Today's adventure was Gus's hydraulic pressure limiter. Thanks Gus, this was straightforward and quick (just over an hour including locating the wrench that younger elves misplaced).

The adventure came in when I noticed that the original hoses were tacky, and then the cladding had already flaked off in various places (see below, but I think many have seen this). I didn't improve this by manipulating the pump, but it's not immediately alarming because the crimps still do not appear to be leaking. But probably the source of long term alarm. E.g.

https://www.jaguarforums.com/forum/x...pistons-71772/

So, I have seen discussed several vendors for these hoses, but frankly, these do not appear, on the surface, to be special hoses for special Jag conditions compared with industrial hoses at higher pressures, larger temperature range, more vibration that last for decades and are cheaper, especially for the 1/8" variety. They are certainly custom build, I suspect. So, quick question, has anyone taken the hose specifications to Parker Hannifin and priced them? Parker is generally pretty cheap, even for custom hoses. Alternatively, does anyone know the exact lengths and fittings for all the hoses (e.g. http://jagrepair.com/ReplacementHydRoofLatchHose.htm for one of them)? Our local Parker people in Raleigh are very helpful and cheap, even for the exotic high pressure stuff I frequently use.

Frankly, looking at the forum on this, it surely looks like hoop burst is not the failure mode for the hoses. I think others may have noticed this. Slipping out from under the crimp after degradation of the crappy cladding seems like a more likely failure mode. If so, this could have little directly to do with peak pressure, but temperature cycle degradation of the cladding, followed by motion/vibration cycling the crappy cladding out from the crimp leading to unraveling and failure.


Degraded cladding on hoses near the pump. Generally flaky everywhere in the trunk.

Based on the markings, seems like the original hoses.

 

when mine failed, I did try a local hydraulic shop but they weren't interested. Thus I used Cabriolet hydraulics out of Bradenton Fl. Others have used TopHydraulics and recently, a UK vendor has been found at much cheaper pricing. Before you have some custom made (if possible) check your passenger side ram lower connection as mine was a bayonet type connection while all others were standard fittings

 

Thanks Steve, will check.

It was the prices from TopHydraulics that seemed high, and I've never had Parker refuse to do a custom job, no matter what it was. They are basically the major source and the standard.

I guess alternatively, if someone has a set of broken/replaced hoses and would send them to me (I'll pay postage), I'm happy to see what Parker can provide that is durable with the right temperature range and pressure at what price. Once one has a Parker number, they can be replicated any time.

I am skeptical you need 15000 psi proof pressure on these hoses, but perhaps.

 

The pump has internal relief valves which limit the pressure to ~ 1600 PSI in the latch circuit, ~ 1200 PSI in the ram circuits. Building in a 100% safety margin we would want hose assemblies rated for ~ 3000 PSI or higher. (A hose assembly will usually be rated for lower pressure than the bulk hose material itself.)

 

Indeed, but usually the margins of safety are included in the rating of the hose/fittings. So, if one's hose does not expect to see more than 1600 psi, a 2000 psi hose would have proof pressure of something much higher (or burst pressure, for the purposes of this discussion, we can assume they're the same). For example, Parker hoses generally are 4:1. So, a 2000 psi hose from Parker would have a 8000 psi proof pressure. That is usually more than sufficient in the real world.

It's so sufficient, that Parker, for special applications, will rerate into the safety margin. For example, I have had them rerate large 5000 psi accumulators for 6000 psi, among other things. The design proof pressure of 20,000 psi did not change when they did that, they just certified that it would be okay to use at 6000 psi with a factor of safety of 3.33:1.

It's also likely that the design proof pressure is lower than the achievable proof pressure, but not by a factor anything like 4.

 

Crbass,

Somewhere in my garage is a old crumbly hose that I kept .... just in case. It was for the LHS ram with standard fittings. Note you may have the different fitting on the lower RHS ram. Pic below. I learnt this the hard, and expensive way! Dcautoparts.com came to my rescue.



PM your address and I’ll sent my “cruddy” hose to you free of charge

 

Crbass


Dims of 3 of the hoses (end to end incl fittings)

RHS top 44”
RHS bottom 56”

LHS 96” not sure top or bottom
Sorry the other one I threw away as it was broken

I”ll post the cruddy RHS bottom. It’s the Ashoora public holiday here, so won’t dispatch until Weds.

 

Beautiful, thanks David! And the same random 'raggedy zebra' color as mine.