New thread: powered aero

[pookie]

How about the "outlaw sprint cars" and their movable wings ,2 of them. They are moved mechanically, some times every lap.Combined with Tom. G. suggestion of using the flatbottom cavitation plate pedal override to control the adjustment of the wing and the sprint car tech of moving the wing forward or backwards seems to me to be a natural in LSR when your looking for more traction capability.

[Blue]

Any power used for the downforce should come from the "prime mover" engine that is regulated by the class rules. 

It has been years since I thought about the 2J Chaparral.  Correct me if I'm wrong, but weren't the fans powered by separate engines?

Getting to your point, Eric, if you were to drive a hypothetical LSR vehicle's active circulation control device off of the engine/drivetrain, you would be burdening the engine at precisely the time that you need peak horsepower for speed.  A  variable speed transmission on the device might work (or pitch control?) - especially if the vehicle design does indeed create greater downforce at greater speed, but transmissions eat power, too.

Possibly a design that would completely shut down the active circulation control at a point that aero downforce takes over?   

Again I apologize for not making my idea as clear as i should have.  Yes, the active circulation fans would run during times when the vehicle is traction limited, not power limited.  The idea came from the fact that many LSR vehicles seem to be traction limited under acceleration and some are even traction limited at record speed.

[roygoodwin]

What about using the exhaust in something like a jet pump ( see http://www.animatedsoftware.com/pumpglos/jet_pump.htm )

I believe that aircraft have used what is called exhaust augmentors to help pull cooling air thru the air cooled engine.  Couldn't the same thing be done with the air under the vehicle ?

Probably easy said, hard done tho.

roy

[Jonny Hotnuts]

Blue, I could have sworn you at one time during a discussion of "flat VS. air under" you said flat was a more ideal configuration.

I am anti flat bottom due to:

1. Increased viscous drag vs air under designs
2. Pitch sensitivity with flat bottoms
3. The sharp edge bottom flat cars WILL catch salt and violently tumble if there is a roll over (whereas a round body will be more apt to slide).

Was it you that mentioned that you thought the flat bottom designs were better?
I have read 2 posts lately were you said otherwise......did I read wrong in the past?


___________________________________________________________________________________


I had mentioned here a long time ago that I thought that someone could use an active spoiler system (on any vehicle class with a spoiler) to increase the angle with high speed actuators, generating more DF, if wheel speed from the drive wheels was faster than non powered wheels. It could also lower the spoiler angle if no wheel spin was detected after a few seconds. This would be a rudimentary form of TC. Still think it’s a good idea but it sure seems like a new rule would come out the next year after it was used.


~JH

[Blue]

JH- I did mention "sooth belly" and "diffuser" in past posts, I also came down against "skirts".  I do not favor flat bottoms, just the opposite, and while downforce can be increased with low ground clearance, the force varies dramatically for very small changes of pitch angle and ground clearance.  The divergent angle in a flat bottom may create downforce with very low ground clearance, but it can easily create a large amount of separation and drag.  Because of all this, I believe we should get up off the ground so that downforce and drag are less susceptable to suspension.  The fastest wheel driven car of all time, Turbinator, had rounded edges and a fair amount of ground clearance.  It went faster on less power than many of the other open class streamliners have.  IMO, drag trumps downforce.

[Jonny Hotnuts]

I will look for the topic where I got this in my head. In fact it may not have been you that said it.

The fastest wheel driven car of all time, Turbinator, had rounded edges and a fair amount of ground clearance.  It went faster on less power than many of the other open class streamliners have.  IMO, drag trumps downforce.

This is true but I feel a better example is illustrated by a flat VS. round using identical powerplants. I must admit that I have taken note of the speed differences in ALL classes of streamliners (car and MC) using H engines and while some rolling resistance friction can be attributed to 4 wheels as apposed to 2 this comparison clearly also supports your statement.

If you suppose I may be headed that direction your assumption would be correct.

~JH

[Blue]

If you suppose I may be headed that direction your assumption would be correct.

Just put some tail on it to make up for that nose;  it is better to be facing the finish line at speed instead of the start!

