Hydrolastic Again! but testing this time

[richardACS]

I have the front and rear displacers from my 1965 Cooper 1275 S on the bench, as the car arrived in boxes from New Zealand I have no idea that what is there are correct to the above car so my first Q being:

1) Are the front and rears the same in both canister dimensions and length of hose? (they all have the same length hose on mine).

2) I'm guessing the displacement would be the same F & R ?

3) There is a flash of orange paint on the side/middle of each canister and also on the rear pushrod - what does this signify?

The hoses are original to type i.e. not replaced and visually are in very good condition - no rust and the rubber hoses and the pad that sits on the displacers have not perished.

4) However, I think it would be prudent to carry out a bench test before assembly into the subframes. I'm wondering therefore whether I could carry out a pressure test just using air? and if so wondering what the air pressure should be? and for how long they should be left? I've plumbed up a section of pipe with a pressure gauge, lock off valve and a typical tyre valve for the purpose....

If these are originals and they work/don't leak it would be quite impressive!

Any other thoughts would be welcomed....

[Peter Laidler]

A quick reply based on my limited practical and theoretical knowledge Richard
1) both are the same externally

2) yep, both have the same internal and external displacement values

3) the orange flash or band was meant to indicate a harder unit. But before I go on, you can be rest assured that the band colour will have no bearing on them now. the internal valves, thoughtfully made from mild steel will have disintegrated by now. That said, without special hydraulic compression and calibrated release equipment - such as that found in field artillery workshop (look at a 25 pounder recoil and recuperation system operating on you tube for an example of what I mean.....) the average 60's or so Cooper S owner had no way of testing whether a unit was a this, that or the other band. EXCEPT for the colour - which you accepted in good faith.

I am sat here with my steel helmet on awaiting the incoming mortar fire for that comment. Now, where were we.....?

4) I have pressure tested with 70psi air using a high pressure air pump. BUT BEWARE. I put each unit into a bucket of water for a few hours to see whether there were any air leak bubbles. I have also pressurised the units using water mains pressure too. Leave it for a few days and if it's going to leak, it will, believe me

Those are my immediate thoughts. I have written this up extensively for the forum in the past but my compu'a technical skills are crap so cannot resurrect them. Regards

[Andrew1967]

If you have a hydraulic press and a suspension pump it is possible to pressurise the displacers to test them. I’ve done that when selecting four good displacers for HOY.

Was quite simple to do but a bit lengthy to write and to make any sense on here .

Happy to send via email with pics of displacer in situ on press to demonstrate.

[Exminiman]

A quick reply based on my limited practical and theoretical knowledge Richard
1) both are the same externally

2) yep, both have the same internal and external displacement values

3) the orange flash or band was meant to indicate a harder unit. But before I go on, you can be rest assured that the band colour will have no bearing on them now. the internal valves, thoughtfully made from mild steel will have disintegrated by now. That said, without special hydraulic compression and calibrated release equipment - such as that found in field artillery workshop (look at a 25 pounder recoil and recuperation system operating on you tube for an example of what I mean.....) the average 60's or so Cooper S owner had no way of testing whether a unit was a this, that or the other band. EXCEPT for the colour - which you accepted in good faith.

I am sat here with my steel helmet on awaiting the incoming mortar fire for that comment. Now, where were we.....?

4) I have pressure tested with 70psi air using a high pressure air pump. BUT BEWARE. I put each unit into a bucket of water for a few hours to see whether there were any air leak bubbles. I have also pressurised the units using water mains pressure too. Leave it for a few days and if it's going to leak, it will, believe me

Those are my immediate thoughts. I have written this up extensively for the forum in the past but my compu'a technical skills are crap so cannot resurrect them. Regards

I know bugger all about Hydro, very interesting, so its just internal valves that control the hardness ? “the internal valves, thoughtfully made from mild steel will have disintegrated by now” are the valves replaceable ?

[Peter Laidler]

You're dead right in your assumption there Exminiman...... The difference between all of the different colour banded hydro units is the mechanical one-chamber-to-another valve. Yep, mild steel and all well rusted out by now, believe me. Even then, in those old dark days, there was no method of testing whether the displacer was this colour or that colour or..... or whatever. Certainly not scientiifically - so far as I am aware without specialist equipment!

