Thank You! That makes sense.
I agree with you that an external clamp would be the best arrangement to
spread the loads over the circumference of TP4. Internal bushings or tubes
would not protect TP12 ( and TP9? ), and since the plastic collars cover
TP12, adding a bushing ( those of use who have not installed TP4 yet )
wouldn't
work either.
John Moran's idea sounds good for those of us who haven't closed the tail
yet.
For maintenance access though, it does sound like a split sleeve clamp would
make life easier.
Shaun
----- Original Message -----
From: "Bob Harrison" <ptag.dev@ukonline.co.uk>
<grasingleton@avnet.co.uk>; <ivor@ivorphillips.flyer.co.uk>;
<europa@avnet.co.uk>
Subject: RE: tailplane torque tube reinforcing
> Hi! Shaun.
> Sorry but it IS confusing if I (and probably Graham!) keep messing up on
> the numbers !.
> The TP6 bushes tend to take rotational load from the PIP pins and become
> loose in the tailplane IF the tailplane rotational driving forces are not
> completely taken by the offending drive pins, which elongate the holes in
> the TP12 plates. Therefore it is recommended that the holes in the TP4 at
> the PIP pins are slightly slotted (rotationally) since they are only there
> to retain the tailplanes from sliding OFF the TP4 torque tube. This saves
> the TP6's becoming loose, but also ensures that all the rotational driving
> load is transmitted by the pins through the drive plates TP12's BUT they
> elongate the TP12 holes being a softer material than the torque tube TP4.
> Since the trailing edge is so far behind the centreline a minute amount
of
> wear at this place allows the trailing edge to move about 35 times as
much!
> I believe the limit between the two tail planes is 3/8ths" before you need
> to take some corrective action. However it seems that in spite of
> considerable care drilling /reeming the holes and in one of mine needing
to
> drive the pin into place with a hammer it still wears/tears the TP12
holes.
> Our proposed clamp arrangement fixes the TP12's to the tube, TP4, and the
> central drive TP9 (one each side) so the whole lot is locked up without
any
> change to the original design, leaving it all still dismantleable and
> coincidentally stiffens the torque tube T4 in bending stresses.
> Hopefully this enables you to come to grips with it all?
> I strongly recommend some action to be taken before the top of the
fuselage
> is put on because it is a "BASTARD" job retrospectively especially if the
> access hole is less than 5 inches diameter. It's bad enough at 5" diameter
> with only one hand and pearing through the small inspection hole above.
> Watch this space!
> Regards
> Bob Harrison. G-PTAG
>
> -----Original Message-----
> From: owner-europa@post.aviators.net
> Subject: Re: tailplane torque tube reinforcing
>
>
> O.K., now I'm REALLY confused.
>
> 1. Bob, just HOW are your tailplanes loose? fore/aft? side/side?
> rotationally?
>
> 2. Graham, it seems to me that the TP14 pins in both TP9 and TP12 serve to
> transfer the
> torques from the pitch pushrod to the tailplanes, so they both have to
> be precisely
> fit. And therefore additional bearing surface would help. Unless
> there's a bit of slop
> between TP12's I.D. and the tailplane torque tube's O.D.
>
> Am I missing something?
>
> Shaun
> A207
> ----- Original Message -----
> From: "Graham Singleton" <grasingleton@avnet.co.uk>
> Subject: Re: tailplane torque tube reinforcing
>
>
> > >hi guys i`m at the point of drilling my tailplane torque tubes and was
> > >thinking of bonding in a small section of aluminise bar inside the tube
> > >directly inline with the pip pins,
> > >would this be a practical idea to increase the surface area of the
pins,
> any
> > >thought`s on the above would be appreciated
> > >ivor phillips
> > >XS486 trike
> >
> > No. These pins are supposed to allow a little fore and aft play, (but
not
> > spanwise) so that torque cannot be transmitted by the pip pins. This
would
> > put too much load on the bonded in TP12s
> >
> > Graham
> >
> >
>
>
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