Tech Notes: A Chaparral Racing IFS Story

Bobby Unser gives rise to modern suspension performance
Eagle River IFS Chaparral
Out of the gate, Larry Omans took the start at Eagle River and led the field into turn one with his IFS Chaparral. What could have been a dominant performance at the ’72 World Championship, ended only seconds later with a broken chain.
If you have been reading the last couple of issues, you probably noticed our stories about old school intuitive engineering and the development process the IFS front suspension went through. In both cases, we credited Bobby Unser with the original IFS design, but for years we have wondered exactly how he came up with this iconic engineering design.

This design ended up being totally dominant when applied by Gilles Villeneuve on his 1976 Skiroule and Bob Eastman on his Polaris RXL sleds.
The basic concept was way ahead of its time back in 1971 when Bobby designed it for the Chaparral race team, and it has proven its sound concept by being adopted by the majority of the manufacturers and has since found its way onto millions of consumer sleds.

■ Straight to the source
We finally decided to ask Bobby himself, and AmSnow’s Editor, Mark Boncher, gave me the go-ahead for a feature story. To most of the world, Bobby Unser is an American superstar on the Indy car circuit, with three Indy 500 wins and USAC Championships. Not only was Bobby a superstar, but so was younger brother Al, with four Indy 500 wins and Al’s son Al Jr, with two Indy 500 wins. That’s a total of nine Indy 500 wins among them, and they are all enthusiastic snowmobilers!

Bobby’s dad Jerry was a self-educated master of his trade. Jerry could do anything, Bobby told me. He could build houses, cars, engines; do fabrication work, plumbing and carpentry. He was also good with slide rules and trigonometry. When the family moved from Colorado Springs to Albuquerque, Jerry opened up a garage on the outskirts, right on the busy US 66. Jerry soon got a reputation as a man who could solve any problem, and he was especially good with foreign cars. Before the boys were old enough to get their driver’s licenses, they thrashed around the fields with an old Model A Ford. They also learned how to work on cars in their dad’s garage, and when they later started racing on the southwest circuits, they worked on and built their own racecars.
Bobby Unser Indy car
Bobby Unser at Indy in 1972.
Building racecars and innovating, testing and developing new ways to stay ahead became second nature. With it came an intimate knowledge of how suspension systems worked, and how to set up the cars to handle in different conditions. This was great education that built up a strong experience base and intuition for what could work even better. Bobby’s adventures on Pikes Peak brought him in early contact with already famous Indy driver Parnelli Jones. Parnelli became a lifelong friend, and insisted that Bobby come to Indianapolis and try his luck.

At first, no one would give Bobby a chance for his rookie test, but Parnelli insisted and finally Harlen Fengler, the boss at Indy let Bobby take the rookie test. Not only did Bobby pass the test, he qualified for the race, in his first try at the “Brick Yard.” This led to a ride in Andy Granatelli’s NOVI racecars. These were powerful supercharged V8 cars that most drivers were afraid of, but Bobby’s experience with big sprint cars meant that he could control slides even on the asphalt as he muscled the big car around.

Bobby’s aggressive driving style was noticed, and he soon ended up with top teams. By 1968 he won his first Indy 500 in Wilke’s Leader Card car. This was a Gurney Eagle chassis with a new and yet unproven Offenhauser – Drake turbocharged engine. The gamble worked out, and when Dan Gurney retired, his main sponsor Goodyear moved Bobby over to Dan’s seat in the Eagle cars. With Dan’s Eagle he won his second Indy 500 in 1975. He finally ended up driving for Rodger Penske and won his third Indy 500 in 1981. Although Bobby was plenty busy with his Indy car and Pikes Peak adventures, he had found a new and exciting hobby in snowmobiling.
Bobby had a ranch up in the mountains in Chama, New Mexico. He was good friends with Don Graham at the Elkhorn Lodge. Don was an excellent hunting guide that had an intimate knowledge of the back country. Don was also heavy into this brand new winter sport of snowmobiling, and let Bobby try some sleds. The Unsers used to rent his restaurant for New Year’s parties, but it did not take long until they became fun snowmobile parties with “grudge” races between the drivers. Through his activities with Don he also came in contact with the Chaparral factory crew who tested in the area. Chaparral was out of Denver and wanted to make a name for themselves, in this new and fast growing industry. Doing well at the Eagle River World Championship would put their brand on the map, but so far they had failed to make it to the final against the brutal full factory efforts of the day.
Chaparral Unser IFS suspension
The IFS suspension was an advantage in cross country races.
■ Chaparral makes deal to win!
Chaparral sleds were of sound design, and Don Brown had won the SOO-500 Enduro race on a Chaparral in 1971, but Eagle River was the BIG prize. George Walker was the company president, and he contacted Bobby to see if he would help them get to the final in the World Championship. Bobby was interested in the challenge, but he had his own special conditions. Through his car racing career, Bobby had earned a reputation as a very demanding hands-on driver with his own ideas about how to set up a car. This often clashed with conventional wisdom of other tuners and made it hard for Bobby to get his way. When they did set the car up his way, he often won, but he did not like fighting the bosses. “I will do it!” he told Walker. “If I am the boss and you give me total freedom and what I need to do the project!”