You could add a bit of stiffness today by reducing the size of the hole in the adaptor between the front to rear pipe and the front displacers. But even those will be totally rusted out internally and oversize. But thoughtfully, Catmint has had those remade in stainless. So big thanks to Gordon for his keeping that part of hydrolastic alive. Don't forget that a valve is simply another word for a restrictor of some sort so when I say valve, it means restrictor or vice verca.

And while we're here...... maybe I ought to carefully and most respectfully tread on the toes of a few purists regarding the mixing of different coloured banded hydro units front to rear. It almost defies the laws of hydraulics, physics and the bleedin' obvious - except in certain circumstances. Once again, field artillery and tank recoil systems being good examples of the exceptions for obvious reasons

The BEST way to see what is happening within a displacer is to machine one apart. NOT by sectioning id from top to bottom but by mechining it apart radially - as assembled - along the radial crimp line

[richardACS]

If you have a hydraulic press and a suspension pump it is possible to pressurise the displacers to test them. I’ve done that when selecting four good displacers for HOY.

Was quite simple to do but a bit lengthy to write and to make any sense on here .

Happy to send via email with pics of displacer in situ on press to demonstrate.

That would be much appreciated...might you have my email address?

[Andrew1967]

Will do Richard but won’t be until early next week as the parts I made up to test are at work and I’m off work this week .

[mk1]

A word of caution!

It is ALWAYS very bad practice to pressurise any sort of pressure bearing vessel without it being restrained.

In situ a Hydro displacer is held in place by the weight of the suspension, if it is pressurised without being held in a similar way you are A) Putting the unit under a huge amount of strain that it wasn't ever designed to accommodate & B) Inviting premature failure due to it being pressurised in a way it was never designed to be.

No point damaging good hydro units by just pumping them up unsupported.

[Peter Laidler]

Agreed with Mk1 above. But testing to 70psi with air pressure or 14psi with mains water pressure is as safe as it gets. This is simply to test for leaks..... with water you can see it drip, with air, in a bucket of water and you'll see the bubbles, believe me. It's nowhere close to the load the unit is subject to while working - or in hydraulic terms. Incidentally, the yellow tracer on the Dunlop HiFlex hydro hoses indicated that they were low pressure. By low pressure, I mean 'low' in terms of hydraulic pressure!

[richardACS]

A word of caution!

It is ALWAYS very bad practice to pressurise any sort of pressure bearing vessel without it being restrained.

In situ a Hydro displacer is held in place by the weight of the suspension, if it is pressurised without being held in a similar way you are A) Putting the unit under a huge amount of strain that it wasn't ever designed to accommodate & B) Inviting premature failure due to it being pressurised in a way it was never designed to be.

No point damaging good hydro units by just pumping them up unsupported.

Point well made, thanks...

[Andrew1967]

This picture shows a very quickly set up displacer and test cap fitted on to our hydraulic press. Obviously to do an actual test, I would use a decent piece of round bar, not a 3/4 to 1/2 reducer !!! You might also note that the ram isn't great and needs replacing !!

As the ram of the press is born down on the test cap and displacer before pressurising the displacer, it is held secure and cannot go anywhere. The base that the displacer is sat in has a square cut out to allow the hose to pass underneath for connection.

Set up a pressure gauge into the system if the Dalek doesn't show pressure (as ours doesn't) and leave for a desired length of time to see if any loss of pressure. I left HOY's on test for 24 hours .

[richardACS]

Thank you Andrew that is clear and I do have a similar press, I don't know but not sure it would be capable of sustaining a 'lock off' preesure for any length of time will have to check this out (it's a few years old).

To address Mark's points on safety - could one alternatively mount the unit into the subframes (which are not yet fitted to the car)?

I need to find a Churchill pump for this test and to use on the car once assembled, are there things to look out for with them i.e. leaky seals on the pumping mechanisim and if so are new seals obtainable?

[mk1]

Probably better to go for something like this, as 99.9999999% of all original Dalek hydro pumps are knackered.

https://www.ebay.co.uk/itm/173823474415 ... R8bwhtCSYg

Almost always the vacuum side doesn't work, sometimes both sides don't work, invariably one of both the gauges are seized up. You can rebuild them, but this is NOT easy or cheap.

M

[Andrew1967]

I can’t see any reason why you can’t fit up into a subframe off the car.

