Greg Churm (22.214.171.124)
|Posted on Thursday, 23 January, 2003 - 20:53: |
I am an enthusiast for that french marque that uses high pressure hydraulics and therefore feel some affinity with RR. I wish to know more about the Silver Shadow hydraulic system and how close it is to Citroen practice. I pose some questions, could I get some comments and maybe some more illumination on the subject.
1. The RR system uses 2 single cylinder pumps, camshaft driven feeding 2 pressure regulators and accumulator spheres. Did Citroen supply these or did RR manufacture them.
2. Are the spheres the two piece type that can be unscrewed and fitted with new diaphrams (like on the Citroen DS) or the forged and welded sphere used on later Citroens.
3. Is there a security valve (Citroen speak) that makes sure the braking system is the last to lose pressure after a catastrophic failure.
4. How is height correction achieved. Is it driven from the anti roll bar. The Citroen height corrector is perhaps the most elegant apparatus on the system. Is it like these and again who supplied them. As you have hydraulic rams over coil springs is there a way the arrangements can counter sagging springs
5. How responsive is the system. Does the car sink and then correct when it is filled with fuel. If people get in the back will it correct with the engine off, if it is short time since the engine was stopped. Do Shadows sink down a little overnight.
6. Is there any connection between the suspension and braking systems to modulate braking effort to the rear wheels.
7. I believe there are several independent braking circuits including one where the force is provided by the driver. Can any of these brake the car effectively alone. ie what happens on a Shadow with flat accumulators when the engine stalls. I guess it must make the brake valve/master cylinder a complex component
8. Are there any other gems in the system I have not heard about
Richard Treacy (126.96.36.199)
|Posted on Friday, 24 January, 2003 - 02:32: |
To answer your questions,
1. The pumps are of R-R design and probably manufacture as well, but may have been sourced form a subsupplier, even Citroen.
2 The spheres can be rebuilt: easy if you have the correct tools and press, impossible without. The solid welded spheres were introduced with the Castrol LHM HSMO.
3. There is no Priority Valve (R-R speak) on the Shadows. They were introduced with LHM mineral oil on Corniches first, then on all cars from Silver Spirits onwards.
4. The height control linkages (one each side) are connected to the trailing arms.
5. A solenoid valve changes the sensitivity of the levelling: fast when parkes, slow when the car is ready to go. A Shadow should not sink at night, only if the springs have sagged. Under normal conditions the hydraulic system should not be doing any work at all. In truth, levelling is usually not necessary on these cars, and aboult half have had the levelling blocked off (not our T-Series by the way). Levelling will correct the height quickly with the engine off and a door open when in park or slowly otherwise. Use of the levelling is a poor but effective correction for sagging springs, but sagged springs should be corrected as it is not intended that the springs sit on activated rams.
6. The systems are fed from the same accumulators. A deceleration-conscious valve limits rear braking while slowing down.
7. Early shadows have three systems, one activated manually by a master cylinder, mainly tp provide feel. Later cars do not have any manual system or master cylinder, and rely purely on the accumulators for braking. Believe me, with no pressure and the motor stopped there are NO brakes at all. I almost drove my Turbo R over a cliff once after letting it stand for a week. It took me a while to remember the parking brake as I was in shock. With the motor running, braking is effective in half a second.
8. The gems are too many to elaborate, especially the Rat Trap brake valve box you mention. Also, you must use the special RR363 fluid: nothing else is safe.
Greg Churm (188.8.131.52)
|Posted on Friday, 24 January, 2003 - 22:47: |
Many thanks Richard
If levelling is not that necessary on Shadows one wonders why RR went to the trouble. Talk about dotting every 'i' and crossing every 't' to make the Shadow the best you could buy at the time. I suppose you are spared the little foibles that we Citroen drivers suffer, like parking next to a high curb and not being able to get in when you return, or worse your passengers; just wouldn't do on a Rolls.
The independent levelling side to side is a neat elaboration that I didn't know about. Must make adjustment a bit tricky as adjusting the height on a Cit is a time consuming operation especially if all safety precautions are taken
Richard Treacy (184.108.40.206)
|Posted on Saturday, 25 January, 2003 - 04:17: |
Adjustment is very simple on an R-R, unlike a Citi. Early Shadows had front levelling too, but that was deleted as it had only a single valve on the antiroll bar. Exiting a corner, the cars maintained their lean, and the levelling was really a waste of space. A routine, factory recommended mod in 1969 was to remove front levelling.
I have quite an experience with DS, CX and GS Citroens. Park on the kerb and forget to close the door: goodbye beautiful alu door. The best is driving on three wheels, one rear removed. Quite an eyeraiser.
