Thanks for that information Darick, Nitrile is the word I was trying to remember. Too often I feel we get all tangled up around "airplane legal" stuff. I would not hesitate to put those seals in mine, in fact if you get an exact size located let me know the part numbers, I will do it in a minute for mine. I would then decide if I want to tell the Fedies about it or not (my brother is a FSDO so I can get some inside information for free). So far I have never seen a ramp check that took Ercoupe struts apart and did a chemical test on the composition of the rubber cups! Why Skyport did not just use cups for hydraulic fluid already in the supply stream, I will never understand. If you don't do your own work it may be a problem to get your A&P to put them in. In that case you need a new A&P who has heard of the 337 process!
--- In [email protected], c.d.gu...@... wrote: > > Don, > You are correct. The cups used for DOT brake fluid is made of EPDM (ethelyene > propelyene -this might be misspelled) rubber. The rubber used for regular oil > base hydraulic fluid is acrylonitrile bunadiene, commonly called buna or > nitrile rubber. This is by far, the most common rubber used in hydraulic > systems like you find in earth moving equipment - Caterpillar, Case, John > Deere, etc. > > > These cups are readily available and are made of buna rubber which is the > rubber of choice for oil base hydraulic fluid, which includes the 5606 > approved for aviation use. Now the problem is that technically we can't go to > a hydraulic seal distributor and buy these cups and put them in an airplane. > Am I right about this? Somebody in the group who is knowledgeable about all > the red tape can tell us. > > > If I'm wrong about this and we can legally put buna cups in our airplanes, > purchased from industrial suppliers, let me know. I've worked in the fluid > power industry for 30 years and I know where to get them. Here's my soap > box... Yes, we can buy parts to put into mobile cranes that lift thousands of > pounds hundreds of feet into the air and put hundreds of people at risk but > you can't put that same part in a two seat airplane. Ok, I'm off my soap box > now. > > > The good news is that the world has a cup that can be used in hydraulic oil > and is readily available. > > > Darick > > > > ----- Original Message ----- > From: "Donald" <dongen...@...> > To: [email protected] > Sent: Friday, May 28, 2010 3:24:03 PM GMT -05:00 US/Canada Eastern > Subject: [ercoupe-tech] Re: Filling the MLG struts > > > > > > > > > What the world really needs is a cup that can be used in hydraulic oil! I > wonder what happens when one puts hydraulic oil into the strut that has been > converted to the rubber cup? Many industrial applications use those same type > cups in hydraulic oil, made of a different compound I suppose. > > --- In [email protected] , William R. Bayne <ercoguru@> wrote: > > > > > > There is more than a little possibility of confusion by the less > > experienced in reading these two posts. > > > > I agree with Alan that the rubber cup is a better design (for proper > > long term oleo seal service) than the O-ring installed in later birds. > > The rubber cup was the earlier design, though. IMHO, the O-ring was > > NOT an improvement; but if your oleos are not worn to the point that > > the O-ring cannot seal properly, or needs replacement often, install > > the Skyport "cup kit" SMK-61. It is the "better now" to which Alan > > refers. Individual cups are available as Skyport part number SS12301. > > > > For anyone interested, the oleo snap ring (part number 415-33229-1, see > > Fig. 12, item 18, NOT clearly shown and perhaps no longer available > > from Univair or Skyport is/was a "Reliance Light External Ring for > > 1.250 shaft, .125 x .620 wire section, .250 gap, style #6 gap" from > > Eaton Mfg. Co., Massilon, OH. > > > > Donald is correct that DOT 3 brake fluid will destroy oleo O-rings > > (just as hydraulic oil will destrot rubber cups). That should come as > > no surprise, as this the lubrication instructions are specific. Many > > mechanics don't know about the Skyport kit, and blindly service oleos > > according to ERCO's serial number recommendations (thus assuring > > failure of installed rubber cups on later birds). If rubber cups are > > installed, brake fluid MUST be used as oleo fluid. It may be that DOT > > 5 (silicone) brake fluid will not destroy AN O-rings...I have not > > tested that. > > > > The "old time spring cap" (and tube) deteoriate. Due to rusting, many > > no longer have spring closure action. Replacements are available from > > Skyport (and perhaps Univair). Forney used Gits Bros. #402, Style "E", > > but there may be other sources of such a generic item. Some mechanics, > > not knowing that