CRT Technology Showcase
Ethos: An Answer to Bad Vibrations
To maintain balance, conventional wisdom says that for every gain, there must be a loss.
But the new Ethos ultralightweight wheelchair from Ki Mobility challenges that notion in significant ways.
The Cost of Vibration
Many of today’s K0005 chairs have minimalist designs and use advanced materials such as aerospace-quality aluminum, titanium or carbon fiber.
Thanks to these incredibly lightweight and highly adjustable chairs, consumers can stay active for longer periods. But those longer durations also expose them to more vibration as they roll through parking lots, go over sidewalks, and transition from flooring to carpet or tile.
Alan Ludovici, Senior Design Engineer at Ki Mobility, the designer of the Ethos and a longtime K0005 user, said pain and fatigue are among the effects that vibration can have on wheelchair users.
“If you are on a relatively fine surface but you get a lot of harmonics going through the chair, that’s when it hurts,” he said. He added that vibration also can trigger spasms and spasticity.
“There are days that I’m just wiped out from the pain I’m in all day,” Ludovici said. “[Vibration] is a normal part of being in a wheelchair, period.”
Ethos keeps in mind that a wheelchair is only successful as long as its consumer can continue to use it. Jacki Rettler, Product Manager for Manual Mobility, said, “Vibration is a part of every day. [Users] can’t choose not to roll across the parking lot. That’s why the vibration-damping aspect of the Ethos is so genius.”
Separating the Seat & Base Frames
Ethos attacks the vibration problem from multiple angles. First, the seat frame and the base frame on the Ethos are separated, and the caster wing isn’t attached to the front of the chair. “Alan isolated the seat frame from the base frame,” Rettler said. “In doing so, the traditional caster wing that acts as a conduit to a lot of the vibration that the user feels was cut off.” (See it in action at www.kimobility.com/ethos/.)
Ethos also addresses residual vibration via ISO TECH, a patent-pending technology that acts as a second shield for the rider. “There are towers that extend out from the base frame that connect to the seat frame, and inside those towers are polymers,” Rettler said. “They are available in different densities or durometers. No matter what density you use, you always get the vibration-damping benefits of the chair design through the seat frame isolation, and then these secondary shields, the polymers. They absorb any of the residual vibrations that traveled through from the base frame up through the towers.”
K0005 Performance Requirements
While reducing everyday vibration is significant, Ethos must also fulfill other K0005 requirements, such as a high level of adjustability, plus an ultralight weight that facilitates propulsion and transporting the chair.
“I didn’t want to lose any energy going to the wheels or efficiency in pushing,” Ludovici explained. “There are other ways to dampen vibration. You can have soft casters on the front; you can have soft wheels on the rear. But that slows you down. You use a lot of energy, and you don’t roll as far. With the Ethos, you’re able to use performance tires front and rear and get the efficiency of the pushing, but the way the seat frame is somewhat separated from the base frame with the elastomers, the seat then becomes part of your body. It’s the difference between riding on top of something and being [part] of something.”
Rettler said Ethos’s design also provides optimal weight distribution: “The benefit of integrating the caster into the base frame and not attaching it to the seat frame is now you have this ability to manage the wheelbase. That caster telescopes in and out of that base frame, so you get about 4" of adjustability of that front caster. No other rigid frame does that.
“The result is that you can optimize the placement of the wheel, you can optimize the chair setup for performance or for more stability, but you’re not sacrificing one for the other anymore. You can also balance the weight of that rider across the wheelbase in such a way that no other chair allows you to do.”
Ludovici agreed: “You can get a fairly aggressive center of gravity and still be able to push the casters way forward for stability. I’ve always had a pretty on-the-edge center of gravity, but if I lean forward to pick something up, I want the front of my chair stable. I get as long a wheel base as I can squeeze into a chair without making it extra long. You can pick up stability that way, and it doesn’t really hurt your performance.”
Experienced K0005 users won’t need to change their routines to use Ethos. “For transfers, because the casters aren’t tied to the front frame, it gets rid of that bar or tube that’s usually there,” Ludovici said. “You can get closer to things when you transfer. As far as pulling it in and out of the car, the crossbrace is placed in pretty close to a medium balance point, so if you pick it up by the cross tube, it’s not heavy one way or the other.
“People say that monotube frames are the easiest and the most compact, but it’s not really true because you’ve got a bunch of parts sticking out from underneath that monotube. If you pull it across your chest to put it in a car, you’ll usually bump yourself. With the Ethos, there are three different heights of the bottom frame to try to keep the distance between the seat and the bottom of the frame relatively minimal.”
Ethos is available in seat widths from 12" to 20" and seat depths from 14" to 20", with a 275-lb. weight capacity. Its transport weight is 11.6 lbs., and seat-to-floor heights are 13.5-20.5" (front) and 13-20" (rear). Choose the best polymer to further dial in the ride; Ki provides the ISO TECH guide to help.
“Alan doesn’t like to sense any compression on the front end of the chair, so he rides a very dense polymer,” Rettler said. “For someone that might go into spasms when they ride over a rough surface, a really soft polymer might be preferred to help minimize spasticity.”
Ethos challenges conventional wisdom: It’s an ultralightweight, highly adjustable chair that can also reduce the vibrations that users feel. No loss, all gain.
“It doesn’t sacrifice weight,” Rettler said. “The chair responds the way a full-custom dual-tube does. The ride is incredible. Then to have this opportunity to tailor the ride experience and have adjustability that no other chair gives you? Through changes in abilities, injury, sensitivity, age, etc., Ethos can adapt. The ability to optimize the ride without a sacrifice to weight or performance while also providing the vibration damping benefits for a more comfortable ride? It’s a beautiful thing.”
This article originally appeared in the July 2019 issue of Mobility Management.