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pneumatic system woes

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samira.h(at)shaw.ca
Guest

Posted: Wed Jan 30, 2013 8:42 pm Post subject: pneumatic system woes

Keith and others,



I usually have my all my check valves

on my CJ overhauled with every annual.



For that purpose I have stocked up springs

and rubber pads but I can't remember the

supplier 



To make a long story short, all those rubber

pads I have used over the years have failed

sooner or later between the annuals, so I

got curious.



Now let's get technical, Brian Lloyd are

you still alive?



The rubber pad in a CJ check valve has a

nominal diameter of 13 mm what translates

into a area of circle of roughly 132 square

millimetres or 1.32 square centimetres.



The physical weight introduced to this little

piece of rubber is around 66kgs/145 lbs at

50 bars/700 psi.



That is a lot of pressure on a small rubber disc

going against the sharp and perforated

seat of the lower check valve assembly.



I have done some tests in my workshop at factor

1.5 over a period of several months and the rubber

pads all disintegrated (with and without air tool oil),

the material seems to be too thin and soft!!!



Any constructive thoughts or ideas?



cheers



Elmar

cpayne(at)joimail.com
Guest

Posted: Thu Jan 31, 2013 4:06 am Post subject: pneumatic system woes

Check valves seals should last a lot longer. Use high strength, high temp, oil-resistant synthetic material with about a 60-70 durometer(A) material. Buna-N grades like Nitrile, silicone rubber or EPDM selected to meet the task. I believe I stamped mine from weather resistant EPDM.



Craig Payne

byronmfox(at)gmail.com
Guest

Posted: Thu Jan 31, 2013 6:17 am Post subject: pneumatic system woes

Craig, where did you find an off-the-shelf stamp or punch to make your seals? 



Blitz Fox

415-307-2405



On Jan 31, 2013, at 4:03 AM, Cpayne <cpayne(at)joimail.com> wrote:



 	  Quote: 	
		   

 

 Check valves seals should last a lot longer. Use high strength, high temp, oil-resistant synthetic material with about a 60-70 durometer(A) material. Buna-N grades like Nitrile, silicone rubber or EPDM selected to meet the task. I believe I stamped mine from weather resistant EPDM.

 

 Craig Payne

wlannon(at)shaw.ca
Guest

Posted: Thu Jan 31, 2013 8:40 am Post subject: pneumatic system woes

Elmar;



I have been making them from 3/32" neoprene.   They don't last forever but 

at least a few years.   Recently changed to VITON.  We'll see how that 

stands up.



The material must be a nitrile, not natural, rubber of a fairly high 

Durometer reading - about 70 as I recall.



Walt



--

hkgibby(at)yahoo.com
Guest

Posted: Thu Jan 31, 2013 9:20 am Post subject: pneumatic system woes

Can you all share the details of how the proper diameter disc is stamped out; type of tool, etc?



Thanks- Hoot



Sent from my iPhone



On Jan 31, 2013, at 11:36 AM, "Walter Lannon" <wlannon(at)shaw.ca> wrote:



[quote] 

 

 Elmar;

 

 I have been making them from 3/32" neoprene.   They don't last forever but at least a few years.   Recently changed to VITON.  We'll see how that stands up.

 

 The material must be a nitrile, not natural, rubber of a fairly high Durometer reading - about 70 as I recall.

 

 Walt

 

 --

dougsappllc(at)gmail.com
Guest

Posted: Thu Jan 31, 2013 9:42 am Post subject: pneumatic system woes

Last week I ordered up a sheet of Viton to try. I'm sure I can easily make a cutter/stamp on the lathe.  If they work I plan to make my own to use in my $13 overhaul kits.  I do agree the life of the Chinese rubber disc seems to be short.  In my opinion several factors are the prime movers in determining the life of the discs, one is the pressure you have you pop off valve set at.  The Chinese set theirs at exactly 45 ATMS, while many US aircraft are set at 50 or higher.  Second is the use of oils which may be attacking the rubber (making it softer).  The Chinese use only castor oil.  Third would be the stainless steel springs, rust particles and broken spring parts from the stock (std steel) Chinese often cause check valves not to seal properly.  

Doug

On Thu, Jan 31, 2013 at 9:17 AM, Hank Gibson <hkgibby(at)yahoo.com (hkgibby(at)yahoo.com)> wrote:

[quote] --> Yak-List message posted by: Hank Gibson <hkgibby(at)yahoo.com (hkgibby(at)yahoo.com)>

 Can you all share the details of how the proper diameter disc is stamped out; type of tool, etc?

