lifting clamp for metal plates

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cbassjr
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Re: lifting clamp for metal plates

Post by cbassjr »

I'm assuming he is using 4 of the and some kind of H lifting bar. looks like the pincher can just be reversed to pinch correctly. Anyway that's the way I'm going to do it. I would think a 4 foot 2x2 heavy wall center section with 36" cross T welded top and bottom with equal chains to the pinch clamps and a double pick up welded to the top side of the pickup H also like to incorporate the chain link things in this post as well to balance the load. That's my 2 cents and as for the engineering part of this there is stuff all over this site that could hurt someone. This site is for DYI'ers and if you don't think it's safe then don't use it. I could see if I was building this kind of thing and selling it but I'm not. Thanks for the post.
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Re: lifting clamp for metal plates

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Re: lifting clamp for metal plates

Post by Thumper »



Double YIKES it has El Cheapo bolts holding it together :shock:
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Re: lifting clamp for metal plates

Post by chasxjs »

Thanks for this post. I will need to tweak the dimensions but it is just what I need.
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Re: lifting clamp for metal plates

Post by Corfabrication »

Thanks for sharing.

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beefy
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Re: lifting clamp for metal plates

Post by beefy »

I wouldn't put much weight on a design like that. The most stressed point of that design is at the weld which is taking a tensile pull. The clamp lever is exerting a downward push on the bottom plate at the opposite end of the weld, effectively making the bottom plate a lever to exert a lot of tensile pull on the weld. Worse is that the strength of this weld is dependent on the quality of the weld.

The picture shown below of the "properly designed" clamp shows how this tensile force is accounted for. It uses a C shaped one-piece beam section, no reliance on a weld taking a tensile pull. OK you lose the low profile feature of flat plate DIY model but it's got strength (= safety).

Sorry to be a killjoy but some people don't have much mechanical understanding and could attempt to load up the flat plate design with some heavy steel.

Take a look at this page for lots of design examples:

https://www.google.com.au/search?q=stee ... d=0CDcQsAQ

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Re: lifting clamp for metal plates

Post by Corfabrication »

While they may not be rated for huge capacity, I'm sure they will work fine for loading one sheet at a time onto the table. 300lbs spread to 4 clamps I'm sure I will be OK. That clamp you posted probably weighs more than my entire plasma table does
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Re: lifting clamp for metal plates

Post by beefy »

Corfabrication wrote:While they may not be rated for huge capacity, I'm sure they will work fine for loading one sheet at a time onto the table. 300lbs spread to 4 clamps I'm sure I will be OK. That clamp you posted probably weighs more than my entire plasma table does
Didn't know you had a 10 inch by 10 inch plasma table :lol:

In any case I'm illustrating the design, not the size. Like anything you scale it up or down to suit. I never once said anything about needing a massive clamp.

If you know anything about rigging, the pull on the rope increases as the angle goes from vertical to leaning over to say a central lifting point for example. There are charts illustrating this. So unless someone has a lifting frame where all the ropes/chains are vertical over the lifting clamps, you've got more than a 75 pound pull (300 divided by 4 clamps) on each clamp. The diagram I've attached illustrates that with 2 ropes at an angle of 30 degrees the tensile pull on each cable equals the weight of the item being lifted.

Next that pull is leveraged several times at the weld point by the clamp lever acting on the end of the metal plate (of the clamp). You'll probably have a few hundred pounds of tensile pull at the weld point when you factor all that in.

I can see people using a 30 degree angle like in the diagram, so if they do the tensile pull on one clamp becomes 150 pound. Judging by the length of the plate on the clamp I'd say a conservative estimate would be to multiply this 150 by 4 due to leverage. My calculated guess is you could easily have 600 pounds of tensile pull directly on the weld point when lifting only a 300 pound plate with 4 clamps.

Not a good design for a less than perfect weld.

I like people to understand what they are doing when making such a tool.

But go ahead and recommend it if you want.

