Project #1 from DaveO: Lifting tripod

[everlastsupport]

Ours is 1 1/4" squared tubing and very strong, over 6 feet tall. We can pull a plant or lift mowers, golf cart, etc with it. Will try to post up a picture, though it's quite simple. We're going to build a rolling gantry soon for large electric pump motor lifting a moving, it will be round tube (well it is on the list).

Nice thing about the bed rails, they are cold steel, adds a little more stiffness and many times free.

[Rambozo]

When I've had to pull fence posts, I've always used a chain looped over a truck rim, then pull on it with a tractor. The rim acts as a pulley and the post comes right out.

[Trip59]

Been trying to iron out details for a gantry build, trying to get legit specs from anyone is like pulling teeth. Weights and spans and the local steel places refuse to provide, tell me to talk to an engineer.

We have a huge scrapper community, they patrol constantly, so it's hard to find discards. I have one guy I'm friendly with who keeps an eye out for certain things for me, but he's on some other projects and hasn't been making runs.

[Rambozo]

There are plenty of online calculators to do the engineering math for you. If you want to calculate the moment of inertia, stress, and maximum deflection for steel beams, this site has all the formulas.

http://www.engineeringtoolbox.com/mechanics-t_52.html

[zoama]

When I've had to pull fence posts, I've always used a chain looped over a truck rim, then pull on it with a tractor. The rim acts as a pulley and the post comes right out.

I use a 4x4 post 3 or 4 feet long. You can pull up most things with a truck... just drive forward, it doesn't take much.

[DaveO]

Nice thing about the bed rails, they are cold steel, adds a little more stiffness and many times free.

Bed frames are cold rolled? I thought that would add expense and strength that a typical bed wouldn't require.

Without getting into the math specifically, do the load / span calculators consider multiple legs in a tripod for instance, whether the legs have cross members, etc? Seems like theres a lot of variables to consider- but that's why we have engineers.

Backatcha, Don, good to have you back!

[Rambozo]

Bed frames are cold rolled?

Without getting into the math specifically, do the load / span calculators consider multiple legs in a tripod for instance, whether the legs have cross members, etc?

I've never seen any but hot rolled angle iron. Usually with the mill scale still on and just painted over. And the newer they are the weaker the steel seems, like cheap recycled stuff, or maybe just thinner.

I haven't seen any that can directly handle a tripod configuration, where there is a mixture of bending and compression loads, you would have to do a few more steps for that as the angle would need to be known to divide the force between compression and bending loads. But for the gantry that was mentioned there are plenty of them for the beam part. Just plug in the support points and the type and amount of load and you will get the stress, and deflection. For a standard steel beam just limit your deflection to around span/250 for a static load and span/360 for a dynamic or shock load.