Floor Structure and Flexibility

[raymondu999]

Another question is regarding the diffuser construction. Why they didn`t do a "multi-decker diffuser" ? I don`t think it`s in place the DDD ban rule, because they don`t do holes in the floor, now they just have to put one above the other, hence multiply the effect ...

Could you elaborate? How do you intend to feed this other diffuser?

[The FOZ]

In engineering terms, a "diffuser" is a passage of increasing cross-sectional area.

In automotive engineering, putting a diffuser at the rear of a flat underbody, which is fed by a nozzle, the air under the car is accelerated, creating a low pressure zone, giving the car downforce.

In other words, the diffuser only works in concert with the underbody - since the rules now say no holes in the underbody, a second layer of diffuser can't happen, plain and simple.

[racer_boy]

Good call, but as you point out the floor is usually not under very high structural loading, so making this part of the floor a sandwich structure to gain bending stiffness seems to be a bit of overkill. My understanding of the rules is that you cannot shape the bottom of the floor forward of the rear axle or outside the immediate area around the 'plank', such that it is not flat when viewed from below, but if you do make the bottom surface flat, you could easily craft a channel between the top and bottom surfaces of the floor couldn't you? In effect, Red Bull have already done something sort of similar with how their exhaust passes over the floor, but the question in my mind is whether or not Mercedes have done something there to some degree. Reasons could be:

- The channel is fed by air from the bottom of the sidepod, and perhaps discharges ahead/to one side of the rear diffuser like the RB7 exhaust

- The channel is there to flow some small amount of cooling air to get past the floor bending effects Merc sufferred with on the W01...by perhaps being stronger in bending

- Its there to fit ballast???! That anyone else could possibly fit in the space between the engine and gearbox?

Some food for thought, might be completely wrong but hey... its fun to speculate.

I don't think they are allowed to "shape" the underside of the floor since ground effect cars were banned.

The reason the floor seems very thick is because of the way it is built. Most teams seem to use a monolithic carbon laminate for the floor, so essentially one thick skin of carbon fiber and epoxy. That makes the floor thinner.
Merc seem to have used a sandwich structure, so two thinner skins of carbon fiber with a foam or honeycomb structure in the middle. This makes a much stiffer structure for the same weight, but is more difficult and more expensive to make, and more fragile against impacts. Also, it's harder to make complex shapes this way.

[marcush.]

the floor needs to be flat by definition on the side facing the ground.this is surely the worst case for getting any kind of stiffness into the panel if not using some core material.To think it´s not important to get the flat portion stiff I ´m pretty sure this is far from reality.On one hand teams look for half millimeters in controlling rideheights and on the other side one would allow the flat floor to flex say 5 or more..That does not fit .If you work a flat flloor car you will quickly experience that it is very rideheight sensitive and a flexing floor will change effectively aero rideheights leading to fluctuations in downforce?

[Raptor22]

The floor is a structural component it is stressed and carries loads of the cooling system, the tub adn the engine gearbox rear suspension. Making it stiff is of paramount importance.

Brawn mentioned that their car is shorter because they needed the FLOOR to be shorter to gain the maximum efficiency from the restrictive diffuser regulations. This makes sense since if we view a diffusor as a nozzle for every throat inlet size there is an ideal throat size and an ideal diffuser size. I think he is refering to them taking time to make sure they had their geometry correct in order to maximise this potential, hence the short car.

They;re either right or they;re wrong wret to this decision. At the moment all indications are that they may be right. If we see teams shortening their cars come May then we know Mercedes are onto the right concept.

[marcush.]

surely the loor cannot be allowed to vibrate against the rads..but if the floor is carrying the rads...I got my doubts.usually we can see cars with all the plumbing and rads but without floors in the pit garages.. so I assume at least some load is carried by the radiator inlet moldings and possibly the rads are attached to the tub sides ?

[atanatizante]

Another question is regarding the diffuser construction. Why they didn`t do a "multi-decker diffuser" ? I don`t think it`s in place the DDD ban rule, because they don`t do holes in the floor, now they just have to put one above the other, hence multiply the effect ...

Could you elaborate? How do you intend to feed this other diffuser?

I mean if you could build a multiple "floor" above the prime one. This "floor" would be connected/bonded at the back and to the side of the sidepod and would end like a rear wing beam or diffuser shape. In this case the hot air which came from the exhaust will create a lower pressure for the clean air which flows at this level/height of the sidepod, hence it creates downforce. Maybe the reason they didn`t build it`s the fact that this could nullify the effect on the prime one ... So (instead of multiplying the downforce effect for a multiple deck/floor system) one deck/floor eliminates the effect produced by the other one placed bellow, if I`m not wrong ...

[raymondu999]

So the low pressure area would be above the floor? I'm thinking that wouldn't do much but just create a low pressure region in the middle, no? It would pull up from the normal floor. Perhaps I understood you wrong. Maybe a diagram would help? Mods, you might wanna split this into a separate thread.

