Spoilers increase downforce but increase drag.

The latter disadvantage to give greater grip from the extra downforce seems unavoidable.

 

I have thought of a possible way to reduce this disadvantage dramatically, without reducing the downforce. So here goes...

 

Design a spoiler which has a 2-position setting. The low acceleration/low speed setting is such that the spoiler provides little drag and hence downforce when it is not needed. But when you boot the car and need the extra downforce, the sudden movement (or high wind speed if cruising at high speed) forces the spoiler into position 2, where normal spoiler function of downforce and unavoidable drag are operational.

 

The advantages over a mechanically operated one are no extra mass or power losses and less to go wrong (one hopes!).

 

Is this cutting-edge or a geeky suggestion ??. Place your bets now !!;) ;) :D

But at low speed there is fvck all drag anyway??? ;)

For position 2 to be effective, you would need to have a car that has 0-60 capability of less than 1 second?

 

Its all to do with air speed passing over the spolier you see, so it would be useless at low speeds!

Originally posted by andyduff

But at low speed there is fvck all drag anyway??? ;)

 

Not quite true - there is a fair amount of drag at, say, 60MPH. Now at steady 60MPH, you don't need a spoiler to aid grip, but if you were going at 120 MPH, you would need extra grip and this would activate the spoiler ?

Originally posted by Nelson MainFella

Not quite true - there is a fair amount of drag at, say, 60MPH. Now at steady 60MPH, you don't need a spoiler to aid grip, but if you were going at 120 MPH, you would need extra grip and this would activate the spoiler ?

 

OK OK 60-120 mph in under a second then!

Originally posted by mxs

For position 2 to be effective, you would need to have a car that has 0-60 capability of less than 1 second?

 

Its all to do with air speed passing over the spolier you see, so it would be useless at low speeds!

 

OK (good point), so it is only effective at high speeds ?

 

So at low speeds, the small amount of drag is reduced slightly (v.minor advantage) while at moderately high speed acceleration and very high speeds, the spoiler behaves as normal providing grip. The major advantage would be at steady state moderate high speeds (motorway cruising?) when you don't need extra grip and can benefit from reduced drag (better fuel economy and power delivery).

 

Maybe this wouldn't work, but it seems logical to me. One thing I have thought tho' is that the new design to have 2 settings would need to maintain the downforce required from existing spoilers while also having a lower drag when in position 1 AND working in the way I have described - whether this is possible is hard to say - there may be undesirable compromises as cars with spoilers usually need all the downforce they can get and any reduction in that would probably not be worth reducing drag slightly at times which are not critical and infrequent (ie. racing conditions).

 

Also, as spoilers for road cas are often as much about aesthetics as functionality, then do people care ??:D

GEEK GEEK GEEK!!!!:D :D :D

 

Interesting idea (as usual Nelson) but how would you actuate it at different speeds without some sort of electro mechanical aid? If it were purely mechanical how would it know when to go up/down (reliably)? Sounds like a lot more mass involved than just a speed sensor and a couple of servos. (doesn't the VW Carrardo have something similar?)

 

Could be noisey too with a bloody great 'fin on springs' clonking around.

 

Just my initial thoughts. Now ready for someone to blow me out of the water (or just being blown would be nice:D :eek: )

Wing forces are calculated using the following formula:

 

F_drag = 0.5×span×cord×coeff. drag(angle+angle of offset)×Air Density×Air Velocity squared... (angles in Rads)

 

The downforce is basically the same calc. Air Density is around 1.225 (kg/cu.M).

 

Wings even at 0 degrees of attack generate LIFT.

 

After you have posted some details I'll tell you if what you propose will work/be of value.

Porsche 968 turbo (I think) has a progressivley active rear tail spoiler, which works out speed versus downforce required to keep the rear wheels at optimum contact with tarmac, so Nelson, ''been there done that mate!''

Originally posted by mxs

Porsche 968 turbo (I think) has a progressivley active rear tail spoiler, which works out speed versus downforce required to keep the rear wheels at optimum contact with tarmac, so Nelson, ''been there done that mate!''

 

But my idea is to have one which is a kind of floating wing which moves into different positions based on wind speed - not mechanically activated, or using springs. There is extra (undesirable) MASS from a motor etc. as on the Porsche cars. As no race cars use such a motorised setup, I am assuming there are disadvantages which outweigh the benefits. The setup I propose would (hopefully) have no disadvantages and therefore be an improvement ?

Originally posted by The Devil

After you have posted some details I'll tell you if what you propose will work/be of value.

 

I'm not gonna make nething - just toying around with a theory. Think of it like a complex 3-dimensional shape which (over a certain horizontal wind speed) is moved into a temporary position which actually increases downforce. The position is like a temporary setting only achievable by the force of the wind laterally. When the wind speed is below a certain setting, the spoiler blade 'falls' back to position 1(the default) where drag is minimised.

 

I'm envisgaing a 3-d blade resing in 2 brackets (1 at each side). It would need to be very smooth to allow free motion of the internal blade.

Originally posted by Nelson MainFella

But my idea is to have one which is a kind of floating wing which moves into different positions based on wind speed - not mechanically activated, or using springs. There is extra (undesirable) MASS from a motor etc. as on the Porsche cars. As no race cars use such a motorised setup, I am assuming there are disadvantages which outweigh the benefits. The setup I propose would (hopefully) have no disadvantages and therefore be an improvement ?