Greg Churm (220.127.116.11)
|Posted on Tuesday, 28 January, 2003 - 12:08: |
Adjustment isn't that difficult on a Citroen however you marvel at the power of hydraulics when you rotate the clamp on the anti-roll bar a tiny fraction and with a gentle hiss the car rises and falls at your command. I had to do this after a rear anti-roll bar broke. For safteys sake the car had to be on ramps, adjustment made and then off the ramps to measure etc etc etc. As the RR can't collapse on you I guess it must be easier.
Further to hydraulics do later RR's go further towards hydropneumatics, Citroen style. I have heard reference to a sphere on the suspension on HSMO cars. Does it support the whole weight of the car or is it in parrallel with a coil spring.
You had a few nice cars at Motorfest which was good to see with one Shadow for sale advertising cheaper to buy and run than an LTD etc. Is this right. How much do you pay for a good Shadow and are running costs reasonable.
Richard Treacy (18.104.22.168)
|Posted on Tuesday, 28 January, 2003 - 20:00: |
The HSMO cars (basically SZ cars onwards, although coachbuilt cars started earlier) have gas springs, and the steel springs are smaller. They sit about 3cm on the gas springs. The gas spring -damper part is like on a Citi, except that the car can drive with no gas spring support if required as the steel spring is the primary support. There are spheres kocated on each rear gas spring Citroen-style.
Re value, where are you located country-wise ? Silver Shadows world-wide are at rock-bottom prices and have been for ten years now. A good one is an absolute bargain. A bad one will be a horror story. The cheapest Shadow will usually be the most expensive at first purchase. Most people prefer Shadow IIs, but they do suffer regular steering rack leaks and a few other foibles much discussed on this forum. Many swear by the very last Silver Shadows (1976-77) as the most reliable and sweetest model.
David Gore (22.214.171.124)
|Posted on Tuesday, 28 January, 2003 - 20:46: |
I know the Shadow II you mentioned and it has been well-cared for by an owner who has high standards and is prepared to spend the necessary time and money for regular maintenance and the records kept allow him to make this claim with considerable justification. Cars such as this are extremely good value-for-money as their history is known and the chance of problems due to poor/neglected maintenance is minimised. The cars are meant to be driven regularly and low-mileage cars can be a problem - around 10,000/15,000Km per year should be a reasonable average for a vehicle that has had regular use. Be wary of recently imported cars, especially those from Hong Kong, they are known to have many problems ranging from body corrosion to engine wear which is way in excess of what would be expected from the distance the car has travelled in its life-time
Bill Coburn (126.96.36.199)
|Posted on Monday, 10 February, 2003 - 10:27: |
I hate to be a complete know-all Richard but your remarks about the SZ cars' rear suspension are not correct. The coil springs on these cars do not support the body, in truth I am not clear as to what function they perform. The weight of the car is actually taken on the oil filled struts. Their pressure is derived from the main accumulator mounted on the engine. If you completely depressurise the struts the rear end of the car will practically sit on the ground! The quaintly named gas springs are a smaller version of the main accumulators complete with gas and diaphragms. When the strut is compressed, the displaced oil is forced back into the gas spring against the gas pressure and thereby provides the quality of ride. There are no lights or warnings about failure of the gas springs, simply the development of callouses on the driver's buttocks since the only 'suspension' left is in the tyres and the seat springs.
As to the Shadow levelling system this was not installed to cater for the gradual loss of weight through the consumption of fuel as the spin doctors would have it, nor to disguise the actual weight of Madam as she inserts her considerable frame into the rear seat of the car, but are there to complement the drive joints in the rear axle half shafts. These are the large trunions that spin either side of the differential casing and are designed to operate within certain angular limits. Keeping the car roughly level ensures that these limits are observed and wear and tear on the joints is minimal.
Richard Treacy (188.8.131.52)
|Posted on Monday, 10 February, 2003 - 19:21: |
Hey, Bill: The steel spring on an SZ is the main suspension component, and the hydraulics are for damping and levelling. The gas springs (ie struts) should only lift the car around 3 cm, otherwise the steel springs have sagged and the gas spring will be excessively overloaded to compensate. With the hydraulic pressure completely exhausted in the whole system, my Turbo R sits 3 cm down. Once the pressure is applied, the steel spring takes over 85% of the weight and the gas springs-struts take the rest. The gas and steel mechanisms work in parallel and share the load.
Bill Coburn (184.108.40.206)
|Posted on Monday, 10 February, 2003 - 20:45: |
I am not prepared to concede - stand by.