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Subject: RE: [FlyRotary] Re: M/T Prop Won't Fit PSRU
Date: Thu, 16 Dec 2004 07:54:12 -0600
Message-ID: <87DBA06C9A5CB84B80439BA09D86E69E6CBE31@MAIL01.austin.utexas.edu>
Thread-Topic: [FlyRotary] Re: M/T Prop Won't Fit PSRU
Thread-Index: AcTi/qIozc/ggYC2RJGxm9XXGmpFxwAda7mA
From: "Mark R Steitle" <mark.steitle@austin.utexas.edu>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

Charlie,
Thanks,... good info.  Too bad they don't list all of the bushing =
dimensions.  I'll check with Jim Ayers (M/T prop distributor) to see if =
he can tell me what the other dimensions are, but its my guess (based on =
measuring the bore in the prop flange) that they are 3/4", then stepped =
down to 5/8".  I'll need to check again, but from looking at the sketch =
of the bushing, it may even be possible for the prop flange to have two =
steps in each hole.  I'll check that tonight. =20

When Jim Ayers and I last spoke, he mentioned something about a ring =
gear and I didn't pay that much attention.  As I understand it, on =
Lycomings, the ring gear fits between the crankshaft flange and the prop =
flange.  It seems logical that it would have 3/4" holes (to match the =
bushings).  Also, from SI-1098G, the illustration shows two steps on the =
bushing, in addition to the shoulder.  That's new information to me too. =
 It would be nice to have the od's of each step.  From what Jim said, =
the Lycoming bushings are internally threaded.  Here again, SI-1098 =
doesn't clearly show if they're internally threaded or not.  =20

Mark S.

   =20

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On =
Behalf Of Charlie England
Sent: Wednesday, December 15, 2004 5:33 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: M/T Prop Won't Fit PSRU

Mark R Steitle wrote:

> I have been working to resolve a problem for more than a month now and =

> thought I would query the group for a possible solution.
>
> If anyone else is running (or planning to run) a 3-blade M/T electric=20
> prop with the RD-2C gearbox, I have discovered a mating problem in=20
> using this prop/gearbox combination for my 20B. The problem is the=20
> RD-2C prop flange comes with 3/8 id x 5/8 od bushings. The M/T prop=20
> has a stepped hole that is =BE" for the first 3/32" and then goes to=20
> 5/8". Tracy is not comfortable with drilling out the 5/8" bushings and =

> M/T adamantly advises against using anything less than =BD" prop bolts =

> with this prop. So, I'm at a standstill until I can get this resolved. =

> The only solution I can see is to press out the existing bushings and=20
> open up the holes to accept =BE" od x =BD" id bushings. But that would =

> require disassembly of the gearbox and some precision machine work,=20
> possible but not my first choice.
>
> Mark S.
>
> Lancair ES - 20B
>
> (with a very pricey lawn ornament)
>
Mark,

On a Lyc the 6 drive lugs on a given installation are all the same=20
diameter where they enter the prop, with no step. I'll bet that the 3/4" =

dia. step, if only 3/32" deep, is to allow mounting the prop directly on =

a Lyc prop flange without the flywheel (one lug in the crank flange has=20
the oversize step on it to index the flywheel). Surely they don't expect =

<3/32" tall lugs to carry torque to the prop(?).


Attached is a snip from Lyc Service Instruction 1098G listing various=20
drive lugs & dimensions, but I can't tell from the chart & drawing=20
whether the .75" prop flange diameter necks down to 5/8" where it enters =

the actual prop. Why not call the US distributor for the prop & get=20
clarification on whether they expect a drive lug (bushing) that's either =

3/4"dia x only 1/16" high (can't be a full 3/32" or the prop might not=20
seat on the flange), or a bushing that's 5/8" OD & 1/2" ID with normal=20
height?

Neither sounds ideal, but if I had to choose, I'd go with door #2. :-)

Charlie

http://www.lycoming.textron.com/support/publications/maintenancePublicati=
ons/serviceInstructions/SI1098G.pdf