Mini gantry crane

[dstig1]

Proof testing ductile materials like steel/alum is risky. You can overstress the material but yet not fail it. If you do that, the material is permanently damaged and can then be weaker causing a failure later on. Proof testing is generally only done on brittle materials like ceramics where they either survive or fail. There is no risk of "some damage" that makes it weaker but you cannot tell. Be very careful in orverstressing metal assemblies. If you are designed 5:1 and you overstress 2:1, then odds are you are fine (IF you welded things right, with the right materials and processes), but if you start pushing 3-4:1, then you are risking hidden damage in a non-certified assembly. And this is a guideline, not a hard ad fast rule. Again, proof testing metals is a sketchy prospect at best.

 

[robstaples]

Sodo, the wheels are from Surplus Center
6x2 RIGID CASTER
New, JARVIS rigid plate caster with Triton polypropylene wheel. High load capacity Zerk fittings on both wheel hub and thru bolt. Roller bearings on axle.

SPECIFICATIONS
Wheel Size 6" x 2"
Load Capacity 1250 lbs.
Top Plate 4" x 4-1/2"
Mounting height 7-1/2""
Mount 2-5/8" x 3-5/8" slotted to 3" x 3"
Bolt Holes 3/8

With the weight of the AL, the pair is good or about 1 ton.

 

[LD1]

The load capacity is not the problem IMO. It's the smaller diameter. Even a small pea sized pebble is gonna stop it cold

 

[Sodo]

Could load it up and roll it over a pebble and see. Polyurethane might accommodate small pebbles.

Personally I'd load it at least double of the 880 lbs and lift 1 inch, bounce on it, shove it, try to see where it's flexing and brace accordingly.

Ignore the purple brace on the red/white juncture, I drew the pic but now I don't think it provides anything. The load on those 1/2" bolts is a tiny fraction of their capacity.

The rolling legs could have a fold-up brace that swings down and double-pins at center for when you travel it. Or maybe if you ever have a real heavy load just bolt a 2x4 across from leg to leg (at that time). You might get a handle on this by rolling it over a pebble with 2x or 3x 880lbs.

And you could hang a shower curtain from it. :thumbsup: Don't need a towel with that blow-dry.

 

[LD1]

Looking things over again, I think the connection to the steel beam with the angle iron and bolts will be fine. Take the aluminum beam out of the equation and I would have any concerns hanging ~1500+ lbs from that pair of angle irons.

Welds still concern me, without seeing pics of the rest of the welds. Aluminum is tricky.

And the legs are still a concern. Mainly if you have to move a ~800# load that requires rolling those casters along. Thats in the weak direction of your aluminum box tube legs. And it is aluminum.

My 4 posts on my bridge crane are 10" i-beams standing 10' tall. They do flex if I bump the end stops pretty hard.

With your setup, I wouldnt want to have a heavy load moving along and and hit a stone ot something with a caster. Would be afraid of a leg buckling

 

[jack707]

Well it I welded I would of use stick welding much deeper penetration then mig. more PSI to! You could of used either 7018 or 8018 IMO.

 

[LD1]

Weld aluminum with 7018?

 

[Jim Timber]

Weld aluminum with 7018?

Someone isn't paying attention.

 

[LD1]

Someone isn't paying attention.

Not only that, but even if it were steel, I disagree with the info he gave.

7018 and er70s mig wire have same tensil psi.

And I can make a cold weld with shallow penetration just as easy with 7018 as I can With mig. Likewise, I can butn holes through 1/4" plage pretty easy with either.

Weld strenght is about proper joint prep and proper heat setting. NOT what process you use

 

[jack707]

Why would he pick aluminum for support beams? LDI stick welds penetrate deeper them mig.

 

[Jim Timber]

He said why, if you'd actually read the thread instead of just dumping comments on the discussion.

 

[jack707]

Yeah Jim bite my head off will ya!

 

[robstaples]

Sodo,
That shower in the corner was to be my eye wash until I priced the finish fittings. The coil is connected to ( worst looking thing I've done) to give me warm filtered water outside the man door or garage. Air is on the left side. Behind the eye wash wall is a full bath. I recently sprayed hydraulic fluid on my face (no pressure) and had to wait a long time for the water to get warm do to the long run-- 30 ft. Somethings get missed in the design process. I'm still thinking about aluminum revisions. Thanks all for your input.