replacements are available may have tapped the oleo > > hole to receive the pipe plug Alan describes. > > > > The pipe plug was "production" on Ercoupes through serial 812 (per > > Parts Catalog Fig. 11, p. 12, (upper) item 14. If this item were > > correctly referred on facing page 13, I believe it is the final item > > listed under 12a as "AN913-1D, Plug - hex (415-33166-3). > > > > Due to the many production changes to Ercoupe design and service parts, > > it is important that posters identify the serial number of the aircraft > > their experience (and information) relates to. A list of many of such > > changes in inside the back of the Service Manual. "One size DOES NOT > > "fit all" in this context, and no one intends to mislead or wants to be > > mislead. > > > > Regards, > > > > William R. Bayne > > .____|-(o)-|____. > > (Copyright 2010) > > > > -- > > > > On May 27, 2010, at 12:17, Donald wrote: > > > > > > > > > > > You speak of a filler plug with safety wire. My two sets of struts > > > have an old time spring cap like was used on oil holes a long time > > > ago, must be a change along somewhere. > > > I opted to use only new O rings, and the red aviation hydraulic fluid, > > > nice and oily. After seeing what brake fluid did to my other set, no > > > brake fluid for me. > > > > > > .--- In [email protected] , ALAN FAIRCLOUGH > > > <texasaviator@> wrote: > > >> > > >> How to and what not to do... > > >> > > >> I have found there are several things to watch out for. > > >> > > >> > > >> First of all, jack up the plane so the weel extends all the way down. > > >> Push the wheel up and down to feel the current hydraulic damping. > > >> > > >> If it is good, your sysyem is working and may just need topping off. > > >> If it is not you will feel it when pushing the wheel up. > > >> > > >> First thing to check is the bumpers. these are little rubber stops on > > >> the landing gear leg and on the strut. When the wheel drops down, the > > >> motion is stopped by a rubber bumper that is attached to this little > > >> arm. If it is missing, which is quite common, you are in trouble. > > >> The wheel has been dropping too far down, the filler hole has a rough > > >> edge on the inside of the > > >> cylinder and it destroys the seal. if you have a seal cup version. If > > >> you have the O'ring version, you need to take it off and get a seal > > >> cup kit from Skyport. > > >> The O'ring version was made to last 10 years at best and none will > > >> last long. It was a great idea at the time but there is better now. > > >> > > >> When you take the cylinder apart, you will see if you have the cup or > > >> the O'ring. You can leave the O'ring on as it will not harm anything. > > >> You will have to wash out the cylinder which is made of steel and > > >> probably has rust on the inside. Go to the auto parts store and buy a > > >> small 3 blade fine ctlinder hone that will fit inside. ( take the > > >> cylinder with you to test if it fits or make a second trip). You then > > >> hone out the inside surface with this device in a power drill and > > >> with diesel or kerosene in the cylinder. If you don't do this, the > > >> rust will eat up your cup seal. > > >> Wash it out well. Clean up the piston surface with sandpaper and > > >> diesel or with a wire wheel brush and install the cup kit as > > >> instructed. > > >> I find it is easier to fill the cylinder before installing it on the > > >> plane. Just pour the fluid into the cylinder and inser the piston > > >> seal and slowly push it down. Any excess fluid will come out the fill > > >> hole. inser the plug into the fill hole and safety wire. > > >> Put it on the plane and test the damping motion. > > >> > > >> If you need to top off the fluid, remove the rubber bumper and > > >> inspect it. Drop the wheel as low as it will go and add fluid through > > >> the filler hole. I use that syringe the dentist gave me to irrigate > > >> my wisdom tooth hole. An old oil can also works. > > >> The U cup seal is now above the filler hole. Do not push the wheel up > > >> now. > > >> Fill with fluid until it runs over and then push a wooden chopstick > > >> into the hole to carefully help the cup lip over the filler hole > > >> inside surface while slowly pushing the wheel up. Once the U cup seal > > >> is below the filler hole, prop the wheel up so it does not drop again > > >> and re-install the filler plug with safety wire and re-install rubber > > >> bumper. > > >> > > >> With the rubber bumper installed, you can now drop the wheel all the > > >> way down again and the U cup seal will remain below the filler hole. > > >> Now test the damping. > > >> > > > > > > > > > > > > > > > ------------------------------------ > > > > > > Yahoo! Groups Links > > > > > > > > > > > >
