Cylinder rebuild question

Greg

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B7100 HST-D 4x4 with FEL, PTO and 3 pt hitch
Dec 7, 2009
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Putnam County, NY
On a hunch that that Johnson built the B219 loader for Kubota, I ordered the cylinder rebuild kits for the B219 from my local Kubota dealer. Turns out the seals are exactly the same size as those on my Johnson 10tc loader.

My question: The main rod seal gets sandwiched between 2 rubber washers. These rubber washers are flat on one side and concave on the other. Does the flat part of the washer go toward or away from the o-ring?

This is my first hydraulic cylinder rebuild, and despite having rebuilt many pneumatic cylinders I have never seen these thin washers with the one side concave before. Even the washers in the cylinders I took apart to not have that concave on them.

If anyone has any experience in this I could use a little help. Thanks.
 

Greg

New member

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B7100 HST-D 4x4 with FEL, PTO and 3 pt hitch
Dec 7, 2009
120
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Putnam County, NY
Thanks Eric,

I appreciate the effort. However that article is just a general description of a repair, that much I do know. My question regarding seal direction is extremely specific. I made a quick drawing detailing the 2 possible layouts of the seals. If anyone can shed some light on which layout will be the correct one it would be most helpful and appreciated. I'm sure in the end either would work, but I am also sure that one is better. I am not sure if the concave shape in the washer is intended to work similar to a U-cup seal, or if it is for lending a little more support to the O-ring.
 

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Greg

New member

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B7100 HST-D 4x4 with FEL, PTO and 3 pt hitch
Dec 7, 2009
120
1
0
Putnam County, NY
Thanks for the help Vic! I think you are right, if had had to guess, I'd have done the same. I also posted this questions on tractorbynet and 2 people confidently answered me the same way.

Is it sacrilege to mention another forum on this forum? :confused:
 

Dan_R_42

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B7100-D, w/ Sims Cab, B219 FEL, ARPS 70 Backhoe, Oversized R4 Tires, LX2610 Cab
Dec 1, 2010
447
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18
Taunton, MA
Digging up an old post...

Thanks Greg for identifying the issue and asking the question, including the drawing too.

GREG: I made a quick drawing detailing the 2 possible layouts of the seals. If anyone can shed some light on which layout will be the correct one it would be most helpful and appreciated. I'm sure in the end either would work, but I am also sure that one is better.

I'm asking the same question as Greg. I do not see the actual answer posted that he received from Vic.
B219_fel_seal_Kit.jpg
.
 

South 40

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L1500DT, 750 Ford backhoe, 49 D4 Cat Repowered with 6.9L Diesel
Nov 12, 2012
168
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Bloomsdale, Mo. USA
Hey Folks,

Hmmm, never seen concave backup washers like that before, but rule of thumb is anything concave goes toward the pressure, so I acts as a wiper, (expands/opens up when pressure is applied), and does not just fold over and allow fluid to pass over it, so I would go with the left pic above.

Cheers
Samantha
 

TheOldHokie

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On a hunch that that Johnson built the B219 loader for Kubota, I ordered the cylinder rebuild kits for the B219 from my local Kubota dealer. Turns out the seals are exactly the same size as those on my Johnson 10tc loader.

My question: The main rod seal gets sandwiched between 2 rubber washers. These rubber washers are flat on one side and concave on the other. Does the flat part of the washer go toward or away from the o-ring?

This is my first hydraulic cylinder rebuild, and despite having rebuilt many pneumatic cylinders I have never seen these thin washers with the one side concave before. Even the washers in the cylinders I took apart to not have that concave on them.

If anyone has any experience in this I could use a little help. Thanks.
Those are backup rings and the concave surface goes against the o-ring. They are structural anti-extrusion devices not seals and they go opposite the pressure side of the o-ring. For a double acting cylinder there is one on both sides of the o-ring. Drawing below taken from the Parker O-ring Handbook. Its 292 pages of just about everything you could ever want to know on the subject.

Dan

1652482545618.png
 
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South 40

Active member

Equipment
L1500DT, 750 Ford backhoe, 49 D4 Cat Repowered with 6.9L Diesel
Nov 12, 2012
168
52
28
Bloomsdale, Mo. USA
Those are backup rings and the concave surface goes against the o-ring. They are structural anti-extrusion devices not seals and they go opposite the pressure side of the o-ring. For a double acting cylinder there is one on both sides of the o-ring. Drawing below taken from teh Parker O-ring Handbook. Its 292 pages of just about everything you could ever want to know on the subject.

Dan

View attachment 79943
Hey Hokie,

Thanks for the correct answer, I have learned something here.

Cheers
Samantha
 

TheOldHokie

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Hey Hokie,

Thanks for the correct answer, I have learned something here.

Cheers
Samantha
You are welcome. Another tidbit - the theory is the curvature compresses the ring inward away from the extrusion gap. The concave style was popularized by Parker and they are commonly called Parback rings (Parker's trademark). Sort of like photocopiers are commonly called Xerox machines.

Dan
 

South 40

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Equipment
L1500DT, 750 Ford backhoe, 49 D4 Cat Repowered with 6.9L Diesel
Nov 12, 2012
168
52
28
Bloomsdale, Mo. USA
You are welcome. Another tidbit - the theory is the curvature compresses the ring inward away from the extrusion gap. The concave style was popularized by Parker and they are commonly called Parback rings (Parker's trademark). Sort of like photocopiers are commonly called Xerox machines.

Dan
Hey Dan,

That is good to know, I never get tired of learning.

Tidbit of my own, when I was young and stupid I knew everything, I knew it all, imagine my shock when I woke up one morning in my early 20's and realized just how stupid I really was!

I have since spent my life trying my best to learn something new everyday, and today you helped, Thanks Tons, :)

Cheers
Samantha
 
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TheOldHokie

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Hey Dan,

That is good to know, I never get tired of learning.

Tidbit of my own, when I was young and stupid I knew everything, I knew it all, imagine my shock when I woke up one morning in my early 20's and realized just how stupid I really was!

I have since spent my life trying my best to learn something new everyday, and today you helped, Thanks Tons, :)

Cheers
Samantha
I was too stupid to figure it out at 20. Had to get beaten up a few more years. I am 71 and like you trying to make every day a learning experience.

Cheers yourself,

Dan
 
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