Nope, because the hole that everyone seems to refer to as the damping hole/orifice is actually the "damper bypass hole", and there is only one of them on a sphere, and the hole is not directional in any way.white exec wrote: C5 spheres are spec'd differently, eg
385/57/1.9-1.3
- two figures for the damping
What do the two figures relate to? Could it be fluid in and fluid out - i.e. bump and rebound?
It's only a small part of the damper valve function - most of the damping is provided by the leaf valves. The damper unit is a cylinder shaped disc with many larger holes drilled in it - I don't remember exactly how many and it has probably changed with the different designs of spheres over time (the DS spheres that can be disassembled differ from the later types quite a bit) but there are approximately 6-8 holes of around 3mm in diameter drilled into the disc towards the outside that you can't see as they are hidden under the spring steel washers that act as leaf valves.
On "modern" spheres (GS/CX/BX/Xantia/XM/C5) there are multiple depressions in the disc under the edge of the spring steel washers to admit oil into these 3mm holes. The depressions are alternated on each side of the disk so that they are only present on one side of each hole. Thus for oil trying to flow in one direction (say into the sphere) half of the holes are blocked by the washers on the near side of the disc (which act as one way valves) and the other half are open, but only on the entrance side.
For oil to actually flow through there has to be enough force to bend the washer on the opposite side to cause it to lift up slightly - then the oil can flow through in that direction. Thus it forms a threshold valve - no oil at all flows below a certain threshold but once enough force is present the valve partially opens and allows oil to flow, but the restriction provided by the partially open hole provides hydraulic damping.
Because the flow restriction in each direction is controlled by a different leaf valve, you can adjust the damping in jounce and rebound directions independently by changing the two different spring steel washer stacks on the two sides of the disc. (Only the outer one is visible without destroying the sphere, but the other one is there, inside the sphere neck)
Shock absorbers in conventional suspensions especially sportier cars typically have different jounce/rebound rates with rebound being stiffer but "normal" Citroen spheres (spheres on non hydractive models and the centre sphere valves in the hydractive block on hydractive models) are actually 50/50 with equal jounce/rebound damping, which gives superior ride.
The Hydractive corner spheres have unequal damping though with more rebound damping than jounce (about 30/70) and the reason for this I believe is that when the car rolls the increased rebound damping means the side of the car on the outside of the corner compresses more than the inside rises - thus during cornering it tends to keep the average height of the car lower and prevent "lift off" on the inside corner that can cause instability in hard cornering. So a hydractive model has near equal damping in soft mode (at least for small movements) for optimal ride and unequal damping in hard mode for improved cornering and stability.
In addition to these large holes that are restricted by leaf valves, there is also a "bypass hole" which is literally a very small hole drilled through the middle of the valve. This hole works equally in both directions and is there largely as an "equalisation" port, which allows the suspension to slowly return to equilibrium after a step in the road has passed. Whilst the diameter of this hole is very important, the stiffness of the leaf valve washers is actually more important to damping, so the damper hole size, pressure, and CC volume of the sphere does not fully characterise the sphere. (EG drilling out the hole size of a hydractive sphere of the same pressure to the hole size of a non hydractive sphere does not make the same sphere - the leaf valves are also much stiffer!)
I agree - there's no way its a tolerance for a single hole, the damping of the bypass hole is related to its area, so 4x is a massive change. The two numbers have some other significance, although I have no idea what, when the table says it is damper hole diameter and there is only one damper bypass hole...white exec wrote:Not convinced, Marc.
Other C5 mushroom spheres' damping figures are 1.75/1.3, 0.7/0.48, 0.9/0.48 1.4/0.94 . . .
Don't see why Citroen would suddenly have gone all approximate with respect to these apertures.
As tolerances, the variance is huge - eg 0.9/0.48 - that's getting on for twice the diameter, ie four times the damping area.
C.
The Citroen sphere has a 3 layer membrane, the so called long life types which were first introduced on the front suspension of some Xantia's - the middle layer is impermeable to gas while the layers to either side of that provide mechanical strength. In a conventional sphere there is only one layer that provides both gas impermeability and strength - but the material is far more porous so it leaks much faster. As far as I know none of the after market sphere suppliers supply the 3 layer long life spheres, that includes Xantia's too.GiveMeABreak wrote:Don't want to go too off topic here, but looking into this Sphere issue - I was interested to find a couple of links to pictures of inside the Saucer spheres - in this case comparing an IFHS Sphere with a Citroen Original Sphere.
Inside an IFHS Sphere Inside a Citroen Original
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The point being that according to the C6 guys the IFHS, MONROE and SUPPLEX saucer spheres are the same inside as the old green LHM spheres in terms of membranes and don't last as long as they still suffer with the nitrogen slowly escaping.
The Citroen genuine spheres have the newer membranes in which seal better, reducing nitrogen seepage and allows Citroen to guarantee them for 5 years / 200k Km.
Guess I know which ones I'll be replacing mine with!
You wouldn't see any damping holes in either of those two pictures - the damper valve is inside the neck of the sphere, not the body, and you're looking at the damper valve side on. The damper is contained entirely in the neck of the sphere and is only about 10mm thick.And back to the topic - no extra damping holes inside the sphere as far as I can see.
A tapered hole would not be directional damping, any more than connecting two different diameter hoses together and feeding it from one end or the other is... directionality is provided by the leaf valves as described above, although many spheres are tuned with equal non-directional damping.elma wrote:Is it possible the dampers are tapered holes?
C5 spheres really aren't any different to the 3 layer (dimpled) Xantia spheres - they work exactly the same way and the damper valves work exactly the same. The only real difference is the change in aspect ratio to a wider flatter shape. What is it you're not sure about in how they work ?white exec wrote:3 and 3+ ? Think not; the table above relates only to Hydractive 3. In addition, a single sphere with a single part number carries the two diameter figures.
Maybe, but I can't see that affecting fluid flow in each direction by much - limiting factor is the smallest diameter.elma wrote:Is it possible the dampers are tapered holes?
white exec wrote:3 and 3+ ? Think not; the table above relates only to Hydractive 3. In addition, a single sphere with a single part number carries the two diameter figures.
Maybe, but I can't see that affecting fluid flow in each direction by much - limiting factor is the smallest diameter.elma wrote:Is it possible the dampers are tapered holes?
Bearing in mind that these mushroom spheres have been around for years now, I'm amazed their workings and specs are not better understood.
The reason for the change in shape was that it was found that the materials forming the low leakage 3 layer diaphragms do not like to flex too far when cold, otherwise they can prematurely fracture and fail - this is why they were only ever trialled on the 3 front suspension spheres on a Xantia, in the warm engine bay, never on the rear spheres that are subject to cold. It's also why they were never used in cold climates, only warm climates.
For the C5 the shape of the sphere was flattened so that the diaphgram could displace as much oil, but without bending back on itself so tightly, thus the problem of cracking/failure of the diaphragms in cold conditions was solved.