What makes hydraulic cylinders twist?

Royse · Nov 10, 2016

I bought these cylinders a few years ago and put them on my
loader as dump cylinders. Granted, they are "cheap" TSC cylinders.
The one pictured is on the left side and twisted clockwise.
The one on the right side twisted counter-clockwise.
So both twisted inward and by about the same amount.

2x4 · Nov 10, 2016

too much weight being lifted?

Sam Womer (PA) · Nov 10, 2016

The only thing that could twist the cylinders is flexibility in the hookup. If your trailer bed or frame is not rigid enough it could flex. Welded
cylinders can't twist but tie rod cylinders like pictured would need to be over tightened to resist the torque. If they don't leak then no harm done.

Janicholson · Nov 10, 2016

If the pressures are normal, running it to the cylinder to the end can do it, slamming the end cap can make it loose enough
to move. I would twist them straight without tightening them (persuasion) then retorque the rods to the spec of the
threads. Jim

Royse · Nov 10, 2016

"slamming the end cap can make it loose enough to move."

This may be a possibility Jim.
They don't "slam", but they do pull up quite tight.
Any idea why they would twist in opposite directions?

Royse · Nov 10, 2016

Thanks Sam. They're the tilt cylinders for my loader bucket.
Not on a trailer. The bodies are only about 20 inches long.
They certainly will flex in their hookup.
Thankfully they do not leak. The ones they replaced "rained"
on me when I lifted the loader to full height.

Royse · Nov 10, 2016

"too much weight being lifted?"

I won't deny that may have happened. Once. Maybe twice. LOL
But I don't understand the twist and why they are opposite twists.

ss55 · Nov 11, 2016

The hydraulic hoses to the rod ends are probably what is putting the twisting forces on the cylinders. That force would be highest when those hoses are under high pressure (retracting). Bottoming out the cylinder at full extension or full retraction or a high shock load while retracting could temporarily stretch the tie rods enough for the end cap to spin. Does the bucket hit hard stops before the cylinders reach their end of stroke or do the cylinder pistons bottom out on the end caps?

If you want a definite answer, I would ask the cylinder manufacturer (the people who build them for TSC).

Duane WI · Nov 11, 2016

Fundamentally the four connecting rods have stretched unevenly. Even though they look identically there are likely small differences in diameter and material strength. Even in the same rod there could be differences along its length in diameter and material strength. When loaded to the limit the weaker ones stretched longer. You could probably correct this by loosening them all. Realigning the ends and retightening the rods.

John B. · Nov 11, 2016

I would agree with those that say lifting too much weight. To me it's causing a twist or actually a BOW in the loader frame itself and
moving the end caps along with it. This would cause the cylinders caps to rotate in opposite directions. I would look from cracks in
the loader frame. You can also try attaching a string across the top and bottom of each loader arms where the cylinders attach and see
if one string gets tighter or looser when you lift something. What I mean is to attach a string to the left arm and run it across to
the right arm. You'll be surprised how much it will bend.

Dave Sherburne, NY · Nov 11, 2016

I'm with Sam , loader frame is flexing

Greg K · Nov 11, 2016

My contact at Prince Hydraulic says it is
side loading causing it (15 years in the
engineering dept experience) .

Royse · Nov 11, 2016

It would not surprise me if the frame flexes.
It is old and has been cracked and repaired/reinforced.
I can check that easy enough.

Royse · Nov 11, 2016

Greg, what is side loading as it pertains to hydraulics?
I know how to side load an app onto my phone, but I'm
certain that has nothing to do with what your guy means.

paul · Nov 11, 2016

Yea I'm curious too, what is side loading as pertains to this?

So the back end of the cyclinders is pinned, and the front yoke is pinned.

Pressure is applied to the piston in both directions, out and in. Side pressure could be applied to the ends by binding, or to the shaft by
misaligned end points.

However, that cap that is twisting is round, centered, and only receives hyd pressure when retracting. It does not get any rotational force, and
only a small amount of side pressure from the piston if the piston is getting side forces. So, the cap the piston goes through doesn't get
anything that would cause it to twist?