 

mmmmmmmmmm....

 

I still fail to see how you are going to achieve this Nelson.

 

As you will need some type of motor to trim the wing, thus optimising down force...thats why planes have adjustable wing arrangements

 

:rolleyes:

So you are talking about an automatic adjustable spoiler.?

 

 

Stuart

Originally posted by mxs

mmmmmmmmmm....

 

I still fail to see how you are going to achieve this Nelson.

 

As you will need some type of motor to trim the wing, thus optimising down force...thats why planes have adjustable wing arrangements

 

:rolleyes:

 

The blade can move forward and backwards in a channel between the brackets which is sloping (ie. higher at back and lower at front). The force of wind from the front cuases the spoiler to be pushed towards the back of the channel. this in trun alters the lateral (front of car) profile of the blade, thus increasing downforce. when the wind is belwo a certain level, the weight of the blade causes it to assume original position which adjusts the blade profile to reduce drag (be default due to gravity).

 

Remember there will be some drag in the No1 position, as the increas in this lateral drag activates the spoiler into position 2 where drag is increased - the spoiler cannot assume then a position of least resistance, as the lateral force is keeping it in the rear (no.2 )position. The extra drag and downforce is unavoidable in position 2 -t he spoiler cannot assume a 'flat' low resistance profile due the the angle of the blade channels in the side brackets.

 

Does that make sense ??:D

Originally posted by SRRAE

So you are talking about an automatic adjustable spoiler.?

 

 

Stuart

 

Yes, EXACTLY.;)

Correct me if I'm wrong, but spoiler by their design disrupt the air flow around them. Would the continualy changing air currents not make the spoler change position continiously thus hampering the drive?

Originally posted by mtrotter

Correct me if I'm wrong, but spoiler by their design disrupt the air flow around them. Would the continualy changing air currents not make the spoler change position continiously thus hampering the drive?

 

I don't think so, as the spoiler enters No.2 position after a pre-define air speed. If the air speed is reduced, then you don't need the spoiler in pos. 2. If you were on the border, the movememnt of the spoiler back and forth would probably not be a problem, and definitley wouldn't hamper the drive as the downforce would simply be altering slightly.

But surely a static spoiler already achieves this by creating a downforce at higher speeds i.e. above 60 miles per hour, as lesser speeds do not create down force...it is all relative, hence the Porsche design, as it only becomes active at higher speeds!

 

But having said that, I can see what you are trying to achieve...any chance of a diagram?

Fair enough.

 

question, how would you ensure that the spoiler moved by the same amount on either side?

 

I figue that cross wind, dodgy runner or simply dirt will change he forces acting on the spoiler and to get each side exactly the same would be tough.

So what you want is really a normal spoiler which is virtually flat when you are at low speeds and then gradually increases the angle with speed.

 

Porsche has it I believe. But they can do it as the spoiler is a huge thing ontop of the rear of the car. It you get ones on stands. (Lets face they look a little silly on normal cars but they are the best performing ones.) You will need to have quite big motors on it. The Firstly to move the spoiler, and then to be able to move the spoiler against such a strong force.

 

If you can do it you can have different settings like. Low drag so the angle doesnt increase as much or as quick. Or a racing setting which gives you plenty of downforce for longer.

 

If you want to be really clever and if the motors can take it. Have a sensor the the brake so when the brake is pressed the angle is increased to the max to slow you down quicker.

 

Stuart

Originally posted by SRRAE

So what you want is really a normal spoiler which is virtually flat when you are at low speeds and then gradually increases the angle with speed.

 

Porsche has it I believe. But they can do it as the spoiler is a huge thing ontop of the rear of the car. It you get ones on stands. (Lets face they look a little silly on normal cars but they are the best performing ones.) You will need to have quite big motors on it. The Firstly to move the spoiler, and then to be able to move the spoiler against such a strong force.

 

If you can do it you can have different settings like. Low drag so the angle doesnt increase as much or as quick. Or a racing setting which gives you plenty of downforce for longer.

 

If you want to be really clever and if the motors can take it. Have a sensor the the brake so when the brake is pressed the angle is increased to the max to slow you down quicker.

 

Stuart

 

 

I said no motors ;)

I dont understand how the spoiler will be able to move then.

Originally posted by SRRAE

I dont understand how the spoiler will be able to move then.

 

The wind:D;)

so basically like the f1 cars of two or so years ago?

on the straights the rear wing would flex and create low downforce?

then under load in corners it corrected itself. was banned lol.

Originally posted by 300z

so basically like the f1 cars of two or so years ago?

on the straights the rear wing would flex and create low downforce?

then under load in corners it corrected itself. was banned lol.

 

Indeed!

 

Possibly a complex system of lightweight ropes and pulleys are in order. Carbon fibre pulleys with 50lb fishing line, lightweight I think everyone will agree. Smoke and mirrors may also be used to change to angle of the spoiler, but the mirror will have to be a chromed perspex mirror :)

Originally posted by Ay3388

Indeed!

 

Possibly a complex system of lightweight ropes and pulleys are in order. Carbon fibre pulleys with 50lb fishing line, lightweight I think everyone will agree. Smoke and mirrors may also be used to change to angle of the spoiler, but the mirror will have to be a chromed perspex mirror :)

 

 

Great idea! You could also attach a sail to the ropes and pulleys and get a few extra mph. Would be fantastic fun 'tacking' accross the M4!!:D :D :D