The future of Hydrolastic suspension

[nileseh]

Thanks. I have seen a difference in the central tower but I haven't paid much attention yet. I will. I'm not sure it matters. It occurs to me that the steel cone bonded to the rubber donut is normally displaced upward by the weight of the car. That will always increase the clearance from the unloaded condition. Since the system uses an incompressible fluid under pressure to transfer the load to the donut it will never be any lower. I also noticed on one of the cross-section views above that a bushing on top of the tower is inserted into the fluid exit port not unlike the needle on a SU carburetor. However under loaded condition with the donut displaced the bushing may be clear of the exit port. I don't know the spring rate of the donut that would allow me to determine the deflection. But it just occurred to me that I can rig up something to measured the spring rate. I think I'll do it.

It seems odd to me that the only difference is the metering valve. This valve really only serves the purpose of an integral shock absorber rather than change the spring rate. But perhaps I'm missing something.

I have a document that lists 21A1872 and 21A1874 as equivalent to 21A2012 and 21A2014, including the 1 silver band and 2 silver bands respectively on the hose. The difference in part number may be related to a manufacture site or time frame or even a price change.

If you have a 21A2012 that you can spare, I'll be able to make full Cooper S sets. After I rebuild my 4, I'll have enough cores to build on additional set.

I just saw the "Spider" post. the comment on tower height makes sense to me. It's just a different stamping, perhaps something easier to fabricate without changing the performance of the device. That may also be the differentiation of the equivalent part numbers noted above. No functional difference, just a manufacturing change.

Niles

[smithyrc30]

Hi Niles, excellent work on the displacers, if Tim cannot find his I have a spare front S displacer with a rotten hose that I can send you.

This is an Australian displacer, I am not sure if it was manufactured in Australia, Winabbey or Spider would most likely know, both post regularly on here or if there are any differences between Australian and UK parts.

I too looked at cutting through the crimp but came to the conclusion that fitting, for want of a better term, a banded displacer back into the front subframe would be very difficult because of the very limited clearance.

Do you have a picture of your solution please?

[winabbey]

There's some detailed discussion here. Also my post with the Oz engineering drawing, if that helps.

viewtopic.php?f=28&t=15392

[Spider]

I'm pretty sure the 'springing' between Cooper S 'Stiff' types and mortal Mini ones were the same in terms of spring rate, however the differences between them being the Damping Rates, so what you've found in regards to the internal Damper Valves sound bang on to me.

If suitable Dampener Valves can be made, this would make it perfectly feasible to convert Mini Bags to Cooper S (and other ST) types.

Great project.

Any photos?

[Spider]

This is an Australian displacer, I am not sure if it was manufactured in Australia, Winabbey or Spider would most likely know, both post regularly on here or if there are any differences between Australian and UK parts.

I can't categorically say with any certainty if our Displacers were exactly the same as those from the UK. At a guess, I'd say they were (I think we only had 2 types ??), Doug would probably be better able to respond to this one.

Ours did have an Aust Part Number, in which that revels that they were both Drawn Here and Manufactured locally (Some parts while manufactured here were done so from UK Drawings & Designs).

[nileseh]

I agree on the spring rates being the same for standard Mini and Cooper S applications. All the displacers I looked at have the 21A1477 part number molded into the face of the donut.
The comment on clearance to fit a banded displacer is absolutely correct. There is none. I tried a number of configurations and techniques to get a banded displacer into the subframe without altering the subframe and finally came to the conclusion that the modified device could be no larger in diameter than the original. This is especially true in the front subframe. The assembly retainer is just that. I have placed it in the subframe many times without difficulty. I didn't want to have to reconfigure the standard subframes.

The dampening valve is a rather simple affair. It can easily be recreated with the original rubber bits or recreated entirely with rubber of the same durometer. That may not be important either because the dampening rate is a function of the opening of the valve. Anything restricted to the same opening should provide the same rate. It just occurred to me that if the function of the metering valve is strictly dampening, perhaps it could be removed altogether and replaced with conventional telescoping shock absorbers. I believe there are kits available to add shock absorbers to Cooper S models that have been converted to coil springs. I’m not sure how that would affect the intent and performance of the front to rear fluid displacement.

In any case, the comment about converting standard hydrolastic to Cooper S specification seems to be correct. All the internal bits are the same. The only difference seems to be adjustment of the valve opening. Cooper S displacers can be created from any displacer with the 21A1477 spring unit once the dampening settings are known.

I have a picture of the retaining ring, but I not proficient in posting things: I don't know how to place an image in this text. I tried to attach it in the dialog box below, but I'm not sure it is successful. If anyone can provide guidance, I'll add images to my nest posting. sorry.

