3/7/2005
When I wrote this incoherent tirade, I was half asleep, so there might be a few typos.
Actually, NASCAR is downright silly! Why do I say this? I say it because I understand what a car can be, and NASCAR is not going there. For one, NASCAR is chasing it's tail, going in circles. NASCAR has built a car that is good at only 2 things: turning left at high speed, and crashing safely.
I just visited www.nascar.com to make sure I knew what I was talking about. Nowhere on the site do they list the rules of the game. There is all this info about decals and the different teams yadda yadda yadda. But what about the machines? Tell me what is so special about a NASCAR engine? How many cylinders (let me guess: 8?), torque/hp curves? Displacement/redline, what kind of fuel injection? photos under-hood.. I don't really care about the ads, I care about the guts of the vehicle. I saw one photo of a NASCAR pickup truck. Now that is really silly! A pickup truck is the last thing I would want to race! The average pickup has the aerodynamics of a barn door, 10% of the vehicle's weight over the driving wheels, very high center of gravity, torsionally limp by virtue of it's dimensions alone and separation of bed and cab for a smooth ride. A pickup truck was designed to do one thing and it does it very well: haul stuff- either from Wal-Mart or to the dump.
NASCAR has greedily held onto the carburetor with white-knuckled hands- Give me my carb or give me death. Fuel injection was adopted as a last resort. Mechanical fuel injection was used on Porsche's racing cars back in the 1950's. They use Bosch mechanical pumps which were tied to the throttle and had a centrifugal portion. There also was a throttle body for each cylinder to help the flow. Once turbocharging came along, fuel injection was a perfect match. Today, people are slowly catching on that an engine can produce a lot more power with fuel injection than carburetion. It will burn less fuel, and can achieve a higher volumetric efficiency at high rpms due to the reduced flow resistance. The lack of a venturi is a big part of this. To do carburetion right, you need a carb for each cylinder. This becomes expensive and complicated. Carbs must be balanced because the fuel flow is based on the venturi effect whereas FI is controlled by a computer. It is very tricky to balance 8 carburetors. With fuel injection, you just need a throttle body for each cylinder, or a single body into a plenum. The throttle bodies are much simpler and take up less space.
I remember when I was in 3rd grade and Metric was being taught in school. Many of my classmates said that they hated metric. I asked them why they hated it and their reason ultimately came down to the fact that their parents hated metric. This same attitude is prevalent in the NASCAR subculture. We like to use inches, because we are familiar with them. We've never been to engineering school, so we don't realize how difficult it is to convert energy types when using english units. Ever heard of a slug? When I was in engineering school, we dreaded using any part of the english system. SI (System International or metric) was so much easier.
The rest of the world doesn't do Oval Track. They generally do either Rally or closed-course. Closed course racing more accurately simulates the stresses placed on a driver and vehicle in the real world than does oval track. I personally think it is more enjoyable. Closed-course does have a few drawbacks: it takes more real-estate, significant coordination and isn't tailored to provide entertainment to thousands of beer-slugging crash-loving merchandise-consuming NASCAR buffs. When your spectators want to sit their hiney in one place and be able to see the whole race, that pretty much kills your options for track layout
Don't get me wrong- I'm not down on America. I'm just tired of so-called experts worldwide whose opinions outweigh their understanding of physics 100 to 1. These folks have absolutely no respect for engineering and certainly don't have an open mind. A major space accident was caused by a seemingly minor oversight. Ever heard of an overflow error? This is what happens when a computer runs of of digits. The control algorithm for the Arianne IV Launch Vehicle was performed on a 16 bit computer. when the European Space Agency developed the Arianne V Launch Vehicle, the chose to reuse the same control system to save time and money. They CHOSE not to re-engineer the system, or even to do a review of whether re-engineering was required. When they launched the first Ariane V Vehicle, it flew up a couple of miles and then SNAPPED IN HALF! The computer was tracking the horizontal velocity and it went up and up and up until it finally exceeded the counting range of the computer. At this point, the rocket thought it was way, way, way off course and decided to go the other direction. The gimbals on the rocket engine went full lock in the direction opposite the way the vehicle was travelling. This kicked the rear of the rocket to the side, inducing enormous forces on the vehicle's structure. This structure then snapped in half and the rocket exploded. This was a major setback for the ESA and cost them much time. Luckily, no humans were aboard the craft.
