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Cobra Trailer Hydraulic Jack Issue



 
 
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  #1  
Old June 19th 10, 03:06 PM posted to rec.aviation.soaring
Paul Remde
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Posts: 1,674
Default Cobra Trailer Hydraulic Jack Issue

Hi,

I am currently flying it in the U.S. Sports Class Nationals in Parowan, UT,
USA. The flying here has been spectacular!

I own a small share of a Cobra trailer for our DG-1000 sailplane. However,
the hydraulic jack used to lift the fuselage of the glider does not seem to
be functioning well. We can't pump it up to the highest position. Can you
please offer advice for fixing the issue. We need to be able to jack it up
to be able to lower the glider's landing gear. Does it perhaps need more
hydraulic fluid, or does it need to be replaced? If it needs hydraulic
fluid, what type of fluid should we use, and how to we do the job of putting
it into the unit?

I'm hoping that someone on this group will have a quick suggestion or tip.
It will be easier for me to receive e-mail than to check this group, so
please reply to my e-mail address directly.

Best Regards,

Paul Remde
Cumulus Soaring, Inc.
Serving the soaring community
http://www.cumulus-soaring.com
1-952-445-9033

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  #2  
Old June 19th 10, 04:26 PM posted to rec.aviation.soaring
Darryl Ramm
external usenet poster
 
Posts: 2,377
Default Cobra Trailer Hydraulic Jack Issue

On Jun 19, 7:06*am, "Paul Remde" wrote:
Hi,

I am currently flying it in the U.S. Sports Class Nationals in Parowan, UT,
USA. *The flying here has been spectacular!

I own a small share of a Cobra trailer for our DG-1000 sailplane. *However,
the hydraulic jack used to lift the fuselage of the glider does not seem to
be functioning well. *We can't pump it up to the highest position. *Can you
please offer advice for fixing the issue. *We need to be able to jack it up
to be able to lower the glider's landing gear. *Does it perhaps need more
hydraulic fluid, or does it need to be replaced? *If it needs hydraulic
fluid, what type of fluid should we use, and how to we do the job of putting
it into the unit?

I'm hoping that someone on this group will have a quick suggestion or tip..
It will be easier for me to receive e-mail than to check this group, so
please reply to my e-mail address directly.

Best Regards,

Paul Remde
Cumulus Soaring, Inc.
Serving the soaring communityhttp://www.cumulus-soaring.com
1-952-445-9033


Does it show signs of leaking fluid?

Are you sure the jack close valve fully closes, sometimes the little
lever slips on the valve nut and won't fully close, loosen it and
position it so that you really feel the valve closing firmly, not say
the lever hitting the ground.

If that does not work add some fluid and see if it fixes this. See
http://www.cobratrailer.com/html/service.html

Hydraulic jack fluid should be available at the H & R Home Center/True
Value Hardware or the NAPA parts dealer both not far from the airport.
The small bottles with pointed nozzle designed for for hydraulic jacks
can make it easier to add through the jack hole, otherwise a bottle of
auto transmission fluid will do (but lacks the nozzle tip). Watch the
rubber plug in the jack when you remove/reinstall it, it can fly off
(been there done that) and if you loose it you'll likely be buying
another jack.

If that still does not work try putting some planks of wood under the
scissor assembly that will get it high enough for you but still let
the fuselage roll out the cradle. Otherwise four people with their
backs under the wings and you can lift the rigged glider up enough to
drop the gear.

Failing that you have something worse wrong. I'd take this Chinese POS
jack out and shoot it, ask around, it's Utah, the locals are friendly
and I'm sure some are packing and would appreciate the chance for some
target practice.

Williams Soaring likely has replacement jacks in stock, hate to think
what overnight airfreight will be on that.

Darryl

  #3  
Old June 20th 10, 08:18 PM posted to rec.aviation.soaring
bumper[_3_]
external usenet poster
 
Posts: 16
Default Cobra Trailer Hydraulic Jack Issue

On Jun 19, 8:26*am, Darryl Ramm wrote:
On Jun 19, 7:06*am, "Paul Remde" wrote:



Failing that you have something worse wrong. I'd take this Chinese POS
jack out and shoot it, ask around, it's Utah, the locals are friendly
and I'm sure some are packing and would appreciate the chance for some
target practice.

Darryl- Hide quoted text -
- Show quoted text -


Shooting it does offer potential entertainment value . . . but if you
decide to go that route or replacinging it, consider the jack can
usually be fixed easily. As Paul posted, a quick fix may be to add
fluid - - but if this doesn't cut it, try draining the jack, flushing
it out with mineral spirits, and refilling with new hydraulic oil. As
they come from the factory, the inside machining is coarse which
results in metal fines in the fluid. This will sometimes prevent the
needle valve or ball check valve from sealing properly and in any case
will cause rapid wear. The jack will then either not lift the load at
all, or will leak-down etc. I recommend draining and flushing one of
these POS jacks after the first season of use. When disassembling,
watch for the little spring and ball!

bumper
MKIV and QV
Minden, NV

  #4  
Old June 29th 10, 01:38 AM posted to rec.aviation.soaring
cernauta
external usenet poster
 
Posts: 121
Default Cobra Trailer Hydraulic Jack Issue

On Sat, 19 Jun 2010 09:06:04 -0500, "Paul Remde"
wrote:


the hydraulic jack used to lift the fuselage of the glider does not seem to
be functioning well. We can't pump it up to the highest position.



I've had the same problem. Do you have the "V" shaped metal lever on
the jack's locking nut? I mean, the one that _should_ automatically
switch the hydraulics of the jack from "up" to "down"?

If it's not precisely adjusted on the nut, and/or it doesn't bear the
correct angle in the metal V braces, it won't work as intended.

You probably need to adjust it, or to shorten one of the braces, or to
remove it and install a very simple circular knob.

Aldo Cernezzi
 




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