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Wing Push Rods

April 8, 2012

So it is time to make the push rods.  There are two in each wing.  The first one connects the bell crank mechanism in the wing to the control stick in the cockpit.  This one is made of 1.5″ aluminum tubing and has a cone shaped adapter in each end.   This adapter holds a threaded bolt that connects to the bell crank and the control stick.  The second rod is considerably smaller and transfers the motion from the bell crank into the up/down motion of the aileron.  It is made from powder coated steel rod stock.  This pipe has threaded metal bolts that you have to attach on either end.

Here's the larger push rod with the cone inserted and the rivets set.

Finally got the rivets set for this push rod. Took forever and I consumed almost all the AN470AD4-12 rivets in the kit.

Once you get the ends inserted into the pipe, you must rivet them in place.  You can also weld the end of the steel rod, but since I’m not a welder and don’t know any, I’m going to rivet them.  The larger pipe requires six evenly spaced rivets.  I puzzled out how to measure and mark them on the tube.  Here’s what I came up with.

I determined the circumference of the pipe.  I then divided this number by 6, the number of rivets in place.  I marked the location of the rivets on a sliver of paper that was the same length as the circumference of the pipe.  I then wrapped the paper around the tube and transferred the marks.

Once the marks were on it I needed to drill the holes.  The larger tube was no problem, really.  I just had to pass through the wall of the pipe and the inserted cone.  The smaller pipe was more difficult.  I had to make a straight, plum, hole completely through the pipe.  It was vital that these holes be straight, otherwise the rivets would not pass completely through.  Both pipes required #30 holes.  I decided to drill them small, then ream them to the final size.  I used a 7/64″ bit for the first pass, then switched to the #30 reamer.  But before I could start drilling, I needed a way to hold the pipes steady and straight.  I had to go to Harbor Freight and buy a drill press jig that can hold pipes steady while drilling.  Michelle helped by holding the pipe level and still.

Drill press jig

Me actually drilling the holes for rivets in the ends of the push rod.

When I got the holes completed, it was just a matter of riveting them.  The blind rivets in the larger pipe were no problem.  I have the pneumatic rivet puller now and it makes short work of them.  The AN470’s on the other hand were a bitch.  They are purposely long because there is so much open space in the center of the steel rod.  The rivets balloon a bit in the pipe and are harder to set due to the length.  The way I got the rivets to work was to do them slowly.  2 second bursts on the rivet gun.  If I tried to do it all at once, the rivet would always bend over, or split in half.

Im a bit at a standstill at the moment.  I made some mistakes last weekend that I am waiting for parts and tools to correct.  When I get to those steps, I’ll try to describe what I did wrong.  I think I’ll make the push rods for the other wing.  Save myself some time when I get to that point.

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