Issue: Volume 37 Issue 2: (Mar/Apr 2014)

American Made

By: Karen Moltenbrey
The competitive bobsled race is hardly the fun sledding experience we all had as children. The track is fraught with dangerous curves, the athletes inside travel Autobahn-like speeds, and the open-top sleds are super sleek and agile, as a fraction of a second can mean the difference between winning and simply competing.

While competitors have no say over the track, they do have control over the design of their sled. And for the recent Olympics in Sochi, Russia, the four-man USA bobsled team turned to American ingenuity and computer design to make their dreams of an Olympic medal come true.

The initial Olympic four-man bobsled race was part of the first winter games, held in Chamonix, France, in 1924. Back then, the sleds were made of wood, and later replaced by steel. Modern-day bobsleds are typically built with a lightweight metal frame and covered with fiberglass or a composite material to increase the aerodynamics. A steering mechanism - comprising a steering pulley, an axle, and a  handle - is situated inside the sled. On the outside, retractable push bars are located in the front and rear, while the brakeman's push bars are on the rear.

Over the years, the US team has increased its bobsled speed in a number of ways, including with optimized manpower and better design. The four-person team consists of a pilot, a brakeman, and two pushers. Athletes for the latter positions are especially selected based on their speed and strength, giving the sled an optimal start in the race. (This year, a number of bobsled teams included track and field Olympians, as was the case for when Lauryn Williams, a three-time Olympic sprinter and 2012 100-meter relay Olympic gold medalist, and Lolo Jones, a two-time Olympic hurdler and two-time World Indoor Champion, became pushers for the women's bobsled teams.) The pilot, meanwhile, must keep the sled on course and prevent it from reducing speed by scraping the sides of the narrow track.

Design is another big factor in determining speed. Sleds must adhere to tight restrictions in size, weight, and other parameters. So, sled designers must find other options where they can shave off precious milliseconds to produce a better sled. And who better to contend with the need for speed than someone who has made his mark on a different fast track: NASCAR?

Racing to Win
With design a huge factor, the USA bobsled teams have been racing with "renovated" sleds from their fierce European competitors. And that bothered former NASCAR driver Geoff Bodine - so much so that he began the not-for-profit Bo-Dyn Bobsled Project Inc. with the goal to build an American-made, medal-winning bobsled. After watching the USA team struggle using discarded European sleds at the 1992 Winter Olympics, Bodine applied his high-speed racing know-how with the design engineering skills of his racing partner, Bob Cuneo, to create a new generation of sleds.


THE DESIGN TEAM used the body shape and aerodynamics of the original Night Train but made vital revisions to the new sled.

"They weren't using US sleds, and they weren't doing well," Bodine says. "It wasn't because of lack of ability. It was the equipment. It was purchased from [USA team] competitors, and they weren't selling them their best. They sold them their worst. I decided to do something about that."

The result of their collaboration led to a new bobsled design, the original Night Train, used by the 2010 American team to win an Olympic gold medal in the sport for the first time in 62 years since their victory at St. Mortiz, Switzerland.

Aware of the strict rules enforced by sport officials and the challenges of achieving even better race times, Bodine knew that the 2D design tools used for the first-generation Night Train would not be enough to up the game of USA Team-1 and build the world's fastest bobsled for the Sochi Games. (He was right. USA Team-2 took to the bobsled track in Sochi with Nick Cunningham driving the original Night Train to 12th place.) Instead, they would need top-level 3D design tools and capabilities.

To this end, the design team turned to SolidWorks, a 3D design application based on Dassault Systèmes' 3DExperience platform, with the lofty goal of creating a faster sled for the challenges of the Sochi course. The original bobsled's aerodynamics had been optimized for the fast downhill track of the Vancouver, Canada, Olympics in 2010. The track at the Sochi Games, however, was filled with three tricky uphill sections that required precise handling to generate the most speed out of the track's curves.

"We knew we needed an accurate and precise 3D design that could give us a realistic and cost-effective way to test and tweak Night Train 2 prototypes," says Bodine. "SolidWorks helped us design using a lighter material (Night Train 2 is made of carbon fiber instead of Kevlar and fiberglass) and creating multiple 3D prototypes of the bobsled on the computer so we could get it just the way we wanted it before we began building and manufacturing it," he explains.
In particular, the digital design software enabled Cuneo to experiment with the weight of the sled and how that impacted the handling. "You win in these races by a very small amount of time (less than one-tenth of a second separated the gold and silver medalists at Sochi), and the key to winning is very small changes in design," Bodine says. "We were able to quickly make those crucial changes."

