Should piston spin freely on shaft?

[J_J]

Torque specs for piston nut. Again, the piston is not supposed to move on the shaft given the torque specs. The figures are in ft lbs.

Locknut Size
½ - 20
5/8 - 18
¾ - 16
7/8 - 14
1 - 14
1 1/8 - 12
1 ¼ - 12
Clamp Load (lbs)
8,997
14,398
20,979
28,658
38,244
48,134
60,353
Torque Min (ft-lbs)
32
64
111
178
271
384
534
Torque Max (ft-lbs)
43
86
151
240
367
519
723
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[Steave]

A piston should not be able to rotate on the rod, any amount of movement there is a place to leak past. Some designs use an O-ring on the shaft, some have O-ring inside the piston, and some seal with machine surface only. Not sure about this, but it looks to me like that piston is on backwards. That recessed face & shoulder facing the nut looks like it would fit tight over the end of the rod to increase seal affect.
Self locking nuts are used to help keep nut form working loose, but do use Loctite and torque to normal specs. for the thread size of the rod if you don't have actual torque spec. for the cylinder.

In the original pictures it does appear the piston could be backwards. You got me thinking so I looked again and it will only go on one way because of the way the shoulders are machined on the shaft. Maybe these pictures will show better. In the first picture I turned the piston around and it only goes to the first shoulder so it must be on the right way. Thanks.

They are right.. If piston face is flat as can be, No oring. If piston has little groove, then oring. Go for it!!!!

With all the good information and all of it telling me to have a good seal I feel confident about putting it back together. Thanks.

Oh by the way the cylinder was operating fine, it had been leaking fluid for a time but got excessive and needed repair. Fluid being almost $50.00/5 gallons not to mention the fluid being spilled on the ground it was time.

 

[Steave]

Torque specs for piston nut. Again, the piston is not supposed to move on the shaft given the torque specs. The figures are in ft lbs.

Thanks for the chart. The thread size is 1 1/8".

My son worked for a hydraulic company while attending college, Offshore-Inland, You may of heard of them since they work in your area as well as Mobile. Once he finished school I guess he was tired of getting his hands dirty so moved on. Great company but a lot of traveling. The company hires a lot of people out of the military.

 

[EE_Bota]

Unless there is a o-ring groove inside the piston (inside the female) I'd forget about 0-rings, and clean the mating surfaces (between piston flat and rod flat) with acetone, allow that to flash off, and then hit it with a bead of Loctite's hydraulic sealant, tighten it down good and call it a day after wiping away any residue that gets expressed.

 

[Steave]

Unless there is a o-ring groove inside the piston (inside the female) I'd forget about 0-rings, and clean the mating surfaces (between piston flat and rod flat) with acetone, allow that to flash off, and then hit it with a bead of Loctite's hydraulic sealant, tighten it down good and call it a day after wiping away any residue that gets expressed.

I thought I'd used every kind of sealant made at one time or another but hydraulic sealant is a new one to me.
I'll get some. I use acetone for cleaning sometimes but most of time I use Goof-Off. I'll use acetone for this because I'm not sure of any contaminates left behind by Goof-Off. Thanks a lot.

 

[CJONE]

Some pistons have a chamfer for a o ring at the base also. it will seal aginst the shaft at the joint. CJ

 

[wdchyd]

Sorry, a little late for the party...

I don't like any of them to spin after torque-up.....I'll machine something to allow to fit snug, then red loctite on the stub and piston, and reef it down, then let it set for a few hours before testing

sometimes I'll add the oring groove for over-kill but not necessary for a tolerance fit sealing

 

[Steave]

Some pistons have a chamfer for a o ring at the base also. it will seal aginst the shaft at the joint. CJ

I checked and double checked and there's no place for a o-ring or seal inside the piston or on the face of the piston facing the shaft. I've been told some only have a machine fit and since the other cylinder I repaired last year from the same tractor was the same type I'm more confident now that it doesn't have one or need one. The cylinder was operating fine except for leaking the fluid out. Thanks for answering.

wdchyd;3148988]Sorry, a little late for the party...

I don't like any of them to spin after torque-up.....I'll machine something to allow to fit snug, then red loctite on the stub and piston, and reef it down, then let it set for a few hours before testing

sometimes I'll add the oring groove for over-kill but not necessary for a tolerance fit sealing

You're never late to a "repair" party around here Thanks for the info. I haven't had time to get some hydraulic sealant and probably use the red loctite I have. I always keep red and blue on hand.

It's raining here again today so I'll work in the shop and put it back together today. When I got my seals I got 2 sets and will repair the other outrigger while I'm at it. It is seeping fluid and normally I would just add fluid as needed with a small seep like this one but I've got everything out for this project so I might as well do it now. Thanks again.

 

[CJONE]

I don't like any of them to spin after torque-up.....I'll machine something to allow to fit snug, then red loctite on the stub and piston, and reef it down, then let it set for a few hours before testing



That is key, like was stated the piston has to be solid or it will leak. Shim it or do what you have to to get it solid. We use red locktite for a sealer also with no problems. CJ

 

[Ken]

After the large nut on end of shaft has been tightened should the piston still be free to spin slightly?

The threads on the shaft are interference type threads and the nut will hold in place most anywhere
you quit tightening.

The pictures are not the best but you can see the machined shoulder on the shaft that holds the piston,
it appears the piston is made to be able to spin if it needs to inside the cylinder.

Should I allow it to slightly spin or tighten it tight.?

If it matters the cylinder is off my outrigger. International backhoe 1980 model.

I would appreciate any help.

Picture #1 looks like the threads on the shaft stop before the nut could pull tight. So was there a spacer on? or the nut was cut so fits over the shafwasher to be put t to pull tight to piston. What ever motion will cause added wear beating forward or backward before fluid pressure took up the space.

Try to locate manufacture of cyl. or book on the back hoe for information.
I just hate to locate a spacer after the machine is working in the bottom of the container for washing parts.
ken