Random thought...

"Rainbow" (rainbeaux) 05/17/2015 at 15:43 • Filed to: None

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Wouldn’t a spoiler be more effective if it was directly above or in front of the rear wheels? Being behind them, any downforce created would also very slightly lift the front wheels. Between both axles, no downforce would be lost at all.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Rainbow 05/17/2015 at 15:47

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It’s all about balance

lonestranger > Rainbow 05/17/2015 at 15:49

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I think you mean a wing. Assuming so:

Leverage. For the same amount of drag, placing a wing further rearward places more effective pressure on the rear axle than if it were placed further forward.

ClassicDatsunDebate > Rainbow 05/17/2015 at 15:50

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Downforce on the rear suspension doesn't equal up force on the front suspension.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Rainbow 05/17/2015 at 15:50

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And also the effect that the rest of the body has on the air. If your only clean air is behind the rear wheels then that’s where you stick your wing.

If only EssExTee could be so grossly incandescent > Rainbow 05/17/2015 at 15:50

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Maybe but it’d look stupid. See: Eagle Talon.

SidewaysOnDirt still misses Bowie > Rainbow 05/17/2015 at 15:51

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Depends on the airflow over the car. Spoilers aren’t really there to create downforce, though. They mostly reduce drag. Wings on the other hand, you want in the air stream, so if you move it forward, it will have to be higher and therefor create more drag and also lift the front wheels because of said drag and leverage.

GhostZ > Rainbow 05/17/2015 at 16:02

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Being over the rear wheels doesn’t matter, it’s a center of gravity thing and polar moment. When you apply force (including downforce) to the body of a car, it flexes first (polar moment) and puts torque on all the little parts, transferring it down the body and chassis.

The force follows a rotation around the center of gravity of the car, including the force of gravity. Since the center of gravity is between the wheels, the ideal place for a spoiler is usually further back so that the fulcrum (where the force is pointing, for the most part, as downward as possible) is over the suspension, which are the only parts that carry that force down to the wheels.

That is my armchair explanation, someone else will probably correct me.

Also, this implies when you’re talking about reducing lift/increasing downforce. Drag coefficient and spoilers are a whole different monster.

f86sabre > Rainbow 05/17/2015 at 16:08

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Aft of the axle line allows for a bit of a moment arm. The lifting of the nose would be balanced by devices on the nose like a splitter. Mitsubishi did play with moving the wing forward on the 2004 WRC car.

StudyStudyStudy > Rainbow 05/17/2015 at 16:20

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For a full on race car, it is part of an aero package, they work together with front canards, underbody spoilers, diffusers etc. For a normal streetish car my naive understanding was that the rear wing is more for braking, and corner exit.

On a straight the wing is actually as you said more harmful in its location as it creates large amounts of drag and also pulls up on the front wheels a bit due to the fulcrum to a certain extent. If you have sufficient front aero then it is not as big a deal, but F1 cars and even higher end cars are starting to have settings to lower the wing to reduce drag on long or high speed straights.

So in braking is where it comes more into play. If you have a traditional layout of FR, then as you brake the weight shifts to the front and the rear wheels loose weight over them and will actually lock up given an equal brake bias. A rear wing helps put more weight on the car although it is diminishing as you loose speed to help with the initial braking and allows you to run larger rear brake bias. On corner exit it can help put a little more power down to the road a little sooner. A lot of this can also be achieved with under body spoilers/diffusers.

So to answer your question for the purpose of traction, yes it would be more beneficial to have the wing forward of the pivot point in a pure traction stand point, granted as a wing does generate more drag, placing it on the roof is going to constantly provide a bit of drag and lift up on the front wheels as well. A balance/application game.

yamahog > Rainbow 05/17/2015 at 17:34

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For starters, let’s make sure everyone is on the same page w. terminology.

“Spoiler” is liek dis:

Airflow very spoiled, much drag reduction

“Wing” is liek dis:

!!! UNKNOWN CONTENT TYPE !!!

!!! UNKNOWN CONTENT TYPE !!!

Very tall (into “clean air), much drag, wow such high downferce

But anywho. In the downferce game, you want to BALANCE it to avoid a hellish pitching moment. So a giant wing will be met with a giant front splitter, a la Viper:

The location of the wing rearward in car (by OEMs) is limited by things like impact testing and pedestrian protection requirements. It would actually be more beneficial (from a downferce standpoint) to have the wing go as far rearward as possible, as long as the pitching moment was balanced by a splitter. Or strakes, or other aero enablers.

Hope that helps!

TheOnelectronic > lonestranger 05/18/2015 at 01:19

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Leverage applies to torque, which is only useful if you’re trying to pull some sick wheelies, bro. The total force pushing down is the same.

lonestranger > TheOnelectronic 05/18/2015 at 02:09

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No, the force isn’t the same. Think of a second class lever, like a nutcracker:

Now, instead of the load (resistance) being a nut, replace it with a spring. And imagine that one handle of the nutcracker is the ground.

The fulcrum is the car’s front axle, the resistance is the car’s rear axle, and the force is the downforce created by the wing.

If you have access to a pickup truck you can try it out. With the tailgate down, stand on it and jump up and down. Then stand directly over the rear axle, and jump just as much.

TheOnelectronic > lonestranger 05/18/2015 at 02:15

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I think I see what you’re saying, but I am apparently way too tired to work out physics right now.