Shop Garage Hoist - How it's going to kill me?

[Martin w]

I have an aviation background? news to me lol

My bad, I was thinking of “That Guy”. Sorry it’s been a long week. And it’s Monday!

 

[mbond]

likely the weakest part of this is the lag screws into the 2x6. A 3" screw will go into the wood about 2 1/2" - and because it is cross grain, that's all the wood that will ever carry any load. And because it has been pierced by the screws themselves, it will be even weaker. Two lag screws on each in close proximity means that the loads from them can't be independently resisted by the wood - effectively the pair of screws has the capacity of a single screw

the good news is that wood framing usually fails in a progressive ductile way - no sudden snapping - with lots of cracking and popping noises. So there should be warning. even the drywall will help somewhat

Not that you can do anything about it now, but if you were doing it again, I would suggest deeper lag screws. Carriage bolts would be better, but there is probably no access from the top. And blocking between the 2x6 to prevent lateral tortional buckling. And of course, if there were some way to put the lag screws farther apart on each joist.

 

[Darren]

in my old shop, I had a 10' chunk of 4" I-beam on the ceiling with a trolley and a chain fall hoist. I slid a 16' wood 4x4 in from the gable end so it would bear on 8 trusses. I used three 3/8"x 3" flat bar straps accross the top of the 4x4 and 1/2" ready rod down to matching straps , orientated like you have. So the 4x4, bottom chord of the truss, and the ceiling OSB was a tight sandwich. It would lift a fully dressed diesel or a big block with no deflection of the ceiling. I didn't die.

 

[SomeGuy]

likely the weakest part of this is the lag screws into the 2x6. A 3" screw will go into the wood about 2 1/2" - and because it is cross grain, that's all the wood that will ever carry any load. And because it has been pierced by the screws themselves, it will be even weaker. Two lag screws on each in close proximity means that the loads from them can't be independently resisted by the wood - effectively the pair of screws has the capacity of a single screw

the good news is that wood framing usually fails in a progressive ductile way - no sudden snapping - with lots of cracking and popping noises. So there should be warning. even the drywall will help somewhat

Not that you can do anything about it now, but if you were doing it again, I would suggest deeper lag screws. Carriage bolts would be better, but there is probably no access from the top. And blocking between the 2x6 to prevent lateral tortional buckling. And of course, if there were some way to put the lag screws farther apart on each joist.

The pull out strength per lag should be ~400-500lbs per the tables I'm seeing, so my limitation is more likely the 2x6's yes. I don't have access above, so there weren't many other options for attachment without making a lot of holes in the drywall. The holes are ~4 inches apart on each plate, so not super wide but at least have a little space between them and also was done to keep torsion on the strut to a minimum (not having a single center bolt that the strut would pivot on.

I could swap out deeper lags easily, I even have some (bought a ton when TSC was closing), but the other challenge was keeping them centered and squared all the way up without seeing the 2x6's, just a stud finder and best efforts to keep things squared up, but there's limits to that if I was driving a 4-5 inch lag. This is why I went with so many connection points, trying to spread the load out...at any given time the load should be seeing at least 2, if not 3 of the 2x6's and hence be spread between 4-6 lags as well. All of the lags tightened down really well (tightened to stall out my old DCF890 - so 100+ ft-lbs torque), so that made me feel better about how well they're in there.

For a few hundred pounds, I'm sure it'll be fine....but I have no plans of testing the full 880lb capacity of the hoist.


My dream shop would have a proper powered bridge crane all engineered and good for say 5+ tons but that's not happening in my lil garage lol

 

[Stuart Samuel]

After you have it in place.
Put a LARGE decal on it that states the ‘safe load’ capacity of the weakest link in the hoist.
Factor of Safety = 4 or more.
(Anchor lags, lifting hooks, etc)

Lifting Equipment should be adequately Engineered for the application.
Especially if you are lifting items near human access and work areas.

We have a variety of Princess Auto hoists at work, all with extended remote cables (the lowest ceilings are 16’, the highest is 26’). I wrote the capacity (single cable and doubled) on the remote, so anyone using it can check.

 

[KeeponDragon]

Definitely some great ideas here, and positive input about safety concerns...will be referring to this when I'm setting up the next shop after our move...

 

[Dan Dubeau]

I'm sure it'll be fine if you use it within reason. Do not side load that at all, as you'll risk spreading the strut. I would love to have something similar in my shop for those awkward things that are just hard to lift and manipulate single handedly. A few of the next couple projects for me are going to be lifting device related, as I'm not getting younger, and the projects seem to keep getting bigger. Of course I said that last year, but other stuff just keeps wiggling it's way into the queue ahead of them. Damn line jumpers.....

