----- Original Message -----

From: Tracy Crook

To: Rotary motors in aircraft

Sent: Tuesday, January 20, 2009 3:52 AM

Subject: [FlyRotary] Re: Thrust bearings

I've learned it's rarely wise to debate these kind of things but FWIW, needle bearing rpm capabilities are not simple to nail down.  You might notice that this same (or very close) sized bearing (a single stage at that) is used in the 13B itself and of course it does not limit the engine to 2800 rpm.  Needle bearing ratings are also sensitive to lubrication schemes.  The thrust bearing in the RD-1 is pressure fed to insure the best possible lubrication and cooling environment.

If it gives you any comfort, check it out on www.Mcmaster.com website (pg 1135 of catalog) and you will note that the 35mm x 52mm needle bearing at a dynamic load of 4000 lbs is rated up to 6500 rpm in a single stack.  In a double stack, that gives you a good margin well over 10,000 rpm.

Hope this puts your mind at ease.

Tracy

On Sun, Jan 18, 2009 at 6:23 PM, George Lendich <lendich@optusnet.com.au> wrote:

Tracy.
On another subject, I was looking at your web site and noticed the different Sun gear thrust bearing stages and notice you went from  Ball bearing ( failed) to roller bearing - to what appears to be  2 back to back needle bearings with their end and intermediate washers.

Looking at the bearing book, I notice a limit of about 2,800 rpm on needle bearings which give only 5.600 rpm limit.

My question is, wouldn't 3 needle thrust bearings be needed and could you use 2 thrust ball bearings back to back which run at 5,600 rpm each?

I guess it would be way over kill but NSK double direction angular contact thrust ball bearings, run to 9,500 rpm.

Did you consider any of these other options? or was space your over riding factor
George (down under)

Steve: Any reaction from the Dept of Homeland Security to that muffler? :>)

Tracy


On Sun, Jan 18, 2009 at 4:01 PM, Steven Boese <sboese@uwyo.edu> wrote:

Mike,



The length of the cylindrical section is 24 inches.  The conical section is
9 inches long.

The dome was made from a Kmart mixing bowl.  Some of it  is less than 0.032
inches thick but has held up so far.

The cylindrical section was made by a local sheet metal shop with a stove
pipe joint that also has been tack welded in a few places.

I made the conical section, inside parts, heat shield, and mount from the
same sheet material as the cylindrical section.  The joint in the conical
section is similar to the stove pipe joint and is also tack welded.



Steve Boese

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