29 replies to this topic

[Ross Stonefeld]

Whats the pros and cons and whats the difference?

Im not sure how it would work if say you have unequal bump on one side and rebound on the other, like hitting a kerb or something

[Ray Bell]

In an area where control is so important, it seems strange to reduce the controlling element in this way...
But maybe they are counting on the billiard-table smoothness of circuits to help out with this task?

[desmo]

The only suspension system I am aware of that used one damper to control both wheel's movements in a racing car is the front suspension employed in the MP4/15 last year. The advantages in the set-up employed by McLaren appear to me to be a reduction in mass (surely the one damper is lighter than the usual pair) and it is mounted nice and low with the bottom mount built into the floor of the tub. In addition, the geometry of the Mac system is such that the damping rate for single-wheel deflection is significantly lower than symmetric loads such as downforce or pitch, allowing superior curb compliance.

[PDA]

Ross - could you be more specific? I believe that e.g. Mac use a three damper system, and most of the others similar, so what 2/1 osre you wishing to compare?

[desmo]

PDA et al: The MP4/15 used three dampers in the rear and only one in front. See the current issue of Racetech for a nice drawing of how this was realised.

[Pioneer]

I must confess my ignorance as to the actual advantages/disadvantages of a single shock system. I do know however (not slighting the McLaren) that CART cars run it on a fairly regular basis at least on the roundy-rounds.

[Ross Stonefeld]

Let me hobble to the end of the hall before you ask me to run to the grocery store

I was referring to something more basic

2000 Mygale Formula Ford = Single damper

2000 Van Diemen Formula Ford = Double damper

why?

[Ray Bell]

A designer of a production race car will go that way because:

a. He sees a performance advantage; or

b. He sees it as something the buyers will see as clever design that might help them win (whether it will or not); or

c. He is trying to save on damper costs.

Marketing will be secondary to performance unless the performance advantage is marked.

[Ross Stonefeld]

The basic thing I cant comprehend is that with a single damper, with one wheel at bump, how can the other be at rebound? A damper can only do one thing at a time



And thats not even getting into the aerodynamics of a top level race car

[Darren Galpin]

The F3 Dallara chassis also uses monoshock suspension, but again only at the front of the car. I was speaking to Gareth Rees at the time, and he believed that it did give an advantage over twin-shocks at the front, but for the life of me I can't remember why!

[Ross Stonefeld]

I cant even understand why it'd work in a non-aero car

I think it wouldnt work at all in an aero car, they use the third damper to control the vertical movement of the car under aero loading, going from 3 dampes to 1 just doesnt seem to make sense

[FlagMan]

I think if you look at a mono-shock set-up you will see that the forces from the push/pull rods in the suspension are directed via a set of bell-cranks/levers.

I cannot claim to have really looked at how they work but as most of the current/recent FF chassis manufacturers seem to be using the system then it must have advantages.

I would hazard a guess that it is better to have a single damper working in a defined manner rather than two dampers working semi-independently. Even where chassis use dual shocks they tend to be linked by an anti-roll bar, or in more modern chassis by bell cranks, so that they work in unison under certain conditions.

[desmo]

Ross, given the smooth surface of all the tracks in F1 the only case I can envision where one might encounter a significant single wheel deflection would be whilst clipping a curbing. This is invariably the least loaded inside wheel that is called on to deflect in response to the bump. I cannot envision a scenario where the outside wheel would be in a rebound motion as the inside wheel was deflecting in response to the curb.

I really wish I could scan in and post the illustration from the current RaceTech of the Mac monoshock arrangement, but with all the paranoia about copyrights I dare not lest I have my front door kicked in at 4AM by jackbooted lawyers bearing subpeonas!

[Ross Stonefeld]

What about bumpy circuits though? Like Track X in the British Formula 3 championship

And aerodynamically with only a single front damper how do you account for the normal 'third spring'

And finally, how come when they run a single front, they sitll run double rears?

[desmo]

The Mac set-up mightn't work on a really bumpy track, although reports were it was superb over curbings. I tried to find an illustration or description of how the Mygale front suspension is designed but couldn't, so I cannot comment on that one.

In the Mac's design wheel deflections are fed down into the damper by two links on each end of a transverse structure in the nose, the link on each end connected to the rocker with the transverse structure beneath the links and above the damper mounted below the structure in it's center. Symmetric loads such as downforce push down on both ends of the transverse structure and thus straight down into the vertically mounted damper beneath it. In the case of a single wheel deflection the load is fed down into the transverse structure by pivoting about an axis defined by the link on the opposite side of the transverse structure, thus only acting on the damper at roughly half the rate as symmetric loads. I know it is almost impossible to picture this from my description, though. I apologise for my inarticulate description. If you are really curious please go to the nearest newsstand which carries RaceTech and have a look for yourself.