 

[robstaples]

What I've learned so far from use, I need to be able to lock the trolleys in place. I'm thinking of a threaded bolt to pinch the beam. With the gantry so easy to roll, the object pulls the gantry instead of vice versi. Came up moving my mmm. Also, everyone is thinking heavy stuff, I'm thinking 200- 400 lbs stuff. My lathe is in line with the wheel path , so I'm thinking lift one end at a time and swing 6 inches. That's all I need to clear it. Thanks again for all the good insight on this forum. Rob

I'm thinking of lettering on the beam "If the winch won't do it, Don't do it". It's cap is listed at 880 lb.

 

[LD1]

Why would he pick aluminum for support beams? LDI stick welds penetrate deeper them mig.

Yeah Jim bite my head off will ya!

Read the thread. You made a comment about welding steel. Clearly you didn't read the thread.I commented about that. You come back AGAIN still thinking it was steel. Should have been the first clue.

About the stick vs mig......forget the process. A blanket statement that stick penetrates more than mig is an ignorant statement.

Sure, stick "can" penetrate mode with proper rod and serup and machine. But mig "can" penetrate more also. Far more to weldnig than just stick or mig.

 

[Jim Timber]

Yeah Jim bite my head off will ya!

It's not like that, but you clearly didn't read this thread before talking about 7018.

I'm far from a crane expert, but I have built one which successfully holds the 4,000# I designed it to and has been proof tested with closer to 5,000#. His 6x2" wheels are what I use on my runway trollies (4 per side) with urethane tires no less. They run real smooth and are load rated to 2,000# each. My bridge and runway beams are rated for a 5:1 or better safety factor even though the casters aren't. Normal working load is well under 500# and anything over 2,000# is infrequent to the point of less than one occurrence per year, so that's fine.

The comment about gravel is valid, but easily prevented with good house keeping. Urethane does handle some grit without causing a problem too. I used them because they run quieter and metal wheels on a 24' track makes some noise.

In the end, we're all second guessing this crane based on some vague photos and the OP's assessment of it's performance. We're not going to be the ones who have to use the crane or suffer the consequences of it's failure, but I do think the majority of people involved in this thread want to see the OP succeed and have a safe implement in his garage. Jumping in with "shoulda done ____" and then having it not even relevant to the materials in use is hardly beneficial to anyone.

Aluminum MIG in a structural application without a mastery of the process is asking for trouble. Welding aluminum at all in a structural application is asking for trouble. I think the OP knows why we have concerns over some of the joints, and that's part of the learning process. Better to wonder about it now than when a load is swinging at you because something cracked loose.

We got a long way without egos here, and I was pretty impressed by that. Lets get back to helping Rob get his crane going.

 

[Jim Timber]

What I've learned so far from use, I need to be able to lock the trolleys in place. I'm thinking of a threaded bolt to pinch the beam. With the gantry so easy to roll, the object pulls the gantry instead of vice versi.

If you use the crane to winch, you'll be applying forces none of the load charts are designed to counteract. Cranes are meant to lift and set, not pull side to side.

 

[jack707]

I have never seen mig used for anything structure in 14 years in field construction we have always use stick to weld the lugs on when we make a pick there is a reason why mig is not used. Sure it has its place but NOT IN STRUCTURE!.

 

[LD1]

The comment about gravel is valid, but easily prevented with good house keeping. Urethane does handle some grit without causing a problem too. I used them because they run quieter and metal wheels on a 24' track makes some noise.

I think you would actually be surprised. My 8" diameter wheels on my end trucks are silent. I can move the thing and you cannot hear it. Both cranes we have at work (a 7.5 ton 50' span yale and a 25 ton 60' span conoco) have metal driven wheels on 40# rail. They are VERY quiet.

Trolleys though...different story

there is a reason why mig is not used

Actually there are several reasons why mig isnt commonly used on most construction sites. But strength and lack of penetration are NOT some of the reasons why.

 

[Jim Timber]

My columns were all constructed with spray-arc via mig. I bolted the connections for my trolleys to the bridge for ease of assembly more than anything.

MIG isn't used in construction because you need shielding gas and it's much harder to ensure good coverage outdoors than with a stick that burns the available oxygen at the puddle, and then there's the logistics of moving that much machine to the joint and still needing a power supply for it.

SMAW on the other hand can be done with 2 leads. That's why you see it on construction sites more.

I have seen MIG on construction projects for structural work when they're putting in elevators. Too much smoke indoors with SMAW.