JEC COMPOSITES MAGAZINE - Issue #117 - November/December 2017 - 56

SOLUTlONS medical

moulding allowed them to have
a much more complex shape and
carbon fibre composites really
gave them advantages in what the
design parameters could be.
The idea was not to take an aluminium part and make it using
carbon fibre. Actually, a carbon
fibre part and an aluminium
part should not look identical,
instead you need to design for the
material and process combined.
It would be almost impossible to
machine or forge the bottom part
of the new fork design.
Long carbon fibre
reinforced composite
materials
Frog Legs' second-generation
caster wheels make use of two
different long carbon fibre-reinforced composite materials from
PlastiComp. Machined aluminium was replaced by a long carbon
fibre-reinforced nylon 6/6
composite in the wheel forks and
a long carbon fibre-reinforced
thermoplastic polyurethane in
the wheel hub.
PlastiComp custom developed
the reinforced polyurethane
composite to bond with the

56

will work in the field differently
than expected with regards to
dynamic loading.

Ultina's "Everyday" model wheelchair makes use of Frog Legs' caster wheels
to reduce vibration from irregular surfaces

urethane used for the outer rolling surface of the wheel. Using
thermoplastic
polyurethane
for the hub made it possible to
obtain a chemical bond while
with an aluminium hub, there are
dissimilar materials that never
fully bond and can slip.
Changing from aluminium to
long carbon fibre-reinforced
composites reduced the weight of
a pair of Frog Legs caster wheels
by 33% - 280 grams lighter - a
reduction that is noticeable and
appreciated by riders.

The new design and materials
passed RESNA (Rehabilitation
Engineering Society of North
America) industry standard
testing that put them up against
million cycle impact and drop
forces. Frog Legs went on to test
them to failure to have data to
compare with traditional metal
caster wheels. Then of course,
real world testing effectively puts
the product through the most
extreme circumstances possible
to try and induce failure. You are
never 100% sure if something

jec composites magazine / N°117 November - December 2017

Much higher efficiency
Frog Legs took advantage of
PlastiComp's application design
and performance analysis services throughout their product
development cycle. "Overall the
efficiency of our product is now
much higher," said Chelgren.
"We could see from the computer
modelling what the benefits were
going to be. I don't think we could
have developed a product nearly
as good as the one we got without
that assistance. In my opinion, the
difference with PlastiComp is they
became our partner in making a
better product, it was more of a
collaborative process - we weren't
going it alone," he continued.
Frog Legs' caster wheels are not
just a solution for wheelchairs,
they can decrease vibration in all
types of rolling equipment where
there is a weight-versus-performance equation.
More information:
www.plasticomp.com
http://www.plasticomp.com http://www.jeccomposites.com
Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #117 - November/December 2017