Actually they run three dampers in back, the third damper only being fed loads as both wheels deflect simultaneously such as is the case with aero downforce or pitch motions, as the packaging constraints in the rear appear to preclude this sort of arrangement there. Piola's 99 book has some great illustrations of how this arrangement works. Most of the teams now use some variation of this concept.

[p][Edited by desmo on 02-10-2001]

[tak]

Not having seen the Mac picture, much of this is speculation, but here goes...
The original single damper systems that appeared on Minardi F3 cars and several FF cars allowed the designers to seperate ride rate springs and roll rate springs. In theory simplifying setup of the car. Of course people soon realized that you need roll damping, and that's difficult in a monoshock setup. So tripple shock setups started to appear.

Perhaps Mclaren have a clever mechanism that when used with a 4 way adjustable damper (high speed rebound and compression, low speed rebound and compression)that still enables a separtion of ride and roll rate springing AND provides independant damping functions for both ride (high speed damping and roll (low speed damping). The weakness of such a system would be an inability to damp out low speed gross chassis motions generated by gentle undulations in the road. Don't know how common those are in F1...On the plus side, this system might not damp chassis dive (under braking)--which will give better compliance under braking (especially when brakes first applied)! Following that line of thinking, reducing damping at the front of a car during squat (acceleration) might reduce power on understeer.

[Darren Galpin]

Nothing like resurrecting an old thread...... It says in this weeks Autosport that the Jordan 191 had monoshock suspension at the front, and that this made it extremely stiff.

[Marco94]

Hadn't seen this thread before. I have visited McLaren in 1999, and had an interesting discussion with one of the mechanics preparing the car for the next race. What he showed me were *two* dampers in the front. I also asked about the MP4/14's excellent handling of curbestones. And he said it was just plain old good engineering, nothing special. I am still not convinced that I believe him though.

[olschak]

Unfortunately I have not seen the one-damper design with my own eyes. Here's my comment: I can imagine that a one-damper design will never develop into a non-symmetric performance a left-right damper design might deliver over a race distance. this may not be because of poor design but because of unequal parts ... you never know before.
I do believe that sometimes simpler design can produce better performance.

[scarbs]

A common misunderstanding is that a monoshock set up rigidly mounts a common bellcrank to the chassis, this would obviously cancel any roll movement . Some degree of compliance is designed into the set up to provide the roll control.

A common monoshock set up works in this way.



Link to Hi Res Image

This the usual quickie image done in pen and scanned in on a customers PC, excuse the quality and if geocities wont let you see it try it here.......

http://www.geocities...Monoshock25.jpg

or here

http://www.geocities.../Monoshock.html


The usual two bellcrank (rocker linkages) operated by each wheel now mount to a common rocker (Orange), the rocker both pivots and slides along its mount (yellow). The other side of the rocker then mounts a single damper. Not shown in this image are the “springs”. There are two springs mounted either side of the rocker, the provide the antiroll control and place the rocker centrally on the pivot. There should be a conventional coil over spring around the damper.
Already you can see the obvious weight and cost reduction benefits, not only the second damper is redundant, but also a large amount of the linkages such the antiroll bar mechanism and the second bell crank.

In pitch,
Both wheels going up or down due to aero load or brakingacceleration (Blue arrows)
Both pushrods move up and the rocker stays central and only pivots to compress the damper

In Roll,
One wheel in bump one in droop due to roll in corners or uneven surfaces.(Red arrows)
The unequal effect pulls the rocker across its pivot and compressing the springs. The damper doesn’t move in this instance.

The advantages of this set up are
*good control of low speed movements pitch roll on smooth surfaces
*Separate control of pitch and roll
*Less components (hence less cost and weight)

The disadvantage of this set up
*Less able to cope high speed movement bumps on bad surfaces
*roll control requires spring changes rather than blade adjustments

[Ben]

I would concur with the posters who've mentioned the need for smooth track surfaces for a monoshock to work well.

I believe the Ferrari F192A (the twin floor car) had a monoshock as well, coming soon after the Jordan 191 it seems that the system was something of a fad at the time.

It is important to note that the McLaren system used a spring (torsion bar) for each wheel and a single damper mounted on the centre of the ARB, whereas the Jordan, Ferrari and Dallara F3 monoshocks have just a single spring and damper with some small disc springs to allow roll.

I suspect McLaren have realised that pitch movements are the most important to damp and that compliance in single wheel bump is worth sacrificing some damping for.

I believe Stewart ran the SF1 at some races with their three spring system configured similarly.

Ben

[desmo]

It is worth noting that scarbs' drawing is nothing like the Mac monoshock arrangement. I would be a bit worried about binding occurring in the sliding aspect of the arrangement scarbs has illustrated.

[Ross Stonefeld]

I thought even the mono-shock F1 cars still have torsion bars for each wheel.