At the Start Gate
Most of the engineering and design work was done by Cuneo, a race-car builder, and his team. Jim "Cheech" Garde, designer and model-maker for Bo-Dyn and owner of Cheech's Creative Concepts, did the majority of the hands-on work. "SolidWorks was used to design the entire sled - everything from maximizing the space in the front of the sled, to where driver Steve Holcomb's heel slid down into the structure, to grips, steering, and ropes. Every piece was designed in SolidWorks before anything was physically made," says Bodine.


DIGITAL DESIGN and analysis helped make the Night Train 2 sled faster than its predecessor that won Olympic gold.

The crew started by analyzing what worked and what didn't with past sleds, including Night Train 1, so they could determine which areas could be improved. This also meant digitally scanning the original Night Train and importing the data to obtain the base shape and aerodynamic technology for Night Train 2 within SolidWorks. The group further used the data for the carbon-fiber body shell molds of the new sled.

After the group imported the Night Train 1 design, they extensively redesigned the steering and chassis to get the performance the Bo-Dyn team believed was needed for Sochi. They tested different chassis and steering configurations in SolidWorks, analyzing the mechanism for motion and interference.

The distribution of weight in the chassis was a big issue, says Craig Therrien, senior product manager at SolidWorks. As a result, the Bo-Dyn team used SolidWorks' mass properties calculations and could see the center of mass as changes were being made to the design. In addition, the cross-sectioning capabilities of SolidWorks enabled the designers to more easily visualize what was happening inside the bobsled to ensure that the four bobsled team members had sufficient room and mobility.

"For Sochi, the track was very technical, and we decided that improving the steering was more important than anything else," says Bodine. "We had already maximized the aerodynamics of our bobsled, so to increase the accuracy and precision of the steering was a top priority. Once we had that focus in mind, we could plug it all into the software and see how it worked."

Even though the body shape and aerodynamics from Night Train 1 were carried over to Night Train 2, the design team was able to make the chassis 50 pounds lighter and about 50 percent stronger via simulation. By reducing the chassis weight, they could be more strategic with the weight limit: The designers placed ballasts that enabled them to tweak the weight of the bobsled to optimize speed. Using the CAD software, they tested various placements of the ballasts to determine the optimal weight distribution.

Because of the course complexity, the group at Bo-Dyn also did an overhaul of the steering mechanism. Bodine's experience with using power steering in NASCAR served as the inspiration for the improvements - even though the bobsled rules still called for ropes, grips, and bungee cords. The team at Bo-Dyn replaced metal brushings with ball bearings to optimize the caster and camber for better front-end handling of the bobsled.

According to Therrien, simulation played a big part in designing the new steering mechanism, as well as configuring it to fit the pilot's unique needs. "Holcomb prefers to steer based on the feel of the runners on the track rather than relying on his actual sight, but simulation helped in designing a new mechanism and enabling it to be adjusted quickly using certain ratios," he says.

In fact, design innovation encompassed just about every facet of the sled. Bodine says the crew had really focused on aerodynamics for Night Train 1, and had done plenty of testing and optimization leading up to the Vancouver Games. "We had our athletes sitting lower to the point where you couldn't even see the last two athletes in our sled. But going into Sochi, everyone had seen that trick and were trying the same thing, so we needed to optimize the sled to improve other aspects, such as weight distribution, steering, and shock absorption," he says.

In a bobsled, common shock absorbers, like springs and suspension, aren't allowed, so most teams build their bobsleds to be slightly flexible so they can absorb the energy through the overall body. This is common practice, but it can also lead to maintenance challenges. So, the Bo-Dyn group decided to use a torsion bar to control the bobsled's spring, so they wouldn't waste that vibrational energy. "Regardless of how small that lost energy may seem, it is important. Most other teams don't do this, but even the slightest advantage counts," Bodine says.

As Bodine explains, the engineers could build the bobsled and see it work directly on the computer - they could move the model, see it, turn it, and twist it - before any actual machining was done. This saved the group time and money - critical factors in a time-sensitive, non-professional sport.

