Where I’ve been- Blowing Off Steam (Andrew Howe)

I’ve been absent from the Blog for quite a while.  This silly thing called a “day job” keeps getting in the way.  While I haven’t had time to blog, I have had the time to keep my sanity.  You see, just down the street from my second office is an old warehouse.  About a decade ago, it was converted to an indoor kart track.  It is dark and cold (it was about 40 degrees in there last night), but it allows me to forget about daily grind for a bit.

You see, once the helmet goes on… it is a different world.

Life in the Left Lane

Disclaimer:  Rant Ahead.  You’ve been warned.

What is the basis for the American driver’s fascination with the left lane?

I would guess that more than half of the vehicle miles travelled on multi-lane highways in America are in the left lane.  And of those miles, nearly all of those are driven with another car pressing close on the back bumper.  And far too many of them are driven with the right lane unoccupied.

Chumptastic – October 12 Hour @ Portland

I know I’ll stir up some feedback with this.  My position is likely to be controversial.

ChumpCar racing is a bunch of drivers that don’t belong on the track driving cars that don’t belong on the track.

Sure, that’s a gross generalization and not all drivers fall into the stereotype.  But it comes from an informed position.  I’m a driver.  I’m even comfortable saying I’m a good driver.  Not great, but good.  I prepare my own car and I’m comfortable saying I’m good at that, too.  Again… not great, but good.

What I saw during my 1 hour stint in our 1981 RX-7 on Saturday afternoon convinced me that one needs to do a driver’s school before going wheel to wheel racing.  Not a classroom session, but an honest on track class with several hours of instruction about how to drive a car.  Similarly, the class needs to include the basics of how to prepare and maintain a race vehicle (on and off the track) – even if it is a $500 crap can.

Slip Angle, Part 2

I promised force diagrams.  Force diagrams you shall have.  As previously discussed, slip angle is the angular difference between the direction a tire is moving and the direction a tire is rolling.  If the slip angle is zero, the tire is rolling straight ahead.

If a slip angle is introduced, the tire will develop a friction force perpendicular to the direction the tire is rolling.  The magnitude of that friction force (and how the car feels it) is dependent upon the velocity of the tire and the slip angle.

Lesson #1:  Turn the wheel as little as possible

Slip Angle, Take 2!

[ From the captions on the photos in the first post of this series, it seems I may need to clear up a little bit of confusion regarding slip angles:  the concept applies to all four tires.  

I left the photos and captioning to my fearless editor (and great karting instructor), Davin.  His captions lead me to believe that he may have only understood part of what I was trying to convey

(Don’t worry, Davin… this isn’t an easy concept to abstract and my upcoming force diagrams will help!).  So, Take 2! ]

High Slip Angle- Take a look at the angle of the front wheels. That’s not the fastest way.

Let’s take the photo of the drift car.  The car is moving from left to right in the frame.  The car, however, is pointed about 45 degrees towards the camera.  Let’s look at the relative slip angles of the front and rear tires.

Front tires:  The front tires are pointed towards the center of the corner.  The driver is turning the wheel left, but the car is so sideways they are effectively acting as if they are turned right (if the car were pointed straight).  Eyeballing the angle, they looks to be turned inward around 15 degrees relative to the direction of travel.

This is a common slip angle, on the upper end of the range on asphalt, for a car near the limit.  This tire is working pretty efficiently, and it knows nothing about what the rear tires are feeling.

Rear tires:  The rear tires are pointed the same direction as the car… about 45 degrees from the direction of travel.  This is an extreme slip angle.  The tires are sliding as much as they are rolling and generating a huge amount of mechanical drag on the car.  The lateral grip offered by straight up static / sliding friction is minimal.

Stability is maintained by the forward (relative to the car, inward and forward relative to the curve) sliding friction generated by the spinning tires.  This action is also what is keeping the car moving forward in spite of the mechanical drag created by the high slip angle.

I’ve driven several race cars that didn’t have  enough power to keep a drift going… they would grind to a stop even under heavy throttle due to the mechanical drag.

