Flying GK Whip last Sunday I noticed that the roll control circuit was
noticeably stiff. Not seriously, just noticeable. Why? Cold day, but I'd
not had the problem before. Puzzle.
2 days later I inspected Brian Allsop's XS cockpit module and control
system. There was more friction than I would have liked but it was
acceptable. 1/2 an hour later we looked at it again and were amazed to find
that now it was too stiff. When originally set up it had been quite free.
What had changed?
It took quite a while to isolate the cause of the friction but eventually
we found it was entirely due to the flanges at the front of the roll
control torque tube pinching the Tufnol bearing. The whole lot had been
cooling down, (heating had switched off for the night,) and I can only
guess but it seems the different cooling rates of Tufnol and aluminium,
maybe too the different coefficient of expansion, caused complete loss of
the original adequate clearance.
Moral;- Make sure you have enough clearance to accomodate these two
factors.
Graham
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