David S. Hotter
After a successful 1996 season in the Indy Racing League (IRL), capped off by sharing the championship with Buzz Calkins, Scott Sharp seemed as though he was on top of the world. He had finally made it to the big leagues.
But, it wasn’t long before he began feeling the crown teetering off his head. The 1996-97 IRL season proved to be a rollercoaster ride for 30-yr-old Sharp, filled with a victory and top-five finish, yet marred by three early departures because of mechanical problems. Reliability was becoming Sharp’s chief concern and greatest hurdle for success.
The 1997 Indy 500 added a new twist to Sharp’s career — the beginning of a string of serious accidents. On the fifth day of qualifying for the Indy 500, Sharp hit the wall on turn four that destroyed the left side of his car. Two days later, he hit the same wall and suffered a concussion. As a result, A.J. Foyt, his team owner at the time, pulled him out of the lineup for the race.
After sitting out the next race at Texas, Sharp hopped back in the saddle for the next race at Pikes Peak International Raceway, where he earned the pole. This time his day ended before it barely began, as Sharp hit the wall on turn two on the first lap of the race. What’s worse, he suffered another head injury, which sidelined him for the rest of the season.
Scott Sharp has had more than his fair share of growing pains since entering the IRL — a league formed by Tony George to take the financial hurdles out of open-wheel racing and encourage young drivers to compete in oval-track racing. But Sharp’s experience is indicative of the greatest concerns and issues being addressed by the IRL after its first full season of racing: reliability and safety.
WITH AN EYE ON SAFETY
After a season filled with lessons learned, the IRL continues to look for ways to add excitement and bring competitive races to the fans by increasing reliability and performance, along with making it safer for drivers to circle tracks at speeds greater than 200 mph.
But don’t expect drastic changes to the racecars. To keep costs down, the League restricts manufacturers to making $35,000 worth of updates on the chassis, bringing the base price to just under $300,000. The cost of engines has climbed only $5,000, although engine builders and teams are free to make modifications to improve performance.
With a 10-race season plagued by engine and mechanical failures and too many accidents, the IRL has swiftly taken measures to improve safety and reliability. “We knew it would be difficult to coordinate new engines and chassis in the same season and expected to deal with reliability issues on the track,” explains Leo Mehl, executive director of the IRL and vice president of Indianapolis Motor Speedway.
“We also realized we needed to make the chassis more crash friendly. The cars handled well right out of the box due to high torsional stiffness.” Mehl continues. “However, this stiffness became a drawback when engine failures sent drivers spinning into retaining walls.”
Accidents on high-speed ovals often send drivers flying backward into concrete retaining walls at speeds in excess of 150 mph. “The data from on-board impact recorders showed us that too much crash energy was transmitted to the cockpit, causing head and back injuries,” says IRL Safety Consultant John Pierce, who recently joined the IRL after 41 years at General Motors Motorsports.
In these types of accidents, the first thing to hit the wall is the gearboxes, which became the IRL safety team’s first focus. The IRL worked with the sole gearbox manufacturer, Emco Gears Inc., Chicago, and the chassis manufacturers to shave weight off of the gearboxes to make them more crushable. Chassis manufacturers also helped by making the bellhousings less rigid.
“When we designed and built the gearbox last year we didn’t consider making it collapsible,” explains Dan Cota, manager of racing transmissions and components at Emco. “Our goal was to design a gearbox strong enough to reliably handle the loads from the engine and drivetrain.”
To make the gearbox more crash friendly this year, Emco engineers added energy-absorbing features that include modifications to the mainshaft, the gearbox housing, bearing carriers, and two threaded components. In the original design, a large nut at the end of the shaft held the main shaft in tension. To make it collapsible, engineers replaced the nut with a pressure-plate arrangement secured with a snap ring and Belleville washer. The pressure plate is attached to the back of the transmission.
“In the event of a rear impact, the snap ring fails and the shaft slides through the transmission into the ring and pinion area, and the gear stack falls apart,” says Cota. “We also added break-away studs on the midplate bearing carrier by reducing them from 5⁄16 3 5⁄16 in. to 5⁄16 3 1⁄4 in. and taking the grip diameter down to 0.150 in. so that the bearing plate will break away.”
On the bottom shaft of the transmission, engineers added collapsible gear spacers that help the shaft crumble without forcing gears through the gearbox wall. “We modified the front bearing carrier so that it knocks out when it gets hit with 1,500 pounds of force and lets the entire bottom shaft move forward,” adds Cota. “Plus, the transfer shaft now telescopes over the clutch shaft and lets the whole gear train move forward 3 inches.”