[bot6]

The floor is a structural component it is stressed and carries loads of the cooling system, the tub adn the engine gearbox rear suspension. Making it stiff is of paramount importance.

The tub is bound to the engine and rear crash structure, which are bound to the transmission. The transmission is usually the part carrying the rear suspension. The rear wing is supported by the crash structure. And the radiators are usually bound to the tub and engine. The floor is designed to be an easily interchangeable part and does not carry the main loads of the car. It does carry some load (own weight and aero mainly) but not the main mechanical loads.

Making a bending floor would cause some downforce fluctuations, but if the floor bent down at high speed it would actually increase downforce. It would, however, also increase drag. And it would very probably be illegal. I think that has been tried by a few teams with the bending tea tray back in the day, and the FIA modified the inspection tests accordingly.

I think we might not be even talking about the same part of the car here. We have to make a distinction between the plank, which is under the driver and engine, and is part of or bound to the tub and carries some of the mechanical loads, and the outer portions of the floor, spanning out from that plank.

It's confusing because instinctively you would expect the floor of the car to be the lowest bit of the car. But generally when teams say they have a new floor, they are not referring to the plank or underside of the tub, but to the slightly higher, outward parts of the bottom of the car which are there purely for aerodynamics.

[atanatizante]

So the low pressure area would be above the floor? I'm thinking that wouldn't do much but just create a low pressure region in the middle, no? It would pull up from the normal floor. Perhaps I understood you wrong. Maybe a diagram would help? Mods, you might wanna split this into a separate thread.

My knowledge in this particular field is not so vast and that`s the reason I made some assumptions which emanated from my own ideas ...

Now the low pressure area is below each floor, but if they are build one above the other then unfortunately this low pressure area is also placed on the floor above, hence nullify the effect ... I.e. if floor no.1 (prime) has the low pressure bellow it, then at the floor nr.2 (which is placed above the prime one) the low pressure it`s also bellow, but from the floor nr.1 point of view this area is above it and I`m afraid that this could nullify the first effect ...

[raymondu999]

Yeah, I think I definitely need a diagram

[atanatizante]

The idea of the Merc exhaust is exactly the same as that of the blown diffuser Red Bull pioneered last year. That is, re-energizing the airflow as it reaches the rear of the car before it gets to the diffuser. This way, the flow on top of the diffuser has more energy, helping to suck air out of the diffuser, hence helping to suck air in under the floor at the front of the car, hence more flow under the car, hence more downforce.

Many cars have a vertical flap placed on each side of the floor edge, most of them in the sidepod area.
That`s the reason to: a) accelerate the air flow in this area?; b) channel the air flow towards the diffuser? or c) suck the adjacent air flow from the car`s proximity, hence more air to feed the back of the car?
In this respect could they build a flap/fence with gills curved outwards in order to add more air to the existing one, or maybe it`s not so efficient because creates more drag?
Regarding the efficiency, generally speaking, maybe a new item introduced on the car even if creates a drag of let`s say one tenth, maybe the secondary effect creates a gain in time of two tenths and in the end of the day when you draw a line you could be faster in the lump ... you know what I mean?

[bot6]

No, don't really know what you mean... Mind posting a picture or diagram, so we're sure we're all talking about the same thing?

[atanatizante]

No, don't really know what you mean... Mind posting a picture or diagram, so we're sure we're all talking about the same thing?

... but far back and with vertical gills on it ...

[Raptor22]

The floor is a structural component it is stressed and carries loads of the cooling system, the tub adn the engine gearbox rear suspension. Making it stiff is of paramount importance.

The tub is bound to the engine and rear crash structure, which are bound to the transmission. The transmission is usually the part carrying the rear suspension. The rear wing is supported by the crash structure. And the radiators are usually bound to the tub and engine. The floor is designed to be an easily interchangeable part and does not carry the main loads of the car. It does carry some load (own weight and aero mainly) but not the main mechanical loads.

Making a bending floor would cause some downforce fluctuations, but if the floor bent down at high speed it would actually increase downforce. It would, however, also increase drag. And it would very probably be illegal. I think that has been tried by a few teams with the bending tea tray back in the day, and the FIA modified the inspection tests accordingly.

I think we might not be even talking about the same part of the car here. We have to make a distinction between the plank, which is under the driver and engine, and is part of or bound to the tub and carries some of the mechanical loads, and the outer portions of the floor, spanning out from that plank.

It's confusing because instinctively you would expect the floor of the car to be the lowest bit of the car. But generally when teams say they have a new floor, they are not referring to the plank or underside of the tub, but to the slightly higher, outward parts of the bottom of the car which are there purely for aerodynamics.

You are correct, a distinction needs to be made between the actual flat bottom and the raised floor directly under the pods. Good catch. I refer to the floor as the component that carries the tube and engine with ancillary equipment. The other edges are easily interchangable parts. Spot on.