 Thanks- Hoot

 Sent from my iPhone

 On Jan 31, 2013, at 11:36 AM, "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:

 > --> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>

 >

 > Elmar;

 >

 > I have been making them from 3/32" neoprene.   They don't last forever but at least a few years.   Recently changed to VITON.  We'll see how that stands up.

 >

 > The material must be a nitrile, not natural, rubber of a fairly high Durometer reading - about 70 as I recall.

 >

 > Walt

 >

 > --

N13472(at)aol.com
Guest

Posted: Thu Jan 31, 2013 9:53 am Post subject: pneumatic system woes

The ones I bought from Gary Bunn have been holding up very well. I do

not know what the material is? Some of them have been in place for 5 + years



Tom Elliott

CJ-6A NX63727

777 Quartz Ave

PMB 7004

Sandy Valley NV

89019

Cell 541-297-5497



--

William Halverson

Joined: 27 Feb 2010
Posts: 88

Posted: Thu Jan 31, 2013 9:54 am Post subject: pneumatic system woes

Are check valves a problem for YAKs?



William



--

dsavarese0812(at)bellsout
Guest

Posted: Thu Jan 31, 2013 10:37 am Post subject: pneumatic system woes

The check valves in the Yak 52 are totally different internally than the 

ones in the CJ.  They also have a rubber seal on the end of a piston.  

The sealing surface does not a sharp edge.  The rubber seal on the 

piston presses up against a smooth, rounded edge surface.

Denni



A. Dennis Savarese

334-285-6263

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1



On 1/31/2013 11:52 AM, William Halverson wrote:

[quote] 

 Are check valves a problem for YAKs?



 William



 --

dsavarese0812(at)bellsout
Guest

Posted: Thu Jan 31, 2013 10:48 am Post subject: pneumatic system woes

I meant, "does not HAVE a sharp edge. Sorry.

Dennis

A. Dennis Savarese

334-285-6263

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1

On 1/31/2013 12:35 PM, A. Dennis Savarese wrote:

[quote] 

 <dsavarese0812(at)bellsouth.net>

 The check valves in the Yak 52 are totally different internally than 

 the ones in the CJ.  They also have a rubber seal on the end of a 

 piston.  The sealing surface does not a sharp edge.  The rubber seal 

 on the piston presses up against a smooth, rounded edge surface.

 Denni

 A. Dennis Savarese

 334-285-6263

 334-546-8182 (mobile)

 www.yak-52.com

 Skype - Yakguy1

 On 1/31/2013 11:52 AM, William Halverson wrote:

> 

> <william(at)netpros.net>

> Are check valves a problem for YAKs?

>

> William

>

> --

William Halverson

Joined: 27 Feb 2010
Posts: 88

Posted: Thu Jan 31, 2013 11:16 am Post subject: pneumatic system woes

OK thanks!  



--

samira.h(at)shaw.ca
Guest

Posted: Thu Jan 31, 2013 12:19 pm Post subject: pneumatic system woes

Hi again,



I would like to thank everybody for

their input and possible solutions.



I will follow the one or other advice

and will do some tests again over

a period of several months before

I introduce the new material to my

aircraft.



Thank you again.



cheers



Elmar



P.S.: Dennis is right, I have one

YAK 52 check valve in my CJ and

it works for 16 years without any

problems.

dennis(at)nickson.biz
Guest

Posted: Fri Feb 01, 2013 4:17 am Post subject: pneumatic system woes

Elmer:

I will forward this to Brian. 

I also have experienced some issues with the soft replacement pads in the check valves.

I think the harder rubber pads are more durable, just my 2 cents.



BL sold his project CJ a few months ago and may be off the list...

 I expect he will check in on this.

dn

-- 

Dennis A. Nickson. DRE #777174                                 530-677-9760 office

Nickson and Associates                                               530-957-9760 cell

 2931 Boeing Road                                                        530-677-1800 fax

Cameron Park, CA. 95682                                             dennis(at)nickson.biz (dennis(at)nickson.biz)

                                                                                    www.nickson.biz

               __!__

      ______( * )______

               o/   \o          

 Real Estate Brokerage and Development

jill(at)m-14p.com
Guest

Posted: Fri Feb 01, 2013 5:31 am Post subject: pneumatic system woes

The seals I sell for the Yak pressure relief valve are 90 durometer.  For

the Yaks, I have rebuild kits for the 636100M checkvalves.  We do not have

as much of a problem with these valves leaking as the CJ valves. The 636100M

now costs $695 per unit - this is without any markup or freight. 

 

Jill

M-14P, Inc.

keithmckinley

Joined: 11 Aug 2008
Posts: 434

Posted: Tue Feb 19, 2013 9:57 am Post subject: Re: pneumatic system woes

For what it's worth:



http://forums.matronics.com/viewtopic.php?t=69293

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