Ok Boomer

[mccutter]

Originally Posted by JohnBoy

I hate to be that guy, but are you sure that wall is solid?

Originally Posted by threepiece

I thought the same.

I was thinking the same but I am far from an engineer. You did mention having to offset a hole because of a reinforcement--was that a piece of embedded rebar?

On a positive note, I think the crane would survive the fall should it detach! don't know about the winch, though.

[Tim KS]

I'm even farther from being an engineer than mccutter, but the original post says that the wall is poured, reinforced concrete which I'm sure has it's limits.

But my question would be, what kind of lift weight are you planning to lift?

[threepiece]

Originally Posted by Tim KS

but the original post says that the wall is poured, reinforced concrete which I'm sure has it's limits.

But my question would be, what kind of lift weight are you planning to lift?

Indeed, and the limit is quite low when loaded in tension.

There is a fulcrum near the middle of the mast where the support struts are attached. Below this fulcrum the mast will be loaded horizontally, away from what is being lifted. This horizontal load will put the wall in tension. Not good. Moreover I would have liked to see some cushion between the steel and concrete like rubber or polyurethane. The hard steel on concrete can create a stress riser that can initiate a crack. Also not good.

The hoist should be sized to the structure it is mounted to so there is no chance of overload.

[Tim KS]

While I'm "acting" like an engineer, I'd like add that I think it would've been very beneficial for the vertical post to extend a bit (several feet) higher than the boomer leg & winch. That would have given room to attach a brace or two to anchor back away from the lift side to anchor points on the roof. (out of the swing of the boomer leg)

Hey....this backseat driving is kinda fun.

[threepiece]

Originally Posted by Tim KS

While I'm "acting" like an engineer, I'd like add that I think it would've been very beneficial for the vertical post to extend a bit (several feet) higher than the boomer leg & winch. That would have given room to attach a brace or two to anchor back away from the lift side to anchor points on the roof. (out of the swing of the boomer leg)

Hey....this backseat driving is kinda fun.

Yes, I guess I see what you mean. In my own words: It would have been better to attach the struts at the top of the mast, this way the fulcrum is eliminated and the side loading of the wall is greatly reduced. The major load on the wall would then be downward in compression. Concrete handles compression loading very well.

[Tim KS]

Originally Posted by threepiece

Yes, I guess I see what you mean. In my own words: It would have been better to attach the struts at the top of the mast, this way the fulcrum is eliminated and the side loading of the wall is greatly reduced. The major load on the wall would then be downward in compression. Concrete handles compression loading very well.

Yep, I think we're on the same track. Like you said, that would put the load downward.....and a large plate at the bottom could spread the load out onto the roof.