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  • Base for hydraulic manipulator

    Discussion in 'Calculations' started by BronkaG, Nov 16, 2014.

    1. BronkaG

      BronkaG New Member

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      Hello,
      i was asked to help make a portable base for hydraulic manipulator arm Palms 680.

      Could anyone give any suggestion on a matter, how to design it.

      does it mater how big base itself should be or its just weight of the base that matters.

      Arms parameters:
      Span- 6.8m
      Max load 47kNm
      max weight at 6.8. is 550 kg
      mass of manipulator itself 1225 kg


      http://www.technikboerse.com/thumbnails/49024770/785939/1272907222_0x0.jpg
       
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    3. Lochnagar

      Lochnagar Well-Known Member

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      The picture you have shown is of a logging crane - which would typically be fitted to what is called a forestry forwarder - which picks up the felled tress - and deposits them on the trailer. For those not familiar with the forestry scene - see pictures below of a small and large forestry forwarder in the links below.

      So normally, the chassis of the forestry forwarder takes the bending moment and provides the counterweight to the weight of the trees that are being lifted - and the hydraulic stabilizers prevent the chassis from over turning/capsizing.

      So what I am unsure about from the question you have posted - is what exactly do you mean by a "portable base". Perhaps you could explain - or show some further pictures of what you are wanting to do?? Are you going to be mounting it on a forestry forwarder - or are you going to be mounting it on frame in the yard??

      http://www.dpforestry.co.uk/9/25/Equipment_Hire/Alstor_mini_forwarder.html

      http://www.directindustry.com/prod/ponsse-oyj/forestry-forwarders-56915-370512.html

      Hope this helps.
       
    4. BronkaG

      BronkaG New Member

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      Tank you Lochnagar for reply.
      i will try to explain it: i have this logging crane separated from the machinery it was attached before. and want to to make some kind of portable pad to attach crane to what i mean by portable pad. is that i can move that pad with attached crane, with forklift to any place around a yard. So in short i need stable pad to assemble my crane onto so i can lift wood or something without worrying that all this assembly will turn over. I hope its more understandable. if not i will try to to some sketches or drawings.
       
    5. Lochnagar

      Lochnagar Well-Known Member

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      O.K. Bronkag - I see what you are trying to do. I have two ideas:

      1) Put the logging crane back on the trailer - because the trailer and the tractor will allow you to easily move the crane around the yard - but it will also provide the "trailer / tractor frame" to resist the manipulator from capsizing - which is very important.

      2) Put it on a frame that you can lift with the forklift. My concerns with this idea are as follows:
      a) If the frame is big - it will prevent you getting the crane up close to the stack/pile of timber
      b) If the frame is small - you will need very substantial counter weights - which might mean your forklift might not be able to lift the frame.

      There is another issue - which is the crane can rotate / slew through 360 degrees - which means that you can theoretically pick something up behind you - as well as in front of you. This is why option 1) above is very attractive - because the tractor provides the counterweight when you are lifting something in front, whereas when you are lifting something up from behind - the trailer provides the counterweight.

      Another option would be secure the crane to a very large slab of concrete in the ground - but with this option - it means you can only use the crane in pre-defined positions in the yard - which is not very flexible.

      So maybe you could have some further thoughts on the practical constraints you have in the yard - and let us know how you want to proceed.

      Hope this helps.
       
    6. BronkaG

      BronkaG New Member

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      Problem is there is no tractor only forklift, and crane will be used inside warehouse.
      all assembly can weight up to 3 tons, forklift can lift it. i was thinking something like a crab like pad rectangular pad with extendable legs on sides prevent it from turning over
       
    7. Lochnagar

      Lochnagar Well-Known Member

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      Hi Bronkag,

      If your forklift is rated at 3 Tonnes - that means the 3 Tonnes will be only 500mm in front of the mast of the forklift - which means the mounting frame will need to be quite small. (There is a possibility that the frame could be made in the shape of an "X" to minimize this issue).

      Yes, as you say you can have extendable legs - but you will still need significant counterweights on the frame. The counterweights could be removable - and quickly "attached" to the frame - which would make the lifting of the frame easier - since if the counterweights are permanently attached - the 3 Tonne forklift will never lift the frame.

      My only other concern is that if you have extendable legs to the mounting frame - then the longer these are - this will severely reduce the reach of the crane.
      So for example - the reach of the crane is 6.8m - but if you put on a rigid mounting frame that is say 3m square - this will reduce your reach by 1.5m - to 5.3m. Additionally, very roughly - to just maintain balance (ignoring dynamic effects for the moment) - you would still need 4 counterweights around the square frame - and each counterweight would need to be very roughly 0.75 Tonnes. However, because there are a lot of dynamics (shock loads - or sudden loads) on these cranes - in reality you would need counterweights that are roughly 2 times 0.75 Tonnes - thus 1.5 Tonnes. Or you could make the frame bigger to reduce the size of the weights - but then you reduce the effective reach of the crane.

      On a 360 degree excavator - you only need one counterweight - however, I think it would be very risky to attach one counterweight to this crane - because the slewing mechanism of this crane will not have been designed to take this load - so I would not go down that route.

      Hope this helps.
       
      Last edited: Nov 29, 2014
    8. Lochnagar

      Lochnagar Well-Known Member

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      Hi Bronkag,

      Just thought I would explain how I arrived at the answer in the previous post.

      Hope this helps.

      [​IMG]
       

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