In message <348CEC05.7906@xtra.co.nz>, Tim Ward <ward.t@xtra.co.nz> writes
>Tony Krzyzewski wrote:
>>
>> >
>> > You should also put Teflon/stainless steel hinge pins in the rudder hinges.
>> > They will tend to wear out very quickly otherwise. In fact I think we will
>> > all be doing that to our aileron hinges by the time we reach 200 hours.
.......
I think we should be very clear on the facts here before everyone changes
their hinges. PTFE has quite good dynamic friction when in contact with
polished steel, but the static friction is appalling. Those of you who were
supplied with PTFE lined bearings by Europa will remember that the static
friction made them unusable. What is more, due to the very high coefficient of
thermal expansion the tightness of fit was quite temperature dependent. It may
be that if the tube is a slack fit on the wire initially the static friction
may be acceptable. I understand that this will also require a thinner hinge
wire which strikes me as a retrograde step. I should like to see a formal
report on this subject. At present I shall be using well-greased standard
issue.
For those of you who intend going down this route may I draw your attention to
the method used by wooden aircraft manufacturers to secure the hinge wire. the
wire has one right angle bend and then is inserted into the hinge. The short
arm is then clamped to the structure by a strap and screws, thus preventing
the hinge wire from leaving the hinge and enabling it to be removed in the
future. Presumably the strap could be replaced by glass fibre/epoxy.
Ken Whiteley
#19
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