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Shop Table top crane

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G

Gennady

Super User
Hello gang.
I am getting into conditions when lifting heavy items is a real pain for my back. I was looking trough internet for some ideas and inspirations and there are few youtube folks that have build "sky hook crane". Tubalcane has several videos with great explanations of his ideas and considerations and I decided that I need something similar for the dividing head, vise, lathe chuck and other heavy items that I have. I browsed trough my pile of metal scrap and found few pieces that might be suitable for building table top crane without whole lot of manufacturing. Main objectives are simplicity, safety and use of what I might already have in hand.
Here are part that will be used: Car shock absorber, spring and spring plate removed, steel plate (brownish colour) that will be mounted on the mill table or lathe, boom (extra parts need to be cut off) . Still missing flange to affix shock absorber on plate, boom support, trailer winch. Any thoughts ?


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I’m interested to see where this is going, I too have heavy items on the mill table.

I’m not sure where the shock comes in unless it’s the boom swivel (clever) but while we’re at it I’m interested to know about the loading on the table slots.

If the crane is using them to mount it I’d want to do my homework on the loads to make sure the cast iron won’t be loaded too much in tension.

While we’re at it I might think about using a treadmill tilt jack to raise a boom to do the lifting. The tilt jacks are quoted between 500 & 1000 lb thrust so probably capable and even better, free!

D :cool:
 
You use the bottle jack to adjust the radius

What the heck are you going to use the shock for ?
 
Gennady said:
why not ? any hidden prob
Click to expand...

Well there isn't actually a bearing in there, it's just turning on the seals, when it's fully extended like that there is only an inch or two into the cylinder, doesn't take much bending moment to bend that joint, and they don't normally stay fully extended with any kind of load, a new shock has some limited rebound, but it's not much

If your using it collapsed, then it's just that you don't have a bearing and it's just the rubber seals turning inside the cylinder

It would be the exact same as using a hydraulic cylinder for a pivot

Better off imo with a pipe inside a pipe as a pivot, less friction, stronger
 
Indeed two pipes pivot is stronger, Just to note - I am using it fully collapsed, no plans and no means to extend it. Regarding friction - it is well lubricated, polished and fitted surfaces. I will see how it will rotates under load.
 
Gennady said:
Indeed two pipes pivot is stronger, Just to note - I am using it fully collapsed, no plans and no means to extend it. Regarding friction - it is well lubricated, polished and fitted surfaces. I will see how it will rotates under load.
Click to expand...

Are you turning the shaft inside the cylinder ? There is a glad nut on the bottom and top with ?rubber? O rings, that's where the friction comes from

But you will have a fair bit of leverage with the boom, so it may not be that big of a concern, assuming your turning the shaft
 
I will be turning external 'tube' around shaft and shaft itself is screwed into base - it is more convenient this way, and the 'tube' has already bracket for the boom.
 
Well I can see the convience, but I don't think it's a great idea. Best to keep the boom real short and the loads real light, the moment force that little threaded section will see is going to be huge. Best hope its not so hard as to snap rather then bend.

its also nice to have some way to change the radius under load, like the bottle jack on the boom of @quitereal hoist, you don't realize how much of a difference that makes until you use something with a fixed radius
 
Good suggestion, thanks Ryan. I will consider telescopic boom. Just need to find rectangular pipe that fits in other pipe. Regarding snapping of the shaft - 20 mm of 1018 steel or an equivalent low grade - should be fine. Will bent but not snap.

phaxtris said:
the moment force that little threaded section will see is going to be huge
Click to expand...
Threaded section is to keep it tightened, I will make flange boss that takes shaft deeper.
You want me to do a calculation from university course of Structural Performance of Materials ? :)
 
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