Landracing Forum
Bonneville Salt Flats Discussion => SCTA Rule Questions => Topic started by: bbarn on October 18, 2012, 07:42:24 PM
-
Can we use a computer to control the flap on our streamliner (NACA 66 Special - A/BGS) to adjust down force or must it be a manual process? Specifically we are looking for an interpretation of rule 2.Q.
-
Wouldn't it be better to use the computer to collect downforce data and manually adjust as speed and traction require.
I would expect you would need 3 computers dedicated to flap control if you went that way. A primary, a secondary and one to ensure they were in agreement prior to moving the surface. If you don't think it is necessary, maybe a little overkill, check into fly by wire airplanes. You might want to do a little analysis into worse case malfunctions, oscillations, how to control and filter them.
-
Already did the worst case scenario malfunction. We are fine. We have a couple of fail safes built in. Wing can never make lift as hard stops will stop the flap from going negative. Also flap will start off with high angle and decrease as speed increases. As flap loses angle of attack, a resettable ratcheting system will keep it from regaining angle and overloading the tires.
-
2.Q Computer
Vehicles may be equipped with a computer which affects engine operations ONLY.
You could argue that the wing changes the load on the tires and is part of your engine traction control system.
Or skip the computer and build an electronic control.
-
2.Q Computer
Vehicles may be equipped with a computer which affects engine operations ONLY.
You could argue that the wing changes the load on the tires and is part of your engine traction control system.
Or skip the computer and build an electronic control.
That's why we are askiing the question, we'd like to know for sure before we execute a plan. There are a few different ways to accomplish the task, we just want to make sure the one that is picked is legal.
-
2.Q seems pretty black and white to me.
-
Wow, does that mean when I carried a laptop in the car to be a data logger it was illeagal? Guess I better look harder at the book :|
-
And make sure that you've stripped the ABS out of your production vehicle!
Mike
-
2.Q seems pretty black and white to me...
No. It's a poor rule. I spent my whole career in electronics- the final couple of decades in software engineering. The term "computer" is too ambiguous in this context.
-
Data logging doesn't affect the operation of the engine. it just records what happens so that a revised tune up can be applied.
Pete
-
And make sure that you've stripped the ABS out of your production vehicle!
Mike
WOW! any newer production vehicle has a computer controlled transmission if it is an automatic.
-
Several years back I "explored" the idea of a spoiler plate that changed angles underway, based on the feedback I got--my conclusion was that if I changed the plate with air cyls. whose controls were actuated by gear shift lever POSITION changes---I would not violate "the spirit" of the rules in place at that time.
-
Wow, does that mean when I carried a laptop in the car to be a data logger it was illeagal? Guess I better look harder at the book :|
Stainless, see the next rule down from 2.Q: 2.R Data Recorders.
No. It's a poor rule. I spent my whole career in electronics- the final couple of decades in software engineering. The term "computer" is too ambiguous in this context.
I'll admit that the verbiage is antiquated but the intent of the rule is still inherent and fine. I don't think computer controlled active aero is allowed.... or at least that's what I'm taking from this rule. If computer controller active aero is allowed, bbarn will need to get verification from the rules committee. Obviously the association allows computerized trans control and I've personally yet to see a race vehicle show up with ABS but have never heard of anyone having to remove their ABS controller so perhaps the rule needs some "word-smithing" but I'm not aware of anyone having previously used a "computer" to control their aero package. Whether that's because no one's tried to do it before or because it's illegal, I don't know. Again, maybe someone has used computer controlled active aero.... I'm just not aware of it.
A conversation has begun about better and more current definitions and descriptions for all this "computer" and "EFI" stuff (mainly as it pertains to the vintage category but it will probably pour over to other things as well). This is why we have the rule change procedure that we do. If you're an SCTA member and you don't like how a rule is written (or want to introduce a new rule or whatever) then you get the opportunity each year to propose a rule change. If computer controlled active aero isn't currently allowed (maybe it is, I don't know) and someone thinks it should be then by all means submit a rule change proposal. Or you can just argue about it here. :wink:
-
Art Arfons jet car had a linkage controlled wing connected to the suspension that changed the wing angle with any lift.
