Comfort and Speed question, A-level Physics Report

[iain_tk]

Hi,
I am an A-level student currently studying Physics, I am in the process of writing a physics report on a topic of physics that interests me. My report is about the link between vehicle comfort and vehicle speed/acceleration. Is it possible to achieve the speed and acceleration on a Formula One car with the comfort of a family passenger vehicle?

I am currently looking at the damping used on F1 cars however I don't really understand how less damping (harder suspension) increases the traction of a car through corners and over bumps. Can someone please explain this to me?

Also I would like to prove this. Using data from both and formula one car and a normal car, is there an equation/formula that I can use that will show and increase of traction with a harder suspension set up?

Any help will be much appreciated,
Ian

[Tim.Wright]

First off, the main thing to look at in comfort would be the transmissibility of the suspension. To reduce (vertical) accelerations at driver seat you want a very low transmissibility which requires low spring/damping rates. This is the primary reason for the harsh ride of a race car, ie much harder suspension.

A lot of people have a misplaced belief that stiffer suspension = more grip, whereas the actual relationship is not so direct. Ideally (theortetically) you want as soft a wheel rate as you can get away with to keep the tyres happy. This reduces force variations at the contact patch and also decouples the sprung mass from the unsprung mass. Both of these characteristics are good for grip. This is typically why you soften the end of a racecar which is not gripping enough.

However, in practice, race car suspensions are stiffer than a road car simply because;
a. There are lower allowables for body movement (for aero and kinematic reasons)
b. There are higher loads in a race suspension

Therefore, higher loads and less displacement requires stiffer springs. Stiffer springs require more damping.

When you throw in requirements to keep the cars as low as possible and be able to withstand large amounts of downforce without bottoming out you will see why vertical stiffnesses on an F1 car are so high. Its not because it gives more grip, but rather to hold the chassis off the ground.

So basically I would have to say there is no way (with a conventional passive suspension system) to achieve passenger car levels of comfort in something as fast as an F1 car.

Also, there is no equation to directly show a relationsship between increasing traction and increased damping rates. If anything I could show characteristics of the tyres which suggest the opposite.

Tim

[ss_collins]

Is it possible to achieve the speed and acceleration on a Formula One car with the comfort of a family passenger vehicle?

No. You can make it more comfortable with softer seating but in no way comfortable. The forces acting on the body are the same, hard acceleration in any direction is uncomfortable, or at more extreme levels - fatal. Speed does not kill, but a sudden lack of it does - thats acceleration.

I am currently looking at the damping used on F1 cars however I don't really understand how less damping (harder suspension) increases the traction of a car through corners and over bumps. Can someone please explain this to me?

This is a huge topic. You sure you want to go into it? The further you look into tyres the more complex it gets, and you must remember the tyres themselves are dampers and springs. Also less damping does not always mean more traction.

Also I would like to prove this. Using data from both and formula one car and a normal car, is there an equation/formula that I can use that will show and increase of traction with a harder suspension set up?

Not really - what would be the best thing for you to do is read the unfair advantage by Mark Donohue, its a great introduction to vehicle dynamics. Pay particular attention to using a skidpad - or read this
http://www.zinio.com/pages/RacecarEngin ... 4223/pg-56

to be honest you should really have a good trawl through the Racecar back issues - they are all on Zinio - post 2004 and are cheap.

Never forget Newton

[Smokes]

How are you going to control the g Forces acting on the body accelarating and braking would feel like ur on a roller coaster ride. You should remember comfort and high performance do not go hand in hand.

You could do it in a similar way to trucks as ALL modern hgvs have a suspended cab so the chassis spring and dampers can take the loaded weight of the trailer. while the cab damps the NVH and road surface from the driver.


F1 car has a stiff supension to control the ride height and tranfer the wing loads to the tyres

If the rules were changed to mount the wing directly to the supension with active aero you could soften the supension to increase mechanical grip.

Currenty the mechanical grip is of an f1 car is dependant on the tyre pressure (type of gas) rubber compound side wall flex and down force.

You should really be looking at a rally car with a off road setup to understnd how the suspension really helps the tyres grip.

Best thing to do is find a copy of vehical dynamics by miliken. And change the subject to tyre performance.

[Just_a_fan]

You could do it in a similar way to trucks as ALL modern hgvs have a suspended cab so the chassis spring and dampers can take the loaded weight of the trailer. while the cab damps the NVH and road surface from the driver.

Chapman tried this very thing with the Lotus 88...

Of course the other teams didn't like it so it was banned. Chapman started to lose interest in F1 after that.

[autogyro]

You could do it in a similar way to trucks as ALL modern hgvs have a suspended cab so the chassis spring and dampers can take the loaded weight of the trailer. while the cab damps the NVH and road surface from the driver.

Chapman tried this very thing with the Lotus 88...

Of course the other teams didn't like it so it was banned. Chapman started to lose interest in F1 after that.

It was certainly the end of inovative F1 and the begining of the aero spec regulated formula that replaced it. I doubt Chunky would bother with it today.

[DaveW]

The posts so far are excellent.

I don't have the relationships you are after, but this might help a little.

To explain (hopefully). The points represent the "Comfort Rating" (CR), a measure of the transmissibility of road inputs to the driver's seat, obtained from rig tests of a broad range of road vehicles. The superimposed curve is a "trend line", representing an "average" of the points plotted as a function of heave mode natural frequency which is, in turn, roughly proportional to (spring stiffness)/(sprung mass). The scatter is large because tyre rates, damping levels, sprung mass integrity, etc. all affect the results, although damping levels are included to an extent because they will, on average, increase with increasing spring stiffness. A "luxury" road vehicle would be expected to have a CR value close to 1. You might be able to guess a typical value for an F1 vehicle, which would be expected to have a heave mode natural frequency of around 5 Hz.

