Marv,
Thanks for the good post of the trim wheel. It explains its
use very well to those that are not familiar with it. I might add
that a stronger spring (which connects to the elevator tube) is necessary
and was included with the mechanism on the originals that Dick built.
Attached is an early image of the mechanism that I have posted a few times
over the years for other interested readers. It may be in the LML
archives. Typically the parts were not anodized in colors, as they came in
a natural finish. The colors do help to point out the many parts and gears
that make the mechanism a bit more understandable, and also shows the complexity
of multiple machining tasks, hence the 'not inexpensive' item that it is.
Testimonial: Every LNC2 which has the original trim lever ought
to be changed to the trim wheel. It is a significant improvement over
the original lever and well worth the time to upgrade to it.
Gary Edwards
LNC2
[I thought I would move this out onto
the LML to invite further discussion and get some assistance from folks who
know more about the intricacies of trim systems than I do.
The
earlier LNC2 was designed with a trim system that used a spring bias applied
to the elevator pushrod to control the overall elevator position. It was
controlled by a small cruciform trim lever that moved the biasing springs
forward and aft. Dick Reichel invented his trim wheel to replace the
lever, allow finer and more precise trim adjustments, and to provide folks
with the same sort of trim wheel that they had flown with in any number of
certified aircraft.
Trimming the location of the entire control
surface is probably aerodynamically preferable (less drag) to moving a trim
tab to use the airflow to move the control surface, and the removal of the
trim tab eliminates its weight and complexity, as well as those of the servo
motor and linkages... ie, less counterweight required for balance. There
are probably other aero issues, but I leave those things to folks more
knowledgable than I in these matters.
Whether or not a a spring
biased trim system would be applicable to the Legacy, I can't see why not, at
least for those folks who are still building and can opt to incorporate it
into their control system... I don't know how the trim tab is built on the
Legacy elevator, but if it's cut from the elevator similarly to the method
used on the LNC2, that part of the process could be bypassed and the work,
weight and complexity of the trim tab mechanism could all be left out.
To my knowledge no one has incorporated this into a Legacy, but that doesn't
mean that it couldn't be done.
The only disadvantage with the
spring bias system at this point is that it is totally manual. Once I
finish with the basic trim wheel system I'm going to look into motorizing it
while still allowing manual
adjustments.]
<Marv>