In all, engineers cut the overall weight of the gearbox from 197 to 165 lb. “The objective was to make safety a priority while still maintaining ruggedness,” says Cota. “I’d much rather go out with a broom after an accident and help the driver sweep up a damaged chassis than see him or her suffer a severe injury.”
ADDING MORE HONEYCOMB
Another new feature aimed at improving safety for IRL racers is an larger impact attenuator bolted to the back of the gearbox. It’s a rectangular- shaped component made of honeycomb material that acts much the same as a 5-mph bumper does to prevent damage to the hood, radiator, and sheet metal on passenger cars. The crushable honeycomb material provides a buffer when racers spin backward into retaining walls. Besides protecting drivers from shock loads, the attenuators also cut down on damage to the cars.
“The original IRL chassis specs called for a 5-in.-thick impact attenuator,” says IRL Technical Director Phil Casey. “We felt we could improve safety without affecting performance by extending the attenuators crushable stroke by 3 inches.” With an 8-in. stroke, the attenuator has more time and distance to absorb impact forces that can reach levels up to 50 g’s.
From behind the racecar, the attenuator resembles a shoebox bolted onto the gearbox. Supplied by Hexcel Corp., Pleasanton, Calif., it’s a 5052 aluminum honeycomb block made of sinusoidally corrugated foil sheets held together by adhesive. The honeycomb core is surrounded by a housing made of 4130 steel. The entire assembly is covered with a carbon-fiber shield for aesthetics.
This particular grade was originally designed to transport plutonium and radioactive material for the nuclear energy industry. It has a cross-core structure providing strength in two axes, with alternating layers of honeycomb positioned 90° to each other.
“Traditional honeycomb material is good only against axial forces and can’t resist side loads, while a cross-core structure resists impacts at different angles” explains Pierce. “We needed a biaxial material because we found that most cars in rear crashes on 1-mile ovals don’t hit the wall at perfect 90° angles, but instead at between 0 and 30° off center.”
To help keep the attenuator in place during crashes, two retainer straps extend forward and bolt to suspension components. The League is developing another change to the impact attenuator which wraps its edges around the sides of the gearbox bell housing, much like a pair of football shoulder pads, to protect drivers when crash angles exceed 30°. The wraparound design will also help secure the attenuator to the gearbox.
General Motors Motorsports, which was responsible for the attenuators specs, validated the honeycomb material by impact testing it at Wayne State University, Detroit. On-track results have also been positive. “We have had a few accidents in the two races so far this season,” says Pierce. “And it’s encouraging to say that all of the drivers involved have been able to climb out of their cars and walk away.”
IN THE BUDGET
In addition to safety improvements, the IRL continues to take strides to keep costs in check — one of the goals of its original charter. One way it controls costs is by making sure new cars don’t become obsolete after one season. “In previous years you couldn’t compete if you didn’t buy a new car,” says Roberto Guerrero, a racer for the Pagan Team. “Now we can run the same cars as last year by making recommended updates.” To keep chassis manufacturers from going overboard, the IRL put a cap of $35,000 on the update kits for car revisions. In addition, the League mandates several modifications to improve safety and performance.
The most significant chassis changes are the raised sidepods and roll-bar hoop. New IRL specs lift the sidepods 11⁄2 to 2 in. to give drivers more protection against wheels flying back into the cockpit during crashes. Additional material on the sidepods also provides more crushable structure to protect drivers.
Raising the roll hoop and airbox, or air intake, 2 in. gives teams more room to install headrests that wrap around the cockpit near the driver’s head. The foam inserts are 3 in. thick behind the driver’s head and 2 in. thick on the sides. To protect drivers, the top of the headrest must be no lower than 4 in. from the top of the helmet. “We’ve been working with GM Motorsports to test different headrest materials by conducting impact tests on different foams to find the best formulation,” says Phil Casey.
The differences are obvious when you compare photos of the racecars from last season. “If you look at last year’s chassis, the driver’s head was almost in the airbox,” says James Morton, co-owner of G Force Precision Engineering Ltd., Fontwell, Sussex, England. “A year of on-track data showed the airbox was supplying plenty of air, so we made it smaller and higher so that now the helmet is underneath the bottom lip of the airbox.”
One of the challenges with headrest foams is finding a material that protects drivers’ heads while maintaining rigidity close to that of seats. “If the foam is too soft or thick, the driver’s torso will remain still during an impact but his or her head will move more freely,” explains John Melvin, senior staff research engineer at GM Research and Development Center in Warren, Mich.
The drivers’ helmets also change the dynamics of energy absorption and add to the complexity of choosing foams. “The helmets distribute loads over a greater surface area,” Melvin continues. “And the contact area continues to grow as the helmet is forced further into the foam, which sharply increases the rate of deceleration.” Softer foams can be used to make deceleration more gradual, but they lack support and can contribute to head and neck injuries.
