The need for speed: casting for high performance.
* The requirements for producing cast components for use in high-performance applications can be every bit as demanding as those placed on the vehicles themselves.
* Detailed within are the unique requirements placed on these castings and how metalcasters and design engineers meet the challenges.
Everything is sped up in the world of high-performance vehicles. Cars, boats and motorcycles are raced under intense conditions in which they are expected to double the speed of normal vehicles while equaling their reliability and durability'. What most people see is a car whizzing around the track in a blur of light and sound as it reaches 200 mph, or a boat skimming effortlessly across the water topping out at more than 100 mph. But what the casual observer won't notice as these vehicles dash across the finish line on race day is the preparation that goes into getting them ready to compete.
That includes making sure that each component within the revved-up vehicle does its job and will not fail. The slightest malfunction of any given component can have catastrophic consequences under such intense conditions. That's part of what makes producing cast components for use in high-performance applications unlike any other task in the metalcasting industry. And let's not forget, not only do the components have to be more durable, but they also are often produced in lower volumes with shorter leadtimes, which goes to show that all areas of high performance production are dependant on one thing--speed.
Playing it Safe
The words "low volume" and "short leadtime" can be terrifying for metalcasters. The demands of producing a component in only a few weeks can be rigorous. But when it is a low-volume component, those demands are magnified because it has to be right the first time. When designing components that will be pushed to their absolute limits, it pays to error on the side of caution.
"We are generally talking about low-volume production with (high performance castings)," said Mike Stahl, Olson Aluminum Castings, Rockford, Ill. "That's a far cry from running 250,000 500,000 of something. When you are going to make a few parts, if anything, you want to overkill to make sure they are good parts. With a higher volume, you have the luxury and responsibility to skim things out. Also, speed to market with these things is relatively important. Those elements cause you to be more on the conservative side. The design has to be safe and conservative going in because you only have one shot at pulling this off in two weeks, and you don't want to get 12 or 13 days into it and realize it won't work."
The conservative approach has helped Olson Aluminum Castings successfully produce several cast components for use in high-performance applications. A drive shaft housing and an adapter plate for American Powerboat Assoc. (APBA) stock outboard engines, as well as a gearbox for Daytona Prototypes are high up on its resume.
The Daytona Prototype gearbox (Fig. 1) is a 44-lb. aluminum casting that was produced in nobake sand. Using 356 aluminum provided the high strength-to-weight ratio needed to withstand the demands of competitive motor sports. And because of the low cost of tooling associated with sand casting, engineers from EMCO Gears, Chicago, were able to quickly make design changes.
[FIGURE 1 OMITTED]
But the process wasn't as simple as that. In addition to being leak-free, the component required some special characteristics such as increased stiffness, reduced weight and excellent machinability. The casting had to be particularly stiff because it served as an attach point for the rear suspension and air foil.
As is typical with most high-performance components, the design started with a rough outline and modifications were made along the way.
"It begins with the chassis manufacturers," said Peter Koenen, EMCO senior engineer. "They give us some general outlines of size and weight of the transmission and where they want it to be in the car. Working from the general envelope, we see where our gear train will be and do some modifications. We begin wrapping the gear train and stretching the material out to where it needs to be for chassis manufacturers. Then we come up with a package and submit it to the chassis guys."
The final design placed an emphasis on strengthening the attach points through the use of webs and ribs to add a degree of rigidity. Extensive machining was going to be needed after casting was complete so it also had to he produced free of voids, porosity, oxides and shrinkage.
And that comes back to the conservative approach.
"You have to be conservative on the side of adequate machine stock," Stahl said. "Machine stock will make or break the casting. Aluminum oxides are death on tooling. Once the tooling is shot, it is difficult to hold dimensional stability. We expect our castings to machine like bar stock."
The final product got its first real test in December 2002 in Daytona Beach, Fla., when it was put through 28 straight hours of testing without experiencing any major problems.
"The car is very impressive right out of the box to be this reliable and steady," said driver Scott Sharp. "The brand new gearbox from EMCO has been doing great."
Speeding Things Up
After completing 28 torturous hours of racing, Stahl and Koenen knew they had succeeded in producing a gearbox that could withstand the rigors of auto racing. But they also knew that their success in getting it to the customer on time was not entirely their own. When dealing with short leadtimes, the dependability of the patternmaker becomes more critical. The ability to quickly produce a reliable pattern be comes essential.
Clinkenbeard & Assoc., Rockford, Ill., a firm that specializes in rapid turnaround of patterns was chosen to work on the Daytona gearbox.
"The digital 3-D modeling is the key because we can shoot our models to the patternmaker," Koenen said. "We probably wouldn't have been able to meet our delivery date if it wasn't for them."
Olson Aluminum and Clinkenbeard & Assoc. also collaborated on high-performance castings to he used in APBA outboard engines. When the engine went out of production, the tooling for the drive shaft housing and adapter plate was lost. But eventually wear and tear brought about the need for replacements, and Olson Aluminum was approached with solid models of the original drawings of the components. The firm was then able to CNC machine the tooling and make minor modifications to improve performance in a short time span.
