Investigating exhaust aided diffusers

[marcush.]

I have always failed to understand why the brake-callipers are mounted the way they are on most F1 cars.

Last year, BrawnGP had them on the bottom of the brake-disc as well, and this year they seem to have repositioned them back. It was actually one of "the" things I looked for during the presentations of the cars in the winter.

I would think the benefist would be 3-fold:
* Lower overall CoG + lower CoG of unsprung-mass, which counts extra + centrifugal forces being placed lower to the group which I could image would aid in grip levels.
* Better aerodynamic placement for cooling purposes

GReetz,

S.

but you sacrifice a lot in terms degree of freedom in posiioning of pushrod ,as well as the inevitable stone and debris collecting at the bottom...=caliper not a good idea ..and the caliper with its hot pads ..cooking the bearings neatly from below at a standstill ...and bleeding the calipers is also surely not nice ...
then there was the new regulation you must use aluminium as upright material now ,so the Cof G benefit is reduced quite a bit with the new regs...

[DaveW]

+ rotor deflection relative to the upright under lateral loads?

[ringo]

I think the exhaust opens into the upper deck of the diffuser. Remember the lower one is basically maximized dimensionally by regulations.
The upper part being much steeper would benefit better from energizing from the exhaust.
One of the problems i think the team engineers had to deal when designing the DDD is the steepness and the separation associated with it. Mclaren pushed theirs to the limit and had to use flow vis to ensure the flow was as expected.
The RB DDD it's seemingly small size and it's shape, could be due to the aid from the exhaust. It's probably packing more punch than the others in terms of performance, and may have a bigger internal area.

Is there any place I could find a cross section of a DDD?

My assumption that the exhaust goes into the lower deck derived from this picture:

It could be in breach of the regulations if it opened into the lower surface.

3.12.7 No bodywork which is visible from beneath the car and which lies between the rear wheel centre line and a point 350mm rearward of it may be more than 175mm above the reference plane. Any intersection of the surfaces in this area with a lateral or longitudinal vertical plane should form one continuous line which is visible from beneath the car. A single break in the surface is permitted solely to allow the minimum required access for the device referred to in Article 5.15.

This single hole is the starter hole. The exhausts can't break into the lower surface of the diffuser.

[autogyro]

+ rotor deflection relative to the upright under lateral loads?

Not sure what you mean Dave.
The position of the calliper does have a major effect on the torque reaction through the hub carrier during braking.
The force generated works through the pull rod geometry to alter ride height.
In effect it jacks up the rear under braking.
I had a beam axled Mini that rolled the axle around 90 degrees under braking.
In that car there was a wedge on the end of the axle that gave negative camber under power which rolled into toe out under braking. This gave an oversteer into an early apex and an earlier power on coverting to corner out understeer.
Worked great.
The point is RB have a way to increase DF into corners.

[marcush.]

+ rotor deflection relative to the upright under lateral loads?

you always tend to miss something ..I have to admit,have not thought about this one..but yes it will be very sensitive with any flexing under lateral loads..but keeps your brakes warmer..

[marcush.]

the opening is so much forward it can only be for the upper deck difusser ,as the lower deck starts further back.

[DaveW]

+ rotor deflection relative to the upright under lateral loads?

Not sure what you mean Dave.

Apologies, I wasn't commenting on your thoughts (I'm still trying to get my head around those), just that the usual reason for not placing the calipers South (or North) is bearing compliance under lateral loads, which can cause interference between the disc & brake pads/caliper.

p.s. Probably need to read my own posts... there is reason behind everything.

[autogyro]

Ah yes, I see exactly what you mean now.
The forces involved are the same that I believe Adrian is using to jack up the car under braking.
Anybody got a handle on the Math?

[vonk]

+ rotor deflection relative to the upright under lateral loads?

Not sure what you mean Dave.

Apologies, I wasn't commenting on your thoughts (I'm still trying to get my head around those), just that the usual reason for not placing the calipers South (or North) is bearing compliance under lateral loads, which can cause interference between the disc & brake pads/caliper.

p.s. Probably need to read my own posts... there is reason behind everything.

This is what I understood you to be hinting at.

[marcush.]

just stumbled over this old Raacecar engineering issue...

page 49 ..quite interesting...


http://www.scn.rain.com/~neighorn/PDF/racecar.pdf

[autogyro]

This is what I understood you to be hinting at.

[/quote]

Not exactly.
I believe that Adrian Newey has harnessed centripetal progression and made use of reactive cetrifugal force, to alter the ride height through the pull rod suspension geometry on the RB6 under braking from the reactive force from the bottom mounted brake calliper.
This results in the rear of the car rising producing a wedge effect to augment the diffuser.
Sorry if this upsets the exhaust debate on its effect on the diffuser but I think the two things may be linked as to where the exhaust exits and how the effect is applied and controlled.

[vonk]

This was in response to DaveW's earlier statement: “+ rotor deflection relative to the upright under lateral loads?”

I believe that Adrian Newey has harnessed centripetal progression and made use of reactive cetrifugal force, to alter the ride height through the pull rod suspension geometry on the RB6 under braking from the reactive force from the bottom mounted brake calliper.

Wow!

The caliper applies a pure torque (couple) to the upright no matter where it is attached. That torque is always reacted by rear wheel load reduction regardless of the suspension geometry. But dive under braking (and squat) can be controlled by suspension geometry, which is nothing new.

[PlatinumZealot]

The brake thing has to be a separate thread though. It's too deep for this thread.

[xpensive]

When I find it rather obvious from the above pictures that exhausts are located on the sides, just ahead of the rear wheel
and below suspension parts, I find it difficult to see that this would aid the diffuser in any significant way?

[autogyro]

The caliper applies a pure torque (couple) to the upright no matter where it is attached. That torque is always reacted by rear wheel load reduction regardless of the suspension geometry. But dive under braking (and squat) can be controlled by suspension geometry, which is nothing new.[/quote]


The calliper does apply a pure torque couple to the upright true but the reaction through the wishbones and pull rod depends on where and at what moments they are mounted on it.
Yes this is not in the right thread, so lets stop now on it.