OK here's one for you mechanical engineers out there........... I want to screw two (2) screw eyebolts into an overhead 2x4 rafter. Then I will attach a 3' long chain to each one so that they hang down. Assuming that the wood of the rafter is excellent and structurally sound as well as any other hardware, such as the chain ...... "Would these two screw eyebolts hold up to 400 pounds (share 200 pounds each)? I have no real good idea of shear factor for this type of fastener........ ie. Would the screw break before the wood?????
The eyebolts that would be used are 3/8" diameter and 3 1/2" - 4" long. The eyebolts would be just standard Home Depot mild steel with galvanized plate plate I suppose. I am thinking that these two bolts would equally share the load and probably be fine but......... The weight of 400 pounds might strip them out of the 2x4s....... Is this likely or would the threads be strong enough ?? Not looking for any promises.... just some good swags. And yes, I am intending to hang from this but I weigh a little over 200 pounds.... safety factor you know..... :~)
I don't have any doubt about the bolt itself, and it would likely hold
200 lb in tension on a 3/8" lag bolt (that's essentially an eyebolt), but I'd first be concerned of the span of the 2x4 rafter (or lower truss chord). I'd not trust it as a mounting technique if I were hanging from it or underneath a suspended load, though.
If I were doing somethng similar, I'd go _through_ (or even better over) the rafter w/ a 3/8" bolt and a couple pieces of strap iron and go through the bottom ends w/ a second bolt for the chain mount. AFTER verifying what the actual 2x4 structure looks like--
I'd consider what you're suggesting for half the load if the load weren't me or there were nobody ever under it, but it's definitely not adequate safety margin in my view for the stated purpose (even w/o looking up actual values). (Your numbers don't account for any dynamic loading, for example.)
I agree the bolt should be fine but I would thru-bolt with a washer and nut on top or one of the ideas dpb gave. But not with a 2x4 rafter!
What is the distance the rafter is spanning? what is the slope of the roof? is the rafter realy a ceiling joist that is part of a truss? Is it a finished ceiling (drywall)? Could you put a beam perpindicular to spread the load over several rafters? Could you sister a larger rafter like a 2x6 or 2x8 to the 2x4?
buck wrote: > OK here's one for you mechanical engineers out there........... I want to > screw two (2) screw eyebolts into an overhead 2x4 rafter. Then I will > attach a 3' long chain to each one so that they hang down. Assuming that > the wood of the rafter is excellent and structurally sound as well as any > other hardware, such as the chain ...... "Would these two screw eyebolts > hold up to 400 pounds (share 200 pounds each)?
I wouldn't touch this one on a bet.
"Why?", you ask.
Because you know ZIP about that 2x4.
What is it's unsupported length?
What existing loads does it support?
What is the condition of that 2x4. (checks, cracks, knots, etc)
There are other considerations, but those above are enough to reject the idea.
Tue, Sep 12, 2006, 6:14pm (EDT-2) snipped-for-privacy@covad.net (buck) doth query: "Would these two screw eyebolts hold up to 400 pounds (share 200 pounds each)?
No prob. Try it, and if it dumps you on your ass you'll know you screwed up.
Me, I wouldn't do it that way, but that's only because I wouldn't trust them to not pull out rom that much weight. That's just me tho.
I'm going on the theory that you're talking about screw-in eyebolts, because that seems to me to be so. Me, I'd use longer ones, that take a nut on the end, and I'd use a large washer under the nut. I'm a candy-ass and I'd reinforce the 2X4s too.
Whatcha making anyway? Sumthin' kinky?
JOAT I am not paranoid. I do not "think" people are after me. I "know" damn well they're after me.
I do chin ups from a bar that hangs from 1 eye bolt in the ceiling and I weigh around 225. It's in a 2X6 though. I'd be much more worried about the 2X4 breaking than the eye bolt coming out. If the span is not too long it might not be a problem though. I also have a porch swing hanging from two eye bolts and it frequently has around 400 pounds in it. They are in 2X6's too though.
OK.... OK....... I THINK I SCREWED UP THE TERMINOLOGY ....... I said RAFTER, but what I should have said was that it is the lower horizontal 2x4 of a common TRUSS. The trusses are 24" on center. I was thinking about lagging in a 2x6 board with lag screws across "three trusses" ..... and then screw in my two eyebolts ....... so all the weight should be spread across the three rafters. The problem is that the ceiling is in the garage and has wallboard on it but I can see that the span is 24" between the trusses. A lot of the townhouses here have wallboard ceilings on 2x4 trusses so I would imagine they are holding up a lot of weight already with no apparent effect. So now that I have everybody thinking about a horizontal 2x4 truss rather than a rafter....... Is this more acceptable or even a worse idea?
-sorry for the wrong verbage. Thanks for all previous responses..... Appreciate it!
