Most people don't think of wheelchairs as a high-endperformance vehicle, but that's not the case for TiLite, a manufacturer of custom-made models.With its customers solely reliant on their chairs as a primary means oftransport for everything from day-to-day commuting to far-out adventure travel,TiLite engineers are continuously chasing the optimal designs and materialschoices that will allow its models to perform reliably even under the hardestconditions.

We're not just talking about wheelchairs that are tough enough tohandle city street potholes or even withstand the bumps of being tossed aroundby airline baggage handlers. TiLite targets an active customer base so it's notuncommon to see its chairs competing in marathons, racing around a basketballcourt or proving their stuff out on the dance floor. Since TiLite models arecustom-built-to-order, some customers push the chairs even further. TiLitewheelchairs have gone on safari in Africa, competed in the Olympics and havetaken owners on the extreme quest of bungee jumping off bridges.

"Our users are everyday people living their life and they want tolive it to the fullest," says Josh Anderson, TiLite's vice president ofmarketing, who says the design team's biggest challenge is to prepare for theextremeness of day-to-day life. "Our customers don't know when they wake up inthe morning what they need to do to be mobile," he says. "Just likeanyone else on vacation, whether hiking in the Yucatan or passing through astream doing wheelies, they're just along for the ride."

It takes quite a bit ofengineering prowess to give the chairs that level of flexibility and customfit. TiLite's engineering group tackles design as if the chair was a prostheticdevice - a very different approach than creating a design for a hospitalwheelchair, which is far more standardized and requires users to conform to itsmode of operation. Using tools like 3D CAD and Finite Element Analysis (FEA),TiLite engineers are able to more easily optimize materials choices, zero in onthe best frame design and outfit the chair with the right mix of extras, gettingthem far closer to the goal of achieving that tailored fit. Because everyindividual is different, "we develop each chair from the ground up," Anderson explains. "It's no different than a pair ofshoes - just because they're your size doesn't mean they are going to fit youright. It's that custom fit that allows for maximum mobility."

Making a Materials Match

Giventhe range of how customers push TiLitewheelchairs, the most difficult engineering challenge is anticipating all thepossible scenarios, says David Berriochoa, design engineer at TiLite. In addition to the frame design, the choiceof materials is a huge factor in determining the performance and durabilitycharacteristics of individual chairs. TiLite uses either high-grade aluminum ortitanium for the frame and related components, and it employs the FEAcapabilities in SolidWorks Simulation to explore which material is the best fitand how much is required for each chair design based on user requirements.Aluminum, for example, offers a high level of rigidity or stiffness, making ita good choice for active, everyday users who require a certain level ofperformance when rolling over or climbing smooth terrain. Titanium, on theother hand, has an unparalleled strength-to-weight ratio, thus less materialcan be used to produce a robust, yet lightweight frame - a scenario that worksfor customers looking to put their chairs to more extreme uses.

The design process actuallykicks off at a TiLite dealer. Customers fill out a detailed 10-pagequestionnaire, which takes into account lifestyle, activity patterns,disability profile, ride preferences, as well as detailed physical measurementsaround size, weight and shape to ensure the resulting chair design is awell-matched custom fit. At thatpoint, there is a hand-off to engineering. Instead of recreating a new designfor every new chair, however, the TiLite engineering group has automated itsdesign process using SolidWorks and CAMWorks, a third-party computer-aidedmanufacturing (CAM) tool. The engineers leverage a variety of base wheelchairtemplate designs modeled in SolidWorks and then configure each variationaccordingly based on the specifications. "We've developed automated productionmodels that allow us to easily input values off of an order form directly intoSolidWorks," Berriochoa says. The models self-configure, and the software combo checks details such asclearances, range of motion or thattubing intersections work correctly formanufacturability, he explains.

Unlike its previous process where the team built a SolidWorks CADmodel from scratch for every order, the SolidWorks templates have shaved bothtime and money off TiLite's design process. Today, instead of taking a fulleight hours to create and generate chair fabrication prints for manufacturing,the automated templates take the process down to a matter of 20 to 30 minutes.In addition, executives estimate the company saves about $400,000 annuallysince it no longer has to have skilled craftsmen on staff or under contract todraw designs from scratch and cut every tube. On average, TiLite produces about10,000 chairs annually.

FEA analysis comes into play when there is any concern about theintegrity of a design decision or to optimize materials choices. Using SolidWorks Simulation, TiLite engineers are able toprove out design concepts, exploring, for example, whether a particular areaneeds reinforcement by adding extra tubing or increasing the thickness ofwalls. In one notable instance, the team employed SolidWorks Simulation to developa better alternative to aluminum footrests, which were found to be prone tooverheating and developing sharp edges. TiLite engineers created a virtualprototype of injection-molded composite replacements in SolidWorks CAD usingthe FEA capabilities of SolidWorks Simulation to validate the design and, inthe end, initiating an $11 savings per chair thanks to
reduced materials costs.

Simulation also spurred development of a lightweight back restbracket used in a variety of TiLite's chair models. Before it ever physicallybuilt a bracket prototype, engineers used FEA analysis to see how the bracketwould work, how light it could be and to check for interferences. Not only wasthe analysis critical for proving out the design, it also ensured materials wereoptimized, helping the team strike that balance between light weight anddurability.

"One thing we don't want to dois overdesign because we don't want to add weight," Anderson says. "Ourcustomers are not only sitting in these chairs, they are propelling them andlifting them up, and in and out of vehicles. Yet we don't want to under-designso they are susceptible to breakage. There are huge trade-offs betweendurability and performance."