I have the following chain hoist setup in my garage.
A cheap chinese 2 ton rated manual chain hoist.
It is hanging on a 2" about 5/16 thick T beam that spans three joists in the garage ceiling. It is attached to these three joists with six
5/16" lag screws, two for each joist. It is about 5 feet away from a wall that supports these joists. The joists are spaced 16" apart. When I screwed the lag bolts, I drilled pilot holes for them with a 3/16" drill bit. None of these bolts was overstressed during screwing in.
Now, I am not asking for what is the maximum weight after which the ceiling will buckle. What I am asking is what is a conservative weight under which it would be extremely unlikely to buckle.
Specifically, would it be able to handle 700-1000 lbs?
I did a quick look through my calculations manual under the heading of lag screws. I would STRONGLY advise against using your setup. A few things to keep in mind:
1) Your 'T' beam is unlikely to be stiff enough to distribute the load across multiple beams. You need to figure all the load is on just one (possibly 2) joist(s).
2) you are hanging all the load verticaly on the threads of the lag bolts. You didn't say how long the bolts are or what kind of wood they are going into but your max load is a low few hundred pounds per bolt. Most lag bolts are pretty wimpy steel so even with good wood you are limited by the break strength of the bolt itself.
3) Even though you used 2 bolts per joist, they are fairly close together, they will tend to pull out together when the wood splits. It's better than just one but not a lot better.
4) Sounds like you plan to pull an engine. A lot of times it will get stuck on something as you pull it out, you lift the car a bit, it pops free. Resulting load can be quite a bit more than the dead weight.
Net: I'd expect this to rip out under your load.
Suggestion: replace the steel with a pair of 2x6 or 2x8's nailed together. Support one end on the wall, prop a temporary 4x4 post under the other end. Use a big 'C' clamp to keep it from popping loose. Pull and replace the engine, remove the post and store if for the next time.
I doubt it. I'd say 500 at the very outer part of outside. I'd certainly test it first using something like a 55 gallon drum into which you can put varying depths of water. Even if you can gently hoist say 800 pounds that is essentially a static loading and you can get peaks if something bounces. It's pretty iffy. However, if you put a beefy jack under each end of your T beam, then yessir. - GWE
ok guys, here's some REAL data on a somewhat similar setup.
I have a taiwan 2 ton chainfall, like the one below, I suppose. I have a small carport with a 4X4 spanning it (7.5 feet span), and into the bottom of the 4X4, I have a 12 inch piece of angle iron. The angle iron is held to the 4X4 with two 3/8 X 3 inch lag bolts. I hang the chainfall from that piece of angle iron - and originally used it to pull engines on cars I worked on - no problem with any engine I pulled, including my 51 dodge, a 61 Mercedes, a 65 chevy PU, and others. In fact on a couple of cars I forgot one or another fastener and ended lifting the whole car up. I also unloaded my Logan 12 inch lathe using that setup - I suppose the lathe weighs at least 800 to 1200 pounds. But a chevy PU front end weighs a lot more than that. So long as you have good wood, and you drill a properly sized pilot hole, lag bolts are quite strong.
The joists I have are probably stronger than your 4x4. Anyhow, with six bolts, I feel that even if the two in the middle fail, it will be supported by 4 bolts at ends. Obviously, I will try to never approach the danger zone, and also, will consider adding a 2x6 on top like another poster suggested.
Simular to mine. I built a over head crane and lag bolted it to the ceiling of my garage. For the most part the weight is shared by the two tracks. One day I needed olift the rear of my John deere tractor and as my floor jack was busy at the time I tried my overhead. It lifted it with no problem. One ton hoist, and a smaller JD tractor. The total weight of the tractor is over3000 lbs, so I got to believe that 2/3 of that is in the rear end, allot of cast iron back there. Would I recommend someone else doing it? No way!
