Issue link: https://digital.copcomm.com/i/298092
DESIGN 36 ■ CGW M a r ch / A p r i l 2 014 was designed in SolidWorks before anything was physically made," says Bodine. The crew started by analyzing what worked and what didn't with past sleds, including Night Train 1, so they could deter- mine 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 Solid- Works, 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 per- cent stronger via simulation. By reducing the chassis weight, they could be more strategic with the weight limit: The design- ers 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 experi- ence 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 design- ing 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 sus- pension, 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 pro- cess for each one. "They saw how it worked directly in Solid- Works, then changed and moved things as needed," Bodine says. "The Night Train 2 was the first time we could entirely ■ DIGITAL DESIGN and analysis helped make the Night Train 2 sled faster than its pre- decessor that won Olympic gold.