adjustable prop bearing

I guess what I don't get is what takes the loads that go forward and
backward (thrust) and also side to side (torsion). Does the blade
"pivot" off of the big bearing (and hence put big loads on the pitch
change mechanism)? IOW why isn't a support further out on the hub
needed.

It would seem like you could grab the end of the blade and just push
it around and the relatively sharp corner on the hub between numbers
25 and 26/27 (looks like an o-ring and the spacer/pre-load shim and
snap ring) would just gouge into the hub sleeve.

Thanks for the comments. It's kind of fun figuring out this
mechanism.

Joe

"Joe" wrote in message
om...
I guess what I don't get is what takes the loads that go forward and
backward (thrust) and also side to side (torsion). Does the blade
"pivot" off of the big bearing (and hence put big loads on the pitch
change mechanism)? IOW why isn't a support further out on the hub
needed.

It would seem like you could grab the end of the blade and just push
it around and the relatively sharp corner on the hub between numbers
25 and 26/27 (looks like an o-ring and the spacer/pre-load shim and
snap ring) would just gouge into the hub sleeve.

Thanks for the comments. It's kind of fun figuring out this
mechanism.

Joe

The whole key is the fact that the forces you mentioned are insignificant,
compared to the force pulling outwards on the spinning blade.

Lets say that your engine can produce 600 foot pounds of force. Not real
numbers, but nice and round, and not off by one magnitude. g

Now divide that number by three, for each blade. Now you have each blade
soaking up 200 foot pounds of torque.

Let's say your prop has a 3 foot radius, and the center of pressure is two
feet out from the center.That means you are pushing with 100 pounds of force
two feet out. If the bearing is 4 inches across, that gives a fulcrum of .3
feet, compared to 2 feet, so a mechanical advantage of 6 to 1. That means
you are trying to lift the one side of the bearing with a force of 600
pounds.

Compared to the outward force of 20 tons (if you believe that is about
right) pulling out on the blade, your 600 pounds of lift, or rocking of the
bearing, is not going to do *very* much. g

Disclaimer: These are cocktails napkin figures, only. If anyone would like
to refine them, knock yourself out! :-)
--
Jim in NC


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