## Do we need suspension?

Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum.
hardingfv32 wrote:You only need a suspension when you have a rough track. A dead smooth track does not require a suspension or improve the cornering abilities of the car.... Fact!

The weight transfer formula for an F1 car: weight transfer = weight x cg height / wheel track x g

You will notice there is no variable/input for wheel or spring rates, roll rate or sway bar size, etc.

Brian

Even go-karts have a form of suspension, they are called Tires.
The impossible often has a kind of integrity which the merely improbable lacks.
djos

Joined: 19 May 2006

This is completely wrong:

"The ECU in overrun mode, retards timing so that the combustion efficiency and the Mean effective pressure is greatly reduced. The engine now puts out the required 200 hp. The other 400hp of air and fuel is sent out the exhaust pipe."

Let's discuss the logic of your proposal:

First, I am going to ASSUME that we are after some serious off throttle air and heat flow. I am also going to assume that we want the throttle open 100% during the off throttle mapping to accomplish that. You said that you want 200 hp. We will need an decent A/F mixture to get the mixture to light. Then we will use the ignition to develop the hp number you want. The goal of the retarded ignition is to limit the combustion pressures to develop only 200 hp. The combustion process will be allowed enough time to create 200 hp before the exhaust valves open effectively ending the combustion process. Combustion pressure = HP. Since you never reach maximum combustion pressure you are not going to get the big high energy exhaust flows that you are proposing.

There will be no 400 hp of exhaust to feed the diffuser.

Brian
hardingfv32

Joined: 3 Apr 2011

"Even go-karts have a form of suspension, they are called Tires. #-o"

And how does this statement relate to the discussion?

Note: My premise states... "a dead smooth track"

Brian
hardingfv32

Joined: 3 Apr 2011

Suspension will always be there. Even if you put your tyres on a steel frame that's still suspension. No material is infinitely rigid, so it will still be sprung suspension, whether we like it or not.

raymondu999

Joined: 4 Feb 2010

"Even if you put your tyres on a steel frame that's still suspension. No material is infinitely rigid, so it will still be sprung suspension"

Then the question is whether this limited suspension you suggest makes the car corner better?

Brian
hardingfv32

Joined: 3 Apr 2011

hardingfv32 wrote:You only need a suspension when you have a rough track. A dead smooth track does not require a suspension or improve the cornering abilities of the car.... Fact!

The weight transfer formula for an F1 car: weight transfer = weight x cg height / wheel track x g

You will notice there is no variable/input for wheel or spring rates, roll rate or sway bar size, etc.

Brian

Won't a car going around a corner on a smooth track still experience chassis movement independent of the line taken based on the car pitching forward and back under braking and acceleration as well as rolling from centrifugal force? And isn't that the reason they camber tires?
Box! Box!
Jeffsvilleusa

Joined: 14 Apr 2011
Location: San Francisco

First, to limit the discussion can we take tire flex out of the discussion. A) I appreciate that a outside tire could compress and cause the chassis to roll a very small amount. B) Tires usually work best with a little negative camber in turns. This could be related to A.

Are we talking about a car pitching forward and back under braking and acceleration as well as rolling from centrifugal force because of suspension movement? If so the camber is just a correction of the negatives caused by the chassis movement.

Brian
hardingfv32

Joined: 3 Apr 2011

No I meant the movement is independent of the suspension, and the suspension is in place to allow the movement which occurs besides track surface, the movement the chassis experiences because you are throwing it around corners.

Anyhow, the proposition is that a higher CoG (including rake) could generate more grip in the corners.
Box! Box!
Jeffsvilleusa

Joined: 14 Apr 2011
Location: San Francisco

hardingfv32 wrote:You only need a suspension when you have a rough track. A dead smooth track does not require a suspension or improve the cornering abilities of the car.... Fact!

The weight transfer formula for an F1 car: weight transfer = weight x cg height / wheel track x g

You will notice there is no variable/input for wheel or spring rates, roll rate or sway bar size, etc.

Brian

This i have a hard time believing. I think grip levels of the track play a big factor aswell and not just how smooth a track is.
The truth will come out...
HampusA

Joined: 16 Feb 2011

"I think grip levels of the track play a big factor"

In what, cornering performance?

I'll refine my assumptions: Dead smooth track, no tire flex or grip issues/effects.

So, why do we need any suspension?

Brian
hardingfv32

Joined: 3 Apr 2011

1) "No I meant the movement is independent of the suspension, and the suspension is in place to allow the movement which occurs besides track surface, the movement the chassis experiences because you are throwing it around corners."

