Page 21 - Mobility Management, April 2018

and the type of stability/performance that is desired,” he says. Critch eld says, “all suspensions intend to add some type of
cushion between what the terrain is providing and what the end user is actually experiencing.” For most, shock and vibration absorption comes from use of a swing-arm and spring design.
“The motors and casters simply pivot on the swing-arm and have some type of damping,” he explains. “This can be a coil spring or rubberized material like elastomer.”
Yet, “many bases mechanically connect front casters with drive wheels to provide downward force, traction and leverage for climbing. It is tough to balance stability and performance when using springs exclusively,” Peterson says. “A spring that is soft enough to ‘give’ and allow the chair to climb may be too soft to provide the needed stability, and springs can also be very sensitive to user weight and orientation.”
Peterson explains that traction doesn’t just come into play for larger obstacles.
“As manufacturers, we are often focused on how big the obstacles are (that) our systems can climb and safely descend. In talking with long-time end-users, their biggest frustrations are the smallest obstacles — cobblestone, pavers, brick walkways, the truncated domes you nd at some crosswalks,” he says. “These types of surfaces deliver a constant, consistent vibration that is felt throughout the entire power base and elicits pain, fatigue and discomfort.”
In fact, Peterson says, many consumers are more concerned with negotiating a 1" threshold than a 3" obstacle.
“A good, balanced suspension will allow someone to navigate these smaller obstacles safely, smoothly, and with almost no jarring or movement of the seat. That is pretty important, powerful stuff, especially if the drive control is digital or not a standard joystick,” Peterson says.
On the ip side, some users will need more from the suspen- sion system.
“That is why there are so many choices out there,” Peterson says. “It is so incredibly important for people to try the power wheelchair in their home environments before choosing. Everything handles great and smoothly on the perfectly smooth hallways in a rehab facility or clinic.”
As traction improves, the end user also experiences an additional bene t — independence.
Melissa Bourque, director of Market Development for Power Wheelchairs at Permobil, explains that traction prevents users
from getting stuck, which is imperative for independence.
Jay Doherty, OTR, ATP/SMS, director of Clinical Education at
Quantum Rehab, agrees. Power chairs enable the user to go outside, which puts them in the places their family and friends go, he says.
In addition, stability created through better traction helps users brake, accelerate and turn, Bourque explains. As a result, stability increases safety and con dence during driving.
The added functional bonus of the reduction of vibration is chair longevity.
“Suspension can also impact the durability of the wheelchair,” Doherty explains. “The less vibration and rattling of the wheel- chair itself, the longer the equipment will hold up.”
So for power chairs, traction is essential for maintaining wheel-to-ground contact. However, traction also helps the user to improve driving capability, to remain as independent as possible and to own a product that lasts.
A Move Toward Functional Comfort
Technology has done much to solve the complications that come with “being con ned to a wheelchair.” The power chair now func- tions as an additional appendage, helping people do more, see more and be more. But there’s still the issue that the user stays
in the chair pretty much all day. If you’re sitting in one spot — especially if you are in motion — then comfort is, and should be, an issue.
Enter the suspension system.
When consumers talk about comfort, a lot of what they expect comes from the suspension itself.
“I live in Rhode Island,” Peterson says. “We are a tiny little state, and the running joke every spring is the preponderance of massive, automobile-eating potholes. From the interstate to the smallest side road, they are everywhere. Imagine your daily commute in your car without suspension. Now imagine spending all day driving in the same ‘suspension-less’ auto, 8 hours plus. How would you feel? Tired, sore, on edge, etc.?”
A suspension system can do much to eliminate this fatigue and pain for power chair users simply by factoring in user comfort and ride quality in the design process, Bourque says.
Reducing shock and vibration is key to increasing comfort.
Doherty explains that suspension systems “can reduce fatigue by impacting how much the individual feels bumps or vibration and can also assist in reducing tonal impact when the wheelchair
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