Hydraulic Cylinder Rotation
Hydraulic Cylinder Rotation
(OP)
Group,
I am looking for ideas. We are trying to qualify a replacement hydraulic cylinder from a new cylinder manufacturer. During cycling of the new cylinder, the cylinder rod rotates which leads to loosening of threaded connections. The new cylinder manufacturer does not have a much, if any, engineering support. Our current cylinder does not have this rotation problem.
My first guess is that there is a "rifling" effect where there are small groves introduced during the machining causing the cylinder rod to rotate. But I am looking for other ideas which could cause the cylinder rod to rotate.
Thanks,
Kirk
I am looking for ideas. We are trying to qualify a replacement hydraulic cylinder from a new cylinder manufacturer. During cycling of the new cylinder, the cylinder rod rotates which leads to loosening of threaded connections. The new cylinder manufacturer does not have a much, if any, engineering support. Our current cylinder does not have this rotation problem.
My first guess is that there is a "rifling" effect where there are small groves introduced during the machining causing the cylinder rod to rotate. But I am looking for other ideas which could cause the cylinder rod to rotate.
Thanks,
Kirk





RE: Hydraulic Cylinder Rotation
(grub screw) and sometimes chemically fixed to the rod-also the clevis or rod eye will be fixed chemically or mechanically by some means. Some design as far as mounting and rod attachment can hide this rotation force but I would never put a cylinder in service without addressing this issue. Bud T, that frequents these forums, worked for Miller Cylinders for years may have some better advise along with some other regulars. Good luck,
Maytag
RE: Hydraulic Cylinder Rotation
Was the new cylinder connected differently than the old?
Ted
RE: Hydraulic Cylinder Rotation
The new cylinder and old cylinder were connected identically.
Thanks,
Kirk
RE: Hydraulic Cylinder Rotation
RE: Hydraulic Cylinder Rotation
In our case, all it took was getting the end fittings torqued up to the manufacturer's spec instead of "matey boy's" "feels about right".
A.
RE: Hydraulic Cylinder Rotation
The difference between the two cylinders may be in the piston/rod seals. Have the seals been checked are they identical in the two cylinders?
One set of seals may have a higher contact ratio with the cylinder wall or rod surface.
Adrian
RE: Hydraulic Cylinder Rotation
Thanks,
Kirk
RE: Hydraulic Cylinder Rotation
If the new cylinder requires a lot more torque to rotate it, is it possible that it is bent slightly or somthing has got misaligned, resulting in a slight "kick" during the stroke which is loosening the screwes block?
Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK
SW2007x64 SP3.0 Pentium P4 3.6Ghz, 4Gb Ram ATI FireGL V7100 Driver: 8.323.0.0
SW2007x32 SP4.0 Pentium P4 3.6Ghz, 2Gb Ram NVIDIA Quadro FX 500 Driver: 6.14.10.7756
RE: Hydraulic Cylinder Rotation
If two, seemingly equal, mechanical components behave differently, there must be either some difference in working conditions (which seems here to be excluded) or in the components themselves.
The posts above have pinpointed some possibillities, and sealings are also in my mind an important checkpoints.
But there might also be another difference: one cylinder better or more precise machined, constructed and mounted (better quality) than the other.
RE: Hydraulic Cylinder Rotation
RE: Hydraulic Cylinder Rotation
"The cylinder is a single acting cylinder with the hydraulic pressure coming in at the end of a hollow rod and the pressure pushing the cylinder casing away from the rod."
The only possible time for the Rod (RAM it is normally called in this type Single Acting construction) to come unscrewed is when it is being pulled out by an external force. The only forces restricting that movement is Seal friction at the Ram, VACUUM of One Atmosphere or other mechanical stiction such as the design of the internal Ram Guide/Guides. That is, UNLESS THE ITEM TH RAM IS SCREWED INTO IS ALSO FREE TO TURN.
Vacuum at maximum would be 14.5 PSI on an average day at Sea Level and would have little consequence umless the Ram is a large size.
Vacuum would be high if movement of the Ram Body was very rapid and/or the drilled hole in the Ram was undersize or Orificed for some reason.
Sloppy thread fit giving less surface contact could account for the problem also. After all a Thread is an Inclined Plane that can always allow movement when acted on by external forces.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: Hydraulic Cylinder Rotation
I have investigated the seals and rod guides, and the only differences are the old cylinder gland has only one rod guide vs. two rod guides for the new cylinder; and the rod seal on the new cylinder has two sealing edges vs. one sealing edge on the old cylinder.
Our next step is to try to isolate if the problem comes from the machining of the cylinder rod.
I am also suspect of the thread quality of the new cylinder.
Thanks,
Kirk
RE: Hydraulic Cylinder Rotation
jetmaker
RE: Hydraulic Cylinder Rotation
Ed Danzer
www.danzcoinc.com
www.dehyds.com
RE: Hydraulic Cylinder Rotation
"The cylinder is rod side down and the return stroke is powered by gravity."
Remove the threads from the Ram or what it is screwed into since the unit is always in compression. That would eliminate any unscrewing possibility.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: Hydraulic Cylinder Rotation
I don't know what grade of Loctite you're using, but you said that you torqued the joint then applied the Loctite; was it the type that will "wick" in and was the thread fit too good to allow this? I prefer to apply prior to assembly to ensure adequate coverage, even then, some combinations of material/surface finish (or oily contaminents) can prevent proper curing. A primer/activator is required on some grades, especially with steels. In the absence of this, you can try rubbing the components with a brass bristled brush or using a piece of brass or copper in a file like action the threads, even applying some very fine dust obtained by rubbing a bit of brass on some clean dry abrasive paper to the loctite just before assembly. The presence of copper ions will trigger the curing process and result in a much stronger bond.
Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK
SW2007x64 SP3.0 Pentium P4 3.6Ghz, 4Gb Ram ATI FireGL V7100 Driver: 8.323.0.0
SW2007x32 SP4.0 Pentium P4 3.6Ghz, 2Gb Ram NVIDIA Quadro FX 500 Driver: 6.14.10.7756