Structural Engineering 101 - How to hang my air compressor.

Discussion in 'The Garage' started by P B G, Mar 22, 2012.

  1. P B G

    P B G Long timer

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    I want to suspend this:

    [​IMG]

    Next to this:

    [​IMG]

    How would one go about ensuring that it is "within" the load limits of the structure...
    #1
  2. deejay_xr

    deejay_xr Been here awhile

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    By not risking it? ...

    Calculating that would be a real challenge, trust me.
    Just by eyeballing it, I wouldn't do it personally.
    Do you have a ballpark on what that thing weighs?
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  3. P B G

    P B G Long timer

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    ~1100 lbs.

    I'm assuming by being unitstrut products that someone knows how to rate those things.

    Atleast in my view point it is largely 4 all thread rods suspending two unistrut rails, ancillary to that are the vibration reduction components, and anchors into the concrete which I view to be more positioning related than weight suspension.

    In terms of roof joists of that style, it is unclear.... It is of course right next to the concrete block structure of an interior wall.
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  4. stainlesscycle

    stainlesscycle Long timer

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    i have one about that size - 2 stage 7.5hp 80 gallon. every bit of 700+lbs just loading it into a truck is a chore.
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  5. P B G

    P B G Long timer

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    Also I am not against augmenting the structure by going next to it to the right.
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  6. deejay_xr

    deejay_xr Been here awhile

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    The strut could maybe still take the extra compressor, I would be more concerned about the struts mount to the roof structure
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  7. P B G

    P B G Long timer

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    This is a bit more than that.

    Its a 10 HP 3 Phase on a 120 Gallon Tank.And being from the 60's it is not wimpy in the castings department. The one from the ceiling is more in that rhelm and is a single phase 220.
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  8. P B G

    P B G Long timer

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    Good feedback, I will get to clambering up and taking a peak at that hardware.
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  9. morerpmfred

    morerpmfred Been here awhile

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    Looks like the strut is attached to another bar stock resting above the steel joist between the q decking. The steel joist is sitting on top a steel i beam. So i would just mount it the same way as the other tank but one joist over.
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  10. stainlesscycle

    stainlesscycle Long timer

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    gotta love the old equip - mine's a mid 60's speedaire - 3ph - rebuilt the head about 10 years ago - still chugging along.
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  11. ttpete

    ttpete Rectum Non Bustibus

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    I'd hang the big compressor closest to the wall and use a piece of channel through bolted to the wall for the stringers to rest on. The stringers really need to be heavier channel iron as well. The roof trusses and threaded rod kind of bother me, though. If the truss is made up of pairs of angle iron with the diagonals welded between them and the suspension rods also run between them with a nut and washer on top, there is a chance that it could spread or the washer deform under load and fail. In any case, it would be a good idea to have a civil engineer or journeyman millwright look it over first.

    What about supporting it in a corner using the two walls and using an I-beam column to the floor on the one unsupported corner? It would be a lot more rigid.

    How do you envision servicing the units? You'll have to install automatic drain valves and pipe the discharge somewhere. My experience is that overhead units like that get neglected because they're so difficult to access.
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  12. P B G

    P B G Long timer

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    By climbing up my fork lift....

    Actually the one that is up there has a remote drain for the tank. I would tie the new compressor directly into the old compressor with T fittings.

    That way both will "share" volume, and both with share a drain, and both will plumb into the shop air distribution.

    The current unit is actually not hung on all thread w/ a washer between the angle irons, it is hung on "clamps" the type that unistrut sells to grab hold on things.

    I'm thinking of going below the other unit. I have the overhead room.

    I can support the current unit on my fork lift, then swap the current all thread ~3/8" with heavier 1/2" acme rod. Suspend another layer directly below the current.

    And yes knowing engineering history the allthread would be joined with a coupler and lock nuts not adjacent holes.

    Swap the current "clamps" with a lock nut over a steel plate,

    The owner to the north has no problem with me punching a hole through the cinderblock, so I can compress an angle iron to that wall. The wall to the right is cinder w/ cosmetic brick, so going through that wall is harder, it is quite thick.

    I can carry the heavier/lower compressor on unistruts doubled back to back and bolted together. Which should be overbuilt. Or perhaps just heavy U channel steel.
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  13. boardrider247

    boardrider247 Weekend Anarchist

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    I don't have my book in front of me, but from memory 1/2" all thread rod is good for about 1100 lbs.
    I think what you have there will hold both compressors.
    That being said I wouldn't do it. I would replace the strut with channel iron. And check to make sure what type of anchors are in that block wall. If it's a poured wall and they are drop-ins your good to go. If it is just toggles bolted to the block I would change those out. And use square washers on the top of the rods connecting it to the joists if possible.
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  14. P B G

    P B G Long timer

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    Its stacked cinder block.
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  15. boardrider247

    boardrider247 Weekend Anarchist

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    I have a strut catalog in my desk at work. I'll try to remember to bring it home with me tomorrow.
    Feel free to shoot me a PM with anything you want me to look up for you. I think there are load limits listed in there.
    #15
  16. muddywater

    muddywater Been here awhile

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    The point loads on the ceiling truss seem to be the hardest to evaluate.
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  17. deejay_xr

    deejay_xr Been here awhile

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    Exactly
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  18. Anorak

    Anorak Woolf Barnato

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    Get a pallet rack.
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  19. P B G

    P B G Long timer

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    I have that... the wall in that area isn't deep enough to have that w/o obscuring the door.
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  20. MJS

    MJS Long timer

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    You can get the strut engineering on line. You'll probably have to go to a double strut. The real concern will be the point load on the truss. Also, it is better to load the top cord of the truss, some trusses have very limited load capacity on the bottom cord. You're adding a fairly large load over a small area ( just a couple of hang points). 1/2" rod is probably strong enough but will the truss support the load?

    This is worth having a structural engineer look at. It shouldn't be to expensive if you can give him/her the building drawings or a detailed description of what is existing.
    #20