High-end Design and Hand Craftsmanship Make Fast Parts

Modern Design and manufacturing tools give racing team reproducible results

—by Larry Olson

Hendrick Motorsports, started by Rick Hendrick as All-Star Racing in 1984, has grown from a one-car race team to a seven-team operation located on a 65-acre racing complex in Harrisburg, NC, close to Lowe’s Motor Speedway near Charlotte. The company has claimed six championships in NASCAR in 18 years, including four back-to-back titles in the premier Winston Cup Series from 1995 to 1998, with drivers like Jeff Gordon, Terry Labonte, Joe Nemechek and Ricky Hendrick. The headquarters complex for Hendrick Motorsports (HMS) includes facilities to design, produce, and test cars and engines for all the race teams. All HMS racecars are constructed start-to-finish at the complex, and more than 700 engines are built on-site each year, including some that are leased to other NASCAR teams.

Custom parts for HMS cars are about 80 percent forward-engineered and 20 percent reverse-engineered. According to Jim Wall, engineering group manager for HMS, “Modifying or creating a part that gives us an edge on our competition is our highest priority. In most cases, we prefer to forward-engineer a part from a clean sheet of paper, where we have a specific need and application. Then, we work with our engineers and craftsmen to build a prototype.” If all goes well, the first prototype is a good working part that has no fit interferences in the final assembly, and HMS engineers can run it through failure modes effects, stress, and thermal analyses to guarantee that the part will perform as intended.

“Our job is to optimize the vehicle for a given set of conditions, in a minimum of time,” says Wall. The problem is that track conditions, such as air temperature, humidity, even the effects of direct sunlight, can differ from one lap to the next. “And that affects the grip of the tires on the track,” he explains. “There are some things that we can do that are in the right direction, and there are other things that are just by chance.” A performance situation during a race usually forces the race team to make a quick turnaround in redesigning a part. “If there is a parts failure at the track,” says Wall, “the team has to find out what went wrong and come up with a fix as quickly as possible.”

Typically, when a design change achieves an advance in performance, there is a corresponding setback in durability, because stress levels are always changing. In fact, very small changes can make a big difference. As Wall points out, “On a 1/2-mile racetrack, cars can turn laps in about 15 seconds. If some change in design makes it possibly to save 0.005 seconds on a single lap, over the course of a 500-lap race, that can mean more than a 2-1/2 second advantage on the last lap. On a fast duty-cycle track, that will probably be the difference between winning and losing.”

Pete Hofferman, chief engineer of the No. 24 and No. 48 car teams, adds, “Traditional designs include a margin of safety, resulting in parts that are over-designed. There is always an opportunity to improve the design and make the part more efficient. Since we don’t have all of the forces, pressures, and stresses that the parts are subjected to in real life, we still have to keep some safety margin in the design.” Hofferman explains that the actual conditions at the time of the race can affect the vehicle suspension’s spring and shock calibration for a particular track. In addition, the engine and power train have to be fine-tuned for racing conditions, including cam calibration, RPM range, and transmission gear ratios.

Critical characteristics of a design are often not on a blueprint, but tend to manifest in the part itself. It’s up to the skilled craftsmen to come up with the creative solution. “Most of our reverse-engineering projects start with a part that does a really good job,” says Wall. “We capture the part’s characteristics by taking measurements on a coordinate measuring machine (CMM) using a touch trigger probe and a PC. Then, we enter the data into our I-deas CAD package (from EDS Corporation, Maryland Heights, MO).” The PC-based program creates curves and surfaces from the digitized points, and EDS CAE and other reverse-engineering tools complete the job of creating a finished part.

“Before we had all these metrology and computer tools,” Wall reports, “there was a lot of hand work and cut-and-try, and not a lot of consistency.” Each engine’s characteristics were unique and completely different since the geometry of its critical parts was just not the same. Wall explains, “A fairly straightforward prismatic part can be reverse-engineered with just a pair of calipers. A part that has some complex 3D relationships requires digitizing equipment to get more accurate measurements.” Since the engineering time involved is directly related to complexity, one part can be reverse-engineered from start to finish in one afternoon, while reverse-engineering cylinder heads may take a couple of days.

