Best diagram explaining the connection between D spheres and antiroll bar
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Thread: Best diagram explaining the connection between D spheres and antiroll bar

  1. #1
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    Default Best diagram explaining the connection between D spheres and antiroll bar

    As a technical novice I have armed myself with a parts book (648 ) and repair manual (814) to help visualise the linkage between the front sphere and the antiroll bar .
    Am I correct that movement of the sphere is transmitted to the antirollbar by a lever and the movement of the antirollbar (ARB) is then transmitted to the height corrector (HC) by a rod clamped to the antirollbar.If the original movement was down the subsequent movement of the ARB and HC leads to the entry of more hydraulic fluid into the sphere resulting in a return to the original height ?

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    Fellow Frogger! Greg's Avatar
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    WTF,

    I'll re read this in the morning, and it might make sense......

    Why do you need to know?

    I think ur right, but not sure.

    I don't think the spheres move, but its too technical for this time of nite? :-))

    I've had a drink!

    Well it is Saturday.......
    Last edited by Greg; 18th March 2017 at 11:48 PM.
    jaahn likes this.
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    Fellow Frogger! Greg's Avatar
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    Btw,

    Please don't take any offence for the above......Yes Ur right about your observations, but I'll confirm that in the morning :-))
    Last edited by Greg; 18th March 2017 at 11:44 PM.
    We Have:
    C5 HDI Exclusive 2.7 '09, Pluriel '09, Berlingo 1.6 HDI '10, C4 VTS coupe. C4 Picasso '08, 2CV Charleston '84 Grey, 2CV, '55 Australian delivered. 15/6 H '55, SM '74 BVM, DS21 EFI BVH, DS21 '67 BVH.
    We Had:
    1930C6F, '73 GS1220 wagon X 2, '75 G special, '75 GS panel van, '74 GS Birotor, '82 GSA panel van with factory AC, '85 CX25GTI BVM, 2002 C5 V6, 2006, C5 S2 HDI, '86 BX19GT, '72 DS21 BVM, '55 15/6H, '54 Lt 15,'73 Dyane, '82 Visa Super X, with Chrono Mecs & factory AC, 1972 SM.

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    BVH Roger Wilkinson's Avatar
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    Hello jackal,

    Your title mentioned a diagram but your text does not. What's going on there?

    Spheres barely move. The anti-roll bars connect the two half axles, and a clamp in the centre of each anti-roll bar is connected to the height corrector. If the car body moves downward (perhaps because of increased load), the wheels move (relatively to the car body) upward, which turns the anti-roll bar. The resulting movement of the height corrector causes fluid to flow into the suspension cylinders, the car rises, and the wheels and the car body regain their equilibrium. What has changed is that the gas in the spheres has compressed and fluid has been pumped into the suspension cylinders to take its place.

    Roger
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    Fellow Frogger
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    Look at one of the many cutaway drawings and you'll get a better idea, but this promo video shows the general principle of how the sphere and suspension interact.
    https://www.youtube.com/watch?v=169cV--FtCA

    The suspension arms on the front and rear are connected by an ARB, the front looking fairly conventional and the rear being that thick short bar that is bolted between the two rear arms.

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    Quote Originally Posted by dayofthejackal View Post
    As a technical novice I have armed myself with a parts book (648 ) and repair manual (814) to help visualise the linkage between the front sphere and the antiroll bar .
    Am I correct that movement of the sphere is transmitted to the antirollbar by a lever and the movement of the antirollbar (ARB) is then transmitted to the height corrector (HC) by a rod clamped to the antirollbar.If the original movement was down the subsequent movement of the ARB and HC leads to the entry of more hydraulic fluid into the sphere resulting in a return to the original height ?
    In reality - the suspension cylinders are locked into position due to just the basic weight of the car - regardless of the cars actual height. The only way hydraulic fluid can be introduced to the actual suspension system is via the height corrector (HC). Now the HC's have two connections that can move their internal control valve. The connection via the so called anti-roll bar and the height control lever located next to the drivers side foot well. And the amount of 'force' that lever can provide will override any input from the anti-roll bar in its most upper and lower setting.

    Now keep in mind that the internal control slide valve in a HC only has to move a mm or so to either allow pressure to either enter or exit the suspension system. And that it is holding some 2250 +/- psi sans any seals is the reason they, after years of use, are a major source of system pressure loss.

    So what happens is this: As the car settles overnight, the lever attached to the anti-roll bar rotates slightly. This in turn moves the HC's slide valve into its "open" position. You start the car. Fluid is pumped into the car's system, including the suspension circuits. As pressure builds the gas in the upper half of the suspension spheres starts compressing. When the pressure in those spheres equals the weigh exerted on each sphere the car will rise up. As it rises the anti-roll bar starts to rotate. When it has rotated just enough, it's lever moves the slide valve in the HC to its 'neutral' or closed position. Now if one adds weight to the car, and if that weight is sufficient enought, the anti-roll bar's lever will move just sufficiently to allow the system to compensate. The same is true in the reverse situation.

    However, if one moves the Height Control lever to either of the intermediate positions, that input moves the HC control valve to the 'open' position (if going up). More fluid enters the suspension circuits, the volume of fluid in the suspension cylinder(s) goes up and the car rises. As it rises the roll bar rotates and its lever can then provide sufficient pressure to close the HC control valve. In the lowest and highest slots the pressure exerted by the that lever overrides any input from the anti-roll bar's connection.

    Now for a bit more - the static gas pressure in the suspension spheres for a D sedan are 59 and 26 bar respectively (front/rear) In psi this equated to 856psi front/377 rear. If one does the calculations you will find that actual weight on the front wheels of D (unladen) is just a bit over 2000 lbs (US) front and about 1150 lbs rear. If you divide by 2 notice that the static pressure in each of those spheres is just a bit less than the weight they need to support. Which means that at normal ride height the internal diaphragms in those units are only slightly lifted off the bottom of the sphere's internal surface to compress the gas in each sphere to negated the cars weight. So the question arises - why at either of the intermediate height settings does the ride get progressively stiffer? The weight from the car has not changed and the actual pressure in the suspension system is still the same as the total weight of the car has not changed. Not 100% sure, but I think the answer lies in the angle of the suspension arms at the intermediate heights. And that thought is bolstered by the factories quite narrow tolerance for setting the initial ride height of the car at its 'normal' setting. Setting that height either a bit to high or low can have a quite detrimental affect on overall ride characteristic.

    I would suggest that you go to the Citroen Manual site (Google) and download 'Hydraulic Course Notes' - #844. An excellent resource on how (and why) things work.

    Good Luck,

    Steve
    Last edited by Citroenfan; 19th March 2017 at 09:37 AM.
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