Jim Musser and Jim Hall, Collaborators in the Chaparrals
By John R. Wright
Photo of Jim Musser courtesy of John R. Wright
Published with permission by Parabolica Publishing, LLC, publishers of Vintage Road & Racecar, March 1, 2017
In the early 1960s the Corvair legal problems brought together Jim Hall and Chevrolet’s Research and Development engineers Frank Winchell and Jim Musser. To defend the Corvair, R & D began a Vehicle Dynamics Program under Musser to study the behaviour of cars at the cornering limit of control. At the time who had more knowledge of such vehicle behavior than race car drivers? Therefore, Chevrolet R & D entered into a contract with Jim Hall to do test driving. An important asset was Hall’s racetrack, Rattlesnake Raceway, in Midland, Texas, and for automobile and tire testing Jim added a skidpad. Chevrolet R & D brought various experimental cars to Midland for testing. To be sure, R & D was not a participant in Jim’s racing activities nor did they work on Jim’s race cars. Detail data was collected on the experimental cars which came to Midland along with the components of tires, suspension and aerodynamics. The program was mutually beneficial. Chevrolet R & D got the data they sought and Jim Hall benefited by adding to his knowledge of race cars. His results in various racing series speak for themselves.
Born in Pennsylvania and educated at the Penn State engineering school in mechanical engineering, Jim Musser possessed an intuitive interest in what made things work. He entered the GM Tech Center just a couple of days after his June 1957 graduation. Immediately, he entered what was called at GM in those days, the rotational training program where new hires moved from one department to another, the better to gain knowledge, training and expertise in all the areas which made up the company. His training at the company was interrupted by military service, but thanks to his service work at the Detroit Arsenal and his placement at the armed forces computer laboratory as its head, he gained invaluable training in computers which would stand him in good stead when he returned to GM.
After his stint in the army, he ended up in the Chevrolet Research and Development Department as the result of an interview with Frank Winchell, head of the laboratory. There he created the Corvair Monza coupe, the first monocoque bodied car General Motors ever made, and he and his team of one draftsman and two technicians created the monocoque chassis in but one month. When the car was shown at Road America in 1962 it was there he first met Jim Hall and Hall’s fellow team driver, Hap Sharp. They were there competing in their Troutman and Barnes’ Chaparral I racecars. This chance meeting led to Frank Winchell’s visit to Midland, and a partnership for the study of vehicle dynamics was formed with GM. The rest, as they say, is history. The cars which the partnership produced displayed some of the most advanced technology at the time. Wherever they are displayed, the Chaparral cars are still magnets for car enthusiasts, as witness the tide of onlookers around the Chaparral tent at the 2005 Monterey Historics. Then, there is the continuation series of Chaparrals as planned by Hall and Musser’s teams today.
John Wright caught up with Jim at his engineering company in Almont, Michigan.
VR: So, Jim to recap please tell me again where you took your degree in engineering.
Jim Musser: I took my degree in Mechanical Engineering at Penn State in 1957. I had dinner with my parents on the Saturday afternoon of my graduation and by Monday I was in Detroit.
VR: But your career at GM was cut short by your time in the service. However, you gained something from the Army you might not have expected.
Jim Musser: I took a leave of absence from GM and my time with the army turned out to be a godsend. I was stationed at the Detroit Arsenal, about one mile away from where I lived. The Arsenal was responsible for the design of tactical vehicles. It had hot and cold rooms and land locomotion rooms to test motion on all kinds of terrain. We designed and built prototypes but farmed out 90% of the projects to outside sources. As luck would have it, the guy who was head of the computer lab left and I was put in charge of that lab. We had analogue and digital computers, and I was using computers for analysis of projects we undertook. Developing expertise in that area stood me in good stead later at GM. I should mention that this computer was filled with vacuum tubes, occupied a large room, and had less power than a hand calculator of today!
VR: So after your service to what department did you go in GM?
Jim Musser: When I returned to GM I went to the Structures and Suspension Department in Engineering Staff. I should mention that I was highly influenced in suspension work by what Colin Chapman was doing. In the GM Tech Center at that time there were four staff activities: Styling Staff, Engineering Staff, Research Staff, and Manufacturing Staff. Each were in separate buildings. Research had a computer, but no one was using computers at that time, you must understand. I was okay with computers because I had learned to write programs in Fortran in the army.
VR: So, how long did you stay in that department?
Jim Musser: I only stayed at the Engineering Staff for one year, working on the concepts of suspension. I should point out that the divisions didn’t rely on Engineering Staff as they had their own engineers in their own divisions and that led to some interesting situations.