One method used to distribute loads more evenly is adding a rigid plate between layers of headrest foam. “The plates act as a load spreader by taking a relatively small contact area initially and distributing forces evenly across the entire headrest,” says Melvin. Safety experts have also investigated ratesensitive urethane foams that change energy- absorption qualities depending on impact velocity. One drawback, however, is these materials are temperature sensitive, which is a concern going from a cool day of testing at Indianapolis in mid-April to the summer heat at a race in Texas.
Besides making the cars safer, a raised airbox makes drivers more comfortable. “Racers told us they were getting a lot of buffeting from the airbox inlet,” says Andrea Toso, program manager at Dallara Automobili da Competizione, Varano Melegari, Parma, Italy. “Raising the roll hoop also let us redesign the air inlet to be more aerodynamically smooth.”
The Dallara chassis now has a distinctive snorkel shape to the air intake, departing from the traditional turtle humpback air intake, a signature of last year’s IRL chassis. Engine manufacturers have commented that they are getting more constant pressures from the raised airboxes, because of less turbulence from drivers’ helmets.
In addition to updating the chassis to meet the new rules, chassis manufacturer are free to provide teams with additional modifications, as long as they stay within the budget. For example, Dallara made changes to the radiators, airbox, engine cover, underwing, front wing, nosebox, and bellhousing, while maintaining the price cap.
In another effort to make racing safer, the IRL is trying to slow cars down by changing the rear-wing setup. It added a vertical wicker bill, or gurney flap, to the trailing edge of the rear wing that acts as an air dam to put more drag on the cars. For shorter tracks, the League now mandates that the first stage of the three-element rear wing be set at 6° to slow the car and help plant the rear end firmly to the ground. It also gives drivers more confidence and control.
REVVING UP FOR INDY
Cost restrictions place a great burden on engine manufacturers, too, as they battle for bragging rights while focusing on reliability and performance. In less than a year, and under tight budgets, engineers at Oldsmobile and Nissan designed and developed racingcaliber engines for last season. Unfortunately, it forced them to conduct testing with very little track time before the first race at Walt Disney World in January.
Oldsmobile emerged as the winner by season’s end, dominating the season by winning all of the races. However, the odds were in its favor, because Olds powered more than 80% of the cars. Also, drivers noted that they got more horsepower out of the Aurora engine. As a result, this year nearly every team is running the Aurora.
Even with a successful year, Oldsmobile engineers didn’t stop improving the engine. “Just like Nissan, we had problems with reliability and performance, mostly attributed to our short development phase,” says Joe Negri manager of GM Motorsports IRL/Road Racing Group.
Though the Olds engine specs were up to expectations, teams had a difficult time adapting engine-support systems to the engine. “It took the first few races to get the bugs worked out of the oil cooling, oil tanks, water, and fuel-tank systems,” says Negri. “Normally you have months and months of testing to work these things out.”
Besides improving system integration, Oldsmobile improved drivability and horsepower. “We updated the electronics and released recommendations to the engine builders for new camshaft profiles with higher lift, improved air intake, and modified the exhaust tuning,” adds Negri.
As the quality and reliability improve, the race teams and engine builders gain confidence in running the engines harder. “At the beginning of the season, guys were only running the engines at 10,000 rpm,” says Negri. “By the middle of the season, they began pushing it to 10,500 rpm, even though we hadn’t validated whether the engine could last 500 miles at such high revs.”
Nissan had similar goals in mind. “We knew we had our work cut out for us this year, after a disappointing season,” says Frank Honsowetz, manager of Nissan Motorsports, Gardena, Calif. “We literally lifted the valve covers off and worked on every single piece underneath them.”
Although nearly identical from the outside, Nissan’s Phase II power plant boasts an additional 60 hp and has shed 36 lb. Engineers got these improvements by tinkering with crankshafts, connecting rods, wrist pins, pistons, flywheels, main bearings, and cylinder blocks.
They also refined the crankcase to minimize windage, or turbulence, and friction in the crankshaft main bearings. “We rounded the crankcase so that the oil has less drag on the crankshaft,” says Honsowetz. “Rotating at speeds greater than 200 mph, the crankshaft slings oil against the sides of the crankcase. A square case ends up with a lot of turbulence, similar to waves in a pool, while the newer round design steadies the flow.”
Concerns for durability last year forced Nissan to reduce compression ratio, restricting cylinder pressure and the load on rod bearings. A year’s worth of work has returned compression levels back to between 14.5 and 14.8:1.
