gantry crane

Rob Mo · Dec 13, 2017

Got this in the shop the other day. I'm afraid to test it & lose a limp in the process. It stands 9'6" tall & 11'6" wide. The caster wheels are 6" bolted to 6" I-beam. Everything else is 8" I-beam. My concern is the 3/8" thick x 14" long x 6" wide plate with 8- 7/16" x 2" bolts holding the horizontal beam together. The previous owner cut it with a torch to haul in on a trailer. The most I will hace to pick up with it is 3-tons with a chain hoist. I am looking for opinions to strengthen it up, maybe gusset plates welded around it?

Rob Mo · Dec 13, 2017

dr sportster · Dec 13, 2017

It would take a lot of force for those bolts to fail. You could always weld up the seam.

Duane WI · Dec 13, 2017

The strength of an I beam is in the top and bottom flange. The web in the middle is just connecting the top and bottom flange together. The highest stress point of an I beam is in the middle right where this one is cut. I think the only way to fix this is to weld it together. In current condition it won't have too much capacity. Needs to be a good welder who knows what they are doing.

jniolon · Dec 13, 2017

did something similar on an A-frame I had to lengthen the top beam. Made a "Z" shaped cut in the top beam to join in the added 4' section. Used an 1/8" gap in the "Z" and aligned everything and clamped angle iron to beams to hold them in line.... Welded the "Z" cuts on both sides to get full penetration then ground the welds out on each web and added 3/8" thick 12" long 'fish' plates to each side and welded them full. Never had a problem with over 3 ton on a hoist...
john

Mike M · Dec 13, 2017

You got enough extra height so you could add another 1 pc. beam to the top and or to replace the cut one entirely. I sure would not want to lift much with that !

Jeff NWOH · Dec 13, 2017

As stated, the strength of an I or H beam is in the top and bottom webs. You will need to weld that beam if you want to pick up any kind of weight with it safely.

This is how I did the wide flange beams I have holding up my house (scrapyard specials of various lengths). I put a doubler on the bottom because it is under tension and I figured the more weld the better. The top is in compression, so I doubt a doubler up there would help much.

I put mine on the inside as I slid some of these under the house on rollers. For your gantry, you would have to double underneath so your hoist will roll. You probably could get by without the extra plate, but it certainly won't hurt anything.

jon f mn · Dec 13, 2017

I'll add mine to those that said that beam won't hold much at all like that. The good news is that you can easily weld it. It's just mild steel so any type rod will work, as will mig. I would weld it with mig if I had it. No need to cut any shape to it either. The important part will be to plate the bottom flange after it's welded. Get a piece of 1/4" flat 1" narrower than the beam flange and 18-24" long. Cut it so it's pointed at 45? or so with 1" flat on the ends. You can also radious the ends. Then weld that onto the bottom 100%. Make sure when you grind the weld flat on top of the bottom flange you keep it nice and flat so the carriage rolls smooth.

jon f mn · Dec 13, 2017

I forgot to add to make sure you get 100% penetration when welding the flanges.

big a · Dec 13, 2017

all good ideas. It's going to be weak the way it is now.
If you really wanted to beef it up, and overhead clearance isn't an issue, it wouldn't take much to add a truss across the top!

WGM · Dec 13, 2017

Was this splice connection certified by a structural engineer?

DoubleO7 · Dec 13, 2017

Assuming your trolley is a bottom runner.....

Replace the entire trolley beam with proper size and type of beam your trolley requires. Get a longer one if you desire it.
Use the old cut beam (which should have been cut off from the top of one leg for transport instead) and add it to the legs for max. overall height possible.

Russ from MN · Dec 13, 2017

I like Jeff's idea!

jon f mn · Dec 14, 2017

The only thing wrong with his is he went straight across the flange with the ends of his plates. If he offset them some so they don't line up it's ok, but when you weld straight across the flange like that you create a haz line across the beam so you end up weakening the beam. If he had cut angles on the ends would be a better way. Otherwise it looks well done.

bjb in TX from Ne · Dec 14, 2017

Its not the bolts that will fail, its the web steel in the beam. Like others have said you need to fully weld the flanges for it to have strength. From a design perspective, the current connection is treated like a hinge and could collapse if you put any weight on it.

bjb - Structural Engineer

old · Dec 14, 2017

If it was me I would grind a good V in the joint and then weld it up plus add a fish plate both top and bottom that are welded on. In my shop I have around 20 of I-Beam welded in the over head and I have split tractor with it and the biggest was an IH656 and I had the rear axles off etc. For that one I had to add 7 more feet to the I-beam

Russ from MN · Dec 14, 2017

That's a good point! I have seen I-beams reinforced bu putting a channel iron upside down on top, then it doesn't interfere with the trolley. When a beam fails, it almost always goes sideways and then down.

gantry crane

Rob Mo

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Rob Mo

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dr sportster

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Duane WI

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jniolon

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Mike M

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Jeff NWOH

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jon f mn

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big a

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old

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