I was talking to a friend the other day about rear suspensions. I stated my opinion that independent suspensions are superior to straight axles with leaf springs. He disagreed and stated that you can't beat a straight axle for strength. Perhaps this is true, but I think the real reason Jeep, Chrysler, Ford and GM have used straight axles since Henry Ford is COST. What's easier than slapping a wheel on the end of a pipe and running a rod through it? Ride too stiff? HMMM. lets see... Get some strips of high carbon steel and then U-bolt them to the pipe... Problem solved. It's been that way for 100 years! I doubt if NASCAR still uses straight axles, but it wouldn't surprise me if they did. If your track is perfectly smooth, then a straight axle would work just fine. How many roads do you drive on that are perfectly flat? Living in Alaska, we don't have any flat roads. Every road has potholes and other surface discontinuities. Ferdinand Porsche designed and built cars that excelled in hill-climbs- much of the time on gravel. If you've ever driven up a hill on a switchback gravel road, you understand what washboard is. No straight-axle car will ever win a hill climb. When one wheel hits a bump, the other wheel bounces as well. You loose all traction until both wheels contact the ground again. If you are applying large amounts of power to the rear-end, you risk destroying the diferential, due to rapid accelleration and decelleration of each half-shaft and wheel. This f=m*a force is tranferred back to the differential in the form of a shock load. Anyway, enough about the old crip, let's talk about the right way to do things. Enter the Independent Suspension
For those of you that have never had the opportunity to see one, an independent suspension consists of a series of linkages to position a wheel spindle relative to the vehicle and provides adequate suspension travel necessary for the intended use of the vehicle. Many different linkage types have been used throughout the years. Some of the more popular types are: Unequal length A-arm, MacPherson Strut and the Trailing Arm. The next component is a spring/shock combination. The spring counters gravitational forces and the shock dampens KMG oscillations. Most independent suspensions utilize a coil spring over a piston type shock absorber. Torsion bars have also been used, most notably in the original Volkwagen on the front suspension and Porsche, late model VW's for the rear suspension. The main benefit of using torsion bars for the rear suspension is for space savings. Late model Later versions of the VW Bug used MacPherson struts for the front suspension to create more space. The final part of an independent suspension is the power transfer shaft. A half-shaft with 2 constant velocity joints is used almost exclusively, although some vehicles used regular universal joints. Regular universal joints introduce a sinusoidal component to the angular velocity of the shaft, which causes noise, wear, power loss and loss of traction. In summary, if you want a kick-gluteus maximus racing vehicle, make the suspension with unequal length A-arms, coil over shocks and constant velocity joints. End of story. Oh, one more thing.... you say this type of suspension isn't durable? The Hummer uses coil-over shock, dual a-arm CV joint suspension on all 4 wheels. One of the design criteria for the Hummer was that it was to be parachuted out of aircraft and had to be able to drive away. There have been cases where the parachute didn't open, the Humvee bounced very high, suffered some body damage, yet was still able to drive away! So yes, fully independent suspensions can be made very durable.
One concept related to automobile performance on bumpy roads is unsprung weight. Dynamics is the portion of physics that deals with objects in motion. One of the classic systems is known as the KMG or spring constant K, mass M and gravity G. If you suspend a weight from a spring and pull down and let go, the mass will oscillate. The heavier the mass, the slower the rate of oscillation. In a vehicle, we normally think of the vehicle as being the mass, but when you travel on a bumpy road, the wheels themselves act as oscillating masses. The heavier the wheel, axle, a-arms, axles etc, the slower the oscillations, and the longer you are without traction. If you can lighten up the wheel, and remove as much weight from the ends of the a-arms, axles and shocks, you will see a marked improvement in handling on bumpy roads.
Both Formula 1, Indy Cars and the ZZ Top Eliminator use open wheels. They have gone to inboard shocks to further reduce the aerodynamic drag related to the suspension.
American cars are known for their boxy appearance. This has pretty much changed from the 60s and 70's, but lets go back and look at the roots of this. My father liked Porsches when I was a kid. He said that the Porsches were round to help reduce air drag. I noticed that most american cars at the time had lots of square corners. He is from Michigan and actually worked in a GM factory. He also taught automotive classes at A.J. Dimond High School. He said that it was more difficult to manufacturer curved body panels and left it at that. I've been searching for the rest of the story my whole life and here it is.
Most automobiles are made from thin pieces of sheet steel, because that is the cheapest construction method/material available. To form sheet metal in to body panels, a series of punches and dies are used. The dies are made from very hard steel that is formed into two parts- punch and die. When these two pieces of metal are put together, there is no gap between them. If a piece of sheet metal is placed between them and they are brought together with great force, they will deform the sheet metal to the shape of the punch/die. A punch is the male tool, the surface of which most resembles the finish part. Making dies is a tricky job. Tool and die makers were the highest paid laborers of all. In order to save money, everything was done to keep the dies as simple as possible. Before CNC milling machines, dies were cut by manually setting up the milling machine. Each different facet would require a new setup. Since many dies were required for each part (the stamping was done in stages, otherwise the metal would tear), the labor costs added up quickly. To manufacture a die with a curved surface was almost out of the question, as it would have to be machined manually, with substantial plans and measuring etc. This cost much more money, and limited the number of body designs and year-to-year changes that US automakers were so well known for. German and Italian bodymakers such as Porsche and Ghia would invest much time developing a single set of dies and kept that particular body type for many years, sometimes decades. American bodymakers didn't have that luxury as marketing pressures demanded that each year have a different body style. This, after all, limits the extent that junkyards can sell used body panels. So, as a result, the standard american car became the front-engine rear wheel drive sedan box car. NASCAR body styles have followed this style, even though it has horrible aerodynamics. They have pushed it to the limit, however, by dropping the hood, sloping the roofline, working on the underbody, but this only goes so far. A real design for a race car is similar to that which Honda, Porsche and the other class C racers have come up with. Closed wheel, center seat for one person, big curved windsheild, rear engine, rear wing. This is aerodynamically superb design. It follows the "coke bottle rule" used by some of the first supersonic jets. The analogy is the space between the windshield and the wheels. This provides a path for the air to move around the windshield, a high pressure region.
Here is a great photo of what I am talking about.