gantry crane material

How are you going to support the beam? If it will be supported separate from the structure of the barn ( and it should be ) you could probably go as light at a 10" I beam. If it was me, I would want at least a 14" I beam with support columns to match. Yes the 14" would probably be over-engineered, but how would you know for sure that 750lb is your max load? For me, I like to go with a safety factor of at least double or even triple when it comes to suspended loads.

You could use six inch "I" beam to span six feet or an eight inch "I" beam to span ten feet. However all is dependant upon the supporting materials which could be two and one half or three inch architectural square tubing or three inch x .090 wall chromoly tubing.

example:

The picture in your post with the beam set on posts attached, but not structurally dependant on the barn, nor will the barn be dependant on this hoist for structure is about what I think will work best. I don't want something I have to move or that takes up alot of space and I have the ability to move anything I will encounter on the floor. Thanks alot, the gantry idea sounded good, but now it sounds like it will be more trouble than it would be worth.

With 6 x 6 posts supporting a 8" "I" beam you'd be safe up to about two tons. Six inch "I" beam just isn't enough for lifting over 500lbs due the span. Be safe

A W8 x10 steel H beam with a 3000 pound load at 4', would deflect .06", using 36K steel. Keep in mind the horizontal component of any load that you are removing from your truck and that the framing for your gantry crane can handle it, such as the truck driving off when you have the load lifted and it catches and starts to swing.

The connection from Beam to column is important, make sure that you have stiffeners on the beam where it connects to the column. You don't want the vertical load being supported by just the web of the beam over the column.

Please clarify if you are interested in installing inverted 'U' type structure.For loading and unloading from the trucks you will need 10' wide and around 10' ht. structure.Selection of the size of H beam will depend on the local availability of the sections.

Don't forget to include the weight of the beam, the trolley and hoist to the 750. I don't have my Bethlehem steel handbook handy, but an eyeball guess would be a 4"x8" I beam with 8"x8" timber columns for end supports. Also tripping brackets where the beam rests on the 8x8.

You have provided little information regarding length of "I" beam and how you intend to support it that no engineer can realistically provide any worth while info except to make assumptions regarding just how one might accomplish what you wish to do.

Gantry cranes are sometimes seen on flat bed trucks that must off load sometimes large and heavy loads. I would suggest that you check with a manufacturer of these kinds of cranes for your information. Remember that the supporting assembly for the truck mounted version is designed to fit under a 12' high opening and is mounted on the bed of said truck. If you are going to erect the gantry system so as to take advantage of your 12' high opening the legs of the supporting system will require a stronger material so as to prevent the legs from buckling when loaded to or beyond capicity.

Toomuchfun

The beam length is 8' per the original post.

Thank you!

Now I must presume that as you have used the term "Gantry" to describe your installation and you state that the door opening is 8 ft wide, the 8 ft Beam will be perpendicular to the door.

Why don't you forget about the term "gantry" and explain just exactly what it is that you imagine this thing should be designed to look like. I described in an earlier response just what a gantry does and how it works. If all that you want is a trolley that runs side to side, say so! If you want it to run length wise so that it extends out ward over the load, lifts it and then travels back toward the other end, this requires an entirely different support system. If it is going to have one end cantilevered this will require a completely different design as one would have to account for holding the unloaded end down.

In short, I am left to assume that you do not know just how a Gantry crane functions. If you really want to construct something that is quite versatile, you could construct 2 A frames mounted on wheels, and attach one to each end of your I beam. This way you could straddle your truck, lift the load, move said truck out from under the load, lower it to a safe height for traveling and roll it inside of your facility. A piece of equipment like this has many uses beyond just unloading or loading a truck, and functions with even more freedom than a gantry crane.

"I constructed a small movable crane that can lift 400+/- lbs."

I used an axial from a golf cart, a 6" piece of eye beam and a 4' piece of heavy C channel for the frame. For the hoist, I used a piece of heavy walled 2" pipe 16 ft long, along with 4 pieces of rebar for strengthening, 2 winches, one to lift the boom and the other to lift the load, a double block pulley that I made up from parts, and a single pulley with a hook that I also assembled from parts, and some 1/4" galvanized cable. I salvaged an Eye ring hook up from a rusted away jeep trailer and I move this thing around with my lawn tractor for light lifting and my jeep for heavy lifting. I recently added a heavy duty bracket so that I can use weights salvaged from a piece of exercise equipment, as a counter weight to fill the gap between using just the lawn tractor and the jeep.

