Jim,
I too have brought up this subject after several failures. There were
lots of replies of lots of failures. Some say replace the nylon legs
annually. I believe that nylon is just not the right material for this
application.
"There is no sign of previous cracks or damage, they have simply snapped
like match sticks." I don't like that failure mode. I have had several
failures, one of which ended with taking out my Airmaster Prop. That
really hurt.
"Also any alternate material suggestions?" I am testing out some legs
made out of 5/8" fiberglass rod material from McMaster-Carr.
I did some load testing in the shop to find that this 5/8" diameter rod
has almost the same flex under the same load as the 1 1/4" nylon.
However, it has a very different failure mode. It of course does not
simply shatter like the nylon. The fibers in tension (on the "leading
edge" of the installed leg flexing back) start to snap and separate from
the rod. It is a more gradual failure. I think partial damage will show
easily during preflight inspection, but I have not yet seen any.
I have attached a drawing that shows the "bushings" that were made (from
broken nylon legs) so the thinner fiberglass rod fits in our OR-1 and
wheel fork. The complete legs are about 3 ounces lighter,each.So far
they are doing well. I just installed them last month before flying to
Florida from California and back.
Now I am making new wheel forks to run 105mm inline skate wheels. These
will have 5/8" ID tube so the lower nylon socket won't be needed.
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