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Dan Schaefer wrote:

>You give up no strength in the hinge pins, nor does the Teflon suffer from
>cold flow in the application to Lancair hinges. I defy anyone to show that
>the shear stresses on the pin material used in the Teflon/SS hinge pin kit
>is anywhere near the shear failure limits of said pins. I've examined mine,
>after about 300 hours of service and find NO indications of undue wear -
>cold flow or otherwise.

When we researched the properties of bushing material for the Carbinge, cold
flow in Teflon was a drawback we were told about.  How significant that
would be in our hinges we don't know because we never tried it, but when we
were told of this property by an engineer we believed it.

In our shear tests on Carbinge and on extruded aluminum tubing, we did in
fact find that pin stiffness is a significant factor in hinge strength.  We
were testing hinges to destruction and happily, the stress on trim tabs in
our aircraft does not come anywhere near the forces we used in our tests.

>The Carbinge hinges probably are good things, but shouldn't be touted at
the
>expense of other equally good things. In politics, it's known as
>"mud-slinging".

I'm glad that your system of sleeving an aluminum hinge with Teflon and then
using a smaller pin has worked for you and for others.  That does not negate
the validity of the points I've taken concerning advantages of a different
system.  Your system is less expensive and, for you, seems to be easy to
apply.  Those are points worthy of discussion also.  I'm sorry you have
taken my comments as mud slinging.  I would rather you consider them as
discussion of a topic of interest to builders.

Regards,

John Barrett



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