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.