Looking at that, the only thing I'd possibly add, which is just me overbuilding/overkilling it, would be some triangular gussets to the mounting plates to keep the strut from potentially spreading if side loaded. Needed? probably not. Worth taking the whole thing down to do it? Probably not either.

 

[Susquatch]

The pull out strength per lag should be ~400-500lbs per the tables I'm seeing, so my limitation is more likely the 2x6's yes.

I almost never give specific advice on lifting systems. It's too easy to get into professional trouble when/if something goes wrong. But at the same time I don't want to stand by and let someone hurt themselves needlessly.

That's why I'm NOT going to help you with the specifics of your design. But I will provide you with a few things to think about.

The tables you have referenced are usually not derated for safety factor. In other words, they list the normal pullout strength of a lag bolt whose entire length is in the center 1/3 of the 1-3/4 width of a perfect (no knots or splits) in a kiln dried joist of the specified wood. It is up to the table user to derate the strength of the completed system for the usual 2x or 3x safety factor for the weakest link.

A usual design approach would never share loads as per your assumption. If a single concentrated load can happen, then that becomes the design objective. Keep in mind that despite the assumption that the joists don't move, they do. Not a little, but a lot. (Everything is rubber.) The pullout strength is reached when the lag bolt slips a small portion of the thread pitch - say 1/32nd of an inch for a 7 tpi bolt. So the joist doesn't need to move much to allow the load to concentrate the failure into just one bolt in one joist. You should not assume a shared load unless the rest of your system is designed to guarantee a shared load.

As stated above, you should always apply a safety factor to the final design. I might use a safety factor of 3 for a system like yours. In other words, derate a calculated worst case load capacity of 600 pounds at the weakest link to 200 pounds.

Will it carry more? Of course it will. But it is not generally considered safe to do so.

If you can provide more detailed drawings, the engineers on here can probably provide additional advice on ways to improve it without getting themselves into trouble.

 

[Junque]

I'll just add that a dual rail system is obviously dependent on getting the rails exactly parallel to each other. A laser level and a lot of measuring is involved.

I staggered the joints in the rails, but hard to say if that's any better than not doing so. Rail comes in 6, 8 & 10 foot lengths, maybe longer by special order?

When drilling into joists there aren't any second chances if you put a hole in the wrong place: not only does the hole weaken the joist, but also the holding power of the screw in the new hole.
Tabs welded onto the rails like you did SomeGuy is probably a good option if the welds and the tabs are as strong as they should be. A drilled hole up into a joist is severing a fair quantity of the fibres when you compare the cross-section of the hole and the cross-section of the joist. If the holes are in line that impact is reduced, but if the holes are offset it's probably a pretty significant reduction in the strength of the joist. Older houses with better quality timber and more blocking between the joists might have an advantage.

 

[SomeGuy]

I'm sure it'll be fine if you use it within reason. Do not side load that at all, as you'll risk spreading the strut. I would love to have something similar in my shop for those awkward things that are just hard to lift and manipulate single handedly. A few of the next couple projects for me are going to be lifting device related, as I'm not getting younger, and the projects seem to keep getting bigger. Of course I said that last year, but other stuff just keeps wiggling it's way into the queue ahead of them. Damn line jumpers.....

Looking at that, the only thing I'd possibly add, which is just me overbuilding/overkilling it, would be some triangular gussets to the mounting plates to keep the strut from potentially spreading if side loaded. Needed? probably not. Worth taking the whole thing down to do it? Probably not either.

Not a terrible idea...I did put cross bolts at the end to prevent the trolleys from leaving the track, they provide some spread resistance in those locations, but I could probably fairly easily weld on a couple gussets mid span without taking the entire thing down, the whip on my welder would reach and a couple magnets would hold the gusset while I weld up on a ladder.

I almost never give specific advice on lifting systems. It's too easy to get into professional trouble when/if something goes wrong. But at the same time I don't want to stand by and let someone hurt themselves needlessly.

That's why I'm NOT going to help you with the specifics of your design. But I will provide you with a few things to think about.

The tables you have referenced are usually not derated for safety factor. In other words, they list the normal pullout strength of a lag bolt whose entire length is in the center 1/3 of the 1-3/4 width of a perfect (no knots or splits) in a kiln dried joist of the specified wood. It is up to the table user to derate the strength of the completed system for the usual 2x or 3x safety factor for the weakest link.

A usual design approach would never share loads as per your assumption. If a single concentrated load can happen, then that becomes the design objective. Keep in mind that despite the assumption that the joists don't move, they do. Not a little, but a lot. (Everything is rubber.) The pullout strength is reached when the lag bolt slips a small portion of the thread pitch - say 1/32nd of an inch for a 7 tpi bolt. So the joist doesn't need to move much to allow the load to concentrate the failure into just one bolt in one joist. You should not assume a shared load unless the rest of your system is designed to guarantee a shared load.

