Posted for "Colyn Case on earthlink" <colyncase@earthlink.net>:

Marv,
I get that the gears provide constant tension on the cables but I don't
get why I care about that. ....but I must be missing something if people
have gone to so much work to solve this problem, whatever it really is.

One thing that occurs to me is that without them the pilot is directly
controlling the amount of tension on the cables and connections. It does
seem that the pilot could develop perhaps more force than is healthy. Is
that the real reason?

Colyn
 

[You've hit the nail on the head.... without the rudder torque tubes tied together in some way, the amount of tension on the rudder cables is controlled solely by how hard the pilot pushes on the pedals.  By gearing the tubes each pedal moves exactly opposite to the other, the tension on the cables remains fixed regardless of pilot input.  In a braking situation without the gears the cables are what determine the pedals' positions and if you put your back into it all of that strain is being taken by the cables and the rudder actuating mechanism. Interconnecting the torgue tubes with the gears eliminates this problem, as the gear teeth are what take the pressure, not the cables.  The gears, BTW, are pretty beefy, they are 20 pitch and have a 1/2" of gear face for the teeth to engage.. I doubt that you could apply enough force against the pedals to fracture the teeth without the addition of a severe shock... since they're seeing constant pressure and are engaged fully (ie, no backlash) they can take a tremedous load without transferring it to the cables.  They are fixed in position with 1/8" roll pins that penetrate the torque tube and, as a result, you wind up with an extremely solid and tough installation.  I hope this answers your questions.   <Marv>   ]