Why F1s don't pull wheelstands like dragsters do?

[g-force_addict]

Unless its Mark Webber over the piano at the China Grand Prix but that's another story.

Why F1s don't pull wheelies under normal off the line acceleration?
There's no way around the laws of physics. For a fast enough acceleration a wheelie is unavoidable as the center of gravity is higher than the tire contact patch.

Maybe:
A. Their tires aren't as sticky or warmed up as dragsters after a rolling burnout.
B. Their rear suspension geometry reduces the contact patch as it squats by going into negative camber.
C. The rear tires are overinflated compared to dragsters wrinkle wall tires.
D. The tires aren't bolted to the rims like those in dragsters. Specially needed for low inflation pressures.

[xpensive]

I think it's about the CoG being close to the rear wheel centerline actually.

[bigpat]

A number of reasons, but the most basic ones are....

The c of g, while above the contact patch is still extremely low on a Grand Prix car. If you draw line from it, to the rear contact patch, it will be very horizontal. A dragster is built with everything stacked to the rear to promote weight transfer only, nothing else.

Yes the tires on dragsters are sticker, yes they are inflated to lower pressure, and yes they are bead locked. The biggest factor is the absolutely enormous torque that a supercharged 500 ci nitro methane engine produces, along with its 9,500-10,000 hp. Yes that's right!

Ultimately a dragster is engineered purely for acceleration only, nothing else. An F1 car must accelerate, brake and corner, for sustained periods, not 4 seconds....

[Lycoming]

Magnitude of acceleration is small (compared to dragster), too much load on the front wheels, center of gravity is too low. Fundamentally, it's due to these three reasons.

As for why the magnitude of the acceleration is so small... well, let's just say F1 engines are built to run for more than 12 seconds at a time.

[bdr529]

I think it's about the CoG being close to the rear wheel centerline actually.

center of gravity has nothing to do with it, It's all about Horsepower and Torque and lots of the latter

[youtube]http://www.youtube.com/watch?feature=pl ... MdAcIQYJ6c[/youtube]

[notApineapple]

I think it's about the CoG being close to the rear wheel centerline actually.

center of gravity has nothing to do with it, It's all about Horsepower and Torque and lots of the latter

http://www.youtube.com/watch?feature=pl ... MdAcIQYJ6c

Actually CG location has everything to do with it...

[flynfrog]

center of gravity has nothing to do with it, It's all about Horsepower and Torque and lots of the latter

Then why can I pop a wheelie on my bike without pedaling?

[Lycoming]

They all have everything to do with it; they're all terms in the equation. No use talking about it and showing some flashy videos; I'll post the equation below. Doing a sensitivity analysis using that equation is easy.



The formula comes from wikipedia, though it can be derived from free body diagrams. Delta weight front is change in weight borne by front wheels, a is acceleration, h is CoG height, w is wheelbase and m is vehicle mass. The vehicle pulls a wheelie when Delta weight front is greater than the weight on the front axle. If you want to see which plays the larger role, do a sensitivty analysis.

[majicmeow]

It has everything to do with grip and torque. Cog has nothing to do with it when it comes to dragsters. If it did, why does a light weight tube framed vehicle with a 500+CID engine behind the front wheels perform wheelies? Not for lack of weight upfront, that's for sure.

When you have thousands of lb/ft of torque channeled through huge grippy tires that are not prone to spinning on acceleration, that torque is going to cause the vehicle to rotate around the rear axle, regardless of where the cog is.

[Lycoming]

When you have thousands of lb/ft of torque channeled through huge grippy tires that are not prone to spinning on acceleration, that torque is going to cause the vehicle to rotate around the rear axle, regardless of where the cog is.

Not if the CoG was at the same height as the contact patch. I know this isn't really possible, but just wanted to point that out.

[aussiegman]

If you have a look at the engine placement in a top fuel dragster, the engine is ahead of the rear wheels however behind the driver. There is little to no weight "up front", most weight is behind the vehicle mid point and the large majority is also very close the the rear pivot point around the rear axle.