-
Several years back I "explored" the idea of a spoiler plate that changed angles underway, based on the feedback I got--my conclusion was that if I changed the plate with air cyls. whose controls were actuated by gear shift lever POSITION changes---I would not violate "the spirit" of the rules in place at that time.
Bill, the Joe Law lakester used a mechanically controlled wing much in the way you've described and it was completely legal.
-
Strictly speaking, a servomechanism is not a computer.
BTW, the first high wing that Jim Hall used on his Chaparral Can-Am car was mechanically linked to the rear uprights; it changed its angle of attack as the ride height changed.
Regards, Neil Tucson, AZ
-
I would imagine that most the people who drive today rely on several computers for safety. If your car is newer than 1989, you have safety computers.
Today's cars can have up to a dozen (or more?) interconnected computers that all have some safety features to them. None of our family cars have fewer than 8.
Some have computer controlled downforce and suspensions. More than you think BTW, not just racecars, some are just family cars.
Why did the auto MFR's do this? Same reason they put in electric starter motors and windshields. Safety.
Best way to survive an accident is to NOT CRASH. No amount of post-crash safety equipment in the world can protect you from a crash.
It just depends on how you define safety. Is safety surviving a crash? Or is safety the whole package?
-
Just to try and keep this thread on track. We are looking to use a computer to maintain the flap angle on the wing of the car. There is a computer program that will evaluate the speed of the vehicle and set the flap to a pre-determined angle. The intent is to keep the down force at a constant through the entire run.
There are alternative manual methods of performing this same function, but the simple question remains, can a computer be used in the streamliner class to move aero devices? We aren't looking to circumvent an existing rule or make a new one, we are just trying to identify the boundaries.
-
You might check with Nivek R&D, best via email, to see if he has a program that might do what you like. He's doing some aviation things and builds the Zeus modules for some types of racing.
-
Can we use a computer to control the flap on our streamliner (NACA 66 Special - A/BGS) to adjust down force or must it be a manual process? Specifically we are looking for an interpretation of rule 2.Q.
Chief Car Inspector Steve Davies flyingkiwi97@aol.com (714) 671-9454
Car Technical Co-Chair Lee Kennedy Lee.Kennedy@AVMetrics.net (805) 522-8134
-
Maybe I wasn't specific enough in my last post about servomechanisms-- it is not necessary to use a computer to adjust a wing so that it provides a constant downforce. Here's how to avoid using any computer at all:
1. Sense the position of a rear upright in relation to a fixed point on the chassis; this change in length will be proportional to the rear spring compression-- which is a function of downforce.
2. Amplify the difference between that sensor output and an output from a voltage reference.
3. Apply the amplified difference voltage to a power amplifier capable of driving a DC motor or linear actuator connected to the wing.
4. The feedback from the sensor will drive the motor to adjust the angle of attack so it will keep the ride height constant-- providing the feedback is negative. If it isn't, just reverse the two wires to the DC motor.
5. The ride height can be adjusted to be the same as the static ride height (no downforce) at speed, lower ride height (downforce), or higher ride height (lift) by setting the reference voltage.
6. Use enough gain in the amplifier so that the loop error is small but not so much gain that it is unstable (oscillates). This is a simple feedback control system but it can be made a bit more complicated by adding integrators and differentiators to form a "PID" loop.
7. At rest or at low speed, with the reference set for downforce the wing will be at maximum angle of attack because the servo is trying to get downforce without any air passing over the wing. As speed increases the wing will assume whatever angle it takes to generate the downforce that you've asked for.
Voila! ...no computer. Now whether this would be legal is another matter. :-P
Regards, Neil Tucson, AZ
-
Neil,
That's very ingenious but we have no rear suspension. :-(
It would be very complicated to add suspension to our current design.
-
I can understand why this would not be legal in the lower production car derived classes but the "special construction" Streamliner and Lakester class is the place where innovation is encouraged. With today's computer availability, I don't understand why this rule applies to the Special Construction category.
