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From: "George Lendich" <lendich@optusnet.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-721665@logan.com>
Subject: Re: [FlyRotary] Re: PSRU - reaction bearing
Date: Thu, 10 Feb 2005 08:22:43 +1000
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OK Ernest,
All that seems OK, considering it's a one-off.
I just get the size of the bearing OD and ID as, I believe, it will be a
standard size.
I believe you will find the thrust adequate.
Building a PSRU is easy enough, having it designed to run as cool as a
design like this can be, by maintaining lubrication, is another. It looks
like it's pressure fed from the engine from your description, so that will
help.

If you find it gives you trouble down the track, get one of Tracy's.
Hope I've been of some help!
George ( down under)

> George Lendich wrote:
>
> >Ernest,
> >This is something I'm familiar with, but can you tell me who makes this
> >particular PSRU and how is the sun gear attacked to drive shaft.
> >
> >
> This is a one-off design done at Lakeridge (8NC8) by Joe Hunt a few
> years ago.  The sun gear apears to be a integral part of the input drive
> shaft.  The propeller shaft is driven from inside splines on the planet
> gear carrier.
>
> > **** Firstly plain ball bearings DO take some thrust. Tracy does use
> > one in
> >
> >the front ( of his PSRU) I believe.
> >I can't say how much thrust it will take but it appears to be quite
large -
> >take the size to your local bearing supplier and they will identify it
and
> >give you a thrust rating.
> >
> >I know there's a 1,000 ft/lbs of thrust there, but how much is carried
> >rearward I'm not sure.
> >
> >
> >
>
> I have a bearing supplier that I've worked with in the past.  I will get
> them in the loop.
> The sun gear is a tight slip fit into and rides on the inside of the
> ball bearing housing, which is 3/4" high.  The balls are 1/2" diameter
> as close as I can measure, but I'm unable to get the calipers down into
> the housing for a really accurate measurement.
>
> I was thinking about this last night when I should've been sleeping, but
> I would think that the reaction forces would be a simple vector based on
> the helix angle of the gears and the input torque.  Assuming a 3" sun
> gear with a 30degree helix and 150ft/lb of torque, the reaction force
> would be:
>
> 150ftlb*12in/ft / 1.5in = 1200lb of force across the helix teeth
> The part absorbed by the rear thrust bearing would be:
> sin(30) * 1200  =  600
>
> I didn't take the time to measure the helix angle this morning like I
> meant to, but if the angle is 20degrees, the force at the rear bearing
> will drop to around 410, and 10 degrees will take it down to 208.
>
> >Question - is the rear teeth of the sun gear turned down before being
> >pressed into the bearing - I'm assuming it is.
> >George ( down under)
> >
> >
> >
> I took a picture last night, but didn't get around to uploading it to
> the computer.  The rear of the sun gear is turn down to be a tight slip
> fit into the ball bearings inner race.
>
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