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PostPosted: Mon Aug 07, 2017 5:59 am 
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Joined: Sat Sep 21, 2013 12:04 pm
Posts: 105
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.


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PostPosted: Mon Aug 07, 2017 3:23 pm 
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Joined: Thu Aug 03, 2017 9:15 pm
Posts: 26
Location: Eugene, Oregon USA
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.


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PostPosted: Mon Aug 07, 2017 10:18 pm 
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Joined: Thu Aug 03, 2017 9:15 pm
Posts: 26
Location: Eugene, Oregon USA
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.


Last edited by nileseh on Tue Aug 08, 2017 4:56 pm, edited 2 times in total.

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PostPosted: Mon Aug 07, 2017 11:06 pm 
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Joined: Fri Jan 14, 2011 7:10 pm
Posts: 1150
Location: West Midlands
Wow , looks impressive .

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

Looks amazing work :o

Ian


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PostPosted: Mon Aug 07, 2017 11:38 pm 
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Joined: Thu Jun 24, 2010 7:08 pm
Posts: 2861
nileseh wrote:
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! 8-)

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]


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PostPosted: Mon Aug 07, 2017 11:57 pm 
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Joined: Thu Aug 03, 2017 9:15 pm
Posts: 26
Location: Eugene, Oregon USA
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.


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PostPosted: Tue Aug 08, 2017 12:03 am 
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Joined: Fri Jan 14, 2011 7:10 pm
Posts: 1150
Location: West Midlands
Great Thanks you

Keep us posted ;)

Ian


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PostPosted: Tue Aug 08, 2017 2:53 am 
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Joined: Thu Aug 03, 2017 9:15 pm
Posts: 26
Location: Eugene, Oregon USA
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.


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PostPosted: Tue Aug 08, 2017 5:44 am 
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Joined: Sun Oct 07, 2012 8:28 pm
Posts: 115
Location: Lugano, Switzerland
Nice system, congratulations. I remain observing the developments.


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PostPosted: Tue Aug 08, 2017 8:03 am 
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Joined: Thu Apr 18, 2013 1:45 am
Posts: 152
Location: Melbourne, Australia
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.

Attachment:
nileseh 01.jpg

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nileseh 02.jpg

Attachment:
nileseh 03.jpg

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nileseh 05.jpg


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