So what happens next?

The danger here is that we project the past into the future regarding suspension design and try and overcome the limitations of metal springs which are constrained to a very narrow operating range.

It seems to me that preload, rebound and the compression damping are features driven by the engineering constraints and mechanical limitations of the assemblies called...shock absorbers and springs which are impacted by the variables of road undulation and onboard load.

The BMW AND Ducati electronic adjustments are step changes and typically have an optimum operating condition, ie better in say Touring set-up than Sport and lack true continuous on the go adjustment......and always will until the metal spring is eliminated......I had to uprate the spring from 80 kilo to 100 kilo despite the apparent sophistication of the Ohlins on my MTS (thus indicating it was limited by Pie intake and too many shoes in the the box).

So what is the answer?

Mclarens pressurised infinitely variable and interconnected damping system instructed in nanoseconds by an on-board Kray Hal 2000 ecu receiving readouts from various on-board sensors. It pressurises the damper depending on requirement.

It adjusts instantly to on-board load, speed/acceleration, road surface at each wheel,steering direction, braking load and demand. This later issue is particularly impressive as it keeps the vehicle from diving and thus allows consistent turn in and corner tracking.

The hydraulic reservoir is compact and driven by the alternator.

The point I'm trying to make here is that bike suspension damping seems to be locked into the past and making what we have better ( no problem ) and needs to get out of the 'box'.

Thanks roundincircles and Dean 15,

Wow, you have given me a lot to think about.

Good information and insite!

Regards,

JAG

Captain, I'm not sure if your views on lack of dive are confusing the issue, particularly with Telelever v. conventional forks but I do acknowledge you are from a World where you are used to being suspended by string!

The 'turn in' you refer to is actually influenced by a reducing radius on conventional forks as the braking force shortens the forks and thus reduces the wheelbase whereas on Telelever (and I think Duolever ) the wheelbase remains unaffected by the braking so the bike turns into a constant radius and thus may feel slower.

I wonder if your experience with faster turn in with conventional forks is the shortening wheelbase 'turning into a reducing radius' feel, ie it speeds up the turn?

Telelever, for me, becomes more predictable and thus 'faster' through the twisty's than diving forks, presuming you brake to the apex when riding recreationally.

The Duolever on my BIG K is even more agile and consistent, especially in tighter turns, than Telelever but I know not why!

I maybe talking bo..cks here but please feel free to discuss!

NOTE:

The hydraulic system I have described so far is NOT a complete system but the first part.

It would not be satisfactory for anything but smooth roads at modest speeds and low cornering speeds.

Another component or feature would be required to handle the potentially high very rapid (measured in thousands of a second) both positive and negative pressure spikes.

Basically, that's where the accumulator comes into play.

What we are trying to go is seperate the effects of gavity and G-forces (turning accelerating braking etc) from road shock.

The pump by changing the RPM of the DC motor would control the gravity and G-forces. The accumulator would control road shock.

Regards,

JAG

RiC said: "The Duolever on my BIG K is even more agile and consistent, especially in tighter turns, than Telelever but I know not why!"

The steering on duo lever seems to happen via pivots at the front of the assembly? Because of the locii described by the wishbones, will the steering leverage vary? Probably not what you're describing, but an interesting thought all the same.

CS

The Duolever system used on the K1300 models does actually employ 'Square' tubes instead of conventional forks so it can be done.

I've just been reading through some of the recent posts on this but I think I'm going to have to read them again more slowly. I'm struggling to keep up!

Having said that it's 0645 so perhaps I just need my first cup of coffee...

Captain scarlet said: "whether telelever is over-engineered. I.e Whether it could get away with thinner (width and material thickness) tubes and / or wishbone assembly? On face value, this may seem a silly comment... I am, after all, not a particularly clever engineer or ow't. However, as an example, think about the KTM Duke 690 'open' swingarm, which has a lattice internal frame on show and no visual outer casing of the arm itself. Aesthetics and 'norm' acceptance aside, why couldn't the telelever tubes be like this. I.e. square rather than round, with an internal lattice and open outer to lower it's sprung weight?"

Talking strictly Telelever here, and not duo lever, don't forget that Telelever forks have to slide, and be lubricated. They also need a good amount of overlap to keep the wheel pointing where it should. But, in principle, and taking you up on your lattice idea, there could be 2 more localised support "bosses" containing bearings, spread apart the appropriate distance, all held together with your lattice framed legs.

And the name for our co designed invention? SKELELEVER!

Would anybody buy it? ......NAH!

Apart from me!

My r1200r doesn't pogo. It's a very good set up. It is a bit harsh if anything. This aspect of Telelever has been pointed out by Kevin a couple of times. Im nurturing my own thoughts on the good and bad aspects of vertical wheel travel. It is not discussed with an open mind anywhere near enough.

The GS's will no doubt be set up differently to the roadster.

What I mean is, I'm not convinced that Telelever is prone to pogo ing as a design principle per se. More likely is that tall bikes with softish, long travel suspension are.

You see, the duo lever we have available to us, is on a low, long, stiffly suspended bike.

Fair point?

RiC, you'll need to somehow convince us that vertical wheel travel is to blame. But then duo lever has that....

The rear suspension will also affect the way the front interacts, and vice versa.

On my bike, the more I use it, the less I want to go back to telescopics. Not sampled duo lever. I really should, although I also don't want to give up the character of the boxer motor for a four cylindr either!

Riding height and road shock

If we could separate them it would be helpful. Today’s systems do not.

