Cobra bottle jack failure

I had a failed jack that I took apart to see why it was not
maintaining the extended position. In my case the ramp would slowly
lower back to collapsed postition, which besides annoying, can be a
danger to the fuselage. Turns out that it was the synthetic plunger
on the main piston leaking. So even under pressure the oil would seep
past the plunger and the piston slowly looses position till it
eventually collapses. The culprit does not seem to be any of the
various ball-bearings in the base of the jack.

Anybody know if a replacement plunger could be obtained. I am sure
its much cheaper than a new jack.

On Oct 28, 1:53*pm, db_sonic wrote:
I had a failed jack that I took apart to see why it was not
maintaining the extended position. In my case the ramp would slowly
lower back to collapsed postition, which besides annoying, can be a
danger to the fuselage. *Turns out that it was the synthetic plunger
on the main piston leaking. *So even under pressure the oil would seep
past the plunger and the piston slowly looses position till it
eventually collapses. *The culprit does not seem to be any of the
various ball-bearings in the base of the jack.

Anybody know if a replacement plunger could be obtained. *I am sure
its much cheaper than a new jack.

Darren

Most people just replace the jack ~$80/$90 or so and not waste time
messing around. Unfortuantely Cobra uses junk jacks and will likely
fail in a few years again.

Williams Soaring should have them.

Darryl

Yep, actually I already did. But before doing that I had attempted
to fix it and was disappointed when I couldn't figure it out. Till
last night when a cracked it open. Incidentally took a monkey wrench
and a propane torch to get the top off and I really had to lean into
it.

You might be right though that any replacement part would just fail
again... Just seems wrong though to toss a 5 lb chunk of metal into
the garbage can.

Darren

Most people just replace the jack ~$80/$90 or so and not waste time
messing around. Unfortuantely Cobra uses junk jacks and will likely
fail in a few years again.

Williams Soaring should have them.

Darryl

On Oct 28, 5:52*pm, db_sonic wrote:
Yep, actually I already did. * But before doing that I had attempted
to fix it and was disappointed when I couldn't figure it out. *Till
last night when a cracked it open. *Incidentally took a monkey wrench
and a propane torch to get the top off and I really had to lean into
it.

You might be right though that any replacement part would just fail
again... *Just seems wrong though to toss a 5 lb chunk of metal into
the garbage can.

Darren

Most people just replace the jack ~$80/$90 or so and not waste time
messing around. Unfortuantely Cobra uses junk jacks and will likely
fail in a few years again.

Williams Soaring should have them.

Darryl

If you figure it out, you could have a nice overhaul biz...

On Oct 28, 4:18*pm, Dave Nadler wrote:
On Oct 28, 5:52*pm, db_sonic wrote:





Yep, actually I already did. * But before doing that I had attempted
to fix it and was disappointed when I couldn't figure it out. *Till
last night when a cracked it open. *Incidentally took a monkey wrench
and a propane torch to get the top off and I really had to lean into
it.

You might be right though that any replacement part would just fail
again... *Just seems wrong though to toss a 5 lb chunk of metal into
the garbage can.

Darren

Most people just replace the jack ~$80/$90 or so and not waste time
messing around. Unfortuantely Cobra uses junk jacks and will likely
fail in a few years again.

Williams Soaring should have them.

Darryl

If you figure it out, you could have a nice overhaul biz...- Hide quoted text -

- Show quoted text -

Changed the subject to something more apropos ; ).

On Oct 28, 4:54*pm, db_sonic wrote:
On Oct 28, 4:18*pm, Dave Nadler wrote:





On Oct 28, 5:52*pm, db_sonic wrote:

Yep, actually I already did. * But before doing that I had attempted
to fix it and was disappointed when I couldn't figure it out. *Till
last night when a cracked it open. *Incidentally took a monkey wrench
and a propane torch to get the top off and I really had to lean into
it.

You might be right though that any replacement part would just fail
again... *Just seems wrong though to toss a 5 lb chunk of metal into
the garbage can.

