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
<texasavia...@...> 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