So far, the improvements made to the second-generation Infiniti engine have yielded promising results as demonstrated in testing at the Phoenix International Raceway. Two Infiniti-powered cars logged a total of 448 trouble-free miles, posting a bestlap speed just 1.1 sec slower than the fastest lap time of an Aurora-powered car. “While we still have a lot of work to do, the Phoenix test went a long way to prove that the Infiniti Indy program is moving in the right direction,” says Honsowetz.
The IRL is confident that improvements in engine reliability will result in more competitive races, especially with qualification fields growing from 16 to 20 cars in past years to 28 to 35 cars for this season. “With more reliable engines, teams don’t have to limit practice laps because of concern about blowing engines,” says Brian Barnhart, IRL director of operations. “Last year we lost 15 engines from 10 different cars in preliminary testing at Phoenix. This year we completed 6,100 miles and only lost parts of two engines out of over 25 cars.”
A key to improving reliability and performance, however, is maintaining competition among the engine makers. “The IRL needs at least two engine manufacturers to keep the competition tight,” says racer Roberto Guerrero. “It would be even better if we added another manufacturer to the mix.”
Guerrero may soon get his wish, as German automaker BMW unveiled a new 4.0-liter race engine at the North American International Auto Show in Detroit this January. If submitted to IRL officials this year, the production-based engine will be ready for competition in the 1999 season.
This is a good sign for Tony George, showing that others are recognizing the IRL as a growing force in auto racing. The backing of a growing number of big-name sponsors is giving George confidence that his league will be around for a long time, providing fans with another choice for exciting and competitive racing.
THE DYNAMICS OF A CRASH
GM Motorsports, Warren, Mich., introduced impact recorders to open-wheel racing at the 1993 Indy 500. The socalled “black boxes,” weighing around 2.5 lb, measure acceleration forces up to 100 g in three axes at sample rates up to 2000 times/sec. Supplied by Instrument Sensor Technology, Okemos, Mich., the impact recorders contain three internal piezoresistive accelerometers. The units are installed before races and run continually for an entire weekend event, powered by eight 9-V batteries.
After sensing the trigger condition, the unit constantly samples all three channels and begins recording forces. The trigger is currently set for forces greater than 5 g lasting for at least 5 msec. Once triggered, the unit saves data from 0.5 sec before the trigger point to 1.5 sec after, for a total of 2 sec. The recorder then resets itself and is ready for the next impact. The unit can record up to 10 impacts, after which it overwrites the least significant measurements.
Safety engineers combine the data from the “black boxes” with crash-site measurements and videotape to develop a play-by-play of each accident, down to accuracies measured in milliseconds. “Over the past five years, we have recorded 180 accidents and used the data to conduct 160 impact-sled tests,” says Herb Fishel, executive director of GM Motorsports. “With impact recorders we’ve been able to refine chassis designs so that drivers can sustain impact forces greater than 100 g without injury.”
HAVE A (SAFER) SEAT
With conventional carbon-fiber seats, teams bolt the seats to the chassis tub and then cover them with foam to make them comfortable. However, the seats don’t always provide the best support in accidents. With molded-seats, drivers get full support down the entire back and torso. “The unit loading is much lower when you have a seat that supports every part of the back,” adds John Pierce, safety consultant for the IRL.
In contrast to headrest foams that absorb impact energy, seat foams are designed to provide rigid, even support. “If the seats aren’t rigid and cushion the driver’s body, the seat belts will slacken during a crash,” says John Melvin, a senior member of the research staff at General Motors in Warren, Mich. “Seat belts are designed to help drivers ride down a crashing car and prevent them from getting loose.”
Guerrero now uses a new foam to fill the empty space around his Kevlar seat. The new system involves filling the cockpit with a bag that looks like a bean-bag chair. It’s filled with polystyrene beads and a slow-cure epoxy. To get it race-ready, the driver sits in the cockpit and works the beads into the crevices along the chassis walls. After the impression is made, a vacuum on the bag holds the beads in place while the epoxy cures for a couple of hours. The final mold resembles a Styrofoam butt-shaped cooler and teams finish it by adding a thin layer of foam for comfort.
One advantage to the slow-cure epoxy is its ability to reshape the mold. “While a vacuum is being pulled on the beads, drivers can shift around and make sure the seat is comfortable,” explains Pierce. “If they don’t like the fit, they simply remove the vacuum and take another impression.”
The foam fills the entire space from the driver’s legs to shoulders. The top of the seat extends up to the driver’s shoulders and tapers into the headrest so there are no voids behind the neck or shoulders. Filling the entire shell also helps secure the seat. In fact, they are so form fitting to the chassis that teams must cut them into sections to remove them from the car.
One of the keys to developing the foam seats was finding the bead size with the best energy-absorbing qualities. “We impact tested different size beads and came up with a mandate for bead size,” says Phil Casey, technical director at the IRL.