Pellerin Reactive Suspension

[desmo]

We now commonly see "third damper" or "third bump stop element" systems in F1. French-Canadian Luc Pellerin has some interesting ideas that take the concept one step further. In his own words:

Conventional Two Spring System:



IN ONE WHEEL BUMP: When one wheel is being raised sharply in relation to the chassis, the contact patch load is increased due to the stiffness of the springs and anti-roll bar. The load and movements are transmitted via the push-pull to the rocker on the left side. This in turn will compress the spring and damper assembly and the load is transmitted to the chassis which induces a roll moment. To make things worst, the rocker rotation on the left tends to rotate the rocker on the right proportionally to the stiffness of the Torsion bar which in turn remove load from the contact patch on the opposite side. This increases the lateral load differential which causes an even higher induced roll moment to the chassis and corner weight differential.



Three Springs & Dampers Conventional Suspension




ONE WHEEL BUMP & LATERAL LOAD TRANSFER

*If the third spring is fully loaded, some of the added contact patch load will be transmitted to the laterally opposed contact patch which is a desirable thing.

Depending on loading of the third spring: the contact patch load will increase or decrease.

**If the third spring is not fully loaded and if a stiff Torsion Bar is used, it is more likely that the load will not be transmitted to the other side. In fact, it could unload the right side same as two springs and dampers suspension as shown in Fig 1.3

Therefore, the behavior of the system will vary according to down force witch makes things more unpredictable.

Generally, roll stiffness will be set to resist the highest expected lateral G’s which occur when high down force is present causing the following problem:

WHEN THE DOWN FORCE IS REDUCED,

THE SYSTEM IS OFTEN TOO STIFF !

CONVENTIONAL SUSPENSIONS 1) When race cars using down force hit a bump with one wheel such as when passing curbs, at times when the down force is minimal we will notice that as one of the front wheels is lifted, it is common to see the laterally opposed wheel coming off the ground. A fraction of a second later, the same will occur when the back wheel is riding the bump.

I will call this the pogo effect! Drivers often have to do all the turning before or after the bump since the rest of the time, they are airborne.

2) The same is true to a lesser degree when we have sudden track camber changes. The front wheels are on a slope that is different from the back wheels. At times when the down force is low, it is common to see wheel lock under braking.

REACTIVE SUSPENSION.

As will be shown after, the proposed REACTIVE SUSPENSION will alleviate these problems greatly since 1) the roll stiffness is proportional to the down force 2) the load generated by a one wheel bump is transmitted to the laterally opposed wheel which results in more even corner weights.



Reactive Suspension By Luc Pellerin




IN HEAVE : Left & right rockers rotate in the same direction causing the Roll Lever (RL) to slide in the slotted guide causing the center spring to be compressed.

Rising wheel rates can be achieved in a number of ways such as with rising-rate springs, bump rubbers and by design of the rockers in the same way that is done with conventional suspensions.

The purpose of adding a third spring in modern day race cars is to de-couple roll rate from heave rate. This system offers the same possibilities. It only does it better. The use of a third damper is optional but it could allow to dampen heave more than roll as is often desired.




IN ROLL, as one wheel goes up relative to the chassis, the laterally opposed wheel goes down causing the rockers to rotate in opposite direction. Therefore, the Roll Lever (RL) will rotate as shown.

Note that the total load on the central spring remains the same. (Unlike conventional suspension where one spring will want to uncoil while the other is being compressed.)

HOW DOES THE SYSTEM GENERATE ANTI-ROLL?

The rotation of the RL will cause the offset of the line that is formed by the base of the spring & damper assembly and the end of the Roll Lever. As we know, a torque or Moment is equal to the Force * Effective lever which is the perpendicular distance between the force and the pivot of the RL. Therefore, we obtain a Moment around the pivot of RF which is proportional to down force. This moment is now available to oppose the contact patch differential from left to right. Plots of the wheel loads and wheel rates in roll and heave can be made to match current race car heave and roll chararteristics.

For example : We could design the system to generate half a degree of chassis roll when 1G Lateral and 1 G of down force are applied.

The same set up would still generate half degree of chassis roll when 3 G lateral and 3G down force are applied.

WHAT YOU GET IS WHAT YOU NEED LEADING TO BETTER TRACK COMPLIANCE




REACTIVE SUSPENSION & ONE WHEEL BUMP

IN A ONE WHEEL BUMP SITUATION

The Roll Lever (RL) is simultaneously rotated around the pivot point (P) and is sliding to compress the spring. "The spring will not be compressed if there is no support from both sides. This characteristic is inherent to this system at all vertical loads unlike conventional suspensions.

