On Thu, 17 Jun 2010 14:26:25 -0700, Tim Wescott
wrote:

On 06/17/2010 02:01 PM, Cross-Slide wrote:
On Jun 17, 3:52 pm, Tim wrote:
The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top& bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

--
Tim "Over Engineered" Wescott
Control system and signal processing consultingwww.wescottdesign.com

Nylon LOVES to absorb water. How will this work on damp days when the
nylon swells up?

This is the problem with design reviews -- the information that's most
likely to make you happy (or at least not deeply unhappy) in the long
run is the information that in the short run is most likely to make you
want to point and scream "you *******!".

When you're ready to go beyond denial, consider acetyl (Delryn) or
Noryl.