Re: PT - Goodyear master cylinder O rings

[Ranchaero Wing Shop]

'I'm trying to find the correct O ring for my Goodyear master cylinders
in a PT-19. Does anyone have dimensional specs for that O-ring?

I need a "Buna-N (nitrile) duro 70", O-ring for the Mil-h-5606 fluid
I'll be using. These are abundantly available online. My challenge is
determining the right size. The piston slot is 3/16" wide so I would
expect a 3/16" C.S. O-ring. It should stretch slightly over the piston
slot I believe, and be a couple or a few thousands larger than the bore
of the cylinder (1"). It should hold the piston in the center of the the
cylinder and not allow the piston to contact the cylinder. It should not
cause much resistance to the motion of the piston inside the cylinder.
I've tried a number of sizes in this range but none quite work so far.
Someone please correct me if I'm wrong about these parameters.

One person I know used a 1/8" C.S. x 1" O.D. O-ring from ACS,
MS-28775-210. He says it works and doesn't leak. I would expect it to be
too small in C.S and I.D., allowing the piston to rub against the
cylinder wall since it would not be tight in the slot due to a too small
C.S. and too small I.D., but would "flop" around in the extra space of
the 3/16" slot, and I would expect it to leak. Am I overthinking this?
I'd like to get this right - before filling the system with fluid if
possible!

Any ideas are much appreciated.

David


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[Robert Barrie]

'Dave You said you are going to use 5606 in the brakes Did you change the brake system ? The expander tubes will NOT work with 5606. They are not compatible If you have new never used expander tubes silicon (DOT5) will work and not make the rubber expand. Only problem with silicon it will seep through the smallest path. 

Sent from my iPhone

On Aug 15, 2017, at 2:38 PM, Ranchaero Wing Shop david@ranchaerowingshop.com [fairchildclub] wrote:

 
I'm trying to find the correct O ring for my Goodyear master cylinders
in a PT-19. Does anyone have dimensional specs for that O-ring?

I need a "Buna-N (nitrile) duro 70", O-ring for the Mil-h-5606 fluid
I'll be using. These are abundantly available online. My challenge is
determining the right size. The piston slot is 3/16" wide so I would
expect a 3/16" C.S. O-ring. It should stretch slightly over the piston
slot I believe, and be a couple or a few thousands larger than the bore
of the cylinder (1"). It should hold the piston in the center of the the
cylinder and not allow the piston to contact the cylinder. It should not
cause much resistance to the motion of the piston inside the cylinder.
I've tried a number of sizes in this range but none quite work so far.
Someone please correct me if I'm wrong about these parameters.

One person I know used a 1/8" C.S. x 1" O.D. O-ring from ACS,
MS-28775-210. He says it works and doesn't leak. I would expect it to be
too small in C.S and I.D., allowing the piston to rub against the
cylinder wall since it would not be tight in the slot due to a too small
C.S. and too small I.D., but would "flop" around in the extra space of
the 3/16" slot, and I would expect it to leak. Am I overthinking this?
I'd like to get this right - before filling the system with fluid if
possible!

Any ideas are much appreciated.

David

---
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'

[Ranchaero Wing Shop]

' Clevelands.

On 8/15/2017 12:00 PM, Robert Barrie barrieaire@aol.com [fairchildclub] wrote:

  Dave  You said you are going to use 5606 in the brakes  Did you change the brake system ? The expander tubes will NOT work with 5606. They are not compatible  If you have new never used expander tubes silicon (DOT5) will work and not make the rubber expand. Only problem with silicon it will seep through the smallest path. 

Sent from my iPhone
On Aug 15, 2017, at 2:38 PM, Ranchaero Wing Shop david@ranchaerowingshop.com [fairchildclub] wrote:

 
I'm trying to find the correct O ring for my Goodyear master cylinders
in a PT-19. Does anyone have dimensional specs for that O-ring?

I need a "Buna-N (nitrile) duro 70", O-ring for the Mil-h-5606 fluid
I'll be using. These are abundantly available online. My challenge is
determining the right size. The piston slot is 3/16" wide so I would
expect a 3/16" C.S. O-ring. It should stretch slightly over the piston
slot I believe, and be a couple or a few thousands larger than the bore
of the cylinder (1"). It should hold the piston in the center of the the
cylinder and not allow the piston to contact the cylinder. It should not
cause much resistance to the motion of the piston inside the cylinder.
I've tried a number of sizes in this range but none quite work so far.
Someone please correct me if I'm wrong about these parameters.

One person I know used a 1/8" C.S. x 1" O.D. O-ring from ACS,
MS-28775-210. He says it works and doesn't leak. I would expect it to be
too small in C.S and I.D., allowing the piston to rub against the
cylinder wall since it would not be tight in the slot due to a too small
C.S. and too small I.D., but would "flop" around in the extra space of
the 3/16" slot, and I would expect it to leak. Am I overthinking this?
I'd like to get this right - before filling the system with fluid if
possible!

Any ideas are much appreciated.

David

---
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[Jack Mitchard]

'David,What Cleveland brakes are installed and do you have a FAA form 337 for them approved? I'm looking for any conversion info for mine. Jack Mitchard

Sent from my iPhone

On Aug 15, 2017, at 3:17 PM, Ranchaero Wing Shop david@ranchaerowingshop.com [fairchildclub] wrote:

 
Clevelands.

On 8/15/2017 12:00 PM, Robert Barrie barrieaire@aol.com [fairchildclub] wrote:
  Dave  You said you are going to use 5606 in the brakes  Did you change the brake system ? The expander tubes will NOT work with 5606. They are not compatible  If you have new never used expander tubes silicon (DOT5) will work and not make the rubber expand. Only problem with silicon it will seep through the smallest path. 

Sent from my iPhone
On Aug 15, 2017, at 2:38 PM, Ranchaero Wing Shop david@ranchaerowingshop.com [fairchildclub] wrote:

 
I'm trying to find the correct O ring for my Goodyear master cylinders
in a PT-19. Does anyone have dimensional specs for that O-ring?

I need a "Buna-N (nitrile) duro 70", O-ring for the Mil-h-5606 fluid
I'll be using. These are abundantly available online. My challenge is
determining the right size. The piston slot is 3/16" wide so I would
expect a 3/16" C.S. O-ring. It should stretch slightly over the piston
slot I believe, and be a couple or a few thousands larger than the bore
of the cylinder (1"). It should hold the piston in the center of the the
cylinder and not allow the piston to contact the cylinder. It should not
cause much resistance to the motion of the piston inside the cylinder.
I've tried a number of sizes in this range but none quite work so far.
Someone please correct me if I'm wrong about these parameters.

One person I know used a 1/8" C.S. x 1" O.D. O-ring from ACS,
MS-28775-210. He says it works and doesn't leak. I would expect it to be
too small in C.S and I.D., allowing the piston to rub against the
cylinder wall since it would not be tight in the slot due to a too small
C.S. and too small I.D., but would "flop" around in the extra space of
the 3/16" slot, and I would expect it to leak. Am I overthinking this?
I'd like to get this right - before filling the system with fluid if
possible!

Any ideas are much appreciated.

David

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[Ranchaero Wing Shop]

' Cessna 310 kit, Cleveland 199-64, or 199-0064. Work with your local IA on the 337. Someone mentioned the group has a 337.


On 8/15/2017 2:02 PM, Jack Mitchard fighterjack@charter.net [fairchildclub] wrote:

  David, What Cleveland brakes are installed and do you have a FAA form 337 for them approved? I'm looking for any conversion info for mine.  Jack Mitchard

Sent from my iPhone

'