Chapter 16: Final Drilling of the CS121 and CS122 Tubes


Step 4: Final Drilling of the CS121 and CS122 Tubes

Again, when I got to the part in Step 4 where the plans had me drill and bolt together the CS122 firewall cranks and CS121 torque tubes, I decided to do that step after I installed and rigged the aileron controls. My reasons why were presented earlier. 


Here's the process I used for doing the final drilling of the CS121 and CS122 tubes:


1.  Remove the control handles and insert some long AN-4 bolts through the bushings.  Clamp the bolts to a 35-inch steel rectangular bar.  This locks the forward controls in their neutral positions.



2.  The plans do not give a spec for how far to set the CS122 cranks away from the firewall, but I inferred the distance from "View K-K" shown on Chapter 16, page  5.  I inferred it to be just over 3/4th-inches, and the pine board jig I used for fabricating the aileron push-tubes was about the right thickness for setting that distance.   I simply chopped off a piece of the jig and slipped it between the firewall and the cranks in order to set the distance.


3.  Block off the ailerons to their neutral positions.   Make index marks between the CS121 and CS122 tubes.  Remove the 35-inch steel bar, remove the long bolts, and re-installed the control sticks.  (I needed to rotate the torque tubes quite a bit to remove the long AN-4 bolts.  Hence the reason for the index marks.)


4.  Now it's time to set the orientation for the port control stick.  This is best done with the stick grip in place on the stub.  Release the ailerons, then lock the starboard aileron to 20 degrees up travel.  (I used wooden blocks and clamps.)  Rotate the port control stick inward (as in right hand roll) until the bottom of the control stick is at a "just-right" distance near the fuselage sidewall.  Index the CS121 and CS122 tubes for reference, then temporarily clamp the tubes together with a small C-clamp.  Release the starboard aileron.


5.  Now it's time to do the same thing for the starboard control stick.  Again, the stick grip should be mounted onto the stub.  Block off the port aileron to its 20-degree up position, adjust the starboard handle to a similar "just-right" distance,  make an index mark, and clamp those two tubes together.  Release the port aileron.


6. Now it's time to verify I was happy with the handle orientations.  Release the ailerons and remove the spacers from between the CS122 firewall cranks and the fuselage.  Roll the control sticks hard-over to the left.  Measure the clearances between the bottoms of the control sticks and the inside of the armrest (port stick) and fuselage sidewall (starboard stick).  Roll the control sticks hard-over to the right and make the same measurements.  The measurements should be reasonably close.  Block off the ailerons to their neutral positions and verify the control sticks are canted by the same amount.  They should be reasonably close.  Mine were close enough.  If not, I would have repeated steps 4, 5, and 6 until I got happy.


7.  Once I thought I was totally happy, I RE-CHECKED the handle orientations, MOVED the sticks fully side to side, and VERIFIED the stick clearances ONE MORE TIME!  Only when I verified twice that I was truly, totally, totally happy was it time to drill out the holes through the CS121 and CS122 tubes.  I felt the match drilling was best done with the tubes installed in the plane.  So, I blocked off the ailerons to their neutral positions to lock out the torque tubes so they won't move/turn/twist as you drill them.  (I even put the pine spacers back in place between the firewall and cranks.)  I left the clamps in place, too.  Starting with a pilot bit, I drilled all the way through the tubes and use progressively larger and larger bits until the final 3/16-inch diameter was reached. 


8.  Before drilling the hole for the other CS121 and CS122 tubes, release the ailerons, remove the spacers, move the controls around, and re-check/verify the handle orientations and clearances.  Repeat the drilling for these tubes.


When I finished rigging the control systems, I measured all tubes and recorded their lengths in my plans.  I also denoted the M-drawings and Chapter 16 drawings to reflect the final configuration, including the new bearings and rod end fittings.


Voila!  More moving parts!  You think the neighbors questioned your sanity when you made engine noises in Chapter 7???  Wait till they hear the kinds of engine noises you can make when you've got control sticks and moving wing surfaces to play with!!!!

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