Turns out that not only is it difficult to drill steel, as I learned with the aileron counterweights, but it's also difficult to drill into steel straight, from one end of a tube to the other. In fact, I totally botched the first pair of steel pushrods and had to drop some $30 for a replacement tube (ST4130-035X1/2X48-PC). To make things easier, one ought to use a drill jig (my approach) or use Mike Bullock's miserly approach. In either case, the jig helps secure the tube in the drill press.
However, after drilling my steel pushrods, I came across the notion of welding the bushings into the pushrods rather than riveting. This notion is fraught with some interesting discussion with respect to the hardness of the steel following the welding. It appears to essentially come down to, yes the steel will be weakened, but it will be far stronger than 2 rivets holding each bushing in. Also, the use of aluminum rivets on steel can promote corrosion due to the dissimilar metals. Apparently, this approach is not permitted in the certified world.
Ultimately, I decided to have a local shop TIG weld my bushings for fifty bones. You can see the holes I previously drilled for the rivets.
And I reprimed the areas where the powder coating was removed. The interiors were primed (not shown) by taping off one and spraying Napa 7220 (reminder, don't use a water-based primer on steel) in the tube and rolling it around until the interior was covered.
I decided to drive rivets into the bushings anyway, as an extra measure of safety, should the welds break. Though ideally I would use MS20615-4M11 (which I can't seem to source), the concern of any associated corrosion is fairly minimal given the thousands of kit planes in the air using that approach. With that in mind, I went with the plans' recommendation of AN470AD4-11. Not the prettiest shop heads in the world but they'll work fine if the welds break. I drenched the area with primer to mitigate corrosion.
Ultimately, I decided to have a local shop TIG weld my bushings for fifty bones. You can see the holes I previously drilled for the rivets.
And I reprimed the areas where the powder coating was removed. The interiors were primed (not shown) by taping off one and spraying Napa 7220 (reminder, don't use a water-based primer on steel) in the tube and rolling it around until the interior was covered.
I decided to drive rivets into the bushings anyway, as an extra measure of safety, should the welds break. Though ideally I would use MS20615-4M11 (which I can't seem to source), the concern of any associated corrosion is fairly minimal given the thousands of kit planes in the air using that approach. With that in mind, I went with the plans' recommendation of AN470AD4-11. Not the prettiest shop heads in the world but they'll work fine if the welds break. I drenched the area with primer to mitigate corrosion.
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