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Date: Mon, 24 Oct 2011 23:25:50 -0400
From: Ernest Christley <echristley@nc.rr.com>
Reply-To: echristley@att.net
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Gear box
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On 10/24/2011 10:56 PM, John wrote:
> Earnest, what are you using for output shaft bearings?   As I reported 
> last year the oil seal came out on the out put shaft of my Marcotte 
> gear box.  Two Eaton gear box engineers are working on a solution to 
> circulate oil to bearings and also cool the oil.  The output shaft has 
> two tapered bearings with the small end of the taper facing each other 
> and the consensus is that the oil will always move from the small to 
> the large end of the taper, which will trap the hot oil next to the 
> seal.  There was no return for the oil or a retainer for the seal.  
> These bearings were totally submerged in 80W oil.  If this is indeed 
> the issue the case expanded and the seal fell out.  JohnD
I don't have the number off the bearing, but they are hefty wheel bearings.

Imagine, if you will, that you took the axle from a NASCAR race car, and 
centered it on the ring gear of the Ford C4 planetary set.  The wheel 
hub is mounted on the axle and spins freely.  The shaft picks up power 
from the planet carriers center splines, passes through the hollow axle, 
and drives a "top hat" that has splines in the center.  The prop fits 
over the top hat, the prop bolts going through it's brim and into the 
wheel hub.

A housing fits around and holds everything.  Oil is fed to and fills the 
hub area through a 1/2" galley in the housing.  Oil at the front drains 
back through the area between the axle and the drive shaft, through the 
planets, and out the side just behind the ring gear.

Lot of big rigs use these oil bath wheel hub designs for years on end 
without issue.  You can't tell me that a little propeller would stress 
the bearing more than a rig goin' 80mph haulin' 40tons of junk.  I would 
suggest adding a seal retention bolt as Lynn suggests and be done with it.

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    On 10/24/2011 10:56 PM, John wrote:
    <blockquote cite="mid:list-5171638@logan.com" type="cite">
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      <div><font face="Arial" size="2">Earnest, what are you using for
          output shaft bearings?   As I reported last year the oil seal
          came out on the out put shaft of my Marcotte gear box.  Two
          Eaton gear box engineers are working on a solution to
          circulate oil to bearings and also cool the oil.  The output
          shaft has two tapered bearings with the small end of the taper
          facing each other and the consensus is that the oil will
          always move from the small to the large end of the taper,
          which will trap the hot oil next to the seal.  There was no
          return for the oil or a retainer for the seal.  These bearings
          were totally submerged in 80W oil.  If this is indeed the
          issue the case expanded and the seal fell out.  JohnD  </font></div>
    </blockquote>
    I don't have the number off the bearing, but they are hefty wheel
    bearings.  <br>
    <br>
    Imagine, if you will, that you took the axle from a NASCAR race car,
    and centered it on the ring gear of the Ford C4 planetary set.  The
    wheel hub is mounted on the axle and spins freely.  The shaft picks
    up power from the planet carriers center splines, passes through the
    hollow axle, and drives a "top hat" that has splines in the center. 
    The prop fits over the top hat, the prop bolts going through it's
    brim and into the wheel hub.  <br>
    <br>
    A housing fits around and holds everything.  Oil is fed to and fills
    the hub area through a 1/2" galley in the housing.  Oil at the front
    drains back through the area between the axle and the drive shaft,
    through the planets, and out the side just behind the ring gear.<br>
    <br>
    Lot of big rigs use these oil bath wheel hub designs for years on
    end without issue.  You can't tell me that a little propeller would
    stress the bearing more than a rig goin' 80mph haulin' 40tons of
    junk.  I would suggest adding a seal retention bolt as Lynn suggests
    and be done with it.<br>
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