The way to separate them is to understand their differences.

The events or conditions that change riding height are slower than road shock.

Road shock involves very rapid high pressure spikes for very short periods of time.

Road shock affects the unsprung weight more than the sprung weight.

How could the bike electronically tell the difference?

Maybe with the use of a 3 axis accelerometer placed on the sprung weight of the bike.

From the 3 axis accelerometer the computer could sense the effects of acceleration, braking and turning forces. Through look up tables and calculations it would control the hydraulic pump’s RPM via the DC motor and so maintain a reasonably constant road height.

From many comments I get the impression a bike who's sprung riding height would, for the most part, remain constant regardless of turning or braking or accelerating forces would be a good thing.

Interesting ideas from Captain Scarlet would be the ability to lower the bike when coming to a stop or even raising the bike to full extension making putting on the center stand easier. The ability to set the riding height to compensate for different loads would also be helpful.

All this could be done hydraulically.

The rider would set the running ride height with the ignition on in neutral with the engine off. If the load changes, (example, with a passenger)the rider would set the riding height with the passenger on board.

The computer would remember this setting (from a pressure sensor connected to the hydraulic system). The setting could not be changed if the engine is running for safety reasons.

As stated before, the accumulator would handle the road shock. Since, for the most part, it does not have to handle the vehicle's weight (support the sprung weight) it can operate at much lower pre charge pressures.

An accumulator is simply an air bag (charged with nitrogen) encased in a metal container. One end of the air bag or bladder is exposed to the hydraulic system pressure. The higher the system pressure, the more it is compressed. Accululators respond very quickly to pressure changes like shock.

JAG

Jag. I think your about there on the hydraulic post. I will dig out a link on Mclarens approach , if I can find it!

Hi roundincircles, thanks for the link to the McLaren suspension system.

Of course there are some fundamental differences between a car suspension and a bike suspension.

The fact that bikes are a single track vehicle is both a blessing and a curse.

It’s easier for a car to create a linkage or lever system to control wheel alignment as the wheel moves up and down.

We are not as lucky. Can you imagine if a car’s suspension system was designed so that the shock alone was used to maintain or control wheel alignment.

That’s basically what we try to do on a bike with a telescope front suspension. The fact that a bike is a single track vehicle is probably the only reason we can get away with it.

The one thing that did surprise me was that with all the attention to good handling characteristics on the McLaren that the drive wheel brakes are in the wheel. Wouldn’t inboard brakes be better? Why not take all that brake weight from the unsprung weight of the wheel and put it inboard to the sprung weight?

The Mclaren system still uses a shock and spring. The shock control seems to be closer to an Ohlin system.

Can you get a Mclaren with a towing package?

Does it come with a trailer light plug?

If I can’t get these, I for one won’t buy one!

Regards,

JAG

Thanks for clearing that up roundincircles,

I do know working on inboards and their discs is a rear pain in the behind.

The heat thing is a good point.

I could not find in the article if they use a hydraulic pump in the suspension system. Did I miss that?

Do they use an accumulator in the hydraulic system? I thought I read they have accumulators and an electric pump for the steering system.

So I can pull a small house trailer with it. Good news! It's back on the short list.

What snow tires would they recommend?

I want something Captain Scarlet would die for so it has to have carbon fiber wheel rims.

Regards,

JAG

Captain scarlet said: "and auto rear preload (okay, not quite ride height, but the next best thing) is handles by ESA II (on the rear) via the elastogran/m (I called it diaphragm earlier, but that's just because I'm a sick puppy!) conduit, thingamy bob"

Doesn't spring preload determine ride height? You're just moving the position of the contact seat where the coil spring attaches to the frame, in esscence. It won't auto maintain it like jag's hydro/pneumatic system. The ESA2 elastomer thingy, if we're talking about the same thing(y), actually alters spring rate, as far as I understand it. Kevin did a tech watch article on it 'bout a year ago. A rare case of genuine innovation, all tucked away under the seat. 99% of people don't even know it exists. Even everyone at my BMW motorrad dealers. Why isn't it available on non ESA boxers? To be adjusted by hand?

Aeration and cavitation in suspension systems,

One of the challenges in our present spring and shock suspension systems is aeration and cavitation in the hydraulic shock absorber.

Aeration and cavitation is a bad thing. The oil in the shock becomes aerated and thus changes the damping characteristics of the oil. These very small bubbles of oil make the oil look milky.

Two common causes of aerated oil:

1. Leaking seals which allow air to leak into the system.

2. Hydraulic oil has dissolved air in it. You can’t see it but it is there. As long as it remains dissolved it’s usually not a problem. If the pressure in the system drops below about 21” Hg, the air comes out of solution and creates very small bubbles. In a sense, the oil starts to boil because the pressure is so low (vacuum).

Cavitation can potentially damage internal components like seals and metal surfaces. Cavitation is the result of low pressures like the number two aeration example. These very small air bubbles are in fact an air bubble made up of air and hydrocarbons. It is very much like a diesel air fuel mixture.

When this fuel mixture bubble is exposed to very high outlet pressures, the bubble implodes (compressed) creating a shock wave that can actually sometime ignite. This is called dieseling. The shockwave it so violent it can actually break off pieces of metal. Imagine what it can do to seals.

The problem with some systems is that the shock is not filled completely with oil. The shock needs an air pocket to allow for the displacement change of the shock as it goes up and down. Oil that is directly exposed to air encourages aeration.

JAG