The barrel of the piston, outer pipe, gets hyd pressure, and can be flexed to the side if the cyclinders is getting side pressures - misaligned. But
to me that would push the tube sideways, cause an end to leak, not twist the tube into a curl?

The rods holding the end caps to the barrel could be of different strengths and stretchiness, that is the most believable explanation here. But
even that, would think oil would push through between the cap and barrel, and really wouldn't rotate one cap for any particular reason?

Hyd pressure pushes out in all directions, binding pins word create straight side pressures, failing rods would create leaks as they lengthened.

Omnidirectional hyd pressure, or misaligned/ binding side pressures in one direction, how does that convert into a twist?

As the piston shaft is free to rotate inside the end cap, I'm still lost what makes the end cap rotate around in a spiral here? where does the twist
come from?

Paul

Royse · Nov 11, 2016

Thank you Paul, that is a very detailed description of my
confusion. They're not leaking and work fine.
I just don't get what makes them twist like that.
And, if they twist much more, they will hit the frame.
The possibility of them hitting is what started my search.

Greg K · Nov 11, 2016

From what I understand it is a twisting/side pressure on the cylinder. Example, if the tilt bed has only 1 cylinder and I load a large amount of weight on only one side but leave the other empty. When I try to dump that load the bed and cylinder will deflect, how much depends on how strong things are built.
As this was being explained to me it was brought up that if the cap was not properly torqued down this could happen too. In my mind it would leak profusely if it was not tight, but I'm no engineer ( I've never even RIDDEN on a train lol).
I am also somewhat confused since the piston and rod are free to twist in the bore unless they tend to lock in place under pressure or when they are dead ended and then the side loads are applied.

Royse · Nov 11, 2016

Thanks Greg, I appreciate your effort here as I'd like to understand.
These aren't on a trailer, they are one on each side of the
loader used to dump and curl the bucket. They will dead
head in the retracted/up position so that may be a clue.

If that were the cause, wouldn't they twist in the same
direction? Mine are twisted in opposite directions.
One clockwise and the other counter clockwise.

Here's a picture of my old NAA with the loader they are
mounted on. They aren't twisted yet in this picture.

It is mostly used with clamp-on forks to move pallets around.
The added length of those forks no doubt adds a lot of
additional stress to the cylinders as far as lift weight goes.

jm. · Nov 11, 2016

I am really going to catch it here but no amount of hydraulic pressure will twist the end caps. Dead give away is fact the each one is twisted IN. Now look at you bucket the rod end hoses are to short and as you roll the bucket they are pulling the head in causing the twist. You are lucky you haven,t pulled a hose. Take a look and come back and say I was wrong but believe that is what you will find.

Greg K · Nov 11, 2016

Well there's the problem! They're on a ford!
Just teasing, sorry, I've been in cellular
hell all day and haven't been able to check
in here or with my consultant lol. I have
another hour or two of work today and I'll
try and get a better answer for you. I don't
understand how they could twist either,
especially different directions. In the
picture the hoses look long enough but it is
a legitimate thought.

Royse · Nov 11, 2016

jm, any post meant to be helpful, as your was, will not "catch it"
from me! I'm asking for help and any suggestions are appreciated.

I'm not seeing what you're seeing. Maybe I'm not looking in the
right place. Here's a picture of the cylinders from the front.
I walked out to the shed and took it just now.
Both hoses have several inches of slack. The one the right in
the picture, left on the tractor, has a foot or more to move.
Both cylinders are twisted the same amount by the way.

Am I missing it?

Royse · Nov 11, 2016

"Well there's the problem! They're on a ford!"

Well duh! Nothing else would have the power to twist them! LOL

Thanks again for the help.

John B. · Nov 11, 2016

Like Royse and I say the loader frame is flexing or bent. I can see the one gusset in the picture on the right side has been repaired
so there is some force there. It could be that the loader is bent too and when the bucket is dumped the cylinders are in a different
position on the not square frame and then they twist to adjust to the bend in the loader. Do the cylinders hit the bucket when it is
bottomed out in the dump position???