Scarbs mentioned uneven surfaces are a problem for monoshock cars, considering how poor the track surfaces, and how severe the kerbing is at most UK tracks im surprised all F3 cars and some Formula Fords are single shock systems

[Ross Stonefeld]

scarbs you rock man. With that drawing i finally am starting to understand this. However, if there are springs to control the roll motion, how do you dampen them so they dont compress and uncompress until they run out of energy? And how come there isnt a spring around the single damper? Did I make an error in looking at double shock systems and assuming that since spring and damper are housed within each other that they work together?

[Ben]

The simple answer is that the springs to allow roll are sometimes damped (see Dallaras IRL car) but often they aren't damped and seem to work fine (probably some friction helps).

The thing about monoshocks in lower formulae (F3 and FF) is that the cars are by no means optimised in the same way as an F1 car for example. Just because Dallara use a monoshock it doesn't mean that this is the optimum solution but more that Dallara happened to make the best F3 car a few years back and now they have no competition.

Ben

[MattPete]

Originally posted by Ross Stonefeld
Let me hobble to the end of the hall before you ask me to run to the grocery store

I was referring to something more basic

2000 Mygale Formula Ford = Single damper

2000 Van Diemen Formula Ford = Double damper

why?

Is it a zero roll front suspension? That is, a single spring and damper unit connect both sides.

...or maybe not, after looking at this picture of a Van Dieman. Maybe I was thinking of old Formula Vee's.

[Ross Stonefeld]

Ill assume the literal translation of zero-roll to mean, well, no roll. Why would you want no roll in the front suspension? I would think that would understeer like crazy

[MattPete]

Originally posted by Ross Stonefeld
Ill assume the literal translation of zero-roll to mean, well, no roll. Why would you want no roll in the front suspension? I would think that would understeer like crazy

Yeah, the names a little confusing. This piece I shameless stole from another web site does a better job of explaining:

"...Since all the engine's torque is being applied to the spinning wheel, the car is coasting out of the turn until sufficient load is returned on the inside tire to regain traction. This particular problem has caused an ingenious type of rear suspension on FVees to become prolific. Called the "zero roll" rear suspension, it does not mean that the rear of the car does not roll, but rather, that no roll stiffness is provided by the rear. All of the roll resistance is provided by the front suspension, which keeps the inner rear always loaded by at least the amount of unsprung weight at that corner. "

The Formula Vee's I've seen I think have a swing axle design with a spring connecting the left and right sides, which provides resistance under droop but not roll (the opposite of a sway bar):

[crosses finger's that ASCII art looks okay]

--							 --|  |		  |///|		|  ||  |		  |	   |		|  ||  |==========o	   o========|  ||  |						   |  ||  |						   |  | --							 --

[scarbs]

This set up is a common set up used a few years ago in F1, I recall Tyrell were one of the first to use it (on the Alesi high nose car, The 016 or 019 I can’t recall). It was used through out the lower end of the grid, as Active suspension was still some way off, teams still ran very stiff short travel suspension and the monoshock was a simple way to decouple Pitch and Roll, the third damper set up was yet to be introduced. This specific set up has since been used in most of the lower formulae, I have to say I cant understand why it is preferred over a third damper, except perhaps for simplicity in set up (and manufacture).
The set up should suffer from some binding as Desmo pointed out, I do not think the movement across the pivot is as large as my diagram shows, a few degrees of roll would not equate to many millimetres of movement across the pivot. The springs acting to control roll are not damped not surprising seeing as most conventional antiroll bars are not damped either, Bump stops have been fitted to have an effect the rate of roll resistance.
This set up clearly could not have individual torsion bars, the current format (e.g. McLaren) is not so much a monoshock arrangement, but more like deleting the individual wheel dampers from a conventional three damper set up. (see my image in the “Jaguar add third damper for Hockenheim” thread).
My understanding is that with Racecars on closed circuits with High aspect ratio racing tyres, the need to control high frequency movements (bumps) on individual wheels is not an issue. But, the need to control the low speed movements (pitch and roll) is more important perhaps due to the effect on underbody aero performance...?

[Ben]

I think Scarbs' last paragraph has a lot of truth in it.

The formula Vee zero-roll system doesn't really come into this discussion because it exists to overcome a fundamental design fault with the swing axle suspension they have to use.

Understeer has more to do with load transfer than actual roll angle (they are related, I know, before I get a barage of complaints) so if you can get a mechanical balance with a front end that's stiff in roll the two don't have to be mutually exclusive.

Another way of looking at this is to say that a twin shock layout with a very stiff ARB is effectively a monoshock system due to the large coupling of two modes that the ARB causes. In this case many people have created similar characteristics with less weight and complexity using a monoshock with some controlled roll compliance (which is probably less underdamped than a bad ARB).

Ben