“We are just beginning to be able to do complete simulations,” adds Hofferman. “Once we have a solid model in the computer, we can do stress, thermal, and flow analysis on the part. Then, we might want to make a few small changes to fine-tune the design.” The software also enables the engineers to do some long-term simulations such as structural analysis. “We do a lot of engine packaging and moving compo-nents around for greater efficiency, such as radiator design changes and modifying ducting,” he concludes. “We are always trying to use fewer parts, lighter parts, and more durable parts.”

Turning garage mechanics into expert designers

NASCAR requires Hendrick Motorsports to use some foundation components that are available to anyone through an automotive dealer. “For example, you can go to a Chevrolet dealer and buy the exact same block, cylinder heads, and intake manifolds that we use for our cars,” says Wall, “If a small garage owner and enthusiast knew what he was doing, he could build a competitive Winston Cup stock car right there in his garage shop.”

The materials for the car body are common materials as well. The frame is made from 1020 steel tubing with a mandated wall thickness and diameter. The only composite materials allowed are air cleaners, brake ducts, cooling parts, and the roof flaps for the lift control. “NASCAR won’t even allow the use of aluminum for the suspension components,” Wall says. “They have to be steel.”

The significant difference is that each car is built basically by craftsmen in the shop. “When the craftsmen come up with a better way to do something,” Wall explains, “they will hand fabricate a part to fit that application. Then, we use CNC machines (from Haas Automation, Oxnard, CA) in the shop to manufacture the parts.” Once the model for a part is completed, the part’s geometry is digitized and the CAD / CAM software generates the G-codes for the machine tools to make the part.

“One example would be a car’s fender,” says Wall, “where we use reverse engineering to capture the character of a handformed piece of sheet metal. Another example would be cylinder heads. We take a port designed by a craftsman using free-forming geometry for a passageway into the engine that has a nice air-flow characteristic on a flow bench. Then we put that design into a cylinder head into eight different places for an eight-cylinder engine. Once that design works out, we might want to get it into 30 or 40 engines. A human being just can’t do that by hand.”

Another example of a creative design change arose from an experience by the engineering staff of the No. 24 car at last year’s Pocono race. The face of the fuel gauge filled up with gasoline in the cockpit during the race, and fuel started dripping out on the floorboards. Luckily, this was not a major leak, and the car was able to finish the competition. In the week that followed, the team used the CAD package to design a gauge isolation block to put a diaphragm between the fuel and the liquid that operated the Bourdon tube-type gauge.

According to Hofferman, “The fuel gauge fix involved building a prototype first and checking it out on the car. It took four days to revise the prototype; and two weeks later the final design was finished, including the tool path for making it on the CNC machine.” The final design for the aluminum housing and diaphragms eliminated the fluid transfer into the cockpit. “We work on other component designs,” he continues, “either for manufacture or for improving parts from stock, to give us an edge. For example, we redesigned an oil filter housing and a remote mounting bracket to minimize size and weight. We have also redesigned the electrical system harness to optimize durability and assembly time. We are always concerned with product life cycle management and an integrated design.”

With all of these skilled professional and engineering advantages, can amateur garage mechanics and part-time car enthusiasts relate to the high-tech accomplishments of Hendrick Motorsports? Hofferman responds: “Anything that we do here is really no different from what a street rodder would do. But, most weekend mechanics would be working on just one engine, where we are doing hundreds of engines. Also, the custom car enthusiast does not have to worry about all the rules and restrictions that are imposed on our cars.

“As for chassis,” he continues, “we have hundreds of cars that we work with over the years. Our situation is more like a production operation. For all of our cars, maintenance and training issues require that the cars be as nearly identical as possible. So, when we make a design improvement, we have to be concerned with the same things that a weekend mechanic would be concerned about, only on a much bigger scale.”

When any company uses high-end design tools to this extent, does it really make a difference in the fit and quality of the parts available to the custom car market? “Actually, craftsmanship is important; but, to-day it can only go so far,” Hofferman concludes. “CAD tools and CNC machining are the keys to better fit and higher quality parts.”