Darren

Most people just replace the jack ~$80/$90 or so and not waste time
messing around. Unfortuantely Cobra uses junk jacks and will likely
fail in a few years again.

Williams Soaring should have them.

Darryl

If you figure it out, you could have a nice overhaul biz...- Hide quoted text -

- Show quoted text -

Changed the subject to something more apropos ; ).- Hide quoted text -

- Show quoted text -

Good move. I think there's a club member here with the standard cobra
bleed-down problem. If he replaces his, I'll try to talk him out of
the old one. It's just a hydraulic jack, and I have more than one
that are over 30 years old and never leaked a bit, so I'm pretty sure
it's possible. I have access to a machine shop. Who knows? I might
make a fortune selling 1 or 2 rebuilt jacks a year!!

On Oct 28, 8:24*pm, Uncle Fuzzy wrote:
On Oct 28, 4:54*pm, db_sonic wrote:



On Oct 28, 4:18*pm, Dave Nadler wrote:

On Oct 28, 5:52*pm, db_sonic wrote:

Yep, actually I already did. * But before doing that I had attempted
to fix it and was disappointed when I couldn't figure it out. *Till
last night when a cracked it open. *Incidentally took a monkey wrench
and a propane torch to get the top off and I really had to lean into
it.

You might be right though that any replacement part would just fail
again... *Just seems wrong though to toss a 5 lb chunk of metal into
the garbage can.

Darren

Most people just replace the jack ~$80/$90 or so and not waste time
messing around. Unfortuantely Cobra uses junk jacks and will likely
fail in a few years again.

Williams Soaring should have them.

Darryl

If you figure it out, you could have a nice overhaul biz...- Hide quoted text -

- Show quoted text -

Changed the subject to something more apropos ; ).- Hide quoted text -

- Show quoted text -

Good move. *I think there's a club member here with the standard cobra
bleed-down problem. *If he replaces his, I'll try to talk him out of
the old one. *It's just a hydraulic jack, and I have more than one
that are over 30 years old and never leaked a bit, so I'm pretty sure
it's possible. *I have access to a machine shop. *Who knows? *I might
make *a fortune selling 1 or 2 rebuilt jacks a year!!

You're thinking way too small.
Its an international market and the dollar is weak !

If you figure it out, you could have a nice overhaul biz...


Do it! I'm ready to buy a reliable, modified Cobra jack that doesn't
bleed down.


Burt
Marfa
Texas
USA

On Oct 28, 6:20*pm, Burt Compton - Marfa wrote:
*If you figure it out, you could have a nice overhaul biz...

Do it! *I'm ready to buy a reliable, modified Cobra jack that doesn't
bleed down.

Burt
Marfa
Texas
USA

I've already emailed the guy with the jack in need of replacement.
Dave, you're right. How about you handle the marketing. I'll use my
profits to pay down the electric motor-glider you advance me. ;-P
My comet trailer had the scissor jack arrangement, and I didn't much
like that (after it failed) so I made this instead:
http://www.youtube.com/watch?v=YP2AD8rtdpA

$25.00 plus some fun working on this project will get you this
hydraulic
scissors jack
http://www.soaridaho.com/Schreder/Co...ssor_Jack.html


On Oct 28, 9:43*pm, Uncle Fuzzy wrote:
On Oct 28, 6:20*pm, Burt Compton - Marfa wrote:

*If you figure it out, you could have a nice overhaul biz...

Do it! *I'm ready to buy a reliable, modified Cobra jack that doesn't
bleed down.

Burt
Marfa
Texas
USA

I've already emailed the guy with the jack in need of replacement.
Dave, you're right. *How about you handle the marketing. *I'll use my
profits to pay down the electric motor-glider you advance me. *;-P
My comet trailer had the scissor jack arrangement, and I didn't much
like that (after it failed) so I made this instead:http://www.youtube.com/watch?v=YP2AD8rtdpA