How your power assisted DS steering rack works.
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Thread: How your power assisted DS steering rack works.

  1. #1
    1000+ Posts forumnoreason's Avatar
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    Default How your power assisted DS steering rack works.

    Not doing much here at work! Just studying the ds id club de France, bienvenue-welcome site and read this, I didn't clearly understand how the steering rack functioned and found the diagrams made it very clear and quite plain. I have just flipped them around for right hand.

    So now you stop looking confused if someone starts talking about cross-over pressures and so forth!

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    Operation: The valve consists of two drawers controlled by a fork acouplement related driving. In an action on the wheel fork based on one of the drawers releasing another (recalled by its spring). The drawer pressed connects the pressure source with the proper side of the piston. The drawer raised establishes a direct connection between the other side of the piston and the reservoir. The piston drives the driven rack which in turn controls the coupling bars, relays and the wheels.
    How your power assisted DS steering rack works.-tchenik_direction1.jpgHow your power assisted DS steering rack works.-tchenik_direction2.jpg
    Last edited by forumnoreason; 28th November 2013 at 06:38 PM.

  2. #2
    Real cars have hydraulics DoubleChevron's Avatar
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    Nice, now all you need is the "straight ahead" diagram, where both sides of the piston are at the same pressure. The hissing and squelching of the DS steering sure does bring a smile to you face I'm really pleased with the way my ID19 drives with the powered rack retro-fitted.

    seeya,
    Shane L.
    'Cit' homepage:
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    1000+ Posts gerrypro's Avatar
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    Quote Originally Posted by DoubleChevron View Post
    Nice, now all you need is the "straight ahead" diagram, where both sides of the piston are at the same pressure.
    seeya,
    Shane L.
    The first drawing in the series of three is the straight ahead position with both valves in equilibrium!
    Cheers Gerry

  4. #4
    Real cars have hydraulics DoubleChevron's Avatar
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    Quote Originally Posted by gerrypro View Post
    The first drawing in the series of three is the straight ahead position with both valves in equilibrium!
    oh yeah ... I missed that one
    'Cit' homepage:
    Citroen Workshop
    Proper cars--
    '85 Series II CX2500 GTi Turbo I
    '63 ID19 http://www.aussiefrogs.com/forum/showthread.php?t=90325
    '72 DS21 ie 5spd pallas (last looked at ... about 15years ago)
    '78 GS1220 pallas
    '92 Range Rover Classic ... 5spd manual.

    Yay ... No Slugomatics


    Modern Junk:
    '07 Poogoe 407 HDi 6spd manual

  5. #5
    Fellow Frogger!
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    The explanation on that site is quite simplistic at best. One major thing left out is the very tiny movement necessary to activate the control valves - on the order of a fraction of a mm. When correctly set there is no mechanical connection between the control fork and the RU under normal operation. This is also the reason that 'rotational' alignment between the RU and the steering column is so critical. Be off just a matter of a degree or and the system will not work as intended.

    X-over pressure(s) are quite misunderstood and changed in pressure depending of the diameter of the power piston used in the
    rack.

    A better explanation is attached (from 844 - Hydraulic Course Notes). Steering_1.pdf

    Steve
    Last edited by Citroenfan; 30th November 2013 at 03:44 AM. Reason: Adding info

  6. #6
    Fellow Frogger! Bruce Llewellyn's Avatar
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    Yer all wrong- It works by engineering cussedness.

    Magic is just science we havn't turned into engineering yet!

  7. #7
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    Quote Originally Posted by Bruce Llewellyn View Post
    Yer all wrong- It works by engineering cussedness.

    Actually no . It is quite straightforward and easy to understand when one realizes that the so-called "X-over" pressure is actually the residual 'holding' pressure inside the power piston. That pressure prevents the front wheels from 'wandering' when driving on uneven road surfaces as well as keeping the little pins that transfer steering yoke movement to the control pistons in constant contact with the setting screws in the yoke. The result is that, when correctly set up, even the tiniest movement of the steering wheel is transmitted to the front wheels so long as the alignment bushings in the trolley are not worn. FWIW that 'holding' or static pressure inside the power piston is set to around 970 psi via the the adjustment screws in the fork.


    Correction - earlier I mentioned that those pressures are different depending on the dia. of the power piston. What I meant to say was that the 'assist' afforded is different - actual pressures are the same. The earlier racks (pre 7/67) used a 21mm dia power piston, after 7/67 it was reduced to 19mm. That change resulted in increase in assist pressure of around 22%.

    Steve
    daffyduck likes this.

  8. #8
    1000+ Posts daffyduck's Avatar
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    Quote Originally Posted by Citroenfan View Post
    Actually no . It is quite straightforward and easy to understand when one realizes that the so-called "X-over" pressure is actually the residual 'holding' pressure inside the power piston. That pressure prevents the front wheels from 'wandering' when driving on uneven road surfaces as well as keeping the little pins that transfer steering yoke movement to the control pistons in constant contact with the setting screws in the yoke. The result is that, when correctly set up, even the tiniest movement of the steering wheel is transmitted to the front wheels so long as the alignment bushings in the trolley are not worn. FWIW that 'holding' or static pressure inside the power piston is set to around 970 psi via the the adjustment screws in the fork.


    Correction - earlier I mentioned that those pressures are different depending on the dia. of the power piston. What I meant to say was that the 'assist' afforded is different - actual pressures are the same. The earlier racks (pre 7/67) used a 21mm dia power piston, after 7/67 it was reduced to 19mm. That change resulted in increase in assist pressure of around 22%.

    Steve
    Do we have post of the day on this site? That was a good one and needs to be kept track of.

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