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Center
of mass

The wide wheelbase on a sports wheelchair
makes it very stable and hard to tip over.

9 With a wheelchair, the center of mass
is made lower by setting the seat lower.
The Quickie also lets athletes adjust the
height themselves. The wheelbase is made
wider by using negative cambered wheels.
This means that the wheels aren’t vertical.
Instead, they’re angled so that the tops
of the wheels are closer together than
the bottoms.
10 Another advantage of the negative
cambered wheels is that the athlete can
reach the wheel more easily. The top part
of the wheel is close to the athlete’s body,
so the hands push almost in line with the
athlete’s shoulders and not out to the side.
This lets you push harder. The diagram Lever Fulcrum Effort Output Force
shows how this works. The shoulder is the
fulcrum, and the muscles in the upper arm Comparing a regular wheelchair and a
provide the effort. The output force is cambered wheel: the cambered wheel on the
delivered through the hand. The left keeps the hand closer to the body. It forms
farther away your hand is from a more efficient lever, delivering a harder push.
your shoulder when you push, the
less output force you have.

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