Friday, August 3, 2007
Idling: Who Cares?
During Q3, the third period of qualifying, the cars circulate the track at speed, trying to burn off as much fuel as possible. As we've discussed, an F1 car is generally faster in 'clean' air than running close behind another car. So what should you do? Since you get fuel credit for each lap you run, if you're really keen on your strategy you may be able to run 1-2 more laps than everyone else, thus burning off more fuel (making the car faster for the last lap of qualifying) and also gaining extra fuel to put back into the car to start the race.
So to get clean air and the maximum possible number of laps in, you want to have your car first onto the track when Q3 starts. So the teams start to line up at the pit exit line early, waiting for the green light. Only one problem with this; F1 cars don't like to sit still.
Normally a regular car's engine has no problem idling, afterall, its designed to. But an F1 engine generates a tremendous amount of power and subsequently heat. It also idles at around 4,000 rpm, much higher than the leisurely 800-900 rpms a street car turns. The car's radiators will easily cool the car, however F1 cars don't have fan's to pull air through the radiator. Fans aren't necessary if the car is moving, and they're a liable to break or imped airflow at speed so they're naturally left off an F1 car. Which brings up a real problem: how do we get our car first in line to get on track and not have it overheat while we wait?
Way back in 1981 Cadillac introduced a mouthful of an engine; the "V8-6-4 (L62)". The part that's important is the V8-6-4. This was the first engine with 'displacement-on-demand' or the ability to turn from a V8 into a V6 into a V4 all electronically. The engine normally worked as a V8 eight cylinder engine, but would deactivate varying cylinders when the engine wasn't working hard, like on the highway, to get better fuel mileage.
It didn't really work out that well and GM eventually withdrew the technology. My neighbor growing up had a car with one of these engines. I always remember it because it had a novel (for the time) talking car module. It would say things like "Door is ajar. Door is ajar." whenever a door was opened or "Fasten seat belts please." Quite annoying actually. Anyway, this guy had so much trouble with the engine that eventually the service center had a GM engineer come out with his suitcase-sized 'laptop' to diagnose the issue.
Later GM did get this technology to work, and they used it on the 'Premium V' engine initially as a failsafe mechanism to save the engine if all the coolant was drained. The coolant (aka 'anti-freeze') is the water/ethylene glycol mixture that circulates inside of the engine block, carrying heat away to the radiator, cooling, and running back into the block again. (The glycol keeps the water from freezing when its cold out). Without coolant, the engine overheats, causing all sorts of warping and general nastiness that quickly results in a useless lump. The point is: by cutting out varying cylinders and running the engine like a V4, the engine does not produce as much heat and can actually cool itself simply with air.
F1 engineers are a clever bunch and resurrected this trick for their own cause. So now you know. Those glorious V8 F1 engines are, at least for the few minutes they wait to exit pit-lane, really just 1.2L 4-cylinder engines.
Which brings up an interesting point. At the 2007 European Grand Prix, after a dry start, torrential rain covered the first corner by lap 3. Six (yes that's right, six world-class drivers) went off the track in turn 1, including one Lewis Hamilton. It was comical. Conditions were so bad that the remaining cars, on full-wet tires, couldn't even keep up with the safety car. The race was red flagged until the rain subsided. However of the cars off in turn 1, only Lewis Hamilton rejoined the race, although several others were undamaged. The reason? He was the only one who kept his engine running. The other cars either stalled or didn't have the software to allow the engine to idle for a long period while the cars were extracted by crane from the gravel-trap. But Hamilton immediately got on his radio asking his engineer what to do so he could engage the idle mode and save his race. Smart lad!
Friday, July 27, 2007
Introduction to the Racing Line or WTF is a 'chicane'?

We can better visualize this idea of available grip with the 'traction circle'. The basic idea is that at any time the tire has 100% of its grip to be allocated to turning, braking, and accelerating. So you can turn and brake at the same time, but only in a combination that doesn't exceed 100%, say 60% braking/40% turning.