To maintain the drift in this photo, the driver can modulate the throttle to adjust the action at the rear of the car or adjust the steering angle to keep the front end pointed the right direction.  The higher the slip angle, the bigger the challenge to smoothly maintain the arc of the track… but that is the art of drifting!

Editor’s Note: Thanks for the flattery, Andy.

Motivating a 6-Year Old…

Is like herding cats.  What worked yesterday is worthless today.

My daughter is six.  Being a racing enthusiast since about that age and having parents that wouldn’t (maybe couldn’t is a better word) buy me a go-kart, I want to make sure that my little girl has the opportunity to try out this racing gig early.  She sees racing all the time, spending quite a bit of time at the track when I’m in the Formula Ford, and she was interested in giving it a go herself.

In our area, kids as young as five can race karts.  They are called Kid Karts in our local club.  50 cubic centimeters of two-stroke fury and a carburetor with an intake opening smaller than a dime.  The karts weigh 150 pounds with driver (and the kids weigh nearly 100 pounds by themselves once they’ve got all the required safety gear on) and everyone uses the same specified sprocket ratio.

These things scream to speeds of up to 30 miles per hour.  You get the idea.  But when you are six, this beast is cool.

Slip Angle

Read the title.  Raise your hand if you know what I’m talking about.  Anyone?  Anyone?  Bueller?

Low slip angle- Notice how the front tires are only slightly angled.

Slip angle is a technical term which is defined as the angle difference (commonly measured in degrees) between the direction a tire is rolling and the direction a tire is traveling.  If a tire has zero slip angle, it is rolling straight down the road.

Any non-zero slip angle implies that there is a cornering force.  Drivers on a typical weekday commute make their trip with entirely unremarkable slip angles – generally so small that the driver doesn’t notice.  Rally drivers, on the other hand, operate with very high slip angles – the tires are often more sliding than rolling.

Convertibles: Why I hate them (and yet own one again)

I cruised down the freeway towards my exit, fortuitously a loop ramp, on the last sunny evening of summer.  It was 70 degrees and almost sunset.  I rev-matched a downshift to 4th gear and dragged the brakes.  Then I dropped another gear, smoothly matching revs as I released the clutch.  Off the brake now, I turn in and ease onto the throttle.

Gently I press the pedal, shifting weight to the back and slowly picking up speed.  I launch out of the loop at 50 miles per hour, well over the currently posted speed limit, and I lift and coast down the highway towards a stoplight.

This is why I own a 1999 Miata.  I can enjoy a moment of driving zen on my commute at 30 miles per gallon or better.  Better than that, I can afford my moment of driving zen… used 1999 Miatas are not particularly expensive and generally low maintenance if treated well.

That the car is a convertible is not a selling point… quite to the contrary.

I hate convertibles.

Memories.

In the interest of getting to know the readers a bit better (and have them get to know me a bit better), I wanted to pose a couple of questions:

What was your first race car?  (If you have never raced, what was the first car that really captured your imagination?)

My first race car was a 2000 Subaru Impreza 2.5RS.  This was the first generation chassis, and it was a 4-door manual.  I beat this car up at autocrosses, rallycrosses, off-pavement TSD rallies, and track days.  It was put into service at the end of 2000 and retired from service at the end of 2005.

This car was pretty darn gutless, but it was also incredibly stable on-throttle.  Even on packed snow, you could just stand on it.

It was a great starter car, but it also taught horrible driving habits.  The only real incident the car suffered was the result of a miscommunication between my co-driver and I on a winter rally (oh… turn here!)… I put the car into a snow bank, but backed right out and kept on going.

If Subaru would sell me a new one of these, I’d buy it.

Squeeze!

There are many skills required to be a championship level driver.  The most significant to entry level drivers is to get on the throttle early.  Brake early, drive a late apex line, and squeeze on the throttle before apex.  Doing this will yield a higher speed at corner exit and you’ll be faster all the way to the next braking zone.