Rowland,
You did not cast doubt on my suggestion, you only wanted to be certain that
you fully understood what you might be doing to your aircraft!
Your looking at the set-up as one rigid unit explains it in
easier-to-understand terms than if I had started explaining how a bending
moment (the torque) applied at one end of a cantilevered beam (the spanner
placed on the prop.nut) without any transverse force (since your hand pull
is axial on the spanner) sets up the same bending moment at all points along
the length of the beam and at its fixed end, i.e. onto the prop. bolt.
Your way of looking at it prompts one word of caution, however: It is
important to apply the hand force parallel to the spanner. If applied at an
angle, the transverse (to the spanner) component of this force acts at the
outer end of the spanner (where the torque wrench is affixed), giving an
additional torque moment on the prop.bolt (equal to the transverse force
component multiplied by the spanner length). This is the reason for
recommending that the torque wrench is orientated at right angle to the
spanner before you begin to apply hand force - it is natural to pull on the
torque wrench handle at right angle and thus the pull is approximately
parallel to the spanner.
Best regards,
Svein
----- Original Message -----
From: "Rowland Carson" <rowil@clara.net>
Sent: Friday, September 08, 2006 9:34 PM
Subject: Re: Europa-List: prop bolts
>
>
> >
> >
> >>I have attached (I hope it comes through!) a rough sketch
> >>illustrating the principle.
>
> >Can you (or anyone else) offer an explanation of why the 90-degree
> >geometry works?
>
> Apologies for replying to my own post, but the penny has finally dropped!
>
> Consider (as they say in all the best textbooks) a virtual lever
> going diagonally from the handle end of the torque wrench to the
> centre of the prop bolt. This will be longer than the actual torque
> wrench, but the component of force effective at right angles to its
> axis will be smaller than the force exerted by the operator, in the
> exact proportion required to apply the required torque to the prop
> bolt.
>
> All I had to do was remember that the torque-wrench & spanner
> assembly is a rigid body (at least until the torque wrench clicks)
> and sketch the components of the operator force. Sorry to be so slow
> on the uptake, and apologies, Svein, for casting doubt on your
> suggestion!
>
> regards
>
> Rowland
> --
> | Rowland Carson PFA #16532 http://home.clara.net/rowil/aviation/
> | 750 hours building Europa #435 G-ROWI e-mail <rowil@clara.net>
>
>
|