As stated above, you should always apply a safety factor to the final design. I might use a safety factor of 3 for a system like yours. In other words, derate a calculated worst case load capacity of 600 pounds at the weakest link to 200 pounds.

Will it carry more? Of course it will. But it is not generally considered safe to do so.

If you can provide more detailed drawings, the engineers on here can probably provide additional advice on ways to improve it without getting themselves into trouble.

These are the posts that always happen on overhead stuff like this

A single concentrated load can't happen, there are two trolleys that spread that load on every lift and it's impossible given their distance apart for their entire weight to be beared by a single joist. Assuming those same things about pull out strength, the tables in perfect conditions give me 750lbs per lag given my embedded length, if I got placement centered, and wood species. So I already assumed some worst cases when I was saying 400-500lbs. That is shared with two lags per joist, so theoretical perfect is 1500lbs, and let's say that the load is at best spread to 2 joists, that's 3000lbs. 5:1 safety factor still puts me at 600lbs safe working load of the lag/joist connection.

The thing is though, and you've pointed it out well, is it's not engineered...nobody has put a stamp on it saying this will 100% carry XXX load and that will never happen in my case (or probably most people who buy and install these hoists). Is it a risk? Yes, but I'm fine with that given my intended use and that I'm the only one using it and if the house were ever to be sold, the hoist would be coming down along with a lot of the equipment in my garage that any future owner would not be getting.

 

[Susquatch]

These are the posts that always happen on overhead stuff like this

Yup. But for good reason. No way the rest of us can know everything you know.

I won't (but could) quibble with almost every assumption you made. Load sharing is almost never as simple or obvious as it looks. Your analysis is not transparent to the rest of us either for the same reason (don't know what you know).

But it sounds like you are happy with it and that's probably about all we can hope for.

Somebody earlier said that noises are your friend when it comes to structures - I'll second that. Pay close attention to them.

Good luck!

 

[Dan Dubeau]

Like when your carbon fiber submersible starts making loud popping sounds?

 

[SomeGuy]

Yup. But for good reason. No way the rest of us can know everything you know.

I won't (but could) quibble with almost every assumption you made. Load sharing is almost never as simple or obvious as it looks. Your analysis is not transparent to the rest of us either for the same reason (don't know what you know).

But it sounds like you are happy with it and that's probably about all we can hope for.

Somebody earlier said that noises are your friend when it comes to structures - I'll second that. Pay close attention to them.

Good luck!

Yup, very fair...as said before, lifting 880lb limit of the hoist and pushing it? Not a chance I'd attempt that and I have an engine hoist for the heavy lifts. Lifting 200-300lbs? Yeah, I am comfortable with that sort of load and that's all it will ever see in my use and would be removed if I ever sold the house. This really is just a helping hand for when I'm doing fab work that has slightly bigger setups...and will also come in handy as a place to hang things for spray painting or similar. Good enough for those purposes

My wife joked about doing her circus arts stuff from it, I said not a chance lol

 

[Susquatch]

My wife joked about doing her circus arts stuff from it, I said not a chance lol

Now wait a minute. I think you are being a bit hasty there..... If my wife volunteered to do some circus acrobatic positions on anything, I wouldn't care if it were made out of sawdust! I'd be all over that!

 

[SomeGuy]

Now wait a minute. I think you are being a bit hasty there..... If my wife volunteered to do some circus acrobatic positions on anything, I wouldn't care if it were made out of sawdust! I'd be all over that!

LoL so that's where you draw the line on structural support? If wife is involved, doesn't matter if it will fail ... because ... maybe it will ... ? lol

She goes to a place dedicated to it with properly rigged stuff, she doesn't really do anything related at home, but it's crazy to see the frankly anti-gravity moves she pulls off.

 

[Susquatch]

LoL so that's where you draw the line on structural support? If wife is involved, doesn't matter if it will fail ... because ... maybe it will ... ? lol

You misunderstood I think. At my age, sex kills. Happens a lot. I always said I want to die in the saddle. It's a good way to go.

If my girl wants to use an uncertified piece of artistic hardware to help her get into some kinky position, I'm game!

 

[JustaDB]

If my girl wants to use an uncertified piece of artistic hardware to help her get into some kinky position, I'm game!

Hence the tape measure? Take a walk on the wild side...

 

[jorogi]

If my girl wants to use an uncertified piece of artistic hardware to help her get into some kinky position, I'm game!

You might want to consider a spotter.

 

[jorogi]

sex kills. Happens a lot.

What, dying or sex ?

 

[JustaDB]

What, dying or sex ?

You know the old fantasy: Shot by a jealous husband at 90.