Therefore, part of the added load at the contact patch is transmitted to the opposite side. (The difference in load from side to side is the energy absorbed by the dampers + Roll Lever Reactive Moment.) (RLRM)

Obviously, when the RLRM becomes too great, no more load is reaching the other side. Anything in between is a net gain from conventional suspensions!!!

Adding this feature to the Reactive to down force feature, we end up with a better compliance when the car is slowing down.

More REACTIVE vs CONVENTIONAL….

A lot of people usually think that the Reactive Suspension will induce more vertical acceleration to the chassis in one wheel bump situations. WRONG!

I will respond by saying that since the two systems are equivalent in roll and heave rates, the vertical acceleration of the chassis will be the same.

This can be explained by the fact that conventional suspensions will resist the bump with both springs since the torsion bar is linking one rocker to the other.

However, there is an important disadvantage due to the fact that since the torsion bar is biasing the opposite wheel upward, and since the wheel has a relative low inertia, it will be easily lifted off the ground losing contact patch load. So much for performance!

In the case of the Reactive Suspension, the added contact patch load when one wheel is passing a bump is transmitted directly to the chassis in two distinct path.

-via the spring that is being compressed

-via the roll lever as energy is being stored by the moment generated around the pivot of the Roll Lever (RL).

Note that nothing is biasing the laterally opposed wheel upward other than if the elevation of the chassis is changed. Since the inertial of the chassis is high, chances are the laterally opposed wheel will remain on the ground.

In how many more ways do I have to say this suspension system is better?!













PACKAGING :

There are now many options for packaging the system. It can be put as commonly seen on top of the car or vertically in front of the driver’s feet. In fact, I proposed this vertical arrangement to various racing teams between the two seasons. In fact, it would be possible to have all the heavy stuff such as the dampers, vertically mounted near the bottom of the car.

If passive hydraulics were more popular, it could be remotely installed under the driver’s legs. If that was done, I would go as far as proposing to link the front and back in the same way that the system is linking the left to the right. Let’s walk before we run!

[Dino IV]

You really like twin-posting here and at Atlas I heard from a friend, desmo. Well do as you please, life and love are mixed with pain.

I really missed any mention of Nakamura's brilliance in the Oddball topic though, but your tech-picture search skills are admirable.

Pellegrin's system is fairly old though. He figured this out in order to make up ground with his FF and was pleased with it. He approached Williams and Benetton in IIRC 1996, but they didn't think it would be any good. One advantage of this system is it's long travel, virtually regardless of aero load, so when the MP4/13 showed long travel and therefore fine handling on bumps and curbs, rumours where all over the place - ************** - they used his system. But nonetheless, cover-off pics showed different configurations so Pellegrin never had any prove it was the above descriped system. Long travels like that can be achieved otherwise too, but engineering wise it seems a fine concept.

[koenda]

I saw it too Dino
(whoops now I gave myself away )

It's pretty usefull to have 2 browsers open 1 at 10-tenths and one at atlas. Then I compare the answers.
But fortunately I don't have to use copy-paste to answer to the topics.

[desmo]

Yes I posted the same topic on the Atlas F1 Tech Board. Unfortunately when the going gets "techy" the replies can get thin, and I like to hear from as many different perspectives as possible. As you can see, there are not likely to be enough responses on any one tech BB to iniitiate a multi-faceted discussion. Sometimes I can cross-pollinate ideas from one forum to another and get the discussion going into places where it would never lead in one forum. If this is considered bad forum etiquette please let me know, as it is absolutely not my intention to offend anyone.

[Dino IV]

Not at all, desmo. I'll blind myself with the idea you appreciate us more.

The reasons are obvious indeed and especially in the case of technical questions the right answers can only be given by people with an engineering background and quite often only by experienced specialists. I am graduating on mechanical engineering so my general engineering knowledge is alright but my field of play is thermodynamics and the subject I am graduating on right now (still 5 months to go finally) is frequency alternation and boosters in low-energy cooling systems (if I translated that correctly as well ). So suspensions leave me cold, so to speak, but I know the principles behind them.
Koenda already has his mechanical engineering degree and he's truly a combustion engine specialist.
You'll know Marco as well at Atlas I guess, graduating mechanical engineer as well and his specialization is tyre behaviour.
So everyone has his own focus and complements a general automotive passion fairly well at a Tech Forum. I wonder what your technical background is, desmo?

[desmo]

Absolutely none at all. I am simply an enthusiastic amateur. My father and I raced karts in the 70s, but as you know there isn't alot of tech crossover between karts and cars. My father was a physics professor, so we tended to be analytical in a structured way at assessing and trying to devise solutions to problems that cropped up. My mechanical experience is more hands-on than an academic in nature though, keeping cars and motorcycles running both for fun and out of necessity. School of bloody knuckles you might say.

