Aerodynamic vs. vehicle stabilty

[saltfever]

Re....the front is pulled around

To clarify...the tire rolling with weight and the coefficient of friction on the salt is what pulls the front end around at spin initiation. After the spin starts and the tire starts sliding aerodynamic forces get involved with the kinetic friction. Spin initiation is the rear kicking out and creating a steering angle.

I have always greatly enjoyed talking with you. . Usually on your favorite piece of real estate. . IMPOUND!    I think you have identified an incredibly important subject. I'm trying to understand what some may consider finer points. But to keep needling away at this will only invite negative feedback from others which breaks down any further education. I’ll buy you a cup of coffee at the Red Flame so we can share some additional thoughts. After all, The Red Flame is not too far from where you are usually parked!

Something I’m struggling with is; once the spin is initiated and the CG is now accelerating around the steering angle, how do you react the CG momentum? With rolling rear tires (i.e. some traction) and zero-friction-sliding front tires (via full braking) I can understand the effect you mention. But if the front tires are turned into the direction of travel and rolling you might cancel out some of the CG momentum. Not sure though . . . maybe it’s the CG’s arm from the pivot point . . . the location of the CP . . . other?  Thanks for introducing a thought-provoking perspective.

[mike mendoza]

 :|is turn into the spin the right answer?

[saltfever]

The car is traveling down a course. It starts revolving (spin). You turn counter to the spin direction or in the direction of the track. Same thing . . . just two ways of describing the same effect.

[jl222]

 
 When I question slow steering I'm not recomending fast steering just normal steering ratio like were used to  and I believe that one has to turn the wheel faster and further on the salt and dirt when a spin starts to happen, more so on short wheelbase cars.
 
 JL222

[maj]

Biggest thing to learn about controlling a slide is not to over react in the steering, and this is usually caused by being too slow to react at the start, your effectively chasing your tail
quick ratio steering can help , but the salt is not a good place to learn,
I raced dirt track cars for 10 yrs and i think it took me a good part of the first 2 to learn to steer properly and now another 10 yrs on would take me a while to fine tune those skills again
most salt racers will never have a chance to develop those skills in the limited track time available and hopefully very limited sideways travel
Much better to develop a vehicle that never needs these inputs

[Steve Walters]

  I find these posts intertaining after spending 40 years of my life driving 72 miles, one way to work, nine months of winter, 3 months of below zero, and every morning glare ice or snow packed roads.  Several times I had to play dukes of hazard through the sage brush to get back up on the road that was down hill both ways.  235 miles north of the Salt Flats.

Steve 

[jl222]

Biggest thing to learn about controlling a slide is not to over react in the steering, and this is usually caused by being too slow to react at the start, your effectively chasing your tail
quick ratio steering can help , but the salt is not a good place to learn,
I raced dirt track cars for 10 yrs and i think it took me a good part of the first 2 to learn to steer properly and now another 10 yrs on would take me a while to fine tune those skills again
most salt racers will never have a chance to develop those skills in the limited track time available and hopefully very limited sideways travel
Much better to develop a vehicle that never needs these inputs

  Eagerly awaiting tips on being able to give full throttle at low speeds on 2500hp and 106'' wheelbase car.
  Not getting sideways after blowing the tires away in the marbles at EL Mirage would be good to know also.

                               JL222
              

[maj]

Well the wheel base is the same but your hp is about 5 x my old Chrysler so i couldn't be sure until i drove it 

the short wheelbase was probably why i liked the quick ratio steering so much

I'll drop by and introduce myself properly at the Sept Elmo 

Back to the aero stuff , tired of blundering my way through the air on hp , trying to add some finesse

[jl222]

Well the wheel base is the same but your hp is about 5 x my old Chrysler so i couldn't be sure until i drove it  

the short wheelbase was probably why i liked the quick ratio steering so much

I'll drop by and introduce myself properly at the Sept Elmo  

Back to the aero stuff , tired of blundering my way through the air on hp , trying to add some finesse

  We probably won't be at elmo untill nov, see you then.

  JL222

[doug odom]

Short wheel base, long wheel base, Bonneville, Daytona, sprint car, stock car, streamliner, front wheel drive or rear wheel drive. It makes no difference. You keep the front wheels pointed in the direction you want to go!

[jl222]

Short wheel base, long wheel base, Bonneville, Daytona, sprint car, stock car, streamliner, front wheel drive or rear wheel drive. It makes no difference. You keep the front wheels pointed in the direction you want to go!

  Doug....next time you watch a sprint car race notice how far the tires turn from the direction they want to go!