If anyone has a known part number displacer, send me an email and I will make arrangements to get it here for analysis.

[timell]

Sensational research, effort & work nileseh

Another difference between S displacers and standard is the distance from the steel 'crown' to the top of the rubber doughnut spring (21A1477)...in S's it is about 30mm and on standards appears to be about 40mm. Have your dissections shown a specific reason for this?
Tim

Wonderful of you Tim to donate a Hydro Bag to the cause.

In regards to the difference in height, when I went through a number of Hydro Bags here a few years back, I found that height difference related to whether it was an early or late type of Bag, not if it was Cooper S.

More than happy to do it, if it helps prolong their availability for our use Spider......should be able to dig it out by Wed hopefully Niles, just hope the part no is still legible.
Regarding the Doughnut height Spider, I wonder if that may be specific to Aussie displacers; the 5 I have date from 66 to 71, and are all from S's with the doughnut recessed by 30mm. I also have 8 standard 21A2008's of various dates, all with the doughnuts at 40mm..another Moulton mystery?

[nileseh]

Thanks. If the part number is not legible (I'm not entirely sure all of them were even marked with a part number, but I have seen some with the part number stenciled on the barrel) the banding on the hose is also indicative: 1 silver band is 21A2012, 2 silver bands is 21A2014.

[geroch]

Very interesting... If you send me photos by mail, I public on the forum. hb9fez(et)gmail.com

[mab01uk]

I have a picture of the retaining ring, but I not proficient in posting things: I don't know how to place an image in this text. I tried to attach it in the dialog box below, but I'm not sure it is successful. If anyone can provide guidance, I'll add images to my nest posting. sorry.

Great work and research on the mysteries of Hydrolastic!

For adding pictures as attachments see Forum help here:-
viewtopic.php?f=33&t=10177

Better still register free with 'Imgur' below to host them, then simply drag your chosen photos over to upload them to your new Imgur account and then copy/paste the image link code for each photo into your post on the Mk1 forum to share the images.
http://imgur.com/

[69k1100]

I would have thought the biggest problem to overcome is the drying and cracking of the rubber spring.

It's true that they generally fail at the hose (as the hose is a thinner wall section, so it degrades quicker) but I have seen a few examples that fail through the spring blowing out.

It would be interesting to see the condition of the spring of any units that are 'refurbished' as it is basically impossible to recondition the rubber once it has cracked. You can delay the onset of degradation, but natural rubber oxidises, cracks, and then the valleys of the cracks oxidise, until the rubber is completely compromised.

Delaying the degradation is as simple as adding some sort of sealer to stop Oxygen getting to the surface. Curing any damage is impossible.

Re-manufacturing dis-placers is not impossible, or even too expensive. It's the commitment to buy. Even if you were to do it as a service and break even, I don't think there would be enough confirmed pre-orders to pay for the tooling.

Refurbishing them is a grand step, and the mini community is better for it, but I can only feel disheartened when I think of the future of these components. By modern standards they're not even particularly good, just something for originality. I'd love to get the wet up and running on mine, and even with my supply of bags I don't think I will get many years on Adelaide roads.

[nileseh]

I've been concerned about the longevity of the rubber parts as well, especially the strut diaphragm. The test unit of unknown heritage exhibits significant cracking on the outside surface. However, the structure of the diaphragm is a multi-layer fabric that is rubberized rather than solid rubber, so the surface cracks do not propagate thru the material and it remains surprisingly supple. I've pressurized it without restraining the movement of the strut cone to a nearly convex shape out of the bottom of the housing without any apparent failure (this is incidentally the easiest way to get the strut cone back in place after a thorough cleaning; the seat in the diaphragm expands to receive the lip on the cone). I suppose eventually all rubber will harden up and fail. The displacers on my car are 50 years old now and seem to have not degraded as much as I have in the last 50 years.
I not concerned about the rubber donut spring unit: its basically the same as the dry suspension unit. Always under compression, never any tensile loading on material or the bond surface. It will probably last very long indeed.

My solution for rebuild does not require tooling as such. It's all machined components so CNC programming is the only tooling. I built a restraining fixture to allow pressurization out of the car. That's about it. Well, and I rebuilt a factory service machine, the one that is a green box with levers on the front and hoses out of the back.

Manufacture of replacement unit would be a different matter. The housing could certainly be machined parts, and could be designed as a serviceable (and therefore adjustable) unit. The spring donut would not be difficult with materials available these days. I have a composites manufacturing company and we work frequently with two component silicone materials that can be poured in place for cure. The diaphragm is a bit more problematic. It could be made from better materials, perhaps a kevlar fabric and a suitable fill elastic material. But it would have to made in a mold to provide sufficient material for the motion of the strut. Perhaps a vacuum infusion technique similar to wet layup fiberglass structures. I've not thought that far into the possibility but I have the equipment that would be used. It just occurred to me that I could design the molding tool and build it on the 3D printer I have. We have recently done as much for high temperature cures of small fiberglass structures. So far it's an interesting thought process. Of course the concours rebuilders would still be out of luck.