We do not need the rule to be changed for our mechanism to be successful but I'm trying to make the driving job as easy as possible.
If the rule cannot be changed, we will use a the dash logger to tell us when to reduce flap angle via indicator light. As speed increases, an indicator light will be activated on the dash and I will press and hold a button on the left side of the steering wheel until it goes out. I will need to repeat this several times during a pass.
-
Modify the wing mounting to incorporate a load cell. That will give you a direct reading of force.
-
Dean's suggestion would also give you the sensor feedback to the servo.
Regards, Neil Tucson, AZ
-
Again, great idea but there is no good place to put the load cell as the wing is integral with the body. We would love to gather data on just how much load wing is generating. We will have to rely on the cfd. Fortunately, this is something that cfd does well.
-
Rob,
what mechanism is being used to move the flap?
could you sense loading on the flap itself and then change attitude?
The issue I see is the wording in the rule book, it specifies no computer control other than engine.
By definition, a computer is any device that reacts with a input or series of inputs to control something.
Many ways to skin this cat, especially with todays small PLC controllers.
-
We will be using a dc linear actuator to move the flap.
We could monitor the load on the flap but it will not be very linear to total loading on wing. I have also thought about ways to spring the flap in the up position and let the air try to flatten it out at high speeds. The more I have learned about airplane controls, the more I understand why this won't work very well.
-
Traction control was illegal in the past. It was made legal because so many racers were using it and
SCTA had no way of even determining if you had one.
I think that you should head in the direction you would like to go and call it good.
Ok, if the load cell on the wing won't work, then move it to the axle attach points. At some point you transition from composite to metal and can read the load. Real load feed back with CFD beats CFD computations alone any day.
-
Dean ---is this the same guy who took issue with the water tank vent system spilling water in to the slip stream :-o--lol
-
Having seen Rob's car the addition of a load cell some place on the rear axle would be difficult to impossible, there might be a chance to use a strain gauge on the real axle housing which would require some load testing to scale the gauge and then a standard type of closed loop controller can be used. It would probably require a displacement transducer on the screw actuator for stability and accuracy. Another method would be to use the surface speed differential between the front (undriven) wheels and the rear drive wheels and then close the loop around the difference to maintain traction. This control could not be very exact as you would be controlling tire spin by trying to control down force through the actuation of the wing flap, lots of uncontrolled variables and probably a pretty slow system.
You could also do a type of open loop control using calculated down force vs. speed and flap angle, Eric should be able to generate these numbers for you. You could then use this "map" of down force vs. speed and flap angle to set the flap angle for the speed you are running and the down force you require. It would require a position feed back on the actuator but it would probably be the simplest system. Similar to how present day top fuel cars set their clutch lockup. You could then increase or decrease down force using a simple off set to the down force map to "tune" the system.
Lots of avenues to go down and a pretty challenging problem.
Rex
-
Don't know the specifics of you gear ratios etc Rob.
Is it as simple as having an angle for each gear or is that too coarse?
I know this doesn't answer your question.
I wouldn't be trying to control the angle with a feedback loop, it's another variable to tune that I can't see the benignity for.
Cheers
Jon
-
Rex, I think you hit the nail on the head in relations to the speed vs flap angle map. The positioner that we have actually has a 0-5v sensor so it is pretty easy. The FAST dash-logger has a configurable output with 16 x 16 map that we could program to give us what we need.
I'm just concerned about rule 2.Q.
-
One other possibility would be to monitor pressure differential between the top and bottom of the air foil, and control angle to maintain a specific pressure differential (ie total down force) for each speed.
As above you would need some wind tunnel or computer modeling to figure out what down force you want at each speed and build a down force vs speed map.
Larry
-
If this was easy ANYBODY could do it.
In the wing was set up neutral with minimal drag and you have no wheel spin then abracadabra done.
That blown A motor makes that not probable.
Without feedback you are relying on computer simulation, and that is only going to get you so far.