What I have done is not to put the supporter through the 2x4 but use hammok rings (a hammok ring is aboit 8mm steel wire and 90mm dia) and rope round the 2x4. Three times round the 2x4 and through the ring with
6mm or 68mm polly. or nylon means that the knot has less stres and the swing is less likly to damage the supporting roap
Close. As you state, given a constant value for "b", moment of inertia is proportional to the cube of the height. (5.5/3.5)^3=3.9, not 4.5. If you meant a literal 2x6 vs. a 2x4 rectangular cross-section, the ratio would be
When I say truss..... I mean that in my garage there are 2x4s that are part of the truss framework that go horizontal across the entire length of the garage and they are on 24" centers. My ceiling drywall is nailed to them. There is no second story over the garage..... just the roof. I can't get to anything other than the side of the 2x4s since they have been wallboarded over...... So I can't loop wires over the top or drill holes in the side of these 2x4, etc. I can either screw into the width of the 2x4 (1.5 inches) or don't do anything. So far, from what I am hearing, is.... Don't do it may be the answer, although I don't know why the ceiling truss 2x4s will hold up a ton of wallboard but not an extra 200 pounds..... puzzled!
I'm a Registered Architect, so let's see if I can lend a little clarity here...
Terminology: If your house was 'conventionally framed' (that is, the old 'stick' method), the sloped members that support the roof deck would be called "RAFTERS" and the horizontal members that are supporting your ceiling are called "CEILING JOISTS".
If (as it appears) your roof structure is framed with wood trusses, these members are called "CHORDS" - the 'top chord' being that which support the roof deck and the 'bottom chord' being that which supports the ceiling.
As you've described this as '2x4' framing, it sounds pretty clear this is, indeed, 'trusses' - as a normal ceiling joist would be quite a bit bigger (like 2x8 or so).
The important point about 'trusses' is that they are designed and assumed to carry their load at the 'panel points' (that point where some of the diagonal members frame into either the top or bottom chord (usually with those little 'prickly' metal plates on each side). Add to this the fact that a truss will resolve the forces into axial ones (i.e. running down the length of the member) and this is why the chords of trusses are smaller - they're not 'bending' as much (other than carrying the actual load of the ceiling or roof decking) -- a truss is just simply more efficient in doing this (that's why they're used).
Another important point to consider when adding some additional load to a truss is to get it as close to one of the 'panel points' as possible
- that way, you are not loading the chords in 'bending' (which they were not assumed to be doing initially). A 200 or 400 pound load is not that much when carried at one of these 'panel points' - but might get 'iffy' if you applied this load midway between two 'panel points'.
Your idea of laying a 2x6 across 3 (or so) truss chords is a good one - but, to improve it a little more, I would suggest making a 'strongback'
- and, by that, I mean laying your 2x6 horizontal across the 3 bottom chords but also nailing (at least) a 2x4 VERTICAL to one side of this
2x6 (better yet - use a 2x6 vertical here, as well). It is difficult to put a bolt through the long axis of a piece of lumber - better to go through the short dimension (like drilling through that flat 2x6) - but this is also the 'weak axis' of the member (the "Moment of Inertia" mentioned earlier) - which is why I suggest turning (and nailing) that vertical 2x6 to it -- making it a 'strongback'. Nail these together with 16d nails about every 8 to 12" (no more) and use machine thread eye-bolts, not the 'lag thread'. One thing I didn't see mentioned is the fact of the eye-bolt opening up under load -- you can get forged eye-bolts (i.e. with a 'closed eye') that is 10 times (or more) stonger that would give you a lot of insurance at only minor cost increase. Lowe's (etc) may have it - or McMaster-Carr online surely does. I might would suggest using those forged ones -- because they are (truly) at least 10 times stronger and if this is a 'human' hanging off of these eyebolts, that about cinches the decision (in my mind).
Main points: Put your load as close to a 'panel point' as possible Add that vertical 'strongback' to the side of your framing member Use forged (closed eye) eyebolts Be careful and look for signs of fatigue when loading it - wood won't fail immediately, it gives warnings (assuming you're paying attention).
I am guessing you mean a joist and not a rafter? And you are talking about an "eyebolt" that has a thread like a lag bolt, correct? If so, I have always called these "screw eyes" and use the term "eyebolt" for a bolt with machine threads that goes in a through-hole, with a nut on the end. Maybe someone here can verify what the correct nomenclature is.
At any rate, if the wood is sound and the pilot hole sized properly to the eyebolt/screw eye, it should able to support 200lbs dead load without pulling the threads out of the wood.
Some thoughts and concerns: You mention that you will be "hanging" from the eyebolts. That's probably OK but if you are "swinging" from them, maybe not, especially in soft wood. No way for instance, that I'd hang a kids swing from a screw eye.
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