For Funny Cars the engine is ahead of the driver but still behind the front axle line.

As said the main factors are
1: weight distribution (CoG)
2: engine torque
3: tyre traction (stiction)
4: tyre action

Drag tyres are not only bead locked and run lower PSI, but they are called "wrinkle walls" for a reason. The side wall is very soft and under initial loading they twist and wrinkle up acting like a spring. This softens the initial torque loading and limits traction loss. As the car starts moving they unwind releasing the energy stored in the tyre.

This action allows the tyre to maintain grip and then releases the torque in a controlled manner.

If the tyre has enough "stiction" then the action of tyre will see the car car will try and rotate around the rear axle as torque is applied.

When this happens either the tyre breaks the stiction threshold and starts to spin, the car overcomes its moment of inertia and starts moving or the action of the torque on the rear axle caused the chassis to start to rotate around this pivot point and lifts the front wheels. Usually it is a combination of all three.

To counter this, drag cars extend the wheelbase (long nose) or effective wheel base (via wheelie bars on the rear on the chassis) to limit front end lift. However, where the rear bars are too stiff or do not extend far enough they can actually reduce the loading on the rear tyres.

Changing the CoG will effect the amount of force needed to lift the front wheels.

Another interesting effect of the wrinkle wall tyres is that as their speed of rotation increases they "stand up" and increase in diameter which changes the final gear ratio allowing a higher top speed.

F1 cars have a much lower CoG, lower torque and less grip. The physics just isn't there to lift the front end of an F1 car.

[aussiegman]

They all have everything to do with it; they're all terms in the equation. No use talking about it and showing some flashy videos; I'll post the equation below. Doing a sensitivity analysis using that equation is easy.

http://upload.wikimedia.org/math/a/8/4/ ... 3ffeb4.png

The formula comes from wikipedia, though it can be derived from free body diagrams. Delta weight front is change in weight borne by front wheels, a is acceleration, h is CoG height, w is wheelbase and m is vehicle mass. The vehicle pulls a wheelie when Delta weight front is greater than the weight on the front axle. If you want to see which plays the larger role, do a sensitivty analysis.

Further to this, as the front wheels get further off the ground it should take less energy to keep it going or increase the height due to the vertical increase the CoG.

[Tommy Cookers]

When you have thousands of lb/ft of torque channeled through huge grippy tires that are not prone to spinning on acceleration, that torque is going to cause the vehicle to rotate around the rear axle, regardless of where the cog is.

Not if the CoG was at the same height as the contact patch. I know this isn't really possible, but just wanted to point that out.

there are 'weight-distribution' effects due both to acceleration (inertial reaction) and to torque (torque reaction)

the torque reaction effect gives a wheelstand tendency related to the wheelbase and the cg position lengthwise (not height)
that's why long 'rail' dragsters became the standard - it was not always so (look at 'fuel altereds')
so this effect occurs even if the cg was at ground height
a wheel-driven dragster would try to wheelstand even if it was tethered and had no acceleration

with acceleration there is an (extra) effect (contributing to wheelstand), this effect does depend on the cg height

a rocket-powered dragster (ie a torqueless propulsion system) would only have effects due to acceleration
and if the rocket thrust was at the height of vehicle cg there would be no change in 'weight distribution' with acceleration

[diffuser]

The answer as to why they don't pull wheelies off the start is that it's hard to steer with the front wheels off the ground! While bringing the front wheels off the ground gives an obvious transfer of weight on to the rear wheels to aid in traction, it makes it impossible to steer. The F1 cars use engine maps to tune the engine to give reduce the amount of torque and HP at lower reves to prevent wheel spin. As the car's speed increases, aero downforce increases, they apply more power and then finally the driver adds KERS. There was a rule change last year which prevents a > 2% torque delta atfer 6k RPM.

[SectorOne]

You could probably make them pull off tiny wheelies if you slap on extremely soft tires that deform coupled with some glue on them.
Maximum power and no loss of grip would probably tip the front end up in the air i think.