               JL222

[hotrod]

Wheel base does make a difference. I had an AMC gremlin and on glare ice you had to really be on top of it. The problem is not just the short wheel base but the position of the driver. If you are sitting half way back in a 20' long car and it yaw's a degree or two the sideways motion of the driver is a lot more than the same yaw in a very short wheel base car. That means it takes more yaw in a short wheel base car for the driver to notice the lateral movement, so he is late in applying steering correction compared to the longer wheel base.

One solution for Bonneville, might be to use a progressive ratio steering box like was used on the 1973 Jeep Cherokee. It was designed so the steering ratio was relatively lazy at center point so the driver could cruise comfortably without constantly twitching the steering wheel but as you got off center point, the ratio quickened so when parking or making an emergency evasive maneuver the faster ratio at higher steering angles helped you catch up to the car.

It was a very nice setup in my opinion, and made driving in really slick conditions very easy.

A minor twitch of the steering wheel near center point did not send you all over the road but if you had to make a quick steering correction the faster ratio off center made it easy to catch up to the car even in conditions that were so slick you could not stand up when you got out of the car.

This steering box might be the sort of steering box as above but it is hard to tell from the advertisement.
http://www.agrperformance.com/catalog/products.php?cat=101

Super Box - SB2 Series
This box is nearly identical in design, brute force and performance to the Super Box 1, but is designed for the vehicle used as a daily driver. The SB2 has firmer valving and 16/13:1 variable ratio gearing for better handling and drivability at highway speeds.

http://www.google.com/patents?hl=en&lr=&vid=USPAT3753378&id=bTEwAAAAEBAJ&oi=fnd&dq=progressive+ratio+steering&printsec=abstract#v=onepage&q=progressive%20ratio%20steering&f=false


Larry

[saltfever]

Wheel base does make a difference. Edit . . .  If you are sitting half way back in a 20' long car and it yaw's a degree or two the sideways motion of the driver is a lot more than the same yaw in a very short wheel base car. That means it takes more yaw in a short wheel base car for the driver to notice the lateral movement, so he is late in applying steering correction compared to the longer wheel base.

Nice post Larry and good point-out regarding variable ratio.

Lets trig this out so we can see the relevance. These examples are extreme only to make the point clear and numbers are rounded up or down for simplicity not precision. Take a 200" wheel base and a 102" wheel base vehicle. Put the driver right on top of the rear axel so line-of-sight is the entire wheel base. For a one degree deviation the driver will move sideways 3.5” for the 200” wheelbase and 1.80” for the 102” wheel base. There is so much going on at speed you can’t differentiate those small changes. It is pretty clear that neither driver is going to detect 1 degree of spin. Change to 10 degrees of spin and you get 35” and 18”.  Some time between 1 and 10 degrees the driver will wake up and discover the situation.

Before everyone gets in a dither let me make another point. You have to differentiate “course deviation” from spin! There is so much going at speed that sensory overload dulls your ability to sharply discriminate what might be important changes in car attitude even though you think you are focusing on the important stuff. When you hit a crosswind gust the whole car can simply deviate from the course line. Yes, all four wheels can depart evenly. Unconsciously, you correct for “drift” and you do that all the way down the course. With drift, the car is still longitudinally straight but it can move from inches to YARDS from its true path! You don’t see the drift as much as feel it. Within that first few inches of course deviation you don’t know if it is drift or the start of a spin. (when only the two rear wheels depart). If you reacted correctly it will become drift but if you were wrong it’s a spin. There is no black line this year and Floating Mountain doesn’t move at all when looking at it through the windshield until you have moved quite a few degrees. I can’t say it is 5-10 degrees because it depends on the driver and the car set-up.

Whether long or short wheel base, your initial visual detection point will be about the same (which varies by driver). Both wheelbase lengths have a critical point were it is to late for a save. The Long wheel base just gives you a few more milliseconds before you get to that point.

[doug odom]

jl 222. look at a still picture of a sprintcar and you will see the front tires are pointed down the race track where he wants to go. I have watched thousands of laps at the sprint car races from the infield.

[akk]

Good points guys...

I was famous at least in my own mind for racing go karts in the rain....?...to set up for a turn I would initiate a slide by quickly making a turn of the wheel into the turn and then countersteer with the drift....I'll bet the dirt cars do the same.

I am guilty of this too...how many of you guys have put less than experienced drivers in a car....The rookie driver makes a pass at low power, never turns the wheel to get a feel of the car or the salt, the rookie does this through the licencing process and then they are expected to drop the hammer for a red hat!!!!!!

Akk