VR: Let’s cut to the chase and discuss how you came to work for Frank Winchell and first came into contact with Jim Hall.
Jim Musser: I requested to interview with the head at Chevrolet. Frank was the chief research and development engineer at the time. They lined up two interviews with the laboratory and R & D. R & D was a separate department, and had its own engineering office and shop area. It was a self-contained entity. Frank told me that he didn’t have an opening, but he had some pull with Ed Cole at Chevrolet. So, in 1960 I ended up at Chevrolet R & D. Now, you have to remember that at this time, Chevrolet was involved in some lawsuits regarding the Corvair. Chevrolet R & D was given the task of preparing the technical defense of the Corvair, and that led to some interesting projects. We dove into vehicle handling. Up to that point, vehicle stability was directed towards the normal driving range that is below 3/10ths of a G. There were no studies on cars at the limit of control. Frank Winchell set out to study it. He was originally a transmission engineer and knew nothing about the subject, and that was a plus. He started from the ground up. He asked who were the experts at the limits of control? The answer was race car drivers in race cars.
VR: So where did that lead Frank, you and the rest of the engineering team?
Jim Musser: In Chevy R & D we studied tires, suspensions, geometry. We studied every facet of handling. We took measurements of every car that was, all the production stuff plus go karts, a Lotus Fjr, and a Cooper. We ran tests on a range of cars and went deep into that area. GM was also looking at small cars with front wheel drive. Frank created teams to compete in the production of prototypes. My team created a front wheel drive version of the Corvair with the Corvair drive train up front and it won over the other groups. Bill Mitchell of Styling saw the prototype and was enthusiastic about it. He wanted me to build a mid-engined sports car version and he would put a body on it. The catch was he wanted it done in two months for Road America. I decided to build a monocoque chassis because that’s what they were doing overseas. I had it done in a month and sent it off to Styling and they had the body done in a month just in time for a Road America race weekend in 1962. Bill Mitchell and Larry Shinoda had a secret studio in a basement where they did clay models, without authorization, and I frequently visited it. That car was called the Monza GT. Bill loved to have a Chevrolet Corral at the track where he would show off what Chevrolet was doing. I went along and that was where I met Jim Hall.
VR: An important meeting.
Jim Musser: Jim and Hap Sharp were there racing their Chaparral Is. Jim saw the new silver coupe and we started talking about handling and other stuff. That led to a visit by Frank Winchell to Midland and it kicked off a program to use the Chaparral facilities to test. We could test outdoors there all year as opposed to Michigan. The only thing Midland lacked was a skid pad and part of the agreement was that if we rented a building for testing and development, Jim would build a skid pad. If you run a vehicle on a skidpad, you can readily determine understeer/oversteer. By the way, we tested every kind of passenger car, go kart, and racecar we could think of on that skidpad. It was not a racing program, however.
VR: I’ll jump ahead a bit, in talking about skidpads to your work with Mark Donohue and Roger Penske on testing their Trans Am Camaro on the skidpad.
Jim Musser: I was involved with Mark and Roger on the Trans-Am Camaro. The car was not working for them. They brought the car to Detroit and we tested there on a skid pad. Initially Mark said,”Why do that at thirty miles per hour?” I showed him what could be done with lateral acceleration. They went back to their shop. Some time later I went to Philadelphia to the Sunoco refinery there. Roger had built a skidpad on the refinery property. Mark was a convert. It got to the point where after they finished building a car, they would run it on a skidpad to check out suspension settings first.
VR: Now back to Midland and your work with Jim Hall.
Jim Musser: We employed Jim for the test work and he was really superb. He could test at the limit and as an engineer he understood what was going on. We collected knowledge at the limits and set up various experimental cars.
VR: You experimented widely at Midland, didn’t you?
Jim Musser: We did quite a bit of work at GM and at Midland. For example, we developed a method of building scale plastic models out of clear vinyl plastic which we welded together using heat guns. We would make 3/8-inch-size vinyl parts and test them, test the deflections. We were working backwards, and we could compute what the full size part would be. You could pick up a model and twist it to see deflections. We could see where certain panels would buckle and we could predict where to reinforce. We would keep modifying the model to get the torsional stiffness we wanted.