Usually the best line through the corner is the one with the widest possible radius. This means that coming into the corner, we want to place the car on the right side of the track; outside for a left-hand turn. After we finish braking, we reach the 'turn-in' point, the point at which we begin to steer the car to the left. We'll aim the car at the left side of the track at the innermost point of the corner. This is the 'apex'. From the apex, we slowly unwind the steering wheel and begin to squeeze the accelerator. We aim the car at the right (outside) edge of the corner.

Now things are not quite that simple. There are various positions of apexes, described as early or late. An early apex means turning the car and continuing to brake into the corner, than adding more steering at the apex. A late apex means keeping the car outside longer, then adding steering to get to the apex, then reducing steering and accelerating. Basically, an early apex is faster into the turn, a late apex is faster out of the turn. So which one is right? Well it depends on the track. If there is a long straight after the turn, a late apex will be faster. But if there is a long straight before the turn, and another turn immediately after, an early apex line may be faster. Generally speaking, the ideal line is a late apex line.



Now maybe you can see why the drivers get paid so much. Finding the line and hitting it consistently lap after lap, with the car on its limits of grip is quite difficult, and even more-so in the pinnacle of cornering which is the F1 car.
Wednesday, July 18, 2007
The Car of Tomorrow: Part 1 - the chassis

Which brings us to the current proposed solutions: active aero. I've been a proponent of this idea for a long time, so I'm very excited to see what will happen. The basics are this: within a given range specified by the FIA, the teams will be able to electronically adjust the angle of their wings. The cars will also have a turbulence sensor fitted, and when turbulence is detected, the ride height of the car will be lowered. This puts the car closer to the track, increasing the downforce the car is able to generate. A leading car cannot lower its ride height below baseline. With active wings and active ride height, the FIA hopes to increase overtaking.
Drag is also created by letting air flow into the car, namely for cooling purposes. Typically, a car (both racing and road) is developed with a radiator opening for largely the worst possible cooling case. However, when the car is traveling at speed, this opening doesn't need to be as large since there is more and flowing over the radiator. By reducing the opening, drag is reduced. This is practical on a road car to increase fuel mileage, and will be allowed in F1 for 2011.
There was talk that the front and rear wings would become spec items, however the FIA has decided that the wings are an important element of styling and the FIA does not wish to have a field of identical-looking cars. However, to control development costs the number of elements (essentially separate wings) in the wing will be limited. The floors of the cars will become spec, with a design that is said to lessen the effectiveness of the front wing.
There are also attempts to ban 'aero-plasticity'; basically a fancy word for wings/floors that bend or move at high speeds. Ferrari developed a rear wing with a slot in it, so that at low speeds the slot would be closed, but at high speeds the air would bend the wing, enlarging the slot and allowing more air through, reducing drag (and increasing top speed). There are also claims that McLaren's front wing and Ferrari's floor both flex at speed. Determining if a part flexes or not is quite difficult, as the FIA specifies a bending test, but this test is carried out in the garage and doesn't use nearly the force that high-speed air puts on a part. The FIA hopes that by allowing other aero technologies, teams won't have to resort to these kind of shenanigans.

