Am I being paranoid?

[Wade Lippman]

I hung a Jet AFS1000 today from 4 small screw eyes screwed into the bottom of the joists.

Afterwards I wondered just how well the hooks would hold, so I screwed another into a 2x4 and hung 50 pounds from it. (The AFS1000 weighs 60 pounds). It was fine until I pushed down with maybe 15 pounds of pressure and the hook straightened out. I thought it might pull out, but never expected the actual hook to fail.
So, I guess it failed at about 65 pounds.

If I have 4 hooks holding it, that is 15 pounds per hook, and I have tested them to fail at 65 pounds. That is a pretty good safety margin isn't it? I could replace them with bigger hooks, but don't want to make any bigger holes in the joists than necessary.

[Thomas Bank]

If one will support 65lbs, that means that four could support 260lbs. I'd say you're probably fine.

[Rod Sheridan]

I hung a Jet AFS1000 today from 4 small screw eyes screwed into the bottom of the joists.

Afterwards I wondered just how well the hooks would hold, so I screwed another into a 2x4 and hung 50 pounds from it. (The AFS1000 weighs 60 pounds). It was fine until I pushed down with maybe 15 pounds of pressure and the hook straightened out. I thought it might pull out, but never expected the actual hook to fail.
So, I guess it failed at about 65 pounds.

If I have 4 hooks holding it, that is 15 pounds per hook, and I have tested them to fail at 65 pounds. That is a pretty good safety margin isn't it? I could replace them with bigger hooks, but don't want to make any bigger holes in the joists than necessary.

It all depends upon hat type you wear when standing under it, whether you're being paranoid

Tin foil hat = paranoid

Hard Hat = Pragmatic

I'd say a 4 to 1 safety factor is good..................Rod.

[David Dockstader]

Add more hooks - if you wear suspenders AND a belt. Otherwise, the safety margin is fine.

[Ole Anderson]

What size hooks did you use?

I may be wrong here, but I think the accepted safety factor for rigging a suspended item overhead is seven to one. Mine is suspended at each corner with a 3/8" lag screwed perpendicular to the face of the joist, about 1.5" from the bottom, with a 5/16" turnbuckle between the air cleaner's eyebolt and the lag. May seem like serious overkill, but I used what I had on hand. What happens if you accidentally whack the cleaner with a 2x6 or otherwise bump it hard, will it just laugh at you or will it get revenge?

[Wade Lippman]

If one will support 65lbs, that means that four could support 260lbs. I'd say you're probably fine.

When you put it that way it does seem perfectly safe. Thanks.

[Michael W. Clark]

At one of my previous jobs, we use a 4:1 for overhead cranes handling hot metal.

I went through the same thing with my air scrubber and finally reasoned it out like you. Each hook holds basically 1/4 the load +/-.

[glenn bradley]

I have mine hanging from rubber straps to kill noise transfer but, I have loose, over-length chain there for safety in the even of a failure. Maybe a couple pieces of chain hooked to something stouter would give you piece of mind?

[Michael Dunn]

I used 3/8" lags into my ceiling joists as well. Over three years, no problems. I could hang on mine if I wanted to. Fortunately, I don't want to.

[Carl Beckett]

I just hung one two weeks ago. At first I used a chain that was too lightweight - and although if all four had been evenly taking the weight I would have been 'ok', just the act of hanging it rested all the weight on one chain (while on a ladder) and the chain links all just bent open! I didnt expect that (expected it to break).

So safety factor is more than just the 'ideal' nominal design point, its intended to take on variation, and to some degree the 'unknown' element in use.

I put pretty heavy duty lag eyebolts in the joist edges. And got a stronger chain. I feel much more comfortable with this, since I dont want it coming down over time or if I hit it with a board or something snags on it or a bolt works loose over time with the wood swelling and contracting, etc etc.

If it falls, it could do some pretty severe damage to someone. Yours sounds marginal to me - I would beef up the hooks (if there is a defect in one it wont be near as strong - again something safety factor is there to help with)

[Lee Schierer]

I would go with an eye that would safely hold the entire weight with at least a 2:1 or 3:1 factor of safety so that if the unit ever needs servicing one support would hold it while you try to get it down or work on it as it hangs.

[Michael W. Clark]

The safety factor is going to be according to the weakest link. My JDS was tapped for 5/16 eye bolts. Even if I used 3/4" lags into studs, the threaded portion in the top of the unit is the limiting factor.
I used machine threaded eye bolts in the unit and in a maple frame I built to attach to the ceiling. Carribeaners connect the two. I built the frame so I could hit the ceiling joists on 16" centers with 3" deck screws.

Mike

[Darrin Vanden Bosch]

Irregardless of the weight factor times four, if you're worried about it, replace it with something stronger. It's all about piece of mind!

[Wade Lippman]

I put in a second set of chains.
I am rationallizing that I have chain I will probably never use; so it cost nothing to do; but I feel wimpy.
But if it fell, it would have landed on my jointer; so I was uneasy about that.

[Rick Potter]

Paranoid

RP