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Testing hydrolastic displacer units
https://www.ausmini.com/forums/viewtopic.php?f=2&t=74680		 Page 1 of 2
Author:  68Rusty [ Mon Dec 19, 2011 3:20 pm ]
Post subject:  Testing hydrolastic displacer units
Hi all,
Just wondering if any of you know how to test the displacer unit. I was talking to John (mini king) and he suggested using compressed air and putting a little in hose to see if unit displaced.

I tried this and the two rear units displace and retract at about the same rate. The front right displaces and retracts quite quickly, front left which i purchased on ebay displaces and retracts slowly.

The units I bought of ebay may be rusted internally?? John suggested a cleaning procedure that I have forgotten now. Any ideas (I can just ring John back but trying to avoid pestering him) :lol:

I was thinking a light mix of caustic soda that’s what I usually use for cleaning rusted parts that have internal areas I cannot get to.
Author:  drmini in aust [ Mon Dec 19, 2011 3:37 pm ]
Post subject: 
My mate Richard puts them in a vice and applies 90psi air. I don't reckon this is good enough (or real safe!) as a real leak test.
I am building a test rig to use my hydro pump to pressurize them with fluid to 250psi, and leave overnight..
It's just the aft quarter of a buggered Cooper S rear subframe, with a piece of RHS tube welded across.
Not welded up yet so no pics taken.
Author:  68Rusty [ Mon Dec 19, 2011 3:56 pm ]
Post subject: 
Sounds like a good idea Kevin, would save a lot of work later changing if stuffed. I might have to try something similar?

I forgot to add the one I bought of ebay is also a 21A2008 single green band unit. Kevin any idea on the speed of displacement/retract issue?
Author:  mini_mad_matt [ Mon Dec 19, 2011 5:31 pm ]
Post subject: 
When i test hydro bags i just use compressed air. It leaves a lot to be desired, but it gives you an idea of how freely the unit moves. Also when the bag is pumped up you can see the condition of the rubber. I just get an air blower and seal the top of the hose with a rag.

If it moves freely and the rubber is in good condition and not showing signs of splitting everywhere then i will suck it and see, fitting it to the car and pumping it up.
Author:  John Smidt [ Mon Dec 19, 2011 7:07 pm ]
Post subject:  Re: Testing hydrolastic displacer units
68Rusty wrote:
Hi all,
Just wondering if any of you know how to test the displacer unit. I was talking to John (mini king) and he suggested using compressed air and putting a little in hose to see if unit displaced.

I tried this and the two rear units displace and retract at about the same rate. The front right displaces and retracts quite quickly, front left which i purchased on ebay displaces and retracts slowly.

The units I bought of ebay may be rusted internally?? John suggested a cleaning procedure that I have forgotten now. Any ideas (I can just ring John back but trying to avoid pestering him) :lol:

I was thinking a light mix of caustic soda that’s what I usually use for cleaning rusted parts that have internal areas I cannot get to.


Pm Sent,
The compressed air is just to see if it still works This is Not a leak test
To test for leaks, I have a jig that Ii put the displacer in and pump it up and leave for 24 hours
Author:  68Rusty [ Mon Dec 19, 2011 7:32 pm ]
Post subject: 
Thanks John :D
Author:  Aussie Brian [ Mon Dec 19, 2011 8:19 pm ]
Post subject: 
[quote="drmini in aust"]
I am building a test rig to use my hydro pump to pressurize them with fluid to 250psi, and leave overnight..
quote]
Kev this sounds good. I was thinking that maybe a higher pressure be applied to try and simulate hittting a pot hole in the road, Just a thought. :idea:
Author:  drmini in aust [ Mon Dec 19, 2011 9:04 pm ]
Post subject: 
Mate these things are all 40+ years old now. I'd say 300psi would be the limit for testing but 250 will do me for starters.
Author:  66S [ Tue Dec 20, 2011 12:52 pm ]
Post subject: 
300 psi is sissy pressure Doc, a car will need close to that to pump it to the correct ride height. I test at 350 psi in a jig and leave it overnight. Oh yes, I also cover it in a sack, just in case something lets go :lol:

Al
Author:  Mick [ Tue Dec 20, 2011 2:44 pm ]
Post subject: 
In operation, what kind of pressures are the displacers seeing?

It's one hting to have a static resting pressure of 300 PSI, but once the cars start seeing shock loads from potholes etc, the pressures must be much more than this.
Author:  66S [ Wed Dec 21, 2011 5:38 am ]
Post subject: 
I've never put a pressure gauge into a system but it probably doesn't go too much higher than pumped pressure because of the rubber bags expanding as the load increases on bumps and cornering. I'm guessing no more than 400 psi.

Regards
Al
Author:  Morris 1100 [ Wed Dec 21, 2011 3:34 pm ]
Post subject: 
66S wrote:
I've never put a pressure gauge into a system but it probably doesn't go too much higher than pumped pressure because of the rubber bags expanding as the load increases on bumps and cornering. I'm guessing no more than 400 psi.

Regards
Al

That is what I would figure, the spring deflects and and the fluid transfers away. I suppose I should hook the pressure gauge to the car and go for a drive.

There is an ******** on this forum that says they will exceed 1000 psi on a bump. :lol:
Author:  66S [ Thu Dec 22, 2011 5:54 am ]
Post subject: 
I'd be very surprised if it ever went that high on a Mini. I can't see the hoses coping with anything like that.

Regards
Al
Author:  miniron [ Fri Dec 23, 2011 6:42 am ]
Post subject: 
:?:
Testing for leaks is the first part.
Has anybody come up with a way to test the effectiveness of the internal damping valve/rubber flap bit?
After 40 years I guess most will be RS but if you have spares it may save putting in a really dodgy one.
If they have been stored with residual fluid in them will they be any good after 20+ years or will the insides be rusted out?
Fluid is supposed to have rust inhibitors included but the last time I had mine pumped up the old fluid that came out was very rusty.
Any actual pics of the internals of a cut up displacer? (Not cutaway drawings from the workshop manual)

Merry Xmas and Happy Miniing for 2012

RonR
Author:  drmini in aust [ Fri Dec 23, 2011 10:50 am ]
Post subject: 
I believe that the damping would be suss after 40+ years, there's no way I would build a hydro car (or our van) without putting some std spec front shocks on.
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