First is the plasma generator, which works by having an electric strip along the leading edge of the wing which ionizes (charges) the air. A second charged strip is placed farther back on the surface, which then attracts the charged air, preventing flow detachment. Another idea is MEMS; Micro-fabricated Electro-Mechanical Systems. Basically it’s a strip very tiny little vibrators on the leading edge that create turbulence in the 'boundary layer', which is the layer of air very close to the surface. This air essentially 'sticks' to the wing, but doesn't flow off, thereby increasing the effective thickness of the wing. Creating turbulence in this layer reduces its thickness, reducing drag and flow detachment. This can also be accomplished by tiny holes in the surface, which jet air into the boundary layer.
One problem in aerodynamics is that its difficult to scale things; meaning you can't use small models. Clearly it would be vastly easier and less expensive to build a 1:10 scale wind tunnel and use 1:10 scale models to test designs. However, it turns out that anything less than a 1:2 model doesn't relate well to the full-size car. Its also important to model the effect of the moving road. Therefore, teams have had to construct full-size wind tunnels with rolling roads to get good information. Obviously building and running these full-size tunnels is very expensive. One of the new techniques to model aero is CFD (computational fluid dynamics); basically a computer simulation. Only recently have computers become powerful enough to approximate the complex airflow seen by an F1 car. In fact, the Williams team just bought a supercomputer for this very purpose!
So the new rules argue that most of the teams already have the aero testing facilities, so the new aero rules won't cost significantly more to implement. In fact, there should be cost savings because the adjustability will allow for easier tuning of the car in all situations, instead of having to build 400 wings just to find the one that is the perfect fit for that week's circuit.
In the next installment we'll explore the powertrain regulations for 2011.
Saturday, July 14, 2007
Tires


In physics terms, all tires work basically the same. The idea is to create a tire that will have high friction in all directions. You need longitudinal grip (along the direction the tire rolls) for good acceleration and braking, and lateral grip (sideways) for cornering. Your typical street tire accomplishes this through mechanical friction. The more rubber that touches the road, the better as far as grip is concerned. So you may wonder why your street tires have various grooves and slots; the "tread pattern". The street tire is designed with the voids to channel away water (and snow and mud) from coming between the tread block (the part that touches the road) and the pavement, which helps to avoid hydroplaning. Hydroplaning happens when water builds up between the pavement and the tread block, leading to a loss of traction.




During the tire war from 2001-2006, the tire engineers went nuts. They developed special compounds for each race of the season, sometimes multiple compounds for different air temperatures at the track. The tires are quite sensitive to heat, and need to be at the proper temperature to work. Too hot or too cold and the grip will be less than optimal, and the surface of the tire may start to degrade. You'll see whenever the cars change tires, the tires are wrapped in special blankets. These are tire warmers that heat up the tires to near track temperature, so when the driver goes back out, there's at least some heat in the tires.
During this period there were several changes in the tire regulations. For a while, the cars had to qualify and complete the race on a single set of tires. This rule was designed to make the teams run harder tires, which have less grip, and therefore slow the cars down. The result was actually more dangerous, as the drivers would still want to run as soft of tire as possible, even if it meant risking a failure, and eventually this lead to the US-GP debacle in 2005.


Unlike many other forms of motorsports, particularly those that compete on ovals, F1 races are not usually cancelled or stopped due to rain. Hence, Bridgestone also supplies 'intermediate' and 'wet' tires for non-dry conditions. (At right is a full wet tire).
The intermediates (on the car in the pits at right) have a shallow tread pattern, and tend to work best on a damp track without standing water or rain. The full wets work quite well in heavy rain and standing water, but on a drying track they can quickly overheat and start shedding chunks of rubber.
Wednesday, July 11, 2007
Politics and Drama


In 1988, McLaren enlisted two amazing drivers; Alain Prost (already a double world champ) and relative F1-newcomer Ayrton Senna. That year between the two of them they won 15 of 16 races, with Senna winning his first championship. As you might imagine, there was a rivalry brewing between the two drivers and the following year it became even more intense.


And won.
However, the FIA (then president Jean-Marie Balestre) decided that Senna did not take the chicane (obviously because of the accident) and that the push-start was illegal, and not only disqualified him from the race, but also gave him a heavy fine and actually suspended his Super Licence (which one needs to race in F1).

Senna was infuriated by what he saw as the FIA conspiring against him, and stated before the race that he would enter the first corner without regards for Prost's car. Prost got the better start his position in 2nd on the left side of the track, and true to Senna's word, he collided with Prost and both cars were out of the race, this time making Senna the champion!