We also built a suspension test car which was infinitely adjustable. I also have a patent on the rear suspension with 100 per cent anti-squat and lift. It also had roll understeer. Maurice Olley, a world renowned suspension expert who also worked for GM, complimented me on it. We built devices to test tires too. We collected data which was valuable for Jim but also for GM in the course of the Corvair lawsuits. When we did the tub of the Chevrolet 2B we got 310 foot/pounds/degree stiffness in the suspension. In order to have the suspension roll stiffness distributed between the front and rear of the car, I kind of arbitrarily said we needed a stiff chassis on the order of 3,000 foot pounds per degree of stiffness. In the 1960s suspensions were relatively soft. So, we had to stiffen them up because of the downforce.
Today, in racing cars there is so much downforce the suspensions would go into compression and therefore an extremely stiff suspension is needed. The chassis requirements of stiffness are now in the order of 10,000 foot-pounds per degree.
VR: You spent some time with the Chevrolet 2B car at the GM proving grounds and came across some interesting moments in testing that car.
Jim Musser: There was a long straightaway at the proving grounds and I decided to wind the car up on the long three mile straight. By the way, the nose piece had two springs holding it on. At any rate, when I got up to speed, the whole front rose up against the springs. A rather unsettling experience. Back to the shop. Frank Winchell said that must mean there was higher pressure under the body. We had a U-tube monometer and could plot the pressure on top of the nose and underneath. We discovered a pressure differential under the body and so we cut holes in the fenders of the nose. We also found a low pressure area at the windshield area. So, on the original Chapparal 2, Jim used louvers in the fenders. When the other competitors noticed the louvers he said that there was a heat problem with the Firestone tires he was using and they accepted that but then they later copied what he had done. If we had fastened the nose more securely on the Chevrolet 2B we wouldn’t have discovered that anomaly.
VR: That’s when you discovered that drag was not as important as downforce.
Jim Musser: Yes, drag is not as important as downforce. If you plot a speed profile around a course, if you reduce drag to an accelerating phase your time drops down. If you do something to increase cornering speed, you brake later and carry more speed down the straightaway. When you increase cornering speed, you increase the speed of the car all around the course. You elevate the entire speed profile of your car. If one car takes a corner one mile per hour faster, the higher cornering speed the car carries that one mile per hour to take the lead over the car with the higher top speed. Jim improved downforce in the Chaparral and improved lap times. You have to understand that these things evolved. No one had a light go on—we all went at it step by step.
VR: You also spent much time at Midland on tire testing.
Jim Musser: At Jim’s shop, we had Rattlesnake Raceway, and we were in a constant development process. That was such an asset and it showed when Jim ended up with cars at the track ready to race. We did spend quite a bit of time at Midland on tires and examining the behavior of tires on the skid pad. The only tire data we had was in the linear range, the normal range—that is, a 3/10th of a G. There had been no tire testing done at high slip angles. We had a device on the skid pad like a merry-go-round. You have to remember that this was before computers were available to do this type of testing. No one else was doing this type of thing at the time, doing data collection. We were not trying to duplicate what Chapman was doing or had done suspension wise. What we had was a clean sheet on suspension. We built an STV, a suspension test vehicle where the suspension front and rear was completely adjustable. It influenced our approach to race car design.
VR: So, then to distill what you were doing outline for me what it was you were studying in vehicle handling.
Jim Musser: We were trying to maximize what I would call the GG diagram—a Bill Milliken term, by the way. Basically the GG diagram is concerned with the non-linear behavior of tires at the limits of their cornering power. Think of a circle drawn around a tire. This circle represents the tire’s capabilities. If the tire is on a road surface, and if it has a coefficient of traction of One, say, you should be able to accelerate at One G, corner at One G and decelerate at One G. Bill Milliken who taught engineering at Cornell University, put the name on this feature in his book, Equations of Motion, which is a standard text at a number of universities. You want to study what a tire was doing when it was moving forwards, what it was doing under braking, and cornering. We wanted to maximize the circle. We also studied brakes, drive train, suspension geometry, and tires.
VR: Now let’s get to the Chaparral racing project. Can you describe for me how you came up with the aluminum tub for the Chaparral 2C? Or as Jim Hall and Hap Sharp called it, the “Eyeball Jiggler?”
Jim Musser: The 2B was our test vehicle before the Chaparral 2C. In the 2, we had a target weight of 1500 pounds, including the driver and a half load of fuel, or 18 gallons of gasoline. We created an aluminum chassis bonded with an adhesive, a 3M product which was like a paste. We troweled it on and put it in a paint oven to cure it. Otherwise it would stay a paste forever. We relied primarily on the adhesive plus some simple pop rivets to hold the chassis together until the adhesive set. Adhesives were just starting to be used experimentally and there was some concern about longevity.