Walker realized Bobby knew how to win races and took a chance on his experience. “How much money do you want?” was the next question. Bobby had plenty of money as a top Indy car driver with a 500 win behind him. “I don’t want any money,” Bobby said. “I will do it for the challenge if you give me what I need and a couple of good fabricators, but if we qualify for the final at Eagle River, I want a big time ‘Bobby Unser party’ at the end of the season.” Walker had no idea what kind of party Bobby was talking about, but he accepted the deal. Now the fun started.

Bobby felt the winning edge would be to get better control of the front end. Tracks were still rough and run on hard packed snow that tore up during the 15 lap World Championship final.

First they laid out the components around the chassis. Bobby wanted real coil-over hydraulic shocks to control the suspension action, but he also wanted a low center of gravity. With the wide triple engines, there was not much room for A-arms, so they built the suspension around the engine bay. This resulted in a large open engine bay, with room for tuned pipes. The Chaparral triple engine had a special mounting system that allowed Bobby to place the engine right on the bottom of the frame without using an engine mounting plate. This resulted in a very low center of gravity which in turn reduced chassis roll in the corners.
Al and Bobby were Indy racing superstars in the summer and doubled as super enthusiastic promoters of snowmobiling in the winter.
Bobby wanted the arms as long as possible, so the ski-spindles were mounted on swing arms located back by the footrests, and the travel geometry followed two long radius rods mounted into the center of the front bulkhead. Steering rods lined up with the front radius rod, in order to minimize the bump steer. The shocks mounted to the front bulkhead and he also added a road race style sway bar. This was an absolutely unique suspension design never before seen on a snowmobile, and as it turns out 10 years ahead of its time before it finally went into production in 1981 on the Polaris TXL Indy.

Two versions were made for racing, a 440 and a 650, both triples. The engine work was farmed out to Harvey Stuska in Denver, famous for his Stuska water brake dyno’s. When the sleds first appeared they created quite a sensation, and many predicted that the design was too “flimsy” and would break during hard racing. In reality, nothing broke on the suspension, although they had plenty of problems with other parts like chains, belts and engines. When the finale lined up at the Eagle River World Championship in 1972, Larry Omans was in the field, so Bobby had accomplished his goal. When the start went, Larry blew away the field and led them all into the first turn. His success was short-lived, however, as the chain broke coming out of turn two and Mike Trapp passed him and took over the lead, winning his second World Championship for Yamaha. Although Larry did not finish the big race, earlier in the World Championship weekend, Mike Bettis of Green Bay had won the 440 Modified class in the cross country event, and later in the year Roger Padie on a Chaparral won the Alaskan “Midnight Sun” cross-country endurance race.

Chaparral was now firmly on everyone’s radar, although IFS suspensions were still only on the race-sleds. Bobby had more ideas; his next project was to mount racecar wings on the sleds. A sled with wings was made and tested, but was nixed by marketing as too radical and “out of the mainstream” for the general public. Bobby’s IFS design was elegant, effective and proven over time by being part of millions of sleds, improving and changing the way designers thought of controlled long travel suspensions.

In the end, Chaparral’s George Walker threw Bobby his party out at Walkers ranch; and what a party it was! Bobby had the racing department build a 21-foot barbeque grill for the meat and two large bowls for boiling the fresh shrimp they brought in from Louisiana, along with the lobster flown in from Maine.

Employees from the race shop, their families and kids, all the management, important racers, crew and sponsors were invited. Bobby also made sure that everyone in the press that had featured their effort was invited, including paid airfare, hotel and rental cars. It was a real “Bobby Unser” party, and when George Walker finally got the bill, he said “It would have been cheaper to PAY HIM!” But no one could deny that the PR value was great, and all the hard work was rewarded with a fun finale to a challenging season!
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