This wasn't the first or last time that drivers would be accused, justified or not, of deliberate accidents and other 'unsporting' conduct, such as blocking. One of the more recent incidents involved one Michael Schumacher at F1's most famous venue, Monaco. Schumacher entered the race behind rival Fernando Alonso of Renault. As 2006 was likely to be Schumacher's last season, he was especially motivated to win at Monaco as it would tie Senna's record for most wins at Monaco (six).

After this there was enormous controversy as to if Schumacher deliberately spun his car, or if it was an honest accident. Some claimed that a driver of his skill would not be likely to make such a mistake at a slow part of the track, on a lap he knew was already slower than his best. Others are adamant that it was an honest and human mistake.
The FIA took issue with Schumacher's actions finding them to "seem deliberate", and moved him to the back of the grid, taking his pole, and promoting Alonso from 2nd to 1st. Ferrari principal Jean Todt said he was disgusted by the decision, but Schumacher was not alone. Renault driver Giancarlo Fisichella ("john-carlo fizzi-kella") was penalized his three fastest laps in qualifying for blocking David Coulthard. Still, Schumacher showed his stuff by starting 22nd and finishing 5th on a track where passing is notoriously difficult. This wasn't Schumacher's first brush with controversy; he was accused of deliberate wrecks in 94 and 97. But he'll still be remembered as one of the modern greats, having won 7 championships, 76 fastest laps, and 68 poles.
Hopefully what I've shown is the drama and controversy that's a part of F1, and the extremes people are willing to go to in order to win. The pressure placed on drivers and teams to win and win consistently is enormous, and the drivers' own personal ambitions and overwhelming desire for victory can be all-consuming. Such is the passion that surrounds F1.
Tuesday, July 10, 2007
Qualifying
Starting up front is a huge advantage in F1 because overtaking (passing) is difficult. The leading car tends to leave so-called 'dirty' air in its wake, which does two things. One, it creates less drag on the car following, allowing the trailing car to accelerate faster. This is called drafting or slip-streaming. Two, the wake also reduces the effectiveness of the trailing car's wings, leading to less grip which slows the trailing car down in the corners.
Therefore the current overtaking strategy is to try to get a draft on the straights, but then fall back enough in the corners to maintain downforce. The passing move itself almost always comes under braking. The trailing driver will try to brake later than the lead driver, get ahead, and stay ahead out of the corner. Sometimes the trailing driver ends up braking too late and either going too far into the corner, or going off-track. Either means the trailing driver's pass won't stick and he'll have to do it all over again.
Qualifying is done in three 15-minute periods in a format known as 'knock-out'. During each period, cars are free to run on the track, trying to set their best single-lap time. Cars can run as many laps as they want, pit, and change tires. If a car has started a lap when the session ends, the car is allowed to finish its current lap. In the first period, the slowest 6 cars are assigned grid spots 17 to 22 and are excluded from the next two sessions. In session two, again the slowest 6 cars are assigned spots 11 to 16 and excluded from the next session.
In the third and final session, the top 10 cars must declare how much fuel they want to start the race with. After the third session, these cars are allowed to refill their cars to account for the fuel used during the qualifying session. This is where race strategy begins to enter into play. An F1 car can carry around 26 gallons of fuel, which weights about 162 lbs, although the cars are rarely filled to capacity. Each lap on-track burns between 4.8 and 6.5 lbs of fuel. Any reduction in weight results in better laptimes, so the amount of fuel on-board is critical. During sessions 1 and 2 the cars run as little fuel as possible. However, since cars in the final session must start with their race fuel load, they start lapping immediately, trying to burn off as much fuel as possible before trying to post a fast lap.
Once qualifying starts, several rules go into effect, putting the cars in a condition known as parc ferme ('park firm-ay') which is a special area of the paddock were the cars are put after qualifying and the race to ensure they are not touched by the teams. Parc ferme also specifies a set of allowable adjustments to the car. During this, the teams can adjust the front wing angle to put more or less front down-force on the car. They can also attach small blowers to cool the brakes and engine. However little else can be changed on the car once qualifying starts. This is to prevent the teams from building special qualifying parts and then changing them before the race.
Top position in qualifying is called Pole Position (as in pretty much every form of motorsports), and history judges drivers not only on how many wins they scored, but also how many poles they captured and how many fast laps they set. Its considered a 'trifecta' when a driver does all three in one race; a display of total dominance over the rest of the field.
Friday, July 6, 2007
Aero
Thus the idea of using an inverted wing was conceived, using the air to push the car down onto the track. Not only does this counteract lift, but it creates downforce which increases the traction of the tires. A modern F1 car generates so much downforce that it could drive upside down at only 60mph!