I think the rebuilding is economically viable. From where I am now, a pre-order is not really required. I don't yet have a reasonable component cost when done in low volume rather than one off prototype. I'll know more once we build the 4 sets I need for my car. My sense is that a build of 50 sets would be less than $200 in component costs each set. I'll finalize the drawings and get it an estimate from the shop. I think I'll also run the design by my engineers here to see if there is a better idea. I've been working on this alone for a number of years and tried a number of solutions to get here. I think it is a good solution, but I'll check in with fresh minds.

And I do appreciate the interest expressed by the individuals who are posting to this thing. I'll work on the advice on posting pictures later today and see what I can do.

[nileseh]

http://imgur.com/XpBsi8j
http://imgur.com/mTsAnKa
http://imgur.com/D2p5W8C
http://imgur.com/4WUjtWM
http://imgur.com/D8FxmOX
http://imgur.com/HHLrTYK



This is my attempt to show pictures. Will these links result in pictures in the published post?

A couple other things this morning:
1. rubber cracking in the diaphragm may be less of an issue. The nylon fabric-rubber structure does not actually contain the fluid; its the butyl membrane, a separate liner inside of the diaphragm. The diaphragm may actually even be vented to avoid an air pocket between it and the liner. This can be seen in some of the cut away images.
2. The mechanical device shown here does work and will allow servicing the unit in the future, however I met with my engineering team this morning and obvious resealing method (that had not occurred to me) was put on the table. We can service the unit, clamp it together as shown, then wrap the seam with a prepreg carbon fiber band, maybe 9 layers thick. that would be about .090", the same thickness as the housing steel. Then while clamped, vacuum bag to hold the material close to the barrel (or even autoclave the thing at 30psi) and cure. We have prepreg carbon that will cure at 250F, barely above boiling water. I don't think that will affect the rubber bits. I think it would have a cleaner look, it would be semi-permanent (could be cut off again in a lathe and done over) and extremely durable. We're going to try it on a junk displacer.

Enough of this today. Please let me know if the pictures come thru, or if not what else I need to do.

[STG95F]

Wow , looks impressive .

Sorry for asking , are you planning on totally remaking hydro displacers or is this to service old ones ?

Looks amazing work

Ian

[mab01uk]

This is my attempt to show pictures. Will these links result in pictures in the published post?

Yes we can see the pictures now by clicking on the links in your post.
Thanks for posting them, very interesting!

If you want the photos to actually display in your post you would need to copy and paste the BBCode (for message boards & forums)
which can be found on Imgur (unique code for each photo where the xx's are in example below) looks something like this:-
[img]http:xxxxxxxxxx.jpg[/img]

[nileseh]

I'll the BBCode noted below the next time I have pictures.

STG95F: This is to rebuild the displacers I need for my car for now. if it all works out I'll get the costs together to see if it is feasible to rebuild them or offer a kit of the components to do so. A kit of parts would require the user to lathe cut the displacer to specific dimensions, clean, set the dampening valves and reassemble with the clamping ring. I've not tried to close it with the axial screws (I've always used the clamping fixture and simply used the screws to seat the clamp) but I think that with care the screws should be able to close it as tight as the fixture.

[STG95F]

Great Thanks you

Keep us posted

Ian

[nileseh]

The notion of building new displacers is one that will require considerable more effort. The bits are easily made, but would probably require new materials and dimensions. That means that the original engineering on these things would have to be largely repeated. My sense is that a fair amount of time and testing went into the concept and implementation. Not impossible to repeat, but non-recurring engineering (NRE in the manufacturing trade) is a big impediment to any new product, and generally needs to be recovered in an amortization over a large production run. This is the businessman talking, not the British car guy. The notion of intellectual property (IP) would also have to be addressed. I have a IP firm we work with in Portland, but we're a little early in the discussion to spend the money to have them look into it.

That said, I'm not opposed, but it is a far bigger discussion. Rebuild, servicing, is the ticket for the moment.

[geroch]

Nice system, congratulations. I remain observing the developments.

[winabbey]

nileseh - I have taken the liberty of uploading the images from your earlier post to the forum image storage so they are displayed in this thread. I find that easier than clicking on each image in imgur.

If you decide to go back and use the Edit facility to change your earlier post so the images display correctly (as mentioned above) I will delete this post. The Edit button is at the bottom right of all of your posts.

Images below.

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