Page 18 - Mobility Management, January 2018

ATP Series
Material Advances
Still, the manufacturer continues to work with and explore other materials.
“TiLite has also built chairs using magnesium alloys, and we are constantly testing and evaluating materials like carbon ber and composites for frame components,” Srinivasan acknowledged. “While carbon ber does have advantages
in terms of weight savings, the way that it is applied in the market today means you lose much of the customization oppor- tunity that we take advantage of using aluminum and titanium.
“We use carbon ber on components today like backrests, sideguards, etc., to shave weight, but use titanium as the
frame material that allows a custom- tting wheelchair that provides an advantage in terms of functionality. An ideal marriage would be a blend of every technology
that best suits the application of the frame or component. That said, one of the challenges that users face today is that reimbursement for chairs made with
Considering Carbon Fiber for CRT
Perhaps the buzziest engineering material in the always- evolving ultralightweight manual wheelchair space
is carbon ber. Very lightweight, very strong and very attractive to look at, carbon ber has often been associ- ated with racing vehicles, where speed, light weight and sleek looks go hand in hand.
In complex rehab, where light weight can translate into such signi cant bene ts as easier transfers and transpor- tation, carbon ber is being used not just for ultralight chair frames, but also in components, such as backrests.
Carbon Fiber Composites
Todd Hargroder of Accessible Designs Inc. (now part of Stealth Products) has worked with carbon ber for years in wheelchair applications and is a long-time ultralight- weight chair user.
“A buddy of mine was building a dragster, and he had made some panels out of carbon ber,” Hargroder said. “That was my rst exposure to it. I saw how pretty and how cool it was, and how lightweight it was. I made a backrest out of it, and just used the mounting hardware off of my old backrest that I had.
“The shell was great, but the mounting hardware was quite ugly, so my next step was to design mounting hard- ware. After putting the two together and going to a show, that pretty much launched a product line.”
As for working with it, Hargroder said, “Carbon ber is a composite. It’s a exible material until it’s mixed with resins
or other materials, and it’s all about the mixture. You can make it exible and bendable, or you can make it as stiff as can be. It’s a recipe that you have to work with depending on your application. It can be at, it can be round. It all depends on how it’s molded and how it’s used. It can certainly be as strong [as aluminum or titanium] depending on how it’s laid up, how it’s used, how it’s engineered.”
He compared working with carbon ber and nding the optimal blends to cooking. “It’s all about the recipe, how much of this, how much of that, and then how it’s cooked, the temperatures,” he said. “There’s certainly an art to composite manufacturing.”
Wheelchair Advantages
Among the traits that Hargroder appreciates is carbon ber’s literal exibility.
“The great thing about carbon ber is it is a composite, so you can have it exible, or you can have it stiff,” he explained. “A backrest made out of aluminum is just made of aluminum. Aluminum is a dead, hard material, and it feels like that. A composite carbon ber backrest will have some exibility. We’ve designed exibility into our backrest so it does absorb vibration, it does take away shock load, it moves with the body much better than a dead, metal back support.”
Hargroder also likes being able to adjust a carbon ber “recipe” to attain the characteristics he wants.
“With the makeup of the composite back, you can add more material, you can add more layers of carbon, you can add different types of resin to make it stronger or more exible — whatever your goal is, whatever you’re trying to achieve,” he said.
Still, while Hargroder has achieved much success from carbon ber designs, he acknowledges the usefulness of different materials in complex rehab situations.
“Most of our mounting hardware is made of aluminum,” he pointed out. “We’ve done some composite mounting, but the majority of our mounting is made of aluminum.
“Aluminum is easier to work with, because you can just put it on a machine and mill it out. Carbon ber certainly takes a lot more involvement. It all depends on your appli- cation. Some things are better made out of aluminum, and some things are better made out of carbon.” m
18 JANUARY2018|MOBILITYMANAGEMENT MobilityMgmt.com
CARBON FIBER: ISTOCKPHOTO.COM/ALLANSWART