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Re: lifting clamp for metal plates

Post by conradestrada »

Now that is some valuable information! Thanks a bunch
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Re: lifting clamp for metal plates

Post by chasxjs »

Very interesting.
I had no idea the load would increase that rapidly.
Thanks.
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Re: lifting clamp for metal plates

Post by beefy »

You're welcome lads, always happy to prevent an accident.

I do mainly stick welding at present even though I've got a big 330 amp mig sitting there. Like many people who may attempt to make that clamp, I'm not a perfect welder. Now and again, when I knock the slag off, I notice a weld bead has a crack running longitudinally it, so effectively it's like the bead is split in half along its length. It's never happened with a mig weld mind you, I only seem to get it once in a while with stick welding. The weld otherwise looks good. Pre-heating the steel seems to stop this happening.

Point is a lot of guys here will do amateur grade welding, you know point and shoot type welding, and that clamp design relies purely on the weld being very sound.

Here's a link to the type of cracking I have sometimes experienced:

http://www.twi-global.com/technical-kno ... cking-044/

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Re: lifting clamp for metal plates

Post by Corfabrication »

Thanks for your concern. I'll post another thank you when I burn the clamp dxf you post.

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beefy
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Re: lifting clamp for metal plates

Post by beefy »

Ooh, you are a sulky boy. Don't worry though you won't have to waste any of your matches or lighter fuel because I won't be posting a dxf of something that is used to lift heavy stuff. I'll leave that for the trained mechanical designers who carry out load tests on such designs. In any case you can't burn a dxf (unless you "burn" it to disk), it's a computer file.

Good one. I point out the potential risks of that clamp design, and you go in the huff because you don't like me doing that.

You obviously wouldn't give a shit if someone gets hurt when that wonderful design gives way.

If the point of posting that picture is to show us how great your tig welding is, that's totally off track to what I said about not everybody is a great welder.

Sorry I upset you, next time I see something I consider an accident risk, I'd better keep my mouth shut in case it gets your bottom lip pouting all over again. Instead I'll try and be happy with the thought that someone could get hurt, all for your satisfaction.

And you don't need to thank me, it wasn't for your benefit, you are obviously happy with using it.

Why don't you do something more constructive like tell me what I said about the design is incorrect, and tell me why. I've tried to give logical mechanical reasoning about the weaknesses of that design, only for safety reasons.
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Re: lifting clamp for metal plates

Post by grindergary »

Keith,

Thanks for your concern. People just don't seem to realize that the way things are going, if you design a product and it fails in use, YOU become liable. Ask how I know.

Its just like when you cut a piece of art for someone with lots of sharp points and some kid gets hurt, then watch the sh*t hit the fan.

Even as a structural fabricator, I am liable for all welds and some design that was not engineered.

I encourage you to speak your mind on any safety issues.

There is no feeling in the world wost than when you build something and someone get seriously injured or killed.

Thank you for your insight.

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Re: lifting clamp for metal plates

Post by beefy »

Thanks for the support Gary, appreciated. Most of the time the thread goes quiet when me and someone else start disagreeing "strongly" on something.

Yes the overseeing bodies in industry seem to look out for who they can crucify when an accident happens. I bet there's a lot of DIY accidents happen that don't really get any attention. I see this clamp design having the potential for a DIY non-mechanically minded person doing a quick weld up then overloading it to breaking point (which could be not much depending on the weld). Might even have a little one there watching Daddy as he loads the steel on the table. The thought is frightening.

I won't say who it was but someone here made a very nice piece of art. Many obviously seen just that, nice art, and lots of nice compliments followed. The first thing that hit me though is what a perfect bunch of sharp steel spikes pointy vertically upward it was. The art sat on the ground. If someone tripped and fell on it they'd get skewered right through. I mentioned it but nobody responded, I couldn't quite figure that out. Maybe it was a complete insult to say such a thing about a piece of art.
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Re: lifting clamp for metal plates

Post by Rex »

THANKS FOR SHARING
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Re: lifting clamp for metal plates

Post by 5mcncmetalart »

german driving same as u s been there england people do it on wrong side
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Re: lifting clamp for metal plates

Post by mikeg53549 »

Thank you East German this was what I was looking for.


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