Good point regarding the Daleks Mark. Our one has never had the vacuum side working (but that’s not necessary in reality). My recently acquired one appears to not be seized but haven’t tested it yet … will be doing so shortly as my mk2 needs pumping up again.

I was sent some NOS seals from Australia so have them to use if required .

[richardACS]

Thank you gents this has been really helpful, I'll set up the system (in the subframes) and would like to give the units and the connecting pipes a thorough flush through, is this best carried out with a vacuum pump?

[Peter Laidler]

Does that e-bay offering offer the evacuation/depression facility too? Doesn't look like it.

Richard..... To set your mind at rest, if you pump up your units with air, to anything close to a VERY safe 50psi (I take mine to 70...) and put the unit into a bucket of water, if it's going to leak, it will. And the air bubbles will be there for all to see. I've done it many many times. DON'T COMPLICATE THINGS

Likewise, connect it to the house water main - 14 or so psi, let it hang by the hose and once again, if it's going to leak, you'll see it.

Don't complicate matters. The system isn't complicated. It is made to frighten you. Where there's a will, there is ALWAYS an easy way.

On the other hand, if you want a workable and simple total evacuation and pressure system that works every time, and have £10 to spare, simply - and I mean simply - make your own as I amply describe elsewhere.

You ask about flushing the units out. Do them in a bucket of water. Fill them up, shake the shit out of them, literally, and keep doing it until the water comes out clean. Flush out, put a slim air line inside and blow-out. Fill with clean hydro fluid and bang a wood or rubber stopper in the end until required for use.

[mk1]

I'm not going to labour the point, but inflating hydro bags without supporting them (even under relatively low pressures) applies forces on them in ways that they were not designed to take. Doing so will likely cause premature failure.

While, as Peter says, if they are going to leak they will, I don't see the point in knackering these Hydro bags if you don't need to.

[Peter Laidler]

Yep, I bought one some years ago that was seized tighter than a ducks arse. Did eventually strip it but the same old rusty shite that is destroying the hydro unit internals had done the same to the internal parts of this unit. And no amount of new seals were going to fix it. So it went into the skip as beyond any sort of repair.

While I also don't want to labour the point either, pumping them up to household mains pressure or 70psi air isn't going to knacker a hydro bag. It is just a testing strategy. They're going to get a LOT more pressure later!

I say better partially test 'em OFF the car that when they're all fitted, only to find that small niggling dribble from the weaker pliable strut end of the bag. There..... my last word on hydrolastic

[TECH396]

I just made a test apparatus for this purpose. It is a great way to test displacers prior to installation.
I'd advise against applying any pressure without controlling the moving side of the displacer, for the risk of overextending the "bag" in a way it wasn't designed to. I'm fortunate to have a Hydro working pump, and was surprised at how well you can observe the valve operation with a little bit of practice.
You watch the pressures change in the way they drop once pressure is released... As Andy said, It's hard to describe, but it's there if you're willing to take the time. I used a spare rear connector and tapped the one side to 1/8 NPT to accept a pressure gauge. You could easily use a small portable air compressor with this set-up if that's all that you have, then spray dish-soap and water or submerge it to look for leaks,, .. I prefer the fluid test because you can observe if the valve is stuck closed, or not functioning at all. You can't do that with air or water. If the valve is stuck closed, the pressure in the hose still builds, but there's nothing getting to the displacer.

[Aussie Bill B]

A couple of suggestions about the hydro system for what they're worth:

1. there is a list of many hydrolastic suspension units and their applications here on this site at:
https://mk1-performance-conversions.co. ... _units.pdf

Orange coloured markers or sleeves on the rear helper springs and struts indicate the upgraded versions of stronger springs and slightly longer struts introduced in UK in 1965. Colours on the displacers themselves indicate the vehicle they were intended for.

2. These displacer units are surprisingly tough and long-lived. Most failures are at either end of the rubber hose due to age. There are repairs possible for failure at either end. Internal failure of mini displacers is very rare.

My suggestion is to not bother with setting up a testing rig; fit the displacers during the rebuild, pressurise the system and watch for leaks - usually fixed by tightening the fittings or the schrader valves in the rear.

3. Don't flush the system with water as it MUST promote rusting of the internal valves. Steel parts will not rust while emersed in hydro fluid. A few pump-ups-and-drains will flush out the system if it's a worry.