How does the car's chassis movement improve cornering force? Weight transfer?

In a F1 car almost all of the weight transfer comes from the formula: weight transfer = weight x cg height / wheel track x g. Where do you plug in the chassis movement into the formula?

2) "Anyhow, the proposition is that a higher CoG (including rake) could generate more grip in the corners."

Weight transfer in the corners ALWAYS means reduced cornering force. Per the formula, a higher CG means more weight transfer.

Brian
hardingfv32

Joined: 3 Apr 2011

hardingfv32 wrote:1) "No I meant the movement is independent of the suspension, and the suspension is in place to allow the movement which occurs besides track surface, the movement the chassis experiences because you are throwing it around corners."

How does the car's chassis movement improve cornering force? Weight transfer?

In a F1 car almost all of the weight transfer comes from the formula: weight transfer = weight x cg height / wheel track x g. Where do you plug in the chassis movement into the formula?

2) "Anyhow, the proposition is that a higher CoG (including rake) could generate more grip in the corners."

Weight transfer in the corners ALWAYS means reduced cornering force. Per the formula, a higher CG means more weight transfer.

Brian

Assuming track-surface grip is equal for everyne (same tarmeac and same tires - where rubber meets the road if you will) and that the moment you break out would be when the forces of weight tranfer are larger then the grip available that would lead to equal maximum weight transfer for everyone.

That would mean that the weight (car-weight + Downforce at speed x), CoG and wheelbase + wheel-track are determining figures. Things I would think that are missing is the radius of the CoG compared to the radius of the turn (ie centrally located weight vs more rearward).

With their, presumably, most efficient EBD, the RB7 would have more rear-ward biassed DF in turns compared to it's competitors given much betetr traction during mid-corner and corner exit where they can have more throttle opening in mid-corner and get earlier on full-throttle towards apex.

I think they need the FFW to counterbalance their rear DF at the back during the straights to avoid the nose being lifted to high killing their front-grip but also killing their diffuser efficiency.
shamikaze

Joined: 6 May 2010

hardingfv32 wrote:So, why do we need any suspension?

Smooth the driver inputs out, even on your perfectly flat glass track...
PhillipM

Joined: 16 May 2011
Location: Over the road from Boothy...

hardingfv32 wrote:This is completely wrong:

"The ECU in overrun mode, retards timing so that the combustion efficiency and the Mean effective pressure is greatly reduced. The engine now puts out the required 200 hp. The other 400hp of air and fuel is sent out the exhaust pipe."

Let's discuss the logic of your proposal:

First, I am going to ASSUME that we are after some serious off throttle air and heat flow. I am also going to assume that we want the throttle open 100% during the off throttle mapping to accomplish that. You said that you want 200 hp. We will need an decent A/F mixture to get the mixture to light. Then we will use the ignition to develop the hp number you want. The goal of the retarded ignition is to limit the combustion pressures to develop only 200 hp. The combustion process will be allowed enough time to create 200 hp before the exhaust valves open effectively ending the combustion process. Combustion pressure = HP. Since you never reach maximum combustion pressure you are not going to get the big high energy exhaust flows that you are proposing.

There will be no 400 hp of exhaust to feed the diffuser.

Brian

My numbers are deliberately exaggerated loony toons numbers. Do not pay too much attention to the numbers.

As for the combustion pressure equals horse power, I think that applies only over the area of the piston. If the exhaust valves are open sometime after the combustion that pressure will act on the gases inside of the exhaust pipes. It will push on the gases in the exhaust pipes. In other words you are treating the pushing of the gas in the exhaust pipes as an additional load for the engine.

In this method it doesn't matter whether car is at zero load(or even engine braking)or full load there must be a cross over point of power transmitted to the pistons using exhaust overrun.
"I was blessed with the ability to understand how cars move," he explains. "You know how in 'The Matrix,' he can see the matrix? When I'm driving, I see the lines."
n smikle

Joined: 12 Jun 2008

n smikle

No, I understood the point of the numbers. I am just trying to make the point that with an engine that produces 600 hp, you can't just harvest 200 and expect to send the other 400 out the exhaust.

I know the exhaust system represents a restriction, but I have never seen a study that expresses it in hp. I do know that this restriction is not the most important criteria when developing the exhaust system, so it ca not be that great. Just the thinness of the exhaust tubing, .020 Inconel, would indicate that there is not much pressure is being created inside the pipes.