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Home > Forums > Mechanical Engineers > Activities > Fluid Power engineering Forum

Telescopic Cylinder query

Read More Threads Like This One

celticmad (Mechanical)

31 May 12 6:15

Hi Everyone

I'm having a telescopic hydraulic cylinder installed on a machine, the cylinder will be used to push a piece along a roller. It will have a rectangular block attached to the end of the cylinder.....My question is this, when pushing will the cylinder rotate ? will i need top have a stabiliser guide fitted ?If it rotates the block will snag on the rollers
Thanks

btrueblood (Mechanical)

31 May 12 10:37

It might. Given that you have a reason for wanting it not to, Murphy's law dictates that it will.

Oldhydroman (Mechanical)

31 May 12 12:07

It probably will rotate - and not just because there's nothing to stop it (Murphy's law).

If the bore of the cylinder was "honed" as part of its manufaturing process then the honing machine will invariably leave microscopic scratches on the bore just like the long shallow helix down the bore of a rifle. When you pressurise either cylinder volume the piston seals become "energised" and press against the inside of the bore. As the cylinder strokes, the seals tend to key into the scratches and make the piston (and rod) rotate. You might find that the cylinder rod consistently rotates one way when extending and then the other way when retracting: effectively mimicing the movement of the original honing machine.

DOL

hydromech (Mechanical)

31 May 12 12:25

The hydrodynamic film between the seal and bore the bore, also between the rod seal and the rod itself will mean the rod can and will rotate if the forces acting on it are not in equilibrium.

If you don't want it to rotate...guide it!!!

Hydromech

celticmad (Mechanical)

31 May 12 18:30

Thats great
Thanks for the info, by any chance does anyone have any links to good guide systems ?....if not i'll figure something out.
Thanks again
CM

Jboggs (Mechanical)

31 May 12 21:08

The devil is in the details. Please post a diagram of the arrangement with some relative dimensions for scale. Worked with several telescoping cylinders over they years, and installed guidance on some of them. But I can't help with the vague description you have given. Thanks.

Cbrunner (Industrial)

10 Jun 12 11:09

As Jboggs has said, the Devil is in the details. Depending on the cylinder and the mounting arrangement the load may be able to overcome the rotational force. Sometimes it just takes placing some runners on the bottom to be enough.

Chris Brunner
Brunner Equipment LLC

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