I need to lower large stones into a hole and need help constructing a crane for this. I want to be able to lift 300kg and the reach from the wheels needs to be 1.5 meters. I have made two variants, the one with a simple lever arm has the advantage of leverage but needs to be rebalanced for each stone, so it takes a bit of time. The variant with an upright crane arm can have a counterweight on all the time but has worse lever effect. Does anyone have a better solution? I know an excavator would make it easy, but I'm building a dry stone wall in a natural pool, so it's probably a 3-week job and an excavator would be too expensive.
The absolute simplest is the lever principle, as your first image shows. If you attach a block and tackle between the rear part of the lever and the rear part of the actual cart, the arm doesn't need to be so long. 1.5 meters forward, and 3-4.5 meters back.
Where should the stones be lifted from? 300 kg sounds quite a lot to roll with a crane by hand to me. I don't like to roll more than 100-150 kg on a cart, but then I don't have such a flat plot, with both small hills and uneven ground.
The stones need to go down in the pit 2.5 meters, so I'm thinking of using a chain hoist to lower them. The arm doesn't have that reach, so it must be balanced when the stone is hanging. If it's a 300 kg stone, I need a 100 kg counterweight, and that's a bit too heavy to lift on and off.Z z_bumbi said:
Quite true that it will be heavy to roll. I was thinking of placing the stones right next to where I have the excavator and then trying to use OSB boards or plastic boards as a base for the cart; I believe Cramo has plastic boards for rent. Jula had a cart with air wheels that could handle 500 kg, which should be a good base.L Lilllen said:
If it's nearby and you can lift and lower in a reasonably straight line, a fixed crane might work. So a boom over the entire pond and a pile of stones. Then a sled that rolls on the boom, and a winch on it. Manual or motorized.
On the other hand, if it takes three weeks to do it by hand, it would probably take a maximum of 3 days to do the same job with a (sufficiently large) excavator. And vice versa. Conservatively estimated.rolcar said:
I've never built a dry stone wall, but isn't it mostly about fitting the stones quite accurately, maybe turning them this way and that and testing? But perhaps that's mostly needed with the smaller ones that fit around larger ones? However, I think a lifting device similar to the one you've drawn would be better, especially with a motor winch, since you can get close when placing the stone. Then, of course, you have to be careful not to pinch yourself or have something fall on your feet. With a long lever arm, it's harder to see and fit in.
If you're going to hoist, you'll definitely anchor better than counterweights that balance? A loosely hanging load that's balanced is the precursor to a catapult.
Support underneath and four solid ground anchors/counterweights with two slings/chains over the boom is the minimum I would use.
I guess you could look at how a stump puller is constructed and base it on that, but make sure you really understand the forces involved.