An insight into everything in and out of a sprintcar

The 36-year-old said the class, which he has driven since he was a late-teen, had unique characteristics to other motorsports. 

“It is like nothing you have ever driven before, it weighs 600 kilograms and has 900 horsepower and you drive it on dirt,” he said. “They get up to speed and change direction very quickly and are certainly a handful to drive but they are a lot of fun to drive.”

Mollenoyux, who will feature in the 47^th South West Conveyancing Grand Annual Sprintcar Classic this weekend, can recall the moment he drove for the first time.

“My first ever drive in a sprintcar was in one of Ken Veals’ car and the seat was a little too big and I slid around inside the seat and felt a little uneasy,” he said. “But it was still a great experience I was only 17 or 18 years old and the sheer power of it and the lack of visibility certainly opened my eyes up.”

The experienced driver said racing sprintcars is often about controlling the controllables well. 

“A lot of it is to do with throttle control, depending on the conditions, and most of it is done by feel as you can’t see your right rear wheel or your right front,” he said.

“It’s all just on how confident you are with the car and how it’s going to perform. If you are confident that it will turn and go around the corner you can always push a little harder.”

The mechanical engineer, who owns and runs Swift Industries, said skill is still a big part of the equation.

“There is a lot of skill involved and a lot comes form experience and you can get by on just raw ability but they are a different beast to tame,” he said. “The longer you can do it for and the better people you can race against and learn off the further up you are going to succeed.”

Mollenoyux said adjustments can be made to suit different types of scenarios. 

“There are a lot of areas you can tune up and a lot you can do with suspension – such as moving wheels around in and out, tyre pressure,” he said.

“Also gear ratio and motor combinations all play a part depending on what tracks and conditions you have to deal with on the night.

“Even where you are starting on the race can dictate what your decision might be and come up with a bit of a strategy and once the gate closes you got to deal with what you got.”

Modern sprint cars are simple and brutally powerful.  

There is no dead weight on the car; if a part doesn't contribute to the car's performance, it is left off.

The chassis is a minimal tube frame with a short 213 cm wheelbase.  The suspension, deliberately crude by modern standards, consists of a live axle in the rear and a dead axle up front, and torsion bars for springs. A V8 engine, fuelled by methanol, is connected to the quick-change rear axle by a coupler called an "in-out box". There's no starter motor, and the battery is only large enough to power the ignition system for the evening. Two huge floppy rear tires of different sizes couple the irresistible force to the soft clay below.

The driver sits atop the rear axle, his legs straddling the drive shaft.  With a power-to-weight ratio comparable to a Formula 1 car and a short, tipsy frame, a sprint car spends most of its time scrabbling for traction, broadsliding around the corners, wheelstanding on the straights, and throwing clay into the stands, while the driver wrestles frantically with the steering wheel.  

Weight:  640 kg (including the driver)

Engine: Up to 900 horsepower (670 kW) around 140-340 more horsepower than 2014 Formula 1 engines. American V8 410 cubic inches (6.7L) capable of engine speeds of 9000 rpm. One engine can cost between $70-$80,000. In the event of an engine failure, a good team can change engines in around 15-20 minutes. Engines generally rebuilt after 15-20 race meets and costs about $20,000. Depending on configuration capable of around 260 km/h.

Chassis

The chassis is called a "downtube chassis" because it has tubes that run from the top of the roll cage down to the front of the car. This provides stiffness to the chassis and limits flex more than a chassis that does not have the tubes (primarily older cars). The chassis is made of chrome-moly steel tubing. The tubes are welded together in jigs that allow the manufacturers to create a consistent line of cars.

Drive line

Sprintcars don't have a transmission. They are either in gear or out of gear. The driver uses T-handle on the end of a cable that runs down to the rear end where the gears are located. When the driver pulls on the T-handle and thus the cable, the gears disconnect. The gears in the rear end determine how fast the car can go and how hard the engine has to work to drive the wheels. A plate on the rear end can be removed and the gear sets can be changed to match the length of a given track (and its conditions).

The driveshaft is a solid bar that runs from the engines crankshaft to the rear end. The torque tube is a pipe between the engine and rear end that the driveshaft spins inside of. There are universal joints at both ends that let the driveshaft turn when the rear axle moves up and down. The torque tube is mounted to the rear end and at the engine slides into a swiveling ball housing.

Engine

Engines in sprintcars come in two main sizes: 360 cubic inch and 410 cubic inch displacement. Some divisions require an iron (or stock) block, while other divisions allow aluminum. Some teams have some titanium internal parts, but these require more maintenance. Most divisions of sprintcars use fuel injection (as opposed to carburetors). They don’t have a distributor like a passenger car, sprintcar engines use magnetos. Magnetos are run with an on/off switch and require the engine to be turning over to start a spark. There are no batteries on sprintcars, they have to be push started. When the car is in gear and pushed by a truck, the oil pressure comes up, the on/off switch is turned on which "lights the mag". The engine "fires off" and the car accelerates away from the push truck. The oil in the engine is distributed by a dry-sump system. The dry sump tank is mounted on the front of the engine next to the water pump. The engine is mounted to the chassis in the rear by a motorplate. The fuel pump and driveline stick through the motorplate and reside between the driver’s legs. It’s a tight cockpit with all the pumps, hoses and pedals and pump housing.