The Lotus before and after aero development:


F1 cars generate downforce in numerous ways. The most important are the front and rear wings. The rules limit how wide these can be, and only the front wing can be adjusted during the race. Wings cannot be designed to move. Most teams will develop specific front and rear wings for every track during the year to meet the downforce requirements of that track. Increasing downforce increases drag, which decreases top speed. Teams try to find the right balance of top speed and downforce to give the best lap time for a given circuit.
The cars also generate downforce through ground effects. By running the car as low as possible, the air beneath the car creates a low-pressure area that effectively sucks the car down towards the track. The rear of the car features guides called 'diffusers' that accelerate the air under the car out the back, preserving the low pressure under the car.

The effect of aerodynamics influences the design of almost every part of the car. Current cars feature high noses, which allows the front wing to run the entire width of the car, and avoids upsetting air that will pass underneath the car. The designs of the transmission, suspension, exhaust, and radiators are all made with aero packaging as a top priority. The suspension members are tear-dropped shaped in profile to better cut through the air.
The cars are also sensitive to lateral air movement. A change in wind direction can affect how the car performs on the track. Also, the car is almost always changing direction, meaning the air is flowing at an angle over the surfaces. Teams work very hard to design aero elements that can utilize this airflow to make good downforce.
Aerodynamics tends to be very complicated and hard to model, which leads to lots of wind tunnel testing. All of the top teams have their own wind tunnels, and generally run them 24/7 during the season. Every tweak to an aero surface requires re-evaluation of the entire aero package. Its not unusual for every bodywork component of the car to change three or four times during the season. Unfortunately, this also means that smaller budget teams lack the resources to compete in aero development.
Electronic aids

Launch control. The start of an F1 race is always a standing start, meaning the cars start from a standstill. Launch control works similar to TC in that it determines the optimal amount of slip for the best start and modulates the power to achieve that.




Contrary to some people's belief, any good modern ABS system will out-perform any non-ABS system, no matter who the driver. This is not only because the computer can react faster, but also because it can control all four wheels independently. However, since ABS is banned, its up to the driver's own reflexes to push the brakes to just below the point of lock-up, and rapidly modulate pressure when a wheel locks up. Some drivers can even emulate a form of ABS by modulating the brake pressure up to five times a second. The drivers can adjust the brake pressure bias from front to rear via a bias bar in the cockpit. This allows them to put more brake pressure up front for more aggressive braking, or adjust bias to compensate for tire wear during the race. However, the bias cannot be adjusted left to right, which could be used for faster turn-in entering corners.
The Transmission

In an F1 car, shifting is done by two paddles on the back of the steering wheel. Typically pulling the right paddle shifts up and the left paddle shifts down. The gears are selected sequentially, meaning the driver cannot skip gears, although they can pull the paddles rapidly to cycle through the gears. The clutch is only used to start the car from a stop. The electronics handle matching engine rpms and cutting power during the actual shift. The driver keeps his foot flat on the throttle. An up-shift takes less than 0.2 seconds. The clutch is also a paddle on the steering wheel since the left foot is used for braking, and there is not much room in the foot-well.
As with the monocoque, Allianz has published an excellent technical graphic on F1 gearboxes.
F1 Engines
The valves of an engine are held closed by valve springs. When the cam turns, its lobe pushes the valve down against the spring and as the lobe passes the valve, the spring pushes the valve back up to close it. This works well until you reach very high redlines at which point something called 'hysteresis' happens to the valve spring. Basically the spring can't push the valve closed fast enough and the valve 'floats', unable to completely close before its opened by the cam again. This is bad.