I would create a speed map and adjust the angle based on speed. You need to log that speed vs wheel spin so that you can dial it in.
That does nothing for your big, fat, right foot. If you plant it hard at any speed the traction control and downforce are never going to keep up.
It's all balance, ain't it?
-
Yes Dean,
It's all balance. The cfd will only get us so far. I have chosen 3000 lbs of downforce as a target downforce number. Maybe we only need 2000 if the salt is good? We will just have to make some runs and get some data, then we can tune the system. The idea here is to actually design and build an easily tunable system. The biggest thing to consider is the cost of spinning the tires. One good spin and there goes $1600. Ouch! We will have to sneak up on the flap tune.
-
Without feedback how do you calibrate cold and dry vs hot and humid?
Records are set by solving for all of the variables.
Yeah, I know, you have to start somewhere.
-
Rob how about have the waste gate and wing flaps advance to preset points each time the transmission shifts .
-
... I'm just concerned about rule 2.Q...
Not easy for folks to stay focused on that. It will be interesting to see whether the rule ever gets changed to remove some ambiguity.
-
John,
I only have two shifts and first one occurs at 200mph. We need to move the flap in smaller increments. This idea would probably work on a five speed.
Because of movable flap feature, we can apply full power by the end of first gear. As of right now, we plan on eliminating the boost controller and replacing it with a simple regulator to the waste gates. I can pedal it through first gear. The waste gate controller is just one more electronic component that can give us issues.
-
Rob then how about a timer that updates the settings .
-
A timer in LSR is a sketchy thing. I do not even like using time based boost controller on my drag car let alone LSR.
From run to run there is too many variables that determine speed vs time.
I guess it would help by starting the timer at the fist gear change.
-
so have you asked the rules committee if your computer controlled aero package would be legal yet?
-
so have you asked the rules committee if your computer controlled aero package would be legal yet?
When I posted the topic in the SCTA Rules questions section, I thought we were asking them. Is there a better/more direct path to take to get the answer?
-
... I'm just concerned about rule 2.Q...
Not easy for folks to stay focused on that. It will be interesting to see whether the rule ever gets changed to remove some ambiguity.
The rule doesn't appear to be ambiguous; it just appears to be dated. Says: Just an engine controller and a datalogger. However, more than one entry has run more computers.
If you break somebodies record and they protest, I can see where they would have a legit beef. Perhaps they DID want to run digital aero controls, but didn't because of the rule.
Sounds like a rule change is right wrench to fix the problem, not a ruling.
-
so have you asked the rules committee if your computer controlled aero package would be legal yet?
When I posted the topic in the SCTA Rules questions section, I thought we were asking them. Is there a better/more direct path to take to get the answer?
Yeaahh... the lr.com forums are definitely not an official channel of communication with the SCTA. See page 172 of the 2012 rule book.
-
for years I have said that rules questions should be directed to the Assoc. that you are going to run. Be it ECTA, SCTA, LTA,USFRA etc. There are committees or contacts for each. The assoc.s are posted on the cover of this web site. A few of us do say which one or who to contact. The other assocs use the primary SCTA/BNI rules book but they do have other rules, classes that they answer.
-
One other possibility would be to monitor pressure differential between the top and bottom of the air foil, and control angle to maintain a specific pressure differential (ie total down force) for each speed.
As above you would need some wind tunnel or computer modeling to figure out what down force you want at each speed and build a down force vs speed map.
Larry
And THIS is why we post here...
We were kind of stuck on this and lots of good ideas have been offered. Not all are practical due to other limitations of the design. I can say that a couple of simple pressure taps can give us +/-10% on actual downforce. That's good enough. It just didn't occur to me until Larry suggested it. Well, Larry, no idea is too good to steal. I'll get to work on it right now.
-
I noticed in the Hot Rod Magazine article on the Speed Demon it said "Speed Demon has a servocontrolled tail rudder that can be clocked to any degree to add stability, depending on wind conditions."
-
That is interesting. I wonder if there is any logic on the controller for that rudder?