[Rex Schimmer]

Could you take the aero down force device, wing or spoiler and hinge it at the very front, and a aerofoil's center of lift, down force in our case, is approx 1/3 of the chord from the front of the aerofoil. Then connect a spring/dampner at the very rear of the wing, you now have a lever system with the spring/dampner keeping the wing at the set angle of attach. Now if you wanted say 500 lbs of down force maximum, you would preload the spring/dampner so that at 500# of down force the spring would start to compress, lessening the angle of attack and maintaining the amount of down force at 500#. You would need to do some analysis of the loads and the spring rate vs down force/angle of attack of the wing and I would think that the dampner would need to be pretty heavily dampned in both directions to prevent any type of flutter , but the system should be stable and it would limit the down force and therefore also the drag of the  wing as you reached max speed.

Just a thought of a way to do it without going to electronics.

Comments?

Rex

[interested bystander]

Doug Kruse did the spring/damper deal on the rear wing of the Jim Dunn / Kruse streamlined dragster circa '75.

[floydjer]

Anyone remember Tom Mc Ewen`s T/F car with the spring loaded wing that flattened out at speed? Talk about bass-ackward thinking!! J.B.

[Blue]

The most radical movable aero device I can think of in LSR was Arfons' front wing.  He linked it to the front suspension so that as the nose lifted the forward downforce increased.  Statically, this is fine.  Dynamically, it could get into a fatal oscillation if it starts to bounce.

[Breck]

My thinking on this..  I agree with the idea that you should set minimum downforce to the targeted max speed,  (how much down force you need to keep your rear tires hooked up and front end just down at max speed) with the wings at their most efficient (best angle of attack, smallest necessary cord, flaps at 0, maybe even hight change for front spoiler,

{ front spoiler genrates most -lift in ground effect, drag also, higher off the ground, less lift, less drag})
http://www.strangeholiday.com/oops/stuff/annurev.fluid.38.050304.092016.pdf

Seems like changing angle of attack would increase drag, decrease efficiency, more than other choices, might lead to stall at some point.  What is it.. 2/3rds lift comes from pressure differential lift (in cars the air under the wing) and 1/3rd from impact lift (the air over/ into the wing).?

Flaps on the other hand change the shape of the wing, basically given it a thicker cord, the flaps could start fully deployed and progressively lay down with speed.  This could be controlled by computer, using wheel rotation (ABS sensors).  And as you slowed down at the end of the run, you down force increases to help slow you down.  Electronics aren't all bad, or I wouldn't be picking your brains from my computer right now. 

I am _no expert_ but this is what has been on my mind.  Learning as fast as I can.

Breck

[maguromic]

Flaps on the other hand change the shape of the wing, basically given it a thicker cord, the flaps could start fully deployed and progressively lay down with speed.  This could be controlled by computer, using wheel rotation (ABS sensors).  And as you slowed down at the end of the run, you down force increases to help slow you down.  Electronics aren't all bad, or I wouldn't be picking your brains from my computer right now. 

I am _no expert_ but this is what has been on my mind.  Learning as fast as I can.

Breck

You would be better off using load cells on the suspension / shocks to add more wing when the system knows the suspension unloading.  I think Jim Feuling controlled the front canards on his stream liner the same way.  Tony

[dw230]

"Still think it’s a good idea but it sure seems like a new rule would come out the next year after it was used."

Nutz,

Why would you say that? The only reason I can think of right now that a rule outlawing the devices in this discussion would be proven safety issues. If, in their current stage of development, a movable aero device failed or caused an accident would a rule be written to stall the development. This is the same as the multiple plates on a spoiler as discussed in another thread, too much was read into the rulebook as to legality.

A perfect example of reading the book occured last Friday night. I was asked about the new rule which mandated SFI rated blower bags. No rule is in effect, the only mention is in section 3.X which mentions a SFI type bag if the blower is located next to the driver. This rule has been in place since approx. 1991 when the late Bruce Johnston was the tech guy.

DW
 

 

[John Burk]

High aspect tapered wings can have drag of under 3% of down force making adjustments during the run less important .

http://www.motorsportsinnovations.com/Bvile-pics/rw-full.jpg