I've explored taper pins today, and IMHO to be effective they would need two
conditions:
1) Through TP4 tube alignment with each other - otherwise shear forces
would tend to 'tilt' them given their limited surface bearing area and 2) a
method for preventing outward movement, which could theoretically have a
threaded
adjustment to tighten inward pressure as the holes wore. Both are significant
challenges and am therefore passing on this solution.
I'm also personally uncomfortable with bonding in the event of the need for
future
removal.
AS the top of my fuselage is not on yet, I've cut my cables today and have
started
removal of the clevis pins.
I am proceeding with the replacement of the Clevis pins using 5/16" diameter
bolts
passing through the male side of a 303 Stainless machined swivel washer.
The machined piece is 5/16" ID x 1/2" OD x .188" thick. This piece basically
looks
like a machined spacer, but has a radius on the outside circumference on
one side.
I will open the TP10 plastic sleeve Clevis pin hole to 1/2" (the od of the
washer)
The washer sits in the hole perfectly, as the thickness is exactly the same
height as the thickness of the TP10 plastic sleeve. There will be one on each
side, with the radiused side of the spacer facing inward (minimal surface
area against the TP5 tube.) The holes in TP5 and the TP4 tube will be reamed
to perfectly fit the 5/16" bolt. Upon tightening, point pressure will be
created
on the edges of the hole, creating a friction fit between TP5's and TP4's.
The additional larger bearing area of the 5/16" bolt will also improve
resistance
to wear. Future disassembly may require some tapping to slide the parts
apart, but will not require any heat. Future tightening of the bolts may
postpone
the need for repair.
The new 1/2" hole size in the plastic sleeve is not important, so long as the
position
remains concentric with the original position, thereby maintaining part
spacing between the bearings. The larger diameter will again also resist wear.
The only drawback is that the ID of the washer is .010" larger than the dia of
the bolt. But if the TP 10 sleeve is positioned properly while tightening the
bolts, there should be no problem. Worst case is .010 side to side slop -
pretty
reasonable.
The washers are available from Berg (a precision mechanical components catalog
house in the US) Berg's number is 800-232-BERG (2374) Outside the U.S.
516-596-1700.
You can ask them to fax you a copy of the catalog page with Swivel Washers
on it. The part is part no PC6-6.
Comments?
Cleve Lee
A198 Mono XS
Detroit, MI
On Fri, 18 January 2002, "Shaun Simpkins" wrote:
>
> So...
> We are back where we started.
> Clamping may or may not work. Saddles avoid having to cut the sleeves to
> allow effective clamping, but may have too little surface area.
> It seems as if the only solution is adhesives.
>
> Shaun
> ----- Original Message -----
> From: "McFadyean" <ami@mcfadyean.freeserve.co.uk>
> Subject: RE: Tail[planes
>
>
> > Taper pins would work until they go loose!
> > It would then be easy to affect a cure by tightening them some more. Not a
> > sustainable solution, however.
> > This assumes that the problem is one of pin/tube-wall bearing failure,
> > which isn't proven.
> >
> > Taper pins would also take out any relative non concentricity of the fore
> > and aft tube holes (generated by mixing up the fitted order of the various
> > parts) which would result in only one of the holes doing most of the work.
> >
> > Duncan McFadyean
> >
> > On Wednesday, January 16, 2002 2:12 AM, Fergus Kyle [SMTP:VE3LVO@rac.ca]
> > wrote:
> > > The subject of the loosening of contact in the tailplane torque
> > tube
> > > has been long and profound. I have archived most of the cogent theories
> > and
> > > solutions for future phase.
> > > However, if the discussion still centres around loose pins in
> > > expanding holes, perhaps it's worth considering the taper pins - how
> they
> > > might recover tight contact somehow.
> > > FergA064
> > >
> > >
> >
>
>
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