw a 4 pounder 1300 feet with a single 2x6 arm and 700 pounds of cw. But if you wanna use a 4x6, use one.
Power racks, squat racks, or you can buy just the uprights from companies sometimes. Rogue has a near constant "garage sale" promotion where they'll sell the uprights for their power racks. Otherwise you can look for scratch and dent sales from other companies, or ebay/craigslist/offerup/etc.
I'm thinking of taking an old Bench press rack I have and using it as the base/frame for a trebuchet. it's almost like a metal A frame with 13 gauge steel square tube construction.
Then using an upright as the lever arm. The uprights are usually already predrilled with holes up and down the entire length, so you can adjust it, and you have holes for the counter weight and to attach the sling set up to.
Scrap metal shops will measure and cut any length of round shaft. For 400 lbs on a 1 food width between bearnings, I'd suggest 1.25"
Cheaper, probably, is to use the rear truck axel out of a wrecked truck. If you can get the bearings too. This will keep the axle from jumping about. Bearings are cheap.
I found a used weight lifting bar and cut it to length for my mine
A good old Olympic weight lifting bar with a lot of "whip" would probably work great.
metal pipe
Not pipe use a solid bar 3 in in diameter. Look in scrap yards. May a car axle?
3"is fn crazy. That's Way over kill.
Probably, what would you suggest?
Build the arm out at the axles, and block the tower in some at the axles.
1" is fine in shear
high pressure pipe
I have an old driveshaft cover that I found on the road that's about 3 inches in diameter. Pipe not bar. I dunno if I'd use it as the lever arm, But I did think about using it as the outer tubing and finding some big 3 inch barrings to fit the inner tubing into.
depends on the span and how well it's supported
Span will be probably 2ftish? Arm is 9ft 5 on on end and 2’6 on other, its a 4x6 so in the wheelhouse of 36 pounds
1 inch solid bar will be fine if you build it right and get the forces on it in shear. I've had over 500 pounds on my HCW with 1 inch bar. My 10 foot whipper has a 1 inch bar, and drops 400 pounds, and generates way more energy then a HCW. Your beam ratio is too low, and do not use a 4x4 for the arm. A single 2x6, tapered, and built out at the axles will work.
Awesome, thanks! I have been using a 3.75/1 ratio for my models, should it be more like 4 or 5ft/1ft then?
You're welcome. 5:1 would be more correct, and you'll only be throwing 2-3 pounders at this scale.
Yeah, i only intend to launch 1lb-ish objects, I’ve been using https://virtualtrebuchet.com for early modeling and getting a rough estimate of distances. I’ll play around with a 5/1 ratio in sketches like you said, i checked out your build and its just about what I intend to make, though, (if all goes to plan) mine is going to be a bit larger and have the fulcrum at 8ft off the ground. I might just be paranoid but i feel like a 2x6 just is too thin, its a whole lotta weight going real fast. Any reason why a 2x6 would be better than a 4x6?
The weight of the arm matters. Lighter is faster. My 15 foot whipper threw a 4 pounder 1300 feet with a single 2x6 arm and 700 pounds of cw. But if you wanna use a 4x6, use one.
These are some of my machines, recorded by my friend Daniel. Study the builds geometry. https://www.youtube.com/watch?v=gpPd12FxQvQ&t=936s
Look for used weight lifting equipment.
Power racks, squat racks, or you can buy just the uprights from companies sometimes. Rogue has a near constant "garage sale" promotion where they'll sell the uprights for their power racks. Otherwise you can look for scratch and dent sales from other companies, or ebay/craigslist/offerup/etc.
I'm thinking of taking an old Bench press rack I have and using it as the base/frame for a trebuchet. it's almost like a metal A frame with 13 gauge steel square tube construction.
Then using an upright as the lever arm. The uprights are usually already predrilled with holes up and down the entire length, so you can adjust it, and you have holes for the counter weight and to attach the sling set up to.
Scrap metal shops will measure and cut any length of round shaft. For 400 lbs on a 1 food width between bearnings, I'd suggest 1.25"
Cheaper, probably, is to use the rear truck axel out of a wrecked truck. If you can get the bearings too. This will keep the axle from jumping about. Bearings are cheap.