Royse · Nov 11, 2016

Thanks John, the cylinders don't hit the bucket or the frame
anywhere. I was watching that carefully since I bought these
to replace the originals. They are not like the originals at all.
But, the originals had bent rods that couldn't be sealed.
It was cheaper to buy new cylinders than to buy new rods.

Janicholson · Nov 11, 2016

I think I have it. The geometry of the bucket allows the frame of the bucket (flanges) that the cylinder rod end pin goes
through to hit the elbow hydraulic fitting. Thos can happen if, and only if the bucket is curled all the way back (short as
cylinder will go) and you push down on something causing the cylinder to go almost over center. The solution would be to
add new holes 1.5 pin diameters higher and 1/2" farther from the bucket for the rod end pin, or use a torch to notch out the
flange where it hit the fitting. Jim

504 · Nov 11, 2016

I think your top mounts have too much side to side movement,then you add some more movement at the bucket. Just my thoughts.

Greg K · Nov 11, 2016

Ok. The official "guess" after viewing your
picture is that they are sized too small for
the application. We're the origional
cylinders bigger by chance? Like I said,
this was the guess with the available info.
When I questioned the ability of a
cylinder to flex considering the piston is
free to spin I got the look of "of course it
will, everyone knows that" lol. I'll never
question that again.

Royse · Nov 11, 2016

Jim, I didn't see any place that anything was rubbing or hitting.
BUT, I will for sure check that in the morning because it makes
perfectly good sense to me as to how it could happen.
Not to mention the ramifications of letting it continue.

jm. · Nov 11, 2016

Nichols has found it and looking at the photos you can see that small inside edge flange is catching the pin. New it was not hydraulic pressure and after looking at the last photos can see the hoses are not the problem but that inside flange is catching the pin.

Janicholson · Nov 11, 2016

It will not rub, or in this case hit and twist, until the bucket is curled all the way (short cylinder length) and the front
edge of the bucket is lifted from pushing down on something with the leading edge. Look closely at the galvanized elbows
for even a light scrape, and a matching scrape on the bucket flange. It will not happen when the hydraulics are used to
stroke the bucket through its range, it is beyond the intended range. Jim

Royse · Nov 11, 2016

Greg, the original cylinders were actually smaller - physically.
They did have a longer stroke though.

I took the originals to the local dealer (JD) to see if they could
be rebuilt with all the leaking. The rods were bent. Consensus
was that it was cheaper to buy these as replacements.
The two that were on it weren't the same anyway.

I will check on the rubbing tomorrow. Too dark out tonight.

Royse · Nov 11, 2016

"that inside flange is catching the pin."

I'm not following jm, what pin?

Royse · Nov 11, 2016

They definitely have side-to-side movement 504.
Janicholson may have hit on the twist issue.
I'll have to wait to check on that until tomorrow.
Appreciate the response!

Greg K · Nov 11, 2016

Ok. I'm thinking Janicholson maybe has it
figured out. That last pic sure makes it
look like it is hitting the fitting. Dad has
a loader on a 2-85 White and the lower
fitting on the lift cylinder would hit if
the loader dropped below wheel level like if
you were digging dirt. It would seep a bit
but it broke one day with a round bales on
the loader.

caterpillar guy · Nov 12, 2016

It is hitting the bucket where the pin flange is. It will only do it with down pressure, or if you push on something with the bucket curled all the way up. So either drill new holes, up and closer to the edge. Or change the cylinder so the hoses are both at the far end from the bucket, or longer cylinders.

Royse · Nov 12, 2016

You got it Jim! If I set the bucket down and put down pressure
on it as is, it doesn't hit, but if I put the clamp-on forks on the
bucket and use down pressure, that increases the curl enough
that they do hit. Looks like I can shave them off with a torch.

Thank you all for pointing me in the right direction.

What makes hydraulic cylinders twist?

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