[mep]

Is it possible to achieve the speed and acceleration on a Formula One car with the comfort of a family passenger vehicle?

When you ask for speed I think of top speed in a straight line.
F1 cars do about 300km/h.
No problem to achieve this with a passenger car and reasonable comfort.
I am sure you will find a few cars on the market that can do this.
The only thing you need for this is low drag and a very powerful engine.
Best would be to get rid of every downforce device so you can make your suspension soft.
It would be a typical American styled car.
The cornering abilities of such a car will suck.

To get similar acceleration values is a bit more difficult because you need downforce for this. At least at low speeds you can get it.
You need a good weight distribution, very sticky tires, low weight and a strong engine for this.

[jon-mullen]

Hey, Ian, welcome to the forum.

Your project sounds very interesting, but I was wondering (if you're not too far into it already) why you wouldn't prefer to compare the passenger car to a WTCC/BTCC/GT/WRC/V8 Super car since these are much more similar as far as geometry goes? You might also have a little more luck getting data since your everyday enthusiasts race cars like these whereas F1 is more obtuse and specialized and the teams are very secretive. I'd try an enthusiast group like the Spec E30 guys. A lot of them could probably tell you the difference between their daily driver E30s and the race prepped ones, and with the Spec ones you know exactly what they've done to them because there's published rules.

Best of luck.

[010010011010]

Hi,

If you do infact mean 'as fast as an F1 car' in terms of top speed then simply study the Bugatti Veyron. Its very comfortable and stabe even at 250mph, which is far quicker that an F1's top speed. It also can do the 0-100kmh sprint in about 2.5sec, which wouldnt be too far of F1 times since they arent build go under about 130kmh anyway.

Heres a Link to james may describing it at high speed (8:10)
http://www.youtube.com/watch?v=jk1t6S737Cs

[Belatti]

Hi,

If you do infact mean 'as fast as an F1 car' in terms of top speed then simply study the Bugatti Veyron. Its very comfortable and stabe even at 250mph, which is far quicker that an F1's top speed. It also can do the 0-100kmh sprint in about 2.5sec, which wouldnt be too far of F1 times since they arent build go under about 130kmh anyway.

Heres a Link to james may describing it at high speed (8:10)
http://www.youtube.com/watch?v=jk1t6S737Cs

The only acceleration where the Veyron is close to an F1 is the positive or... aceleration.

Just lift the throttle of an F1 car at 320kmh and you wont be far away to the max braking acceleration a Veyron may reach.

And I doubt its stable at 250mph, unless you are in a flat straight road... and dont you dare to move the steering wheel too much.

[Belatti]

Is it possible to achieve the speed and acceleration on a Formula One car with the comfort of a family passenger vehicle?

As I told in my previous post, maybe is it possible to achieve the speed and acceleration on a Formula One car like the Veyron does: in a foward direction.
For lateral accelerations I really dont think so.

I am currently looking at the damping used on F1 cars however I don't really understand how less damping (harder suspension) increases the traction of a car through corners and over bumps. Can someone please explain this to me?

There is a general misunderstood about what a hard or soft suspension is.
One thing is damping and the other thing is a hard suspension.

The vehicle mass and the springs stiffness is what determines suspension "hardness".
A bus with F1 springs wont be hard, but way too soft.
A bike with "soft" passenger car springs will be as hard as if it has no suspension.

Then, for the damping, the dampers or shocks. A suspension with no shocks will oscillate for a very very long time. The dampers are incharge of mitigating that oscillations as fast as they can.

Also I would like to prove this. Using data from both and formula one car and a normal car, is there an equation/formula that I can use that will show and increase of traction with a harder suspension set up?

A formula you can use to compare suspension "hardness" or stiffness is the one of the natural frequency.



where:
f = natural frequency [Hz or 1/second]
K = spring constant [N/m or Kg/sec2]
M = mass [Kg]

Mind that this is for an ideal mass/spring system and does not take into account many things, as tires, motion ratios to the wheel, etc.

Some aproximate benchmarks can be passenger cars arround 2 Hz and F1 above 5 Hz.

[010010011010]

And I doubt its stable at 250mph, unless you are in a flat straight road... and dont you dare to move the steering wheel too much.

Ya your right it was on the VW 'top secrect' test track, i.e a HUGE oval.

Also you need to put it into a special mode using an second 'special' key in order to go to top speed, and if you turn the wheel more than 15 degrees it automatically disengages and slows down

Still pretty cool tho

[iain_tk]

First off, the main thing to look at in comfort would be the transmissibility of the suspension. To reduce (vertical) accelerations at driver seat you want a very low transmissibility which requires low spring/damping rates. This is the primary reason for the harsh ride of a race car, ie much harder suspension.....

Tim

^not going to quote it all but Thank you Tim for spending your time typing this for me. I really didn't have a clue about the subject before reading what your typed but its really helped me write my report. Greatly appreciated

Can I also just saying sorry to not replying to everyones posts for a while, I really should have.

[iain_tk]

How are you going to control the g Forces acting on the body accelarating and braking would feel like ur on a roller coaster ride. You should remember comfort and high performance do not go hand in hand.

^Not going to quote it all.

Its not a very large report I am writing so I have only decided to look at the vertical acceleration of the driver only. In my conclusion I plan to explain the g-forces cause by the actual acceleration of the car would actually make it very uncomfortable. I can not thank you enough for suggesting that book, even though its at a much higher level than what I am studying I could understand the basic principles it talked about and have referenced it alot in my work .
Thanks for the help.