Optimal length of lag screws

[Ignoramus7553]

I have a wooden cart on casters on which I will have a generator. Its weight is 1,400 lbs, and the weight of the entire stucture would be

1,600 lbs. This cart may one day be winched into a trailer on ramps.

To the front of the cart, I want to attach a lifting eye. It is a big lifting eye with the threaded stem removed, and welded to a 1/4" plate, which would be attached to the cart by means of four 5/16" lag screws.

My question is, what is the optimal length of these lag screws. The wood is regular soft wood. I assume that beyond some length, the extra grip given by extra length is meaningless.

[Rick Samuel]

[Lee Michaels]

I have worked with lag screws extensively and I do not feel confident that lag screws will hold consistently any heavy load if the stress is being applied vertically. Horizontally (to the lag screw) perhaps, but not vertically.

If the lag screws are stressed sideways, I would want at least 3 1/2" to 4" minimum.

I would suggest some kind of threaded BIG bolts, another plate on the other side from the eye plate, and extra nuts.

I have built platforms that needed to be winched onto a trailer or truck before. What I did was to jrill a big hole and run a bolt throough it. I cut out a section near the middle of the bolt. I then threaded the bolt through a big iron ring. This was sufficent for any kind of hook or other means of attaching the cart to the cable.

[RicodJour]

Here's a lag screw load calculator:

[dpb]

I agree w/ Lee the way to do this is w/ a through connection.

Lags aren't reliable enough for the job at hand and aren't intended for tension loads at all and certainly shouldn't be used for lifting scenarios.

[Rusty]

I would use bolts and bottom plate lag screws would be silly. If you do use lag screws get video of the first lift,

[mac davis]

Define "wood cart", please.. especially the material it's made of..

It seems to weigh 200 pounds? Will the lag bolts be in a 2x4" a 4x4" or maybe 1/4" ply? Why specifically 5/15" lags?

mac

Please remove splinters before emailing

[Ignoramus6193]

three 2x12 6' long. Three crossmembers, at front, aft and rear,

2x10s. The crossmembers are attached to lengthwise 2x12s by means of wood glue and screws.

Maybe 150 or 170.

Lag bolts are 5" long, 5/16 in diameter, there is four of them, screwed into those 2x12 and 2x10s.

This is for pulling, not lifting.

[dpb]

Ignoramus6193 wrote: ...

In which direction?

Same problem -- load isn't as great, but it's still a safety issue if it pulls out while somebody is behind the ramp.

It's not at all an optimal design choice and it would seem essentially trivial to make the lags machine bolts, ideally w/ the plate also on the back side.

Note the pulling resistance of lags is only slightly over the weight from the calculator posted which provides essentially a safety factor of

1.0 -- again an indication you're under-designed.

--

[Nova]

It sounds like the glue joint would have to be end grain to long grain making it just about useless. What do you suppose the shear strength of the screws are for the cross member that the "lifting eye" will be attached to?

[Morris Dovey]

Actually, it also for bolts, wood screws, and nails...

[joe]

EXCELLENT link! that one's going into the favorites.

jc

Here's a lag screw load calculator:

[krw]

I'm planning something akin to what the OP is doing. I have an=20 unfinished room above my garage with access only to the second floor=20 of the house (it's where they generally put the "bonus room"). My=20 plan is to use if as my shop (convert it to the bonus room if I=20 move).

I'm trying to think of a way to get tools and materials up there, so=20 was considering a hoist (what's the difference between a "hoist" and=20 "winch"?) with an access door down to the garage. I'd have to lift=20 a table saw (~600lbs.), hence the interest in this load calculator.

--=20 Keith

[dpb]

krw wrote: ...

Hoists are for lifting, winches are for pulling.

As well as the connection, need to be sure you're attaching it to something that can hold the load.

A FWW a couple years ago had a shop in upstairs over garage w/ the same idea. It, of course, was designed dedicated so he designed for and installed a full length trolley beam, but a simple block and tackle was sufficient for lifting even larger qear. (IIRC, he had an old 20+" jointer which would have been roughly twice your weight...

--

[Puckdropper]

dpb wrote in news:gb5u9p$c8d$ [e-mail]:

*snip*

*snip*

One thing to consider is that with lag bolts you have to drive the entire bolt in. At 4" long, that's a lot of driving to do. Conversely, with machine bolts (such as carriage bolts) all you've got to do is drill a through hole and attach the nut.

Just something to think about as you get to building. On my ice rink last year I switched after the second lag bolt to carriage bolts and got the thing assembled.

Puckdropper

[Ignoramus6193]

It is long grain to long grain, if I understand you correctly. One board under another but perpendicular.

[Ignoramus6193]

I used an impact. It was not a problem. I think that I would not hesitate to use this ring for general pulling of this around the yard, but when it comes to winching it into the trailer, I may attach a slig somewhere else.

[Bored Borg]

Through bolts, BIG washers or second plate.

[David G. Nagel]

Yes; use an impact wrench, just be careful that you don't twist the shaft in two when you do.

Dave N

[Ignoramus6193]

I drilled pilot holes. So driving these screws took only a couple of minutes. You guys convinced me to not use it for winching it up the trailer ramps. Otherwise using it for general moving about, should not be a problem.