real function of spoiler starts beyond what speed..?

It fulfils its main design function at any speed... to attract chicks bro!

fully sik

On a (slightly) more serious note, a spoiler uses an aerodynamic foil (like an inverted wing) to provide down-force over the rear axle to give better traction. This aerodynamic force is proportional to the square of the car's velocity (relative to the air moving past the spoiler). Hence, it doesn't 'start' or 'kick in' at a certain speed, as I've heard many people say - its always functional, but its effect becomes increasingly noticable at higher speeds, due to the V^2 relationship. The benefits are most noticable during acceleration and cornering at higher speeds - traction is maintained past the limit where the car would otherwise lose more of the power that its throwing down onto the track - so you need to be traveling close to the limits (as in... fast) of the stock standard car to see the spoiler start to fulfil its primary function.

Cheers,

TinTin

Think about your question. Function would vary depending on the shape and size of the spoiler, shape and size of the car, relative location of spoiler to body, wind speed, direction, etc. etc. etc.

TinTin is correct. for 99.99999% of the applications in the world, it's for style.

The real function of the spoiler is seen at racing speed.

Gud day to all..

The reason why I asked this question is, I saw a video of "Buggati Vayron" running on racing track (with spoiler completely stick to the car body) n after having certain speed ,the spoiler comes up n again after gaining some more speed it changed its inclination...may I have any clarification for thiss..??

Ronak Shah

India

Hi Ronak,

Yes I'm familiar with the veyron. The spoiler hydraulics actually have their own radiator! Okay, so at normal speeds it doesn't need the spoiler. At track speeds, it uses the spoiler to provide additional traction. When its travelling even faster, it tilts the spoiler to change its 'angle of attack' (look that term up), in order to provide more aerodynamic force. The down force is (roughly) linearly proportional to the aerofoil's angle of attack.

Regards,

TinTin

As you said Veyron spoiler has its radiator, operates only beyond such "Track Speed"…, just wanting to know that figure of such speed..? is there any long n tedious calculations for that. Any basic principle,,

well, its actually the driver who activates the spoiler (actually, you have to stop the vehilcle and use a key to release it). The tilting occurs automatically, but I don't know the precise speed at which it changes its angle of attack. It probably varies it with speed. There are no calculations you can do, as the problem is ill defined. If you asked "at what speed does the veyron's spoiler produce 1000N of downforce?" - then you can calculate it, if you had the spoilers specs:

1. Coefficient of lift (Cl) - dependant on the spoiler geometry and 2:
2. Angle of attack (α) (because it varies, you need a plot of α vs speed) - note* this variable is absorbed in the coefficient of lift variable - ie Cl varies (not exclusively) with α.
3. Wetted surface area of the foil (the foil's area preceeding the fluid separation points)

Lift/downforce (N) = 0.5*(air density)*(speed^2)*(wetted surface area)*(Cl)

therefore:

speed = (2*(Lift/downforce)/((wetted surface area)*(Cl)*(air density)))^0.5

almost undestood...

thanx..

no worries - note that when i typed "lift/downforce" - iIdidn't mean "lift divided by downforce' - I meant "lift" or downforce (which is just the lift of an inverted wing, or spoiler). Different names for the same thing. Look up "aerodynamic lift equation" in google to see some explainations and diagrams of what all the different variables mean.

Ohh k…well apart from this can you give any suggestions on my que. tital "Bicycle wid boosters.." it was posted on 17^th of July.. I really want to have such kind of system..

a cycle wid boosters...isn't it amazing..!!

Hey - welcome to CR4! Nice avatar btw - i'll get back to you about the rocket bike later - gotta go to bed now.

catchya!