In the drive shaft housing (Fig. 2), the firm added stock in critical areas and increased the overall thickness to prevent breakage that was common with age. The cast component was designed 1.5 lbs. heavier than the original version, which increased the life of the component.
[FIGURE 2 OMITTED]
The added weight was an accept able trade-off for the added security of a more durable piece.
"It is of primary importance to remember that failures can be catastrophic when you are running at 80 mph in an 11-foot boat with a field of competitors in close proximity," said Olson Aluminum president. Tad Olson.
Again, the quick turnaround of the components was due in large part to the ability of the patternmaker to quickly find an acceptable solution. But of course, it is possible to save time by skipping that step altogether.
Buckley Systems, Ltd., a New Zealand Grand Prix motorcycle team, found itself in a bind and needed to cast a new engine block for its 500cc motor cycle (Fig, 3) in a hurry. It turned to Soligen, Inc., Northridge, Calif., to have the piece produced via the direct shell production method. The process uses 3-D printing to make a ceramic mold complete with integral cores and gating directly from the CAD data. It used to take 5-6 weeks to make conventional patterns and coreboxes to cast the engine. Soligen had the engine ready for testing in 18 business days.
[FIGURE 3 OMITTED]
"The complexity of our design, along with the need for a short leadtime led us to this patternless casting method," said Paul Tracey, Buckley project engineer. "We were in crisis mode and only this process could get us a race-ready part when we needed it."
Just producing the part in time was feat in itself, but the new casting delivered a 25% increase in horsepower and significant cost reductions.
Sometimes, to further complicate the process of designing components for high-performance applications, aesthetics play a part. Roush Performance Products, Livonia, Mich., wanted to produce a new, custom intake manifold for the Stage III Mustang (Fig. 4), a high-performance version of Ford's Mustang GT. Traditional aluminum castings lacked dimensional stability and increased machining time, which led to higher costs. After enlisting the help of TPi Alcade. Arcade, N.Y., and its V-Process casting method, the components had improved consistency and less machining time.
[FIGURE 4 OMITTED]
The manifold has to be geometrically precise because it mates with the supercharger, cylinder heads and inter-cooler. It also includes a number of mounting holes for rails and coil packs.
"Dimensional stability in the casting is critical because it affects the machining we do to create the mating surface and the mounting holes," said Mark Yagelo, Roush design engineer. "Dimensionally stable parts eliminate additional setup time, reduce machining and cycle time and allow the part to be produced at a lower cost."
Because the manifold was a low-volume part (1,000 components), the higher cost of the process was balanced out by lower tooling costs. In addition, the manifold now takes only 90 min. to machine, compared with 150 min. with the previous component.
The other advantage to the new" manifold is the appearance. The Stage III Mustang has a 360-hp engine that can take the car from 0-60 mph in 4.3 sec. It is a race car in it street car frame, which means its owners like to show it of--all of it. The smoother appearance of the new manifold fits in perfectly.
"The manifold sits on top of the engine so when you pick up the hood, it is the focal point," Yagelo said. "The overall appearance of the part is very clean and pleasing to the eye."
Time for Fun
While the process of producing a component for use in high-performance applications is often times demanding, it is not without its perks. A concern engineers normally don't have hanging over their heads is cost. As Koenen explains, customers for these types of components want to make sure they are getting the highest quality material possible. And the price tag is not normally in the forefront of everyone's mind.
"Material expenses don't normally play a factor in the components we make for these applications," he said. "To a certain point they do, but because the quantities are so small, there is a modest margin there. The cost can be pretty high."
In addition to having the added benefit of knowing they don't necessarily have to reduce costs at every step of the process, Koenen admitted it is satisfying to see the end product hold up.
"It is fun," Koenen said. "You get to see a product go from conception to reality in nine months. And to see it complete a 28-hour test is pretty cool when you know you were intimately involved with it."
While there are a lot of differences between castings for everyday use and those used in high-performance applications, at least one part of the process should remain same--upfront planning. The initial stages of the process are vital to the component's success.
"We made sure from as early as we could that we were meeting with the metalcaster and patternmaker and deciding what the goals were and what limitations we were bringing to the table," Koenen said. "We had to figure out how we were going to make the cores and put the tooling together, and that took all three of us coming to an agreement."
Getting to an agreement was not always easy, but end results speak for themselves. And if discussions occur early on, the component has a better chance of meeting expectations.
"Generally the design comes to us pretty much as they want it," Stahl said. "They give us some features they want us to look at and then we make compromises. A number of different things get thrown on the table. A lot of ideas are nuts and off the wall, but from some of them come some very good ideas, If you plan up front, you can save on the back side. I don't honestly think every body in the industry devotes enough time to that front-end thinking," MC
For More Information
"Prototyping Produces Sand Molds, Cores for Production Casting, s," R. Gustafson and A. T. Spada, MODERN CASTING, August 2002, p. 38 39.
"Improve Casting Quality, Reduce Leadtime Via Rapid Prototyping," R. Gustafson, Engineered Casting Solutions, Fall 1999, p. 37-40.
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|Article Type:||Cover Story|
|Date:||Jun 1, 2004|
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