Replacement fluid for corba hydraulic jack???

On Tuesday, April 19, 2016 at 9:27:38 AM UTC-7, wrote:
I lower the wheel, and lower the jack until the wheel just touches the ground, then hold that jack position. There is then no further down pressure on the jack. The fuselage weight is supported by the main wheel, but the fuselage is still snug in the cradle, which keeps the fuselage upright as the wings are attached.

Saw a cheap fix in photographs on the ASW27 newsgroup, posted by Gregg Leslie.
Tractor Supply, Home Depot etc have a floor jack for $40 that has the same cheap Chinese hydraulic ram. Just removed the ram from one, the part is still the same.
http://www.homedepot.com/p/Big-Red-2...2-BR/100595182
Remove that part from the jack, drain the hydraulic fluid, clean it out, add new fluid and swap parts out with the one from the trailer.
Jim

In general, if you replace seals, you can use a fluid that is compatible with them. I believe Viton seals work with lots of fluids, like DOT 3 or 4 brake fluid. Pretty easy to find and used in most automotive brake systems.

I would NEVER use brake fluid in a hydraulic system unless specifically required by the manufacturer, nor would I use hydraulic fluid in a brake system. The systems are only similar in function and principle. The demands are entirely different. Brakes get hot- real hot. The fluid that is used to withstand the heat is very corrosive to rubber and neoprene. These are the seals normally used in simple hydraulic systems.

On Tuesday, April 19, 2016 at 8:15:29 PM UTC-4, Mark628CA wrote:
I would NEVER use brake fluid in a hydraulic system unless specifically
required by the manufacturer, nor would I use hydraulic fluid in a brake
system. The systems are only similar in function and principle...

Say WHAT?

Hydraulic brake systems can use a variety of fluids.
DOT and "red mil style" are both common.
The Tost conversions (of Cleveland) I have use DOT type, Beringer uses DOT type,
but some gliders use mil-type with original unmolested Clevelands.

The design of a brake system addresses corrosion (materials selection),
heat tolerance, seal type, etc. Except when they screw it up (see
Tost conversions of Cleveland brake systems and corrosion).

For heavens sake, read YOUR MANUAL,
and use what the manufacturer of YOUR glider specifies,
and not what you thought you understood from RAS...

Similarly, bottle jacks used in a trailer or car can use
a variety of fluids, though I think DOT style (which specific?) most common.

Hope that helps,
Best Regards, Dave

PS: Perhaps Bumper can further clarify...

Really?

For a fuselage jack, you could use 30wt engine oil, mineral oil etc.

You don't have to worry about temps, etc.

Biggest issue? Corrosion inside the cylinder. I also would be concerned with (long term) fluid compatibility with the seals.

In a brake system, I would look at DOT 4, or DOT 5 depending on what the system was set up for. Any other hydraulic system I would need to know what it requires.

On Tuesday, April 19, 2016 at 7:08:01 AM UTC-7, Dave Nadler wrote:
On Wednesday, April 13, 2016 at 3:57:48 PM UTC-4, bumper wrote:
Cobra uses about the cheapest Chinese junk jack they can get their hands on...

To be fair, the Spindelbergers have bemoaned the lack of available
quality jacks; as all jack production has been driven overseas to
the lowest cost with barely acceptable quality. They've told me
they'd be happy to buy better stuff if it could be found.

Spindelberger has always provided great support!
See ya, Dave

Yo Dave

As much as I admire the Spindelbergers/Cobra and have had wonderful support from them in the past, I'm just not sure this story rings true. For example I have a nice low-profile workshop floor jack made by AC Hydraulic in Denmark. They claim to make their products in Denmark, but maybe their bottle jacks are Chinese made, I have not seen a recent one to be sure. But worse case somebody like AC Hydraulic in Europe should be able to make a high quality jack assembly. And yes you'd pay for it, but I expect many owners of a Cobra trailer would rather do that than put up with the current used junk bottle jacks.

Darryl

On Tuesday, April 19, 2016 at 10:28:11 PM UTC-4, Darryl Ramm wrote:
On Tuesday, April 19, 2016 at 7:08:01 AM UTC-7, Dave Nadler wrote:
To be fair, the Spindelbergers have bemoaned the lack of available
quality jacks

Yo Dave

As much as I admire the Spindelbergers/Cobra and have had wonderful
support from them in the past, I'm just not sure this story rings true.

That's what they have told me when I asked about this...