As For the original poster, he would be better to attach to the top run of the roof truss. The lower cord is not made to support weight. Greg
OOOOOOOwwwww, this is getting REALLY scarey. I had assumed, incorrectly apparently, that the T-beam (I don't know what that is..... is it like a length of elevator rail?) was ABOVE the joists, although for my comment now it wouldn't really matter. If the "T-beam" is lag-bolted UP into the floor joist, and the two lags in the centre beam were to pull loose, you would not only lose the load, but the whole ceiling. Any weight that is enough to pull the lags out of the centre joist in tension, would then see the outer two joist lags in shear, and would just either split out (weakening the joist considerably0) or pull towards the center and pull the joists with it. You can demonstrate this very simply yourself. Get two pieces of rope that are still about 3 feet long after you put loops at each end of each rope. With the first rope, fasten one loop to a 10 pound weight one and pass the second rope through the loop at the other end of the first rope (form a "T" so to speak). The second rope then has one loop "fastened" at 5 feet height to something solid. Hold the last loop (the other end from the "fastened" one) straight up above the load so the load is lifted clear of the ground....no problem. Then start pulling the rope sideways, and the "weight" on your pulling will increase dramatically as you get closer to pulling the rope straight horizontally.
Somewhere there is a formula for this, but the empirical means more when you feel it.
The only way that spreading a load across more than two supports works, is if the "spreader" is strong enough to hold the load with-out deflecting itself. Your 2 inch anything will bend.
It would seem worth asking a few questions before making recommendations. Like, for example, how big are the joists? What load are they carrying? What is their span? I didn't see the answers to any of these in the thread, though I may have missed something.
If it was me, I'd design a wooden beam to go above the joists that was strong enough to hold the load, then support it on each end with a post. I'd only use the joists to provide lateral support, not vertical load carrying.
The withdrawal design values for 3/8" lag bolts in lbs/inch of depth not including the tapered tip into the wood vary between 104 lbs (corrected) and 538 lbs depending on the type of wood it is screwed into, service conditions, and the pilot hole diameter. With the correct pilot hole, if the 4 x 4 is DF-LARCH the value is 305 lbs per inch as modified by service condition correction factors - use 213 lbs and its probably conservative. If it is Southern Pine, it is around 218 lbs/inch as modified by service condition correction factors - use 149 lbs and its probably conservative. =20
The correction factors used to modify the starting table values are related to wet service (wood moisture content), temperature (0.8 for dry service at 100F - 125F - desert dwellers take note. Its 0.7 for the same temperatures and wet wood which is wood with moisture content greater than 19% in the case of lag bolt withdrawal loads. There are also correction factors for fire retardant treatment, and what is called a group action factor. =20
Reference: ANSI/AF&PA NDS-2001, sections 10 and 11. (AKA the NDS, National Design Sepcification for wood construction).
Other things will have an effect on the strength of the connection, like the eccentricity of the load as applied to the bolts. The table values are concentrically applied loads.
Voice from the gloom. What happened, the Trick or Treaters wake you up!?!? So, speaking of designing, how's your big project coming along? Enquiring minds want to know.
Nice to see you following a few threads here now and again!
Take care.
Brian Lawson, Bothwell, Ontario.
ohhh...and ps.... on the original thread........
My new back-shop (garage) is 24' X 24', and uses a 4-in-12 pitch truss roof on 24" centres. The trusses are made like a widespread "W", where the wings of the W are "laid down" a bit, to be perpendicular to the rafters, and the bottom of the wings attach to the 24 foot long 2 X 4 joists at 8' from the ends, and the top of the W centre is the ridge pole support. After erection, there is a 2 X 4 tie plate laid in the notches at the bottom of the W to act as bridging between the trusses. Hmm....tough to describe, but I'm sure you get what I mean.
Anyway, for my 2 Ton chain-hoist, I laid an 8' long hunk of 2 X 4 across as many rafter joists as it would straddle, laid against the tie-plate, to give me effectively a 4" X 4" along that 8', and laid in that W notch it places it 8' out from and parallel to a wall. I looped a piece of chain around this new " 4 X 4 " , centred between two of the trusses, to hold the chain-fall. In use, I lifted a 1400 pound machine. For safety, I did make up two 2 X 4 uprights to set on the concrete floor to hold up the trusses as close to the lifting as I could. I cut them 1/2" short, and had to wedge them in slightly with the 1400 pound load, so I know that the deflection was less than 1/2".
Hope my "empirical" data helps somebody. XXXXXXXXXXXXXXXXXXXXXX
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