As regards the 2C’s flapper, at that time it was hard to set up racecars for high speed and low speed turns- they would either push or be loose. One thing which came out of the Chapparal program was we would set up the car for a lower speed turn on the skid pad and then leave the suspension alone and deal with the aerodynamics for high speed turns, balancing the aerodynamics at the front and at the rear. The things we did to downforce led to drag and the problem was to eliminate the drag at high speeds. We learned that at high speeds and downforce the suspension would bottom out with the soft springs we were using in those days. Therefore we came up with the idea of feeding the downforce into the suspension with the wing struts on the 2E into the suspension of the car.
VR: Then the FIA banned high wings.
Jim Musser: There were failures, that’s true. Generally we liked the USRRC and the Can-Am because it was an unlimited class and Jim was an innovator. For example, when he did the sucker car which was banned, he decided to get out. As for that idea, I am not sure where it came from. Jim did say in an interview that it was a kid who wrote him a letter mentioning the idea.
VR: Then, there was the Chaparral 2H
Jim Musser: That car was strictly Jim’s. He deviated from what we had learned in the previous cars. He wanted to reduce drag and created a narrow vehicle. He incorporated a DeDion rear suspension at the back of the car because with the wide tires there wasn’t room for a conventional suspension. The real problem was the rear De Dion suspension had violent hopping under acceleration which was never totally cured. That car was very innovative but that suspension was a problem.
VR: Then there was the famous and secret transmission which no one figured out until a couple of races into the 1964 season.
Jim Musser: The Halibrand axle center section was the inspiration for the transmission. We needed a reverse gear though and we created a rear section like Halibrand where the reverse gears were ahead and the forward gears where were you could see them and therefore you could get at them to change ratios. We used a torque converter to fill in the gaps to make a good start. The torque converter provided the start and it would allow you to start off with a wide open throttle. We went to a 1:1 ratio. As tires became better, we had more traction and we couldn’t get a good starting torque and couldn’t get a higher top speed with a single gear ratio. Then, we needed more forward speeds in the transmission and then we went to two speeds and no reverse. By the time of Le Mans we had gone to three speeds in the transmission.
VR: No one knew at first what they were up against.
Jim Musser: the Chaparral 2 ran two races with the torque converter/ transmission and no one noticed. I found that surprising as I thought the sound of the car on the track would give it away. It had a Buick Dynaflow sound.
VR: There is life after racing they say. What paths did your career lead you after your work with Chaparral?
Jim Musser: I was made head of Chevrolet Research and Development and then assistant chief engineer of Chevrolet. I got to know Bunky Knudsen a race enthusiast. When Ed Cole became president, Bunky went to Ford but it didn’t work out and he left after one and a half years there. Bunky then called me and asked me to go into business with him building motorhomes. I had always wanted to become an entrepreneur and decided to leave on January 31, 1970. After 14 months, White Motors acquired our company, Bunky became CEO of White, and I became vice-president of engineering. When Bunky retired in 1980, he and I started Knusaga Engineering—New Saga—based on the first syllables of his last name and saga for story. I had a friend from GM who developed a seating package for the Chrysler van and we set up to produce this package for their minivan.
VR: How did you become involved in the continuation series Chaparral project with Jim Hall?
Jim Musser: My business activities were winding down but I still had my love for cars. I loved that 2B car. The car still exists in Midland. I told Jim I would like to come down to Midland, measure it and build one. In talking to Jim’s mechanic he told me that the most expensive part is doing the body. Furthermore the molds still existed for the 2E. I talked to Jim and told him I would like to build a 2E. I said the problem in vintage Can-Am racing is that there are so many McLarens and Lolas but no Chapparals. Jim thought it was a good idea and we became partners in building a 2E.
It took longer than I thought though. It was my experience in building prototype cars which helped, but the last 10 per cent of construction takes as long as the previous 90 per cent. As they say, God is in the details. It’s a pretty complicated car. When we looked at the gearchange for example it was backwards at first. There were details with the wings—we had to make everything from scratch, the wheels, the rear uprights, and we didn’t have a big crew to work on it.
VR: Where is the car now?
Jim Musser: It’s been at Midland for a while. The car was tested by Mark Gillies in Car & Driver magazine. He was impressed by it.
VR: So, what is in the future for you, Jim?
Jim Musser: Well, we have family out on the west coast, but we have asked ourselves if we want to leave the area. We’re having second thoughts about making a major move.
VR: Jim, thanks for your time and for the history of your involvement in suspension design and with Jim Hall and the Chaparrals.
Thanks to John R. Wright for providing his article.