Thread: Self Levelling Unit for RR Classic

Originally Posted by uninformed

Bill, was it only the rears on the Hybrid that were rubbing/ As you stated they are 110 coils which are a larger Dia...how much more rim offset would be required? If wanting to run 750-16 or 235/85 r 16'S would they rub on stock suspension set up? If so would getting 1 inch longer springs with 1 inch longer bumpstops do the job with out loosing to much of the system as a whole?

Yes Serg,Just the rears that rubbed/fouled. The hybrid doesn't have 110 coils.I mentioned that in brackets to indicate that tyre fouling would be worse with the wider/larger dia 110 springs and perches.I estimate the maximum 50mm extra allowable track width still wouldn't be enough on the hybrid to keep the tyre healthy, and the situation on a 110 would be worse.
The bump stops on the compressed side didn't make contact with the axle on either vehicle. The RangeRover bumpstop was clear of the axle by about 1cm, and the hybrids bumpstop cleared by around 10cm.
The RangeRover bumpstop may have come into play had the tyre not fouled on the wheel arches but the spring on that side was well coil bound so maybe not.
When I get a bit more time I will remove the 4cm thick spacers from under the hybrids rear springs and check again to see if the tyre clears the perch. If not I've got a 1'' thick wheel spacer that i can fit to see if that does the trick.One thing is certain, and that is the hybrids spring/damper combination wasn't particularly well thought out and tested after the vehicle was built.
Wagoo.

Originally Posted by wagoo

As an interesting aside.Although I recognise that ramp travel isn't necessarily an indication of a a vehicles off road ability, my humble 1989 Holden Jackaroo that has virtually no articulation, drove up the ramp to the 1 metre vertical height mark with the left front wheel about 95cm off the ground and the lateral chassis angle almost zero. So if there was an off road obstacle that replicated the ramp, the Jack would win that contest.
Wagoo.

Interesting thought... the 89 Paj has a similar suspension setup, torsion front end with little travel and cart springs on the rear. Wonder how that would perform up your ramp...

The Renault 16 also had huge suspension travel and soft springs. - and would almost roll over as you backed out of your driveway.

- But did they hang on !!!

Originally Posted by uninformed

I would have thought the front have a higher roll stiffness due to it being radius arm. Is the difference coming when retaining medium rate coils up front and going to a heavier coil out back.....as a side note, the OEM springs on my 110 Def cabchassis, where a pergressive rate up front not to sure what rate but around the 200-220ib and the rears were atleast 350lb. It has never had a boge load leveler.

Yes the front does have higher roll stiffness with the radius arms. But it needs even more to make for "safe" handling. "Safe handling" being the opposite of "Scary but Fun handling".

Originally Posted by uninformed

Dougal, can you describe the workings of these magical self energizing units?

Sorry I can't. I can only assume they have a preferred length and either bleed or pump gas from one side to another to try and maintain that length. It's impressive they can hold whatever high pressure they have in them for so long. My one is 26 years old.

This website appears to explain how they work

Self-leveling suspension

Whilst here is a page on replacing the Boge unit with a Mazda 323 spring.
http://www.landroverclub.net/Club/HT...conversion.htm

I find it amusing that there should be a flurry of interest just months after the last supplies dry up from mobs like Paddocks.

If one does turn up it's toes, you could always convert it to a pneumatic over hydraulic spring with external pressure control.

Simply gut, fit an external hose and fill with suspension fluid. On the end of the external hose fit an air over hydraulic pack with sufficient volume and intensification to work at convenient air pressures.

Ok Serg, I retained the top of the right rear spring and disconnected the damper on the RangeRover and put it back up the ramp until it lost traction to retake the measurements.Previous measurements in brackets.
Vertical distance from bottom of front wheel to ground =76cm [82cm]
Angular displacement of axle =18 degrees [21]
Length of spring =47.5 cm static height =43cm = 4.5 cm stretch.
Distance between upper and lower damper mounts = 67cm [70cm]

As expected, the measured articulation and traction is reduced,and retaining the spring has reduced the downforce on the right rear tyre by around 240lbs [108kgs],and possibly reduced downforce on left front tyre as well. but as before, top of left rear tyre fouling on wheel arch tub and load leveller horn fouling on diff has reduced maximum possible articulation.The only way I can see to get optimum articulation from the rear of a RangeRover is to lift the body or cut and raise the wheel arch tubs.And that is only on 29'' dia tyres.