In F1, you must qualify and race the same engine in two consecutive races. This rule was designed to control costs so that the teams did not build 'grenade' engines that would only last 1 qualifying session or one race. In practice, teams are free to run of their engines and change at any time. If your designated race engine blows up in its first qualifying or first race, you must take a 10-spot grid penalty for the next race.


Engines: output
Displacement. Displacement is total volume inside the cylinders of an engine if every piston was at its bottom-most position. So if you have a 4 cylinder engine and each cylinder is 500 cubic centimeters (cc's) the total displacement is 2 liters (500 * 4 = 2000 cc's). The more the displacement, the more air and fuel can be taken into the engine, resulting in more power. Displacement is in general an excellent measure of how much power an engine can make.
Torque. Torque is a measure of force. Its an instantaneous measurement, meaning it doesn't take into account time. You can think of torque like trying to turn a wrench; the torque is the force you are applying to the handle. We express torque in terms of force over a distance; typically the force of 1 pound over 1 foot, aka ft-lb (foot-pounds). The amount of torque an engine makes varies based on how fast the engine is turning.
RPM's. Revolutions per minute. This is how many times the crankshaft of the engine turns in one minute.
Horsepower. Horsepower is how we measure the power of an engine. Hp = torque*revolutions-per-minute / 5252. The '5252' is a constant, and it also means that at 5252 rpm's, torque and hp will always be equal. Since the amount of hp is based on how fast the engine is turning, hp will almost always increase as rpm's increase. In terms of how fast our car can accelerate, hp is the most useful figure.
RWHP or BHP. Rear-wheel horsepower or brake horsepower. This refers to horsepower that was actually measured at the wheels of a car using a device called a dynamometer, (or dyno for short). This tells us how much power is actually getting to the ground. This is less than the horsepower at the crankshaft of the engine since there are frictional losses in the transmission and differential.
Redline. The maximum rpm it is safe to spin the engine at. For a production car, this is typically 6-7k rpms. For an F1 car, it is capped at 19k rpms.


Anyway, because the engine is making its best power in a narrow range, it would benefit from a gearbox with closely spaced gears, shifting more frequently to keep the rpm's up. In that respect, this engine is similar to an F1 engine. Both like to be rev'ed high and kept high to make the best power.
Engines: the basics
Suck (intake): The engine works by taking in air, mixing fuel into the air, and then burning this mixture. The first step is to get the mixture into the cylinder. A cam pushes the intake valves open while at the same time the piston is moving down in the cylinder. This sucks air into the cylinder. Fuel injectors spray a fine mist of fuel into the air that is being sucked in.
Squish (compression): The intake valves close, trapping the mixture in the cylinder. The piston now moves up, compressing the mixture.
Bang (ignition): At the top of the cylinder is the spark plug. The plug has two metal electrodes that are separated by a tiny gap. When electricity is applied to both of these electrodes, it jumps across the gap, creating a spark. This spark ignites the fuel-air mixture, which then burns, creating heat and pressure, and pushing the piston down. This is where the engine is actually doing work and creating power.
Blow (exhaust): Once the cylinder has been pushed all the way down, the mixture is completely burned and what remains are by-products of the combustion. The cam now opens the exhaust valves and the piston moves back up, pushing the spent gases out of the cylinder. Then the cycle starts all over again.
To make more sense of this, take a look at the animation on this page.