Raccolta casi Working Model, visualNastran & SimWise - Snowmobile

Contatto Editoriale:
Paolo Lista, Lista Studio srl®
Borgo Belvigo 33, 36016 Thiene Vi ITALY
tel/fax 0445,372479 o info@lista.it

Renowned high-performance snowmobile manufacturer
uses engineering software solutions to re-establish performance identity

In its formative years, the snowmobile industry consisted of a small group of specialized manufacturers whose success and reputation relied on function and performance. These days, manufacturing giants rich in development and marketing dollars are pursuing a piece of the pie too, meaning serious competition for smaller companies like Illinois' Scorpion Recreational Products (SRP). To stay ahead of their larger rivals, Scorpion banks on a name rich in heritage and the performance and quality that comes through careful, innovative design and engineering.

One advantage Scorpion maintains in product development is an arsenal of engineering software including Working Model 3D dynamic simulation software. "It's a great piece of software," says engineer John Mitchell. "As part of a larger solution using SolidWorks and finite element analysis software, Working Model helps us get a very complete idea of how a sled will shape up from our desktops."

SRP is the newest incarnation of Scorpion Snowmobiles, one of the sport’s legendary manufacturers. For years Scorpion was renowned for engineering the fastest snowmobiles in the business, but when the sport was hit hard by the recessions of the 70’s the company was unable to survive. In 1997, Scorpion was resurrected by a team of enthusiasts and engineers determined to revive the company’s prestige. And even though their first product, the Sidewinder is not scheduled to reach consumers until the 2000 snowmobiling season, reviewers are raving about Scorpion prototypes and customers are advance ordering in the thousands.

According to Mitchell, simulation software was vital to delivering prototypes capable of generating positive reaction from press and potential customers. "Working Model simulations enabled us to take a lot of scenarios to the extreme," says Mitchell. "We confirmed our beliefs about what the sled could do and diagnosed potential problems long before we committed it to metal."

Challenging Industry, Challenging Sport

Whether in competition or in simple recreational use, snowmobiles live rough lives. Regular exposure to cold wreaks havoc on metal and plastic components and the jarring, uneven terrain that typifies trail riding can shake inferior snowmobiles to pieces in a few seasons.

With the Sidewinder, SRP wanted to deliver the performance that made the Scorpion name famous in a more reliable and rugged sled. To meet their objectives, Scorpion designed the Sidewinder to specifications never before seen on a commercially available snowmobile and tested design feasibility in SolidWorks using Working Model 3D.

With an eye toward rider comfort and safety and racing-level performance, Scorpion paid special attention to the Sidewinder's suspension. Early on, the design crew decided that a break from conventional suspension design might solve some long-standing problems. "Since the beginning, snowmobiles have used coil-over-spring suspension," explains Mitchell. "They're rugged enough, but don't give you much flexibility. We decided we could get a lot more flexibility, reduce the number of parts and minimize our unsprung weight with a combined spring and torsion bar suspension."

A nimble sled wasn't the only design objective. As riders themselves, SRP engineers know the torture a snowmobile endures in common use and sought to make the most rugged sled possible. With that objective in mind, SRP engineers subjected the Sidewinder and its suspension to some grueling virtual tests including a ten foot drop of the Sidewinder onto concrete. As Mitchell explains, the results occasionally raised eyebrows. "When we simulated the ten foot drop in Working Model, we determined that we would need our coils to handle 600 lbs per square inch. We took that figure to our subcontractor and they looked at us like we were nuts. But we wanted this sled to do anything the wildest snowcross competitor could imagine."

While SRP’s subcontractor did not have 600 lb/square inch springs available, the simulation proved the viability of the concept and helped the spring manufacturer develop the necessary hardware. "The fact that we had a clear simulation running on proven formulas helped us demonstrate to our sub-contractor that it could be done.”

Optimizing Transmission Design

Not every component of the Sidewinder was devised from scratch. For many components, Scorpion turned to the best available suppliers and fine tuned their products. The Sidewinder's variable transmission, for example, was optimized for higher output using Working Model simulations. “The transmission we elected to use is a fine unit by itself,” explains Mitchell “But for the power figures we wanted to attain, we found that the cam angles were a little bit gentle.”

Most variable speed transmissions lose approximately 50% of the horsepower between the crankshaft and the track, but Mitchell believed that the transmission was capable of significantly higher output if reconfigured. Scorpion optimized the design by constructing the transmission in SolidWorks and exporting various combinations of geometry to Working Model. Once the assembly was constructed in Working Model, Mitchell adjusted parameters for friction and angle using simple pull-down commands to find the ideal shift pattern. As Mitchell explains, “the transmission simulations were particularly satisfying because we took a solid, mature design, improved it’s out put by 20%, and it didn’t take months or cost an arm and a leg.”

If the opinions of the snowmobiling press are valid testament, SRP’s efforts to create a more complete and superior performing sled faster and cheaper have been successful. The Sidewinder promises to be one of the most efficient and powerful sleds ever, and thanks to parts reduction and optimization achieved through simulation it will be 150 pounds lighter than any sled in its class.

“Simulation has given us such an advantage because we can get our designs so close to perfect by the time we actually build and field test them,” says Mitchell “The reason the press is excited about the Sidewinder is because it is performing exactly like we calculated it would in our simulations. Our design software is helping us make a more competitive product than a small company like ours ever could before.”