Why F1s don't pull wheelstands like dragsters do?

[gixxer_drew]

Every five years or so I get into a debate about this. Every time nobody believes me.

Forget all the steady state calculations. Forget that you need a bunch of power. What you need is: soft suspension, rapid increase in drive wheel torque (clutch drop, etc) very sticky tires or 4wd. One day a friend took up my bet using his mom's car and brought a camera with him for evidence:
http://home.tiora.net/andrew/misc/TercelWheelie3_2.jpg

[Lycoming]

Every five years or so I get into a debate about this. Every time nobody believes me.

Forget all the steady state calculations. Forget that you need a bunch of power. What you need is: soft suspension, rapid increase in drive wheel torque (clutch drop, etc) very sticky tires or 4wd. One day a friend took up my bet using his mom's car and brought a camera with him for evidence:
http://home.tiora.net/andrew/misc/TercelWheelie3_2.jpg

Well that's one way to do it. I wonder if it would be practical to accomplish the same thing by just jacking your center of gravity up really high... The additional weight transfer onto the back wheels will help, though I'm not sure if that happens fast enough. Though you are correct that the act of dropping the clutch sends some serious torque to the wheels given the drivetrain can handle it.

[gixxer_drew]

Every five years or so I get into a debate about this. Every time nobody believes me.

Forget all the steady state calculations. Forget that you need a bunch of power. What you need is: soft suspension, rapid increase in drive wheel torque (clutch drop, etc) very sticky tires or 4wd. One day a friend took up my bet using his mom's car and brought a camera with him for evidence:
http://home.tiora.net/andrew/misc/TercelWheelie3_2.jpg

Well that's one way to do it. I wonder if it would be practical to accomplish the same thing by just jacking your center of gravity up really high... The additional weight transfer onto the back wheels will help, though I'm not sure if that happens fast enough. Though you are correct that the act of dropping the clutch sends some serious torque to the wheels given the drivetrain can handle it.

... Apply enough torque (and inertia) to lift the front. Inertia is assisted by the soft suspension, the initial hit and suspension extension gets the cog higher and reduces the required torque. You could turn an F1 car into a wheelie machine... no doubt....

[Greg Locock]

gixxer drew, you friends moms car has a high cg.

[riff_raff]

GP motorcycles are constantly doing wheelstands during a race lap. Often (during braking) it's the rear wheel that lifts off the ground.

[piast9]

Well, I can do a wheelie or lift rear wheel during braking while riding a bicycle. But what does it prove?

[gixxer_drew]

gixxer drew, you friends moms car has a high cg.

It also has a short wheelbase, but I have done this in sports cars, even big front heavy and low CoG ones. The point being, theres a little more to it than the steady state calcs... there always is.

[strad]

[youtube]http://www.youtube.com/watch?v=aiz7sfverPU[/youtube]

[diffuser]

Well that pretty much describes F1 tires. They are heated to 100 degrees C (212 F) in those blankets. So they are pretty soft and the stick like glue. I think it does have to do with the diameter of those rear tires.

[Reca]

gixxer drew, you friends moms car has a high cg.

It also has a short wheelbase, but I have done this in sports cars, even big front heavy and low CoG ones. The point being, theres a little more to it than the steady state calcs... there always is.

There is also a bit of difference between "low cg" in the sense of a production car and "low cg" in the F1 sense, which means less than a span off the ground.

Also, as everybody who has seen one close knows, the measure of a F1 that surprises you the most is the absurd length... for wheelbase we are talking about 330-340cm (that's some 15-20cm over that of a Mercedes S class...), that means that even with weight rear biased, the distance of cg from rear axle is still in the order of a meter and half.

So as front heavy can be, and as low cg can have the production cars you played with, still it would have a ratio between cg distance from rear axle and cg height nowhere close to that of a F1, which is in the order of 6.5-7.

[I LOVE F1]

I think it may also be to do with the gearing. I wouldnt have thought that its very good for the tires or the stresses on the car if the front of the car lifts off the ground as you accelerate. I believe that moto gp bikes have an anti-wheelie system as they loose time whilst on one wheel. I dont think the drivers would appreciate their car doing wheelies anyway.

[gixxer_drew]

gixxer drew, you friends moms car has a high cg.

It also has a short wheelbase, but I have done this in sports cars, even big front heavy and low CoG ones. The point being, theres a little more to it than the steady state calcs... there always is.

There is also a bit of difference between "low cg" in the sense of a production car and "low cg" in the F1 sense, which means less than a span off the ground.

Also, as everybody who has seen one close knows, the measure of a F1 that surprises you the most is the absurd length... for wheelbase we are talking about 330-340cm (that's some 15-20cm over that of a Mercedes S class...), that means that even with weight rear biased, the distance of cg from rear axle is still in the order of a meter and half.

So as front heavy can be, and as low cg can have the production cars you played with, still it would have a ratio between cg distance from rear axle and cg height nowhere close to that of a F1, which is in the order of 6.5-7.

Yes, I agree with all of the above. Top fuel dragsters as well, very long wheelbase low weight in the nose and they are geared for 300+MPH. The simplest way to think of it, IMO is a simple statics moment calculation. Apply more force or change the leverage, you can lift anything. But there are factors beyond that because to get that force applied can be complicated and you can make it require a lot less force than you think and still lift the front if you take advantage of the suspension. I hope that makes sense.

[riff_raff]

When it comes to lifting the front wheels during a standing start, the only thing that matters is whether a positive net torque moment occurring at the rear axle (drivetrain torque/chassis inertia) does not exceed the traction capability of the rear tires. Top Fuel dragsters are actually designed to transfer as much weight as possible to the rear tires during launch, since this allows the maximum traction from the rear tires. The maximum drive torque that a car can produce is limited by the traction capability of the drive tires.

It would be possible for an F1 car to do a wheelie if the car were geared lower.

[gixxer_drew]

When it comes to lifting the front wheels during a standing start, the only thing that matters is whether a positive net torque moment occurring at the rear axle (drivetrain torque/chassis inertia) does not exceed the traction capability of the rear tires. Top Fuel dragsters are actually designed to transfer as much weight as possible to the rear tires during launch, since this allows the maximum traction from the rear tires. The maximum drive torque that a car can produce is limited by the traction capability of the drive tires.

It would be possible for an F1 car to do a wheelie if the car were geared lower.

Im not following that, not spinning is the only factor? You can fail to spin by having a very small amount of drive torque and that wont lift the front. That is determined by moments that are not static since either...the car is not static.

[pwlucas]

Dragsters are a totally different animal. Back in my college days, I was an engineering intern with a top fuel team and worked on chassis development to gain more rear traction. My capstone was actually damping of a top fuel chassis. Dragsters pull wheelies for a combination of reasons. Its main reasons are high, very high center of gravity and the massive amounts of acceleration. the dragsters also lift up the rear left tire. This is from the torque of the motor.

Top Fuel dragsters do not have suspension. The spring rate of the front is dictated by chassis geometry and design. Rear spring rate comes from the rear tires only (minor movement in the rear by chassis). Also top fuel dragsters do not have a transmission. It is greared by the rear tire and rear axle. The clutch doesn't lock up until almost the end of the track.