We're not just talking about wheelchairs that are tough enough to handle city street potholes or even withstand the bumps of being tossed around by airline baggage handlers. TiLite targets an active customer base so it's not uncommon to see its chairs competing in marathons, racing around a basketball court or proving their stuff out on the dance floor. Since TiLite models are custom-built-to-order, some customers push the chairs even further. TiLite wheelchairs have gone on safari in Africa, competed in the Olympics and have taken owners on the extreme quest of bungee jumping off bridges.
"Our users are everyday people living their life and they want to live it to the fullest," says Josh Anderson, TiLite's vice president of marketing, who says the design team's biggest challenge is to prepare for the extremeness of day-to-day life. "Our customers don't know when they wake up in the morning what they need to do to be mobile," he says. "Just like anyone else on vacation, whether hiking in the Yucatan or passing through a stream doing wheelies, they're just along for the ride."
It takes quite a bit of engineering prowess to give the chairs that level of flexibility and custom fit. TiLite's engineering group tackles design as if the chair was a prosthetic device - a very different approach than creating a design for a hospital wheelchair, which is far more standardized and requires users to conform to its mode of operation. Using tools like 3D CAD and Finite Element Analysis (FEA), TiLite engineers are able to more easily optimize materials choices, zero in on the best frame design and outfit the chair with the right mix of extras, getting them far closer to the goal of achieving that tailored fit. Because every individual is different, "we develop each chair from the ground up," Anderson explains. "It's no different than a pair of shoes - just because they're your size doesn't mean they are going to fit you right. It's that custom fit that allows for maximum mobility."
Given the range of how customers push TiLite wheelchairs, the most difficult engineering challenge is anticipating all the possible scenarios, says David Berriochoa, design engineer at TiLite. In addition to the frame design, the choice of materials is a huge factor in determining the performance and durability characteristics of individual chairs. TiLite uses either high-grade aluminum or titanium for the frame and related components, and it employs the FEA capabilities in SolidWorks Simulation to explore which material is the best fit and how much is required for each chair design based on user requirements. Aluminum, for example, offers a high level of rigidity or stiffness, making it a good choice for active, everyday users who require a certain level of performance when rolling over or climbing smooth terrain. Titanium, on the other hand, has an unparalleled strength-to-weight ratio, thus less material can be used to produce a robust, yet lightweight frame - a scenario that works for customers looking to put their chairs to more extreme uses.
The design process actually kicks off at a TiLite dealer. Customers fill out a detailed 10-page questionnaire, which takes into account lifestyle, activity patterns, disability profile, ride preferences, as well as detailed physical measurements around size, weight and shape to ensure the resulting chair design is a well-matched custom fit. At that point, there is a hand-off to engineering. Instead of recreating a new design for every new chair, however, the TiLite engineering group has automated its design process using SolidWorks and CAMWorks, a third-party computer-aided manufacturing (CAM) tool. The engineers leverage a variety of base wheelchair template designs modeled in SolidWorks and then configure each variation accordingly based on the specifications. "We've developed automated production models that allow us to easily input values off of an order form directly into SolidWorks," Berriochoa says. The models self-configure, and the software combo checks details such as clearances, range of motion or that tubing intersections work correctly for manufacturability, he explains.
FEA analysis comes into play when there is any concern about the integrity of a design decision or to optimize materials choices. Using SolidWorks Simulation, TiLite engineers are able to prove out design concepts, exploring, for example, whether a particular area needs reinforcement by adding extra tubing or increasing the thickness of walls. In one notable instance, the team employed SolidWorks Simulation to develop a better alternative to aluminum footrests, which were found to be prone to overheating and developing sharp edges. TiLite engineers created a virtual prototype of injection-molded composite replacements in SolidWorks CAD using the FEA capabilities of SolidWorks Simulation to validate the design and, in the end, initiating an $11 savings per chair thanks to
reduced materials costs.
Simulation also spurred development of a lightweight back rest bracket used in a variety of TiLite's chair models. Before it ever physically built a bracket prototype, engineers used FEA analysis to see how the bracket would work, how light it could be and to check for interferences. Not only was the analysis critical for proving out the design, it also ensured materials were optimized, helping the team strike that balance between light weight and durability.
"One thing we don't want to do is overdesign because we don't want to add weight," Anderson says. "Our customers are not only sitting in these chairs, they are propelling them and lifting them up, and in and out of vehicles. Yet we don't want to under-design so they are susceptible to breakage. There are huge trade-offs between durability and performance."