Renault F1 Rear suspension

[richard_sykes]

Can anybody please explain what the rear spring does in this set up. It seems to be mounted to the centre of the pivot (by the air box) and to the top of the gear box (the chassis being a stressed casing)?

http://www.gurneyflap.com/Resources/renaultsus.jpg

Thank you

Richard

[ian_w]

One end of the spring/damper unit is connected to the back of the gearbox case, the other is connected to the 'T' bar arrangement.

In one wheel bump ( i.e. one wheel moves more than the other e.g. roll ), the 'T' bar assembly will twist providing a springing force. Note each rocker has its own damper assembly so this roll mode damping can be controlled.

In two wheel bump ( i.e. both wheels move same amount ) the 'T' bar assembly does not twist put pivots in the fore-aft plane about its lower end ( somewhere deep within the gearbox case ). In this mode, the seperate spring/damper comes into play to control the suspension motion.

This suspension design is not that unusual on single seater cars, the idea is to de-couple the roll and bump modes. On a 'normal' car with 2 springs and an anti-roll bar, the bump mode is controlled by the springs whilst roll is a combination of springs and anti-roll bar. This means that the roll mode is stiffer than the bump mode, as it has the additional force of the anti-roll bar.

On a high downforce car, this is the complete opposite of that is required - you need a very stiff bump set-up to stop the car hitting the ground. With a conventional system , this bump springing required is way too stiff for optimum cornering grip. The de-coupled system, allows you to have the stiff bump springing required along with much softer roll springing for optimum cornering. The use of 3 dampers also allows independant tuning of the damping rates in bump and roll.

[JulianF]

Beautiful picture BTW. They are true works of art aren't they?
Cheers
JulianF

[LOLA-Christian]

Originally Posted by richard_sykes

Can anybody please explain what the rear spring does in this set up. It seems to be mounted to the centre of the pivot (by the air box) and to the top of the gear box (the chassis being a stressed casing)?

http://www.gurneyflap.com/Resources/renaultsus.jpg

Thank you

Richard

May I take the opportunity to ask you all what the "bright" part (like a "finger", or something like that) around the right hand half shaft, close to the transmission case could be?

[gti5notrkt]

Looking at the base of the half shaft near the transmission there is a serrated wheel, somewhat like a timing wheel used for an ignition trigger. However in this case I would guess that the 'finger' you are referring to is a either a magnetic or optical sensor use to record the half shaft RPM, could be for differential control (one on the other side as well), or for data logging/telemetry. The use of the serrated wheel simply increases the resolution of the signal.

Jon.

[TEAM78]

torque sensor maybe? dunno, puts us out of our misery..

[ian_w]

The toothed disc will be used to measure wheel speed.

The driveshaft will have some strain gauges attached to it, this is used to measure the torque thro the shaft. The 'finger' type device is used to pick up the signal from the strain gauges.

[TEAM78]

Originally Posted by ian_w

The toothed disc will be used to measure wheel speed.

The driveshaft will have some strain gauges attached to it, this is used to measure the torque thro the shaft. The 'finger' type device is used to pick up the signal from the strain gauges.

doh, I should of known that

[Hitech]

Another interesting thing to note in the picture is the 'Flexures' used on the inner ends of the top wishbones. They appear to be welded in to the wishbone ends and simply clamped under the damper mounts.
Does anyone know what these are made from as the rear end does see some significant movement duringrunning, particularly over curbs.
Phil

[Lukin]

Originally Posted by Hitech

Another interesting thing to note in the picture is the 'Flexures' used on the inner ends of the top wishbones. They appear to be welded in to the wishbone ends and simply clamped under the damper mounts.
Does anyone know what these are made from as the rear end does see some significant movement duringrunning, particularly over curbs.
Phil

I think it's a graphic illustration of how much suspension movement they don't expect!

I would think it's a titanium alloy.

It has a modulus of elasticity of around 110-120 GPa (compared to steel of 205-210 GPa) so it will flex twice as much and it's fatigue strength will mean it's controlled flex (at least over a race distance I would guess). I remember reading Ferrari did this a few years back.

[Lukin]

With the pic, it looks like they have Pi Looms, or connected based on Pi Looms at least.

