-------------- Original message from Ernest Christley <echristl@cisco.com>: --------------


> George Lendich wrote:
>
> > Tracy,
> > I guess that was directed at me, and that's a Yes!
> > I had requested that info from the Chief Engineer at Timken Australia,
> > who provide those figures. If memory serves me I quoted 3,000 RPM.
> >
> > Butch suggested that 250,000 hrs was way overkill !
> > That's not to say they are the best bearing for the job, but they are
> > a very robust bearing - that's for sure.
> >
> > The big problem for any bearing is cooling, so a TRB with much larger
> > surface area than ( for instance) a plain ball bearing, requires more
> > cooling.
> >
> > I had originally wanted to use TRB on my own Aussie design, as an
> > engineer mate explained - their so robust, but have been since coerced
> > by Butch to consider other options.
> > George ( down under)
> >
> I'd like to share as much of the details of this design with y'all as I
> can. The more I look at it, the more I realize how ingenious and how
> much overkill it is. I think it would probably drive a B-52 to an
> aerobatic championship. It's heavy at around 45lbs, but a lot of that
> weight was for cosmetic purposes. Joe was trying to emulate the center
> section of a radial, AND need to add weight to the nose for CG purposes,
> so the housing is about 2" thick at the rear. The wheel axle 'thingy'
> (feel free to correct my terminology) is welded directly to the gearset
> housing, and carries ALL of the flight loads. The prop shaft does
> nothing but actually turn the propeller (not that that is a small job).
> The hollow shaft that the hub rides on is 1.98" in diameter and has a
> .2010" thick wall.
>
> The ball bearing at the rear can probably handle the reaction thrust,
> but I'm going to add a plain bearing anyway. I have to supply oil to
> the center of the sun gear, and the easiest way for me to do that is to
> pump it forward through the sun gear shaft (vs backward through the prop
> shaft as Tracy does). I'll only have to drill about 1" through a
> hardened shaft, vs the 10" to do it the other way. I'll drill an oil
> gallery in the plain bearing, and make it just large enough to backup
> the inner race of the ball bearing.
>
> I'll feed oil at the rear in this method, and then I'll block off the
> oil gallery at the other end so that it's supply will only feed
> forward. It will be forced to travel down the inside of the hub and
> return back between the propeller drive shaft and it's housing to a
> single return at a low point in the planet gear housing. The front
> bearings will ride in an oil bath about 1/3 of it's diameter; oil that
> has just come through the cooler. This, combined with the hub spinning
> out in the 200mph wind, should keep it cool.
>
> The only part that worries me is that it uses a 3-planet gearset. I
> believe I can swap in a 4-planet set without further modification, but
> that is still under investigation.
>
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