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  #11  
Old 02-10-2021, 09:14 PM
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mccutter mccutter is offline
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Originally Posted by JohnBoy View Post
I hate to be that guy, but are you sure that wall is solid?
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Originally Posted by threepiece View Post
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.
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  #12  
Old 02-11-2021, 11:02 AM
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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?
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  #13  
Old 02-11-2021, 01:48 PM
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Originally Posted by Tim KS View Post
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.
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Last edited by threepiece; 02-11-2021 at 01:54 PM.
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  #14  
Old 02-11-2021, 02:37 PM
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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.
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  #15  
Old 02-11-2021, 10:02 PM
threepiece threepiece is offline
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Quote:
Originally Posted by Tim KS View Post
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.
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With the amount of energy that is being consumed I expect most people on earth should be living in Utopia. And now this?

It started hitting the fan in the 1950's https://m.youtube.com/watch?v=nRnNDkHb0MU

A technologically advanced society would teach their children how to start a fire by rubbing two sticks together before teaching them how to use a lighter.

If you are not having fun then you are doing it wrong.
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  #16  
Old 02-11-2021, 10:09 PM
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Originally Posted by threepiece View Post
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.
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