I assume the blade from the ballcrank where the 3 spring/damper arrangements connect to is the anti-roll bar. I guess rotating it will vary the blade inertia and the effective roll stiffness. For changing their roll 'region' I guess they would vary the raduis from the blade to the outer ball joints?

I think I saw something similar on a FCR Car at Indy.

[1200Datto27]

I'm suprised that they are using metal wishbones, I wonder if it has someting to do with the failures that they experienced last year at Canada?

[scarbs]

Renault use Marrelli electronics, but the connectors may be similar to Pi?

The top wishbone is in one piece and was changed to Ti after Trullis unexplained Silverstone crash, the lower wishbone is still commonly in metal in F1. Flexures are almost always in Ti even if the main wishbone in in carbon fibre.

I don't understand the post on the anti roll bar? the bell cranks operated from the pushrods, then operate the links to a yolk shaped lever, this is mounted a vertical torsion bar. F1 cars now rarely use adjustable ARBs but tend to alter the bar itself, As the driver cannot adjust the ARB himself the solution is lighter single rate set ups.

[ian_w]

The electrical connectors are all Deutsch AS type which are a standard connector used on most high end race cars. ( AS stands for Auto Sport ).

[youngoldy]

Flipin heck took me about 20 mins to get my head around that one.

A round of aplause for the designer in my book!

[StephenRae]

How are cornerweights done on cars with flextures? is there a way of slackening them off so that they don't preload the suspension?
By the way the word 'flextures' hasn't made it into the dictionary yet!

[Hitech]

Try looking in your dictionary under 'flexure' rather than 'flexture'
Phil

[StephenRae]

Originally Posted by Hitech

Try looking in your dictionary under 'flexure' rather than 'flexture'
Phil

I stand corrected on the spelling....now how do they get rid of the 'stiction' in the joints?

[Hitech]

I think that the main point of a flexure is that it removes any possible stiction from the joint, though it will add a small increase to the wheel rate in addition to the spring(s). As this is a constant though, I think that it can effectively be ignored for the purpose of corner weights.
Phil

[mamba]

since launch control was ban was in place they placed the shocks behind the axles to get a beter traction at the rear. so thats how every one was thinking the renault team was cheating at the time they came up with a hi tech idea and easy one.

[ngpe]

Originally Posted by scarbs

Flexures are almost always in Ti even if the main wishbone in in carbon fibre.

I don't understand the post on the anti roll bar? the bell cranks operated from the pushrods, then operate the links to a yolk shaped lever, this is mounted a vertical torsion bar. F1 cars now rarely use adjustable ARBs but tend to alter the bar itself, As the driver cannot adjust the ARB himself the solution is lighter single rate set ups.

compleate carbon flexures and wishbones were used but after failures they reverted back to ti bones for reliability (belt and braces)

The rear torsion springs are in the rockers (bellcranks) you can see the top of the one clearly painted green, the other will be painted red to denote which side they belong. The roll bar is then situated underneath the yolk shape leaver and can just be seen vertically underneath,These can then be changed as required.

[JohnD]

ngpe,
Now you've got me really confused. You say that there are torsion bars in the bell cranks controlling single wheels in conjunction with the dampers on the other end of the cranks, not the bar under the yoke acting as a torsion bar. So the yoke just pivots on the bar below it, and doesn't twist it at all?

In fact, that makes more sense - to engineer a lower mount for the yoke bar that will resist torsion AND still pivot, would seem a difficult problem.

John

[ngpe]

Sorry to confuse you but there is a torsion roll bar arangement under the yoke as well, the bar pivots back and forth from about half way inside the gear box. The bottom of the bar is then fixed (not alowed to rotate just pivot forward and back) and the top is fixed to the yoke which will twist when the car is in roll. The size of the bar can be changed to give more or less twist in the bar which will in turn control the roll.

[TEAM78]

im thinking of using flexures, anyone know who does these things and is there any technical info on them, has race car eng covered them at all?

[ubrben]

Originally Posted by TEAM78

im thinking of using flexures, anyone know who does these things and is there any technical info on them, has race car eng covered them at all?

Just get a mechanics book and calculate the bending moment and stresses in a cantilever beam. Even if RE had done an article (which I don't think they have) it's still a fairly basic thing to design.

Ben