# Car turning with external force help from spoiler

1. Aug 7, 2011

### mark77

Ok, so when a car turns, the tires provide the acceleration pointing toward the center of the turn. If for some reason, I put a spoiler on my car with two rectanglular pieces, one on each side that are tilted, to the left, mocking an airplane rudder, thus when the wind has contact with them, there is a force with a component backwards and to the right. If my car is turning to the right with this spoiler system, this will help with the turn and take some of the force off the tires, or even allow the car to take the turn faster as now the tires can have the same maximum component of before and then the extra from te spoiler (correct me if I am wrong). Also, with this system, how do I ensure that yaw still occurs around the proper side and the car rotates arround a corner? Thanks for the help.

2. Aug 7, 2011

### mark77

If I can get any one of the questions answered, the most helpful for me would be if I took a corner at the same speed with and without the spoiler, the lateral friction on the wheels would decrease with the spoiler than without it...?

3. Aug 7, 2011

### DaveC426913

I am not an expert but, if I understand correctly, a "rudder" is not really going to do a lot - it might be be detrimental. Anything that turns the car, that is not related to the wheels is actually going to increase likelihood of a fishtail or spin out.

The idea is to is ensure the spoiler applies a maximum downforce on the rear wheels so the car doesn't fishtail.

4. Aug 7, 2011

### mark77

Ok, thanks for the help. My way of seeing this is that to go around a turn you need x amount of cent. force. With the spoiler in place allowing for an extra component of force towards the center of the turn, the force towards the center in the rear wheels decrease by the amount of the force that is now in the spoiler a that way the cent. force remains x...I dont think the force of the rear wheels remains the same is my point. I believe it decreases by the amount of cent force acting on the spoiler. I am not sure tho, I would need some kind of evidence forme to change my mind...

Thanks again for your input though Dave

5. Aug 7, 2011

### DaveC426913

I cannot imagine any spoiler configuration that would lessen the force on the rear wheels; it would have to pull the rear of the car inward.

I guess if you were making a sharp left turn and you turned your "rudders" hard right (exactly opposite to what you'd do in an airplane), it would result in the rear of the vehicle experiencing a force to the left, which is what you're looking for.

6. Aug 7, 2011

### mark77

Yes, exactly with that configuration set up lets say

before

<---- <----

after

<-- <--

<-- <--

where bottom is force on tires and top is on spoiler

this way total cent. force is the same ( 4 "bars" as an illustration), just location of force is a bit different. So will something like this occur or no?

7. Aug 7, 2011

### DaveC426913

But to do so is to generate a strong force that wants to turn the car exactly the opposite direction you want to go. The moment you turned left, your rudders would try to turn your car right. This is not good for control.

8. Aug 7, 2011

### mark77

Hey, Dave I am a little confused on what you mean here. If the "rudder" is angled so the front is to the right, back is to the left and I turn right, there would be a force with components to the right and to the back on the rudder, thus that should help with turning as the right is were the centripetal force needs to be, not the opposite way...

9. Aug 8, 2011

### Ranger Mike

adding a rear spoiler to a " stock car" will provide minimal additional turning capability. It may in fact take away total performance.
Question- what are you trying to accomplish? Are you talking about round track racing only? road course? street racing?

I suggest you read Race car suspension Class in this forum to gain insight on what happens when you turn left

10. Aug 8, 2011

### mark77

Round track, thus the rectangular sides of the "spoiler" will be angled in a similar direction (with the left towrad the front, right toward the back for a left loop.

11. Aug 8, 2011

### DaveC426913

But that's not what you'd want.

Assume you want to make a left turn (I am imagining you are going around the track counter-clockwise).

To cause the rear of the car to experience a force to the left (taking strain off the rear tires), your rudders would have to point front-to-left, back-to-right - as if it is making a right turn.

The problem you're encountering is that a car is not an airplane. A car gets its drive and direction from its wheels, not the flow of air. A car pivots on its wheels. If you attempt to control its movement by way of air, you end up moving the wrong parts of the car. The most obvious example is that any airflow that puts torque on the car will work to make it more likely that the wheels will lose traction.

