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  • 180 Degree rotation applied with single hydraulic Ram

    Discussion in 'The main mechanical design forum' started by weatly28, Apr 23, 2010.

    1. weatly28

      weatly28 New Member

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      I am trying to figure out a way to provide 180 degree rotation to a pivot point with a single ram. I had drawn up some sketches where the ram would be able to move slightly in the rotational direction of the point. To explain what I am trying to show with out a picture, just imagine trying to spin a tire 180 degrees with a hydraulic ram. Almost in the same manner a locomotive piston turns the wheels on an old steam train. Only problem is as you get closer to full rotation(180) there would be tremendous forces on the structure based on the angle the ram had to apply power. I am assume this has been done before, so if there are any pictures,products,or links you can point me to that would be great. The design is for retractable hydrofoils on concept boat. I also would have many other applications for this 180 degree movement with a single ram,rather than 2 rams.

      I need the ram for its power, marine use, and adjustment accuracy in tuning the foils while foil borne. Non submerged foils.
       
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    3. PWASS

      PWASS Well-Known Member

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      Use a Rotary Actuator, they are usually based on a rack and pinion, the cylinder moves the rack and the pinion would be attached to the hydrofoil, although other types are available.
       
    4. Valmiki

      Valmiki Member

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      Only got a minute to answer this: I don't know how much experience you've had with machinery, but if you look at the hydraulic cylinder and linkage which hinges the digging BUCKET of a back acter at the end of the dipper arm, you'll see it can be done.

      NOTE: I'm not talking about the mechanism that rotates the boom and dipper around the kingpin, only the hinge point at the end of the dipper arm, where the bucket is attached.

      Having looked at a back acter (on the back end of a Tractor Digger Loader (like a JCB 3CX)), if you still can't see how you can do it, then e-mail me and I'll try to make some time to put the priciples down for you.

      Rotary actuators are available (and expensive), but you have more freedom with a hydraulic cylinger and your own linkage.
       
    5. mvalenti

      mvalenti Well-Known Member

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      Going to be tough to accomplish with a single cylinder. can you have a rack and pinion system? have the cylinder move the rack back and forth? I dont think excavators travel a full 180, at least the ones I have seen. Good Luck.
       
    6. Valmiki

      Valmiki Member

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      Just to be sure that it was not in fact 179.5 degrees, I pulled up the specs of the Caterpillar 430d, one of many run of the mill 7Ton class backhoe loaders available from the likes of JCB, New Holland, Case, Terex, JD, etc..etc...

      The spec sheet states "Bucket rotation 205 degrees".

      Note that this applies to the small bucket at the back end of the machine (the Backhoe part), at the end of the long digging arm.

      This large angle of rotation is required due to the fact that the long arm (dipper arm) can be working at a wide range of angles relative to the ground, and to ensure that the bucket has sufficient articulation for it's job of digging in a trench (maybe around 120 degrees would do, 60 degrees either side of vertical) then consequently the amount of articulation - relative to the DIPPER ARM - has to be far in excess of the amount of articulation relative to the ground (or vertical). Hence the high angle of aritculation between dipper arm and bucket.

      This is achieved with a single hydraulic cylinder and a short linkage.

      As I've suggested, the best way to convince yourself is to go outside and actually look at one - a real one, not a picture or drawing. Then you can see how easy it is, and how you can apply it to your marine foils. There is nothing inherently "un-accurate" about the arrangement, but as there are a few pivot points, appropriate selection of pins and bushes will control any free-play, which would contribute to inaccuracy. From a ruggedness, strength and reliability point, well the fact that this mechanism is using in direct contact with mud, in a trench, connected to a seven ton machine, may lead you to believe that there is little to worry about.

      I hope this satisfies some of the doubts.
       
    7. Karl A Petersen

      Karl A Petersen Member

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      None of the suggestions appear to apply to a hydraulic ram, but would be fine for a double acting cylinder. Did you find your answer already?
       
    8. ordogarci

      ordogarci Member

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      Instead of using the kinematic system you have raised must use an articulated quadrilateral, do you have information on this system?
       
    9. PWASS

      PWASS Well-Known Member

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      In my first post I recommended a Rotary Actuator, these use a Ram (Cylinder) operating a rack and pinion gearbox in a self contained assembly, see below
      [​IMG]

      This is a self contained unit but it could be in 2 parts, a normal ram (cylinder) operating a rack and pinion gearbox.
       
    10. PWASS

      PWASS Well-Known Member

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      I don't appear to be able to edit my last post, the picture has changed, heres the correct one.


      [​IMG]
       
    11. CarolRobles

      CarolRobles Guest

      I also don't have much idea about hydraulic rams. So, if you will get success in fixing your error then let me know.
       

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