17 replies to this topic

[TecnoRacing]

Just a stupid question from someone who knows little about aerodynamics...
Of course movable aerodynamic devices are banned but theorethically would there be any effect of having a rudder (or series of them)linked to the steering. Would they just generate drag or could they be worked to actually increase cornering forces? Or What about say a pivoting front/rear wing?

In general I'm curious about the effects generated by vertical surfaces on race cars (the finned d-type jag, and Champcars of the mid-nineties spring to mind.) I assume they are intended to increase high speed stability, but what actually occurs when the cars are cornering?...

[GregorV]

Indeed such surfaces would increase cornering forces without putting strain on the tyres, but they would probably be a waste. Racing tyres generate a grip coefficient that is higher than one, so, at least in theory, for the same drag it's more efficient to direct any "lift" forces downwards, as the additional lateral force produced by the tyre would be larger than the "lift" produced by the surface itself.

[mat1]

And they are forbidden, at least in Formula 1.

It is a movable aerodynamic device.

mat1

[jimclark]

mat1 - fer is aware that they are..'stated so in his first sentence.

GregorV - What would all in your post after the first comma have to do with rudders?

"Would they just generate drag or could they be worked to actually increase cornering forces? Or What about say a pivoting front/rear wing?"

Simply put, they would be advantageous as the drag would be minimal while flat on straights and producing the additional cornering forces whilst being utilized in the corners and under braking....just ask Jim Hall (father of the movable devices on his Chaparrals in the 60s).

Proof positive requested? Look at just about any aircraft...

[Clatter]

Originally posted by jimclark
Proof positive requested? Look at just about any aircraft...

Aircraft use the rudder to control yaw, it does not turn the aircraft.

[phantom II]

Old cars didnt have downforce. The tires keep directional stability now.

Originally posted by fer312t
Just a stupid question from someone who knows little about aerodynamics...
Of course movable aerodynamic devices are banned but theorethically would there be any effect of having a rudder (or series of them)linked to the steering. Would they just generate drag or could they be worked to actually increase cornering forces? Or What about say a pivoting front/rear wing?

In general I'm curious about the effects generated by vertical surfaces on race cars (the finned d-type jag, and Champcars of the mid-nineties spring to mind.) I assume they are intended to increase high speed stability, but what actually occurs when the cars are cornering?...

[Wolf]

IIRC Mercedes tried that on car they planned to run in Indy in early fifties- the results in tests were promising but the project was abandoned because of another reason...

[jimclark]

"Aircraft use the rudder to control yaw, it does not turn the aircraft."

Understood. I would not expect the rudders to turn the car

By stating "Simply put, " I was indicating that I was keeping the answer as brief as possible. I'll elaborate a tad.

If appropriately sized rudders could be afixed front and rear, they could counter some of the forces
acting on the tires allowing the tires to do the same amount of work, thus achieving a higher cornering speed.

A good thought fer312t...I tried using the idea many years ago whilst racing slot cars...tried attaching a rudder activated by the pickup shoe as the car slid out at the rear while cornering. Too complicated a linkage and the weight of our cars were too high to get any affect from the size rudder that could be practically used... On real cars today, however, I think there would be rather significant gains.

[GregorV]

Originally posted by jimclark
GregorV - What would all in your post after the first comma have to do with rudders?

Efficiency If you were to have any moveable device that you wanted to produce extra lateral forces, you'd better direct those forces down instead of sideways, as it will produce larger gains.

[imaginesix]

Originally posted by jimclark
A good thought fer312t...I tried using the idea many years ago whilst racing slot cars...tried attaching a rudder activated by the pickup shoe as the car slid out at the rear while cornering. Too complicated a linkage and the weight of our cars were too high to get any affect from the size rudder that could be practically used...

Sounds like fun, but did you try a fixed rudder? Seems to me that for the weight of a slot car, if you can stick a fixed rudder out far enough behind the car it should be impossible to spin.

[Paolo]

A vertical surface at the rear could be useful, for example, in order to achieve stability if for some reason the vertical forces' resultant is much ahead of the CG. For example, if for some reason I want a big front wing and a small rear wing but I don't like the idea of spinning on straights...
Also, it can be useful on high speed tracks like Indy, where one could benefit from a yawing torque opposing any kind of oversteer.
I have seen vertical fins on F3 cars, in the late 80's , running at Monza with no wings.

[desmo]

IIRC, Wright in F1 Technology states that the RWEPs provide significant yaw stabilization against large OS angles.

[jimclark]

d - "RWEPs provide significant yaw stabilization against large OS angles."

Wonderful...but what in bloody 'ell are RWEPs and OSs?????

Tanx in advance...


GregorV - Efficiency indeed...why inflict more stress on the tyres and suspensionwhen you can just counter the lateral forces directly thru the use of air ???


imaginesix - "for the weight of a slot car" sounds as tho you're talking present day slots...I'm referring to approximately '68 when brass rod and/or plate sidewinder sportcar chassis for the add'l weight (I'm guessing about 1/2 to 3/4 of a pound...'haven't taken the time to dig one out of storage for weighing) and distribution were the way to go to.

[desmo]

Sorry, was too lazy to write it out in longhand, Rear Wing End Plate & OverSteer.

[jimclark]

Errrrgggg...
But of course....I just didna see...

[GregorV]

Originally posted by jimclark
GregorV - Efficiency indeed...why inflict more stress on the tyres and suspensionwhen you can just counter the lateral forces directly thru the use of air ???

Assume you have two kiloNewtons of additional aerodynamic force. If you apply it laterally, you get exactly the same ammount of additional lateral force. If you now direct the aerodynamic force downards, and the (differential) grip coefficient of the tyres is, say, 1.5, the tyres will be able to produce an additional three kiloNewtons of lateral force, which is surely more than two kiloNewtons if you do aerodynamic in the lateral direction directly.

[jimclark]

'Unnerstood...but again, what of the add'l tyre wear and beefier components that would not be dictated by rudders? Enuff....

[jimclark]

Of course, this is just a straight line, but here is fer312t's rudder in use on an F1 car.

click on: http://www.bonnevill...sh/default.aspx

then go to NEWS, and the article of 6 November 2005, BONNEVILLE TEAM CRACK 400 IN MOJAVE
The rudder is mentioned in the 8th and 9th paragraph.