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Knights of Reason - Forums • View topic - How to drive cars fast
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How to drive cars fast

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Curved

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Post Sun Jun 06, 2010 10:10 am

How to drive cars fast

In addition to being a complete wanker on Tremulous, my other hobby is as an amateur race car driver.

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(me driving)

Driving cars fast is fun and extremely practical to the real world. Knowing the limits of a vehicle makes you a much safer driver. With high performance driving experience, you can react to unexpected situations in a manner which will prevent you from losing control of the car, which is often the big danger in highway driving. That said, bringing a car to its limit is dangerous without experience. That leads to ground rules which I condone:

Rule #1: To drive the fastest, the best attitude a driver can have is a relaxed one. When I'm going 120 mph down a front straight, I'm as calm as when I stroll down the street. For inexperienced drivers, this rule applies especially: never go beyond the comfort zone; never "push it"; if you're unsure of something, always be "slow" as opposed to being "fast". This isn't just for safety reasons. According to the physics of nature which will be discussed later, going beyond the limits of a car is always slower than going under them. Take it one step at a time, and slowly raise your comfort and knowledge of a car ... it took me 2 years from being a normal driver to learn the basics.

Rule #2: This one is also very important. Don't be reckless on public roads. Don't go above the speed of traffic, and also NEVER endanger other citizens. If you want to do things that are beyond what is legal on public roads, I recommend you do what I do, and get out to an autocross or track day. Also I condone never driving fast during twilight or night, never driving fast when there is traffic, and never driving fast in residential or commercial areas. Always respect all laws to the T! Signal your intentions and always be courteous. That said, there is a lot that can be learned while staying within the limits of the laws and safety. Truly fast driving is not necessarily above the speed limit or reckless.

So where to start? Physics!

==Friction==

Contrary to popular belief, motors do not matter much in driving fast. I've passed ferraris and all sorts of high power cars with my stock hatchback. How do I do this? Average speed is more important than maximum speed. Having a high average speed is accomplished by going around the non-straight parts of the track the fastest, and therefore coming on to the straight parts with an already high speed.

How do you go fast in the turns? Friction! Tires control the direction of your car, and thus are the most important component for going fast. You can give a Prius good tires and a Ferrari bad tires and the same driver driving both cars will often be faster in the Prius. Lets talk about how friction works exactly.

What is the definition of friction? In layman's terms, friction is when two pieces of matter rub against each other. Friction converts kinetic energy (movement), into heat. The amount of kinetic energy converted into heat is dictated by the coefficient of friction between the two surfaces. For instance, an ice skater has a low coefficient of friction, since it takes so long to slow down on ice. A car's tires have a high coefficient of friction.

There are two distinct states of friction: static and dynamic. Dynamic friction is the "normal" friction -- its when you rub two things together -- the two things move in relation to each other. Static friction is the force that happens that causes two things to stay still relative to eachother -- for instance, if you pushed a table across the floor, it doesn't just immediately start moving until you generate enough force to get it "started". The force acting against you is called static friction.

The difference between static and dynamic friction is important because static friction is almost always a more powerful force than dynamic friction. Once you "break" static on pushing the table, it becomes easier to push. Once you break static on your mouse, it might jump because the force required for dynamic is less. The same applies to tires. They are normally in static contact with the ground, and once they enter dynamic (sliding), they generate less friction, and thus are unable to laterally accelerate you.

==Lateral Acceleration==

If your speed is how much your location is changing, acceleration is how much your speed is changing. When you push the accelerator, you accelerate forward so your velocity becomes greater in that direction. When you push the brake, you accelerate negatively (you accelerate toward the rear of the car) so you stop going forward. When you turn the wheel, you are orienting in a different direction. In laymans terms, you are resisting centripetal force. However, in reality, centripetal force is just an effect caused by constantly accelerating in a changing direction. It is the same as simply holding down the go-pedal, except globally the direction of the acceleration is constantly changing and all the while in relation to the car, the acceleration is in the same constant direction (toward the center of the turning circle). Your mass attempts to retain its momentum, so it feels like you are constantly being pulled outward. The static friction of the tires resists this outward force.

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==The Friction Circle==

So if all of your controls are generating acceleration, and your tires are what cause the friction with the road which allow you to accelerate, what is the limitation? The tires can only resist so much force before their static friction is overwhelmed, and they slip into less powerful dynamic friction. All of the different directions of acceleration add to the same overall force that is exerted against the friction. What this means is you can't have maximum braking and maximum turning at the same time. The "Friction Circle" is a common diagram which represents this relationship:

Image

So, according to this diagram, you could do about 70% turning and 70% braking at the same time, but no more or you would begin to slip.