The cars do run mufflers and are very loud. At most races though, there is a 95 decibel sound limit.

Suspension

Suspension on a sprintcar is called 4-bar torsion. There are two torsion bars in front and two in back. One bar springs each corner of the car. The torsion arm is on the end of the bar and supports the axle on that corner. On the other end of the bar is a piece called a torsion stop. It clamps to the bar and rests against the frame so the torsion bar wont spin. While the torsion arms determine the upward movement of the axle, the shock absorber keeps the axle from falling out the bottom. It's attached at the top to the frame and attached to the axle at the bottom. Right to left movement is limited by the panhard rod which mounts one end to the frame and the other to the axle. It's like a hinge, but keeps the axle in place. The other parts to the front suspension are the radius rods. They mount one end to the side of the car and the other to the axle. This locates and squares up the axle so it won’t move front to back.

In the rear of the car, the same design technology is used, but instead of a panhard rod to stabilise the right-left movement, a “w”-shaped piece called a jacobs ladder is used. The two ends of the "w" are mounted to the chassis and the centre peak is mounted to the the birdcage. A birdcage contains the rear wheel bearings that the axle rides in and provides mounting points for the shock absorbers as well.

The shock absorbers on a sprintcar are special items. They are designed with different rebound and compression rates to make the car soft, or hard and keep the wheels on the ground.

Brakes

Sprintcars use disc brakes. In the front of the car, there is one disc on the left wheel and that’s it! In the back there is one behind the driver’s seat on the rear axle (under the fuel tank) and sometimes one on the right rear wheel. When the car is fast and the driver drags the brakes in the turns, they glow orange, sometimes they throw sparks.

Wings

Sprintcars did not always use wings, but in the 1970s they began to show up. In the beginning they were huge. Todays series limit wings on top of the car to about two-and-a-half square metres. There are also smaller front wings that can be mounted to the car with tubes. Sliders on the top wing which allow the driver to move the wing back and forth using hydraulic levers. On a fast and heavy track, the wing will be forward, if the track is dry, the wing will be moved back. If a division does not allow sliders, the team has to position the wing before the race to a spot and angle that they think will make the car handle the best in the closing stages of the race.

Steering

Driving a sprintcar requires power steering. The steering wheel is made of lightweight metal and has a quick-disconnect hub for easy removal. The steering box it mounts to is right above the driver’s knees and exits the left side of the car to a lever it rotates called a pitman arm. The pitman arm has holes in it to adjust how much steering input is required to turn the cars front wheels. The pitman arm is connected to a bar called a drag link. The drag link connects to the left front spindle and then another bar goes to the right front spindle that is used to not only turn both wheels at the same time, but also allow alignment adjustments to be made.

Tyres

Hoosier WAV or harder (105x16x15) right rear.

Hoosier DT3, RC3, and VRA right rear are legal.

Hoosier RD12 or harder left rears and front only.

Fuel

Most sprintcars use methanol. Some use normal fuel, but not many. Sprint cars carry a fuel cell in the back of the car that looks like a bumble bee's tail. The capacity ranges on the tanks, some use 130-litre tanks, while others use a 90-litre tank. Less is lighter but if you run out of fuel during the race, there is no time to refuel and you're done for the night.

Cockpit

The driver sits in a custom fitted, high-back aluminum seat with 10cm-wide belts in a five-point harness configuration. As you sit in the car, the driveline and some pumps are between your legs, fuel lines from the tank come from behind you and wrap around to the right and into the pumps. The brake pedal is on the left and is a swing arm type lever. The gas pedal is a spring loaded stirrup and on the right. Ahead of the steering wheel is the dashboard. On the dashboard is the oil pressure and water temperature gauges. Also on the dash is the mag switch and a fire extinguisher switch. There is also a fuel mixture knob to lean out or richen up the engine. To the left of the steering wheel is the wing slider lever.

The driver wears a nomex firesuit with nomex underwear. Shoes and gloves are also special fireproof material. It doesn't breathe well and the driver is pretty warm and sometimes sweaty by the end of the race (even on a cool night!). The driver wears a nomex hood on his head and then puts the helmet on. Many drivers put a foam collar on below the helmet that keeps their head from bouncing around. Looking down is not an option. Left and right motion is about it. With the helmet visor down, the driver uses tear-off strips of plastic on the lens when the dirt gets too thick to see.

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