Has anyone looked at the possibility of putting a new set of holes at
90 degrees to the original set, in order to allow the original bits
to be re-used with parallel pins in Jim and Heather's situation?
One small but important thing I learned when I retrofitted mod 62 is
that grease is much better than oil as a lubricant when you fit the
pins into into what ought to be a slight undersize hole. I did
several trial assemblies on the bench by way of a rehearsal as I
didn't want to discover a problem half way through fitting for real.
I found that the grease prevented the pins from seizing/picking up/
scuffing as you tap then into place, but ordinary oil allowed then to
seize up before they were fully in place. Funny stuff, stainless steel.
By the way, I have a set of slight undersize reamers which I bought
for this and any member is welcome to borrow them.
80 flying hours later there is still not the slightest sign of any
play at all. I do my best to protect the tail plane from unusual
forces, eg banging from stop to stop if left pointing downwind in the
fuel queue.
Willie Harrison
G-BZNY - now got the ratio of flying to fettling time up to 10:1 and
rising...
On 24 Oct 2006, at 00:05, Jim Butcher wrote:
> Recent inspection has revealed excessive play in our port
> tailplane. The problem is play in the torque tube pin. We
> incorporated Mod 62 (larger pins) during our build so that=92s not an
> option.
>
> Our Tech Counselor suggested using AN386 taper pins. He said they
> are commonly used for similar applications in certificated
> aircraft. AC 43-13 confirms that AN386 pins are used in joints
> where "the absence of play is essential".
>
> A search of this forum suggested that the inner tube (TP4) would
> crush and bind in the bearing (TP11) if tapered pins were used. Our
> thoughts are to Loctite a 12" length of 1.375" OD .093" wall 4130
> steel tubing centered inside of TP4. This would prevent the
> crushing of TP4 and 12" allows it to span the TP11 bearings. We
> would use a machine shop to accurately make the tapered holes for
> AN386-3 pins. The tapered pins would be installed vertically since
> there is not much material left on TP9 (the center bracket) from
> the installation of 3/8", Mod 62 pins.
>
> In the original design, the pins also locate TP10 sleeves against
> TP11 bearings inside the fuselage to prevent left - right torque
> tube movement. We would like to locate TP10 independently of the
> pins. Our thoughts are to machine TP10 sleeves to fit outside the
> fuselage between TP12 and TP11 to achieve the same purpose.
> Alternatively, we could split or slot TP10 and secure them to TP12
> inside the fuselage with hose clamps (Oetiker style for 360 deg
> contact).
>
> Comments?
>
> Jim & Heather Butcher
>
> N241BW XS, Mono, 914
>
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