Thanks to the creators of this forum I have a place to toss around some ideas which have piqued my interest.

Regards,
Kurt Sperry

[koenda]

Hmmm, you give me too much credit Dino

I still haven't graduated. But this week is the last week I have to work, so next week I can continue finishing my report. These weeks I have been able to spend less time on the forum so it should go faster

Then I am finally allowed to call myself Master of Science(and have to look for a job )

Dino>
this friday I'm going to VA-engineering to take a look at some Ford Focusses they are preparing. Sjaak will also give me a call when they get the Lexusses they have to prepare for Cavallino. (I'll ask if I can bring a camera )

[Dino IV]

Desmo:
That's the best school! My probably someday to be father-in-law is a physics professor too and I guess we have about the same discussions. Only difference is that cars leave him cold, but in general fashion discussing energy transformation or constructive questions is good fun as well and I know where to link cars in it at some point. Appreciate to have you around; keep up the great input!

Koenda:
Thought so, just wanted to be on the positive side of things ...
(wanneer en waar is het feest?

I'd love to come along at VA but I am obliged to regular office-hours now sadly.
But maybe I am off for some library research thursday and friday, so there's a small chance. Which city is VA in?

What about the SAE-papers? Some interesting stuff?
Can you tell me where I can get those?
Still couldn't find that Lambo F1-SAE ...

[koenda]

Yep, got some interesting stuff...
I'll give you a message where you can get them.

VA-engineering is in Nijnsel, so city is a large word

I'll give you a message where you can get them

[Lucpellerin]

Hello. I am the guy that invented this so called reactive suspension. For fun, i did a search on google and found this thread. More or less 12 years have gone by. i never made a penny from this project but it allowed me to live my passion. My system was used at Arrows F1 when Mike Coughlan was Chief Design Engineer. It was only used in one track testing but it proved the principle. it was only fitted in the front of the car. The roll stiffness increased with aerodynamic down force which developed high speed under steer. A few weeks later, the team ceased its operations. Unfortunately, the system had not been fully tested and developped to itsmfull potential but... Mike Coughlan remainded a friend. He is the only one that beleived my system had merit.
In my book, Mike is the best racecar engineer in the world. If I recall correctly, McLaren won 3 Constructors championship under his direction as Chief Design Engineer.
Most of you know what happened to Mike after those success. I will not comment and I hope there will be respect for the man that paid a heavy price for what he was blamed for.
Last week, i watched the Spanish GP and I had a shock. Williams F1 won the pole and went on to win the race. This is extraordinary!
Mike Coughlan started working for Williams last fall 2011.
This proves clearly that Mike is the best Engineer. Out there.

Now about my suspension system, I will say that I do not think it was ever used to the full extent of what i had designed. If it was, nobody came to tell me but when a man of the caliber of Mike Coughlan tells you it is a very clever idea, it means something.

This project allowed me to meet men like Pat Simmonds, Adrien Newey, Steeve Nichols. I Met them all in the UK with a scaled model that I had built.
The meetings all went like this. initially, i would be greeted by a junior engineer that saw my mockup. I never took long to see the guys I mentioned above to come see this idea.
Adrian Newey than at Williams in the Jacques Villeneuve days was very impressed. He had lunch with me and they showed me the trophy room. They all promissed me a study and that they would get back to me.
Apparently, in those days, packaging was a problem. Plus, for every dollar spent, the best results were from working on aerodynamics. Mike tells me it is still the case after all these years.
Let me say that I do not think they used my system. My system did two things. First, it connected the two sides of the suspension allowing to use a single spring. Secondly, a very clever rocker arrangement generated self centering force that was proportional to vertical load.
In those days, everybody was using four springs with rockers and a sway bar.
Doing my presentations, I realised that they liked the first part very much. I could see the lights in their eyes.
Nowdays, many cars use a single spring. I like to think I made them realise.
I think McLaren were the first to incorporate this.
I can only guess but in the following years, the race community was talking about the McLaren suspensions. But my guess is also that they never used the full system. Even when Mike Coughlan was there.

I had two patents on this thing which was kind of stupid, I admit to this because it is all secret what they put in those cars. So I ended up loosing mucho $$.

I have no hopes other than one day, some team will use my system to the fullest extent, front and back of the car. Thensystem is described in detail in the 1999 thread.
Thats it for now Friends.
I have pics from those days that prove where I have been. So dont call me names unless you are willing to give your real name.
cheers!
Luc Pellerin

[Bill Sherwood]

It's a very clever system, Luc, thanks for posting here.

(And me posting here as well for the first time in many years as well)

A friend of mine used use link in one of his sports cars here in Australia. I can't remember the details but it seemed to work well.