Dave Arbogast wrote:

        I had an idea concerning your hollow prop shaft PSRU. The idea of welding
 pinion shafts onto the hollow prop shaft has always bothered me. In fact,
I know of aircraft manufacturers that would never allow a part with the
kinds of stresses on a prop shaft to be held together with a weld. Still
yet I liked the idea. I think I found a solution that would not only
eliminate the weld but also make it much simpler to mass-produce.
Unfortunately it would make it heavier, but not that much. Instead of
 welding pinion shafts to the prop shaft simply thicken the walls, then
drill out and tap holes in the end of the thicker walls in the ends and
use bolts to hold the planet gears on one end and the prop flange and
prop on the other. I think this would increase the reliability, cause
fewer problems with the prop shaft becoming imbalanced, and mass production
much simpler. It would be slightly heavier due to the increased metal
in between where the pinion shafts were on your original design.
This way it could be made very easily with a lathe, drill press,
and tap, and eliminate welding.
        Just an idea, Tell me what you think.

Thanks,
Mark

When I did die design, we would solve this problem with an interference fit of
several thousands of an inch. You'd have a small radius on the outside of the
shaft. You'd freeze the shaft with a CO2 extinguisher, bake the gear to 500 F in
an oven (not hot enough to distort it) and press them together. You
need to do the calculations on how much the IO & OD change with the temp delta...

Once together, it may as well be a weld, w/o the stress & metal crystal changes.

Thoughts?

--
-dave    mailto:dave@arb.net   http://arb.net

 
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