Although there were several iterations of the design, the team did not have to contend with the entire machining process for each one. "They saw how it worked directly in SolidWorks, then changed and moved things as needed," Bodine says. "The Night Train 2 was the first time we could entirely design a bobsled in a virtual environment and actually see how it would move down a run. Once we built it, there were a few minor adjustments that needed to be made, but overall there were very few. It was absolutely amazing."

Once everyone was pleased with the design, the bobsled was fabricated in real time with the actual materials, but without any of the guesswork, Bodine points out. "It's great to see it all work so smoothly. Years ago, that wasn't how it worked - you had to re-machine if something was just slightly off," he says.


BO-DYN APPLIED NASCAR know-how to build an Olympic bobsled that recently earned USA Team-1 a bronze medal.

All the components were manufactured directly from the 3D CAD models. Hans Debot at Debotech used the data to create a "repair kit," including a new piece of the bobsled after the team's crash in Germany at the Winterberg Bobsled World Cup in early January, when part of the sled was damaged and needed repair.

Once the sled was designed, it was put through its test paces, which included time in a wind tunnel. Even so, the team sees the design phase for Night Train 2 as a shorter process than for previous designs. As a result, the team was able to spend more time with the sled and in the wind tunnel tests, which is always a plus. "It's unbelievable what they have been able to do in just one year," noted Brakeman Curtis Tomasevicz prior to the games.

The software was so instrumental to the Night Train 2 athletes that those who travel with the team are trained on the application to facilitate quick repairs or to collaborate on adjustments to sled components. "He makes changes on the road. He calls back to Bob Cuneo and works with Bob's company to make it happen," says pusher Chris Fogt.

How important is that relationship with the engineer? "Extremely important," says Holcomb. "I am constantly giving feedback to Cheech [Garde] on how to make this thing faster, what I am feeling on the track, and how we can make the changes that I need in order to maintain control of the sled. He has been essential in our victories this year."

The group members who were unfamiliar with the software were able to get up to speed quickly, and that included Garde, who built the chassis and serves as the team's mechanic.
 
Another pusher, Steve Langton, sums it up by saying, "I've learned that Cheech knows exactly what he is doing. And [Steve Holcomb] can drive just about anything. Cheech has been instrumental in this whole process. This is a big win for us but also for the program and the mechanics who do all the hard work."

Cool Runnings
Even though the 2014 Olympics are over and USA Team-1 walked away with bronze medals, there are still plenty of bobsled World Cup competitions remaining until the next Winter Olympics. And plenty of technical challenges that have to be overcome. Looking back, one of the biggest challenges going into Sochi was in reducing the development and testing phases for Night Train 2, and no doubt that challenge will remain. That's because the design process itself has become so technical and complex.

"The amount of trial and error required to design and optimize each piece of the bobsled and ensure that all the parts work seamlessly together is a feat that can't be accomplished using the hand calculations and physical prototypes of the past," Therrien points out.

It almost seems ironic that technology plays such a vital role in creating a machine that appears basic in its fundamental parts but extremely complex in the design of those components.
 
"In bobsledding, they measure each run to the hundredths of a second. NASCAR actually goes a bit further and often comes down to thousandths of a second. You can be extremely close, and it sounds easy to get those thousandths of a second, but it's a huge challenge to improve your time and to be the best," Bodine explains. "Every click of time is important, and it's extremely difficult to eliminate those clicks. The same is true for bobsledding - it is so important to have everything from the weight of the sled to the weight distribution and steering optimized in order to get that thousandth of a second. Every little thing is critical to get that little tick of the clock."

Cuneo agrees. "There's no such thing as light-years better. We tried to make it a little better," Cuneo has said about the new sled. "In this sport, as in auto racing, there are no giant breakthroughs. You work hard to find a little bit more time. If you don't upgrade, you will fall behind."

According to Bodine, the engineering team - namely Cuneo and Garde - could use every ounce of material and design every part to be strong, but also as light and functional as possible. "Without using digital technology to build Night Train 2, there's no question in my mind that it would have been extremely difficult, as close as the competition ended up being in Sochi, for Steve Holcomb and the team to finish where they did. With SolidWorks, we really did end up with the ultimate driving machine."

Karen Moltenbrey is the chief editor of CGW.
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