TMF

A welder friend of mine has pretty much what Guest describes at his shop. He also has a small chainmotor to lift, instead of say, a block and tackle. Ten foot 8" I Beam I think weighs 22 pounds a foot, though I could well be wrong and don't want to be quoted. I've often had to move such beams into place, and seems like they are heavier than that. Nobody seemed to carry a block and tackle and it seems like you always end up with some tense moments trying to set such things from 12 foot ladders. I myself am fond of boomtrucks which are not that expensive to hire, but you could probably use your block and tackle or chain motor rigged off roof truss to lift the beam, and save some backache "on the day".

It might be interesting to see if a wooden beam would do the job, for a 12" 1 and 3/4 LVL, is right strong.

In one era of my life I had a Pole Barn to mess around in, and it is a wonderful thing to have for a guy. I suppose you could call it The Shed Theory of Domestic Tranquility.

P.S. I also find few people in general who even know what a Gin Pole is.

Hello Transcendian,

If all this poster wants to do is off load the loads that he is posting, he might do well to get an old beater of a truck and mount a"gin pole" system on it, and use it only when he needs it, or if he has a concrete floor in his barn, he might find an older used forklift truck that will suffice for his needs. Any of these options offer other uses as opposed to a stationary gantry system.

Toomuchfun

I agree.

My friend also has an old forklift that he poured Pro Long lubricant on to get it to work so as to lift stuff.

It is a bear of a machine, and very hard to drive.

I ran a boomtruck, and have run Lulls, and a small crane, not to mention directing rigs where Chain motors were used, and, well other stuff.

I did think of just a couple of 8 by 8"s in the open of a ten foot span, and rudimentary track to the barn, so as to allow for a variety of heavy stuff, but attempted to answer the question from my experiences, considering the question.

Forklifts are not really designed in my experience to work well on any surface other than the flat of a concrete factory floor.

This is why I am partial to the Lull, or a Boom Truck for outdoor work.

The Lull that you can at least level from side to side is a fine machine, though there is a temptation to pick-up too much and extend too far.

When putting people in the air on one building I sweat my balls off at the extremes of the angles and reach of the boom.

Build to budget, or budget to build is another factor.

The modern age is demarked by sailing tech of the 1500s when great sailing ships were deployed dependent on the block and tackle and knowledge of how to sail into the wind.

If I had any money to spend on machines to lift heavy stuff, I'd probably just buy a 5 ton boom truck, since it will move around and lift a lot, and they work outdoors and are not that rare.

The Op has given a fair description of the intended use and application. However the term gantry crane does not fix the description.

What is a better adjective for what the Op is talking about?

Fixed overhead crane, or monorail, as I explained here in this thread.

I learned a few things about cranes when I did drafting work for a crane manufacturer.

An overhead girder with trolley chain hoist

Don't forget to consider the weight bearing capacity of the barn trusses (or whatever holds up the barn roof)!

As an alternative, consider running two parallel beams, putting a frame between them on wheels, and putting the hoist on wheels on the cross frame. That will let you spot loads exactly where you want them. My advice is to engineer it as heavy as you can afford. This will let you upgrade to a serious shop crane if desired. A good chain fall (chain version of a block & tackle) will let you pull a diesel engine, swap a truck body, etc. Just remember Murphy's Law when figuring capacities of chains, cables, beams, etc.- Granddad always insisted that Murphy was an optimist.

I would purchase a fork lift. Would have many other uses. Once you get your load to the ground with the hoist then you would have to man handle it around. With a fork lift you can pick it up and put it where you want it. I looked at a used 2000 lb truck for a customer that we was ship to a island in the Caribbean. Has given him years of good service all for $900.00. Your investment in your hoist and supporting structure has limited use over a fork lift.

Sorry I haven't been able to check in for a few days. I'll try to be a little more specific. The reason for the whole thing is that I live in the booneys with my wife and I have alot of equipment that is too much for one person to deal with. I don't really need a trolley on the thing as long as I can get the load lifted so I can back the truck or trailer under it. There is the possibility of pulling a motor out of one of the vehicles, but that is remote and will be avoided if possible. The beam will be supported by 6 x 6 pressure treated posts and will be just inside the structure. I carry a gang box for jobs and it could be loaded and unloaded without having to empty all of the tools out. Since I posted this I have checked out what I am working with a little closer and I can't see myself exceeding the 750 lbs, but doubling that for safety is a good idea. I have a steel distributor nearby so availability is not a problem, nor is fabrication of brackets for attachment. Thanks to all you've been a big help.