We tested a number of lubricants on our Tufnol bearings not so long ago.
Our choice of lubricants would be as follows
(1) WD40
(2) PTFE spray
(3) Light Oil
We found that grease was the worst choice as it dried out over time and made
everything stiffen up.
The only drawback with the above is that as they are thin oils they need
regular re-application but if there is a small hole drilled in the tops of
the bearings this is no problem. Even the rear bearings are accessible with
a suitably elongated nozzle and syringe. With hindsight we could have glued
long pieces of plastic tube (the hard stuff our cables run through) so that
these could have been accessed from the wing holes.
With WD 40 our bearings are now incredibly smooth. Works well on the rod
ends too.
Carl P
----- Original Message -----
From: "ami mcfadyean" <ami@mcfadyean.freeserve.co.uk>
Subject: Re: Front Bearing setup
>
> -----Original Message-----
> Subject: Re: Front Bearing setup
>
>
> >Duncan if
> >the expansion you got to the tufnol would have occurred with a graphite
> >lubricant
>
> I wouldn`t know. Unless the graphite is in an oil/grease carrier.
>
> >small hole in the top of the tufnol bearings to
> >allow the insertion of a tubular applicator to inject atomised grease
with
> >a medium that later evaporates leaving the grease in place.
>
> The solvent carriers in many spray lubs. REALLY make the Tufnol swell. But
> it does seem to go back down with time as the solvent slowly disappears.
>
> > Is the general
> >consensus that the friction comes from the tufnol swelling throughout its
> >thickness which effects the rear face of the CS03 bush against it, or is
it
> >the shrinking nature of the hole in the bearing constricting on the CS03
> >bush?>
>
> The swelling takes place mostly perpendicular to the direction of the
fabric
> in the Tufnol. There was plenty of radial play left in mine. Although
> conical misalignment of either bearing can cause friction in addition.
>
> Tightening of the four bolts on the front bearing seems to pull it well
out
> of line, even when its been set up square on a (by now) well cured flox
pad.
>
> I liked Fred Fillinger`s idea of using fishing line to maintain
> axial/conical AND radial alignment and would certainly try this on the
back
> bearing.
>
> Even when all this is done, accurate set up in the inner module is still
> just as critical.
> Nevertheless, I really think its worthwhile on any aircraft to spend alot
of
> time in getting the controls friction-free and free from slop; it makes
for
> far sweeter handling, especially on a first flight when control friction
can
> mask out-of -trim asymmetries.
>
> Duncan McFadyean
>
>
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