I've thought of a way you might be able to get this to work but it'll need some verification: place the rudder at the central vertical axis of the car (i.e. where a taxi has its light). In a left turn this will provide a force that pushes the car left (which is good), but does not impart a torque on the car (which would be bad).

Last edited: Aug 8, 2011
12. Aug 8, 2011

### Ranger Mike

mark77
what is the purpose of this rear spoiler?
why are you thinking of adding it?
what reason?
also thanks for the PM..slip angel and cornering G force is covered in the race car suspension class

Dave 426913
To cause the rear of the car to experience a force to the left (taking strain off the rear tires), your rudders would have to point front-to-left, back-to-right - as if it is making a right turn.

this is not correct..rear spoiler adds "strain" on rear tires

The problem you're encountering is that a car is not an airplane. A car gets its drive and direction from its wheels, not the flow of air. A car pivots on its wheels.
Dave..some what true but the suspension pivots thru its roll centers.

If you attempt to control its movement by way of air, you end up moving the wrong parts of the car. The most obvious example is that any airflow that puts torque on the car will work to make it more likely that the wheels will lose traction.
dave..depending upon the race car, and aero package..spoiler can add huge amount of down force on the rear tires, thus huge traction advantage. I think you are correct about air flow under the car with no provision for channeling air over the top side will cause the front end to float..usually about 130 mph (my experience) and the steering gets way spooky and loose

Last edited: Aug 8, 2011
13. Aug 8, 2011

### Ranger Mike

Tire Slip Coefficient
Apr2-10, 07:57 AM

Aerodynamics of sportscars
Mar9-09, 07:41 PM

Calculating G Forces or the Centripical force
Dec27-08, 01:43 AM

Race car physics
Dec29-08, 11:31 AM

does friction increases as speed increases?
Dec31-08, 07:37 AM

Tyres - why is wider better for lateral grip?
Nov5-09, 11:38 PM

14. Aug 8, 2011

### DaveC426913

Mike, please use the quote feature, or it becomes very difficult to read posts.
The OP has explained that he wants to takes strain off the tires.

You are not following along.

A spoiler provides downforce, true, but Mark77 is talking about a vertical spoiler to create lateral forces.

No that's not what I'm saying. When I say pivoting I mean yaw, not roll. I'm saying you can't use airflow to turn the car because it gets its traction for turning into a corner via the wheels. If you try to use airflow to turn the car, you will get slippage and lose traction.

Again, Mark77 wants to talk about lateral forces.

I've explained that the idea is really to provide downforce on the rear wheels, which will provide traction. But Mark77 is speculating about reducing stress on wheels, so we're talking about lateral forces.

15. Aug 8, 2011

### mark77

I agree with what you are saying above Dave, I am looking more into lateral forces. I also see where you are going when it comes to the yaw, which is were I stil am not 100 percent sure. First of all, do you agree with me that strain is taken off the rear tires on a turn, if not why? Also how will yaw be affected if the same size components of force will remain on the rear and front. I honestly dont really understand the concept of yaw on cars too well so any help on that if I am wrong or right would be great.

Thanks,
Mark

16. Aug 8, 2011

### DaveC426913

Well, there is certainly little strain on the tires if the car continues to go straight, instead turning left - which is exactly what the rudders are trying to do - cancel out the turn (by applying a leftward force at the rear of the car, causing the the car to want to pivot to the right).

17. Aug 8, 2011

### xxChrisxx

As tyres are the only points of contact all forces must go through them.

All an angled spoiler will do is alter (read: ruin) the balance of a car. Angled wings were used on open wheel oval racing years ago but were ditched for destroying aero balance and shredding the tyres on straights.

Last edited: Aug 8, 2011
18. Aug 8, 2011

### mark77

Ok, any ideas on how I can make the car do the "yawing" part of the turn with this system in place. More weight in the front?

19. Aug 8, 2011

### mark77

Also, Dave I am thinking about placing the spoiler directly abpve the CG that way the foprces will only go towards roll as opposed to torque because I think there are complications neither of us know about specially the yaw aspect (as I am no car expert either) having it back there. Any improvements in car handling youll see by having it at the top, or any tips in general...thanks

20. Aug 8, 2011

### xxChrisxx

What on earth are you trying to do?