Managing traction according to this idea is one of the two main "games" in driving fast. The idea is to get as close to the outside of the circle as possible without exceeding it, because that will be the fastest you can go around a corner, the fastest you can brake, and the fastest you can accelerate forward.

==The Racing Line==

The second "game" in driving fast is approaching the perfect fastest sub-route on a road surface.

Image

The basics are simple: put the car on a path that is the largest radius a corner can fit. Doing this allows you to have the highest average speed for a turn. The basics of accomplishing this are simple: enter a corner on the "outside", move to the "inside" of the curve in the middle, and then go back to the "outside" to finish the turn.

Here is a video of a very fast hotlap of mine at a local track that demonstrates this idea to an extent:
http://www.youtube.com/watch?v=RmYq3mBbwPg

However, as the video demonstrates, it becomes more complex to find the perfect racing line when you account for a non-flat surface. For instance, many roads have a crown, or a surface that makes a peak in the middle of the road for water drainage. Hills and road camber, or the slope of a road from side to side, drastically alter the fastest line. Lastly, different parts of a road can have different traction characteristics. For instance smooth asphalt will have worse traction than a slightly rough asphalt. Also, areas of a road will dry faster than others. Many different circumstances alter what is the fastest line, so mathematically plotting them is very difficult! The best way to learn about the fastest line of a road is to try different techniques and watch what experienced people do.

==Automobiles==

Many people have a conception that sporty cars are fast and normal cars are slow. As I have mentioned previously, the actual car is not nearly as important as the driver. I have seen 20 year old cars with 100 hp pass 1 year old cars with 500 hp. Some minor preparation is necessary to make a car endure the extremely high temperatures and wear a track puts on a car, but after that, what you have is not very important.

Here's a video of me passing a bunch of cars at my last event. Many of them had 100-200 hp power advantages:
http://www.youtube.com/watch?v=lscJtVlwnLo&feature=fvw

So, that said, if you have a car (not a truck), you are able to participate, and if you were a good enough driver, you could probably excel in what you have.

The basic preparation a car requires for track duty specifically, if you are interested in that, is:
*Good oil and coolant condition
*Excellent brake fluid
*High temperature brake pads
*Summer tires or race tires

One of my personal goals when I started doing track events was to learn more about how cars work. When I started, I couldn't tell you the difference between a manifold and an alternator. Now I do all the maintenance on my cars: oil changes, brake jobs, spark plugs, and so on. Its not very difficult to do, but it does take some time to learn about where to get the correct parts, tools, and instructions to do the jobs. I feel that even if someone doesn't actually do the labor on their car, they have a lot to benefit from knowing what's going on under the hood so they can protect themselves from the people they are paying to work on their car.

==Summary==

This concludes my basic tutorial about how to drive fast. If you're interested in learning more, there is a lot to learn! I'll do my best to answer any questions. :)
Last edited by Curved on Tue Jun 08, 2010 12:32 pm, edited 5 times in total.
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Faced00d

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Post Mon Jun 07, 2010 3:13 am

Re: How to drive cars fast

Not to be a PITA, but I have always wondered: IS there apoint to wearing that helmet?
I mean if anything happens where that helmet might help, doesn't it stand to reason that you're fucked anyway?
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Saturn

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Post Mon Jun 07, 2010 8:27 am

Re: How to drive cars fast

It probably reduces the damage when the front of your head hits the steering wheel.

Your going too fast, then you swerved hard and wa-la..your helmet just practically saved you..
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Curved

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Post Tue Jun 08, 2010 11:54 am

Re: How to drive cars fast

Yeah, its like an omnidirectional airbag just for your head. Helmets are real lifesavers in a lot of situations. The more modern development of a helmet is something called a "Hans Device" that you wear on your shoulders that connects to the helmet and prevents whiplash.

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A helmet, hans device, 6 point harness, and roll cage make a car safe enough to be able to walk away from a 150 mph crash. If it was practical to put that kind of safety on road cars, it would be rare to have fatalities, and they would probably be from stuff entering through the windows. :)
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Curved

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Post Tue Jun 08, 2010 12:35 pm

Re: How to drive cars fast

Updated with racing line and automobiles sections.
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AndyDemon

Post Mon Jun 28, 2010 4:23 pm

Re: How to drive cars fast

Driving fast isn't hard just respect the road and car your driving and know you're engines help, good guide btw keep up the work.

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