After further examination of the hybrid I deduced that its poor showing against the RangeRover was down to 3 factors. #1- greater static suspension height. #2- left side damper bottomed out. #3- higher spring rate.
So to eliminate 2 of these factors I removed the 4cm thick spring spacers and disconnected both rear dampers before putting it back up the ramp and take some new measurements.Previous measurements in brackets

Vertical height from bottom of front tyre to ground =72 [68cm]
distance between upper and lower damper mounts= 82 cms [83cms]
angular displacement of axle= 17 degrees [ 14degrees ]
Length of spring on compressed side = 23cm [ 24cm ]
distance between upper and lower spring seats = 58.5cm [ 53cm ]

Observations.
Left sidewall of tyre was only lightly pressed into spring perch by about 10mm. So 25mm less backspacing on 110 rim should clear its perch.
The additional articulation was gained by compressing the left spring more.The previously bottomed out left damper and the high rate spring wouldn't permit the left springto compress enough or right rear wheel to droop enough.
Further rear articulation was hampered by the high spring rate.
Relocated upper damper mounting is still far too low, and would require raising a further 7.5cm to acheive even this articulation, and even higher if softer springs were fitted.
Of course raising top damper mounts will reduce how far the wheel can droop for a given length damper.
Although articulation was improved only marginally, it was enough to transfer enough weight to the left front wheel for it to keep pulling the vehicle up the ramp easily to the 1 metre mark where I stopped for fear of it falling over.So this time I disengaged the centre difflock and drove up until the right rear wheel lifted and traction lost before taking all measurements.
I would like to have retained the tops of the springs on the hybrid and done a similar test to the Rangey but it has 80 series relocation cones welded to the upper perches, so I'll have to drill them to get the hose clamps through.
After putting both vehicles back where they live on the side of a 24 degree hill I notice that the Rangey chassis and axle are parrallel, whereas the hybrid chassis leans over a few degrees, so maybe the Boge unit isn't dead after all.
Wagoo.

To my knowledge the boge self leveling unit is a SLOW bleed down HIGH rebound bypass shocky.

Basically it opens a foot valve for extension willingly but is much harder to bypass oil with compression. This results in a vehicle hydraulically JACKING its self (no not trying to be rude here ) over bumps. Thus the self energizing label. When stationary a boge unit makes virtually no difference. But adds to the available spring rate when driving. You can get the same effect fitting heavy shocks to a light car, basically they are mismatched to the application. But The boge unit cleverly adds nothing to the roll stiffness.

I agree that Spen King was a master at suspension and drivetrain design. The early Rovers were the least compromising from an engineering point of view and achieved trully remarkable results with simple yet well engineered design. Spen also wanted to produce all wheel drive sports cars in the same time frame as the Range Rover, most never got past his conceptual drawing stages.....Wonder if he called any Subaru??

Im afraid handing it all over to a computer is no fix for poor handling to start with.....EBC, ACE etc. Not to say these systems have no merit.

once again Bill, thanks for all your time and work.

If the dampener was long enough stroke, would the extended side apply any downward force on the axle?

As this topic was started about the Boge self levelling unit, and that is one part of a whole system....my next question is related to the changing of part of the system but how it effects the whole: Hopefully Bill, John and Dougal will put forward their ideas here (and anyone else of course)

Taking the stock original Range Rover as the base. The suspension system as a whole seems to be pretty well designed, given its offroad ability, its offroad comfort, its onroad handling and yes even its onroad feel...the last being much more a personal thing than the others. Not only is this a result of the soft springs, wheelbase, COG, static ride height etc but in there is Roll centers and Roll axis (both axle and vehicle). I have read many times on the interweb that when building a custom link suspension, one wants to shoot for close to 0° axle roll under/oversteer. From the stock Range Rover's I have seen they appear to be about 0° front axle roll axis (neither under or oversteer at static ride height) the rear appears to be about 4° rear axle roll oversteer. The rear Roll center is higher than the front. Which gives the vehicle a sloping down to the front roll axis, which I believe will make the rear "let go" first....So the question is, from an onroad handling and offroad high speed handling point of view, how would lowing the rear roll axis and the rear Antisquat effect the behavior of the vehicle. This would be achived in my mind, by taking the trailing arms right out to the ends of the axle (as far as physically possible), reloctaing the dampner location. lengthing the trailing arm somewhat, say 150mm but keeping the chassis end height the same as stock....this small amount of triangulation when viewed from above and reduction in trailing arm angle (when viewed from the side) will reduce the rear axle roll axis, and by lowering the angle of the trailing arm, which inturn brings it a little more parrallel with the Aframe angle, and therefore changes the convergence point of the 2,being lower in relation to the COG at front axle line.....As you go into a corner, the body leans to the outside, which is making the Link arms move, and on a RR this is actually making the rear axle steer around the corner... this coupled with the roll centers gives it its handleing and feel onroad....now if you reduce the steer in the rear how will it feel? Squat: this is normally applied to acceleration forces (for the rear) if you have braked into then drive through a corner, will the reduction in antisquat, effect the feel (maybe by changing the amount of load on front or rear??????????

Ive lost the plot havent I