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  #11  
Old 07-18-2019, 03:20 PM
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titanhank titanhank is offline
 
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The ring gear is cyro fixed to the flywheel. The flywheel is normally dropped in a freezer overnight while the ring gear is heated in oil. When the ring gear is slipped over the flywheel and cools, it is fixed into place with an interference fit. Never heard of a ring gear support. The sabre spacer bolt directly to the crankshaft and drive lugs.

This is what it should look like.

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  #12  
Old 07-18-2019, 03:20 PM
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Quote:
Originally Posted by Ed_Wischmeyer View Post
Time to learn something new - what is a ring gear support,
Thanks!

Ed
It is what most folks call the flywheel.
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  #13  
Old 07-18-2019, 03:21 PM
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Quote:
Originally Posted by Ed_Wischmeyer View Post
Time to learn something new - what is a ring gear support, and where is there a picture of same? We haven't touched the ring gear. And then there's the issue of making sure the starter still engages properly.

The original builder did some "original" things, and there have been a few surprises already...

Thanks!

Ed
Ring gear support is the flywheel. The ring gear is a separate piece that is installed with heat and shrinks itself onto the outside of the flywheel.
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  #14  
Old 07-18-2019, 03:26 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Ed_Wischmeyer View Post
Time to learn something new - what is a ring gear support, and where is there a picture of same?
Quote:
Originally Posted by titanhank View Post
Never heard of a ring gear support. The sabre spacer bolt directly to the crankshaft and drive lugs.

This is what it should look like.
As Mike said, it is the official "Lycoming" name but what many people call Fly Wheel. It doesn't really have enough mass to warrant the Fly Wheel name, so I think Lycomings' name is more correct.... but when in a foreign country, I guess you need to speak the local slang to be understood
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  #15  
Old 07-19-2019, 08:16 AM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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Default Figured it out - spacer is the way to do

Quote:
Originally Posted by titanhank View Post
Call sam at sabre manufacturing and order a constant speed prop spacer at whatever thickness you want.
Finally figured it all out in my old age...

First, consider the fixed pitch prop with a 2 1/4" spacer, and consider the front of the spacer as the datum for this discussion.
* For a fixed pitch prop, the *aft* side of the rear spinner bulkhead is immediately forward of the datum;
* For a constant speed prop, that datum is on the propeller hub. The *forward* edge of the rear spinner bulkhead is aft of the datum, moved further aft by two washers and a 3/8" spacer, for a total of about a half inch.

There's the problem.

Had a great talk with Sam just now (www.sabermfg.com/), and the thinnest spacer he can manufacture is 1.25". The easy solution appears to be to:
* Install the constant speed prop with the 1.25" spacer;
* Keep the present cowl, but extend the cowl right behind the prop with foam and fiberglass. Probably doesn't have to be all that stout because all the cowling loads are carried by the existing structure. The extension would be just shy of 3/4". And if I needed to, I could fly without the cowling extension;
* Install the new spinner.

$377 spacer, $45 bolts, $4 O ring. And he makes 3" spacers that pull 10Gs on Red Bull racers.

Yes, the present cowl would need touch up paint, but so would a new cowl -- and the new spinner will need paint, too.

Anybody want a brand new Van's cowl in Georgia for an RV-7/9, O-320?
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  #16  
Old 07-19-2019, 10:05 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Ed_Wischmeyer View Post
Finally figured it all out in my old age...

First, consider the fixed pitch prop with a 2 1/4" spacer, and consider the front of the spacer as the datum for this discussion.
* For a fixed pitch prop, the *aft* side of the rear spinner bulkhead is immediately forward of the datum;
* For a constant speed prop, that datum is on the propeller hub. The *forward* edge of the rear spinner bulkhead is aft of the datum, moved further aft by two washers and a 3/8" spacer, for a total of about a half inch.

There's the problem.
As I wrote in my other post, the distance from the back side of the spacer bushing on a standard Hartzell propeller hub (with one thick washer installed as well), to the aft face of the hub where it interfaces with the engine is 2 1/4" so the spacer and washer are not reducing the 2 1/4" dimension.

The only variation in bulkhead position that should happen is the influence of the thickness of the bulkhead since the fwd face of it is now positioned against the 2 1/4" datum instead of the aft face.
As I mentioned before, if you installed the doubler on the wrong side of the aft bulkhead (It should be on the aft side), this would push the spinner bulkhead even further aft from where it is supposed to be.

You are not the only one to make a switch between fixed pitch and a constant speed. Many of them work fine. If it doesn't, it is like because something is nonstandard or not assembled as intended (or a bit of both).
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  #17  
Old 07-19-2019, 10:13 AM
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Mike S Mike S is offline
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Quote:
Originally Posted by Ed_Wischmeyer View Post

First, consider the fixed pitch prop with a 2 1/4" spacer, and consider the front of the spacer as the datum for this discussion.
Are you saying you still have the 2 1/4" spacer in place when you are trying to fit up the new prop???
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  #18  
Old 07-19-2019, 11:28 AM
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Ed- be sure to do some W/B calcs before opting for the extension. Moving a 55# prop forward by an inch and a half is significant, and will amplify the negative impact of polar mass on handling and spin recovery. Could be fine, just know before you go, especially considering that you have to do some cowling work anyway. You should be able to use your old W/B data to predict CG impact of new installation pretty closely.

I’m grateful to Hartzell for having made a custom hub just for Vans with a built-in 1” extension for the composite CS. That bolts right on with the standard cowl with no mods.- Otis
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  #19  
Old 07-19-2019, 11:44 AM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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Quote:
Originally Posted by Mike S View Post
Are you saying you still have the 2 1/4" spacer in place when you are trying to fit up the new prop???
No. I was just establishing a datum.
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  #20  
Old 07-19-2019, 11:51 AM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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Quote:
Originally Posted by Hartstoc View Post
Ed- be sure to do some W/B calcs before opting for the extension. Moving a 55# prop forward by an inch and a half is significant, and will amplify the negative impact of polar mass on handling and spin recovery. Could be fine, just know before you go, especially considering that you have to do some cowling work anyway. You should be able to use your old W/B data to predict CG impact of new installation pretty closely.

Im grateful to Hartzell for having made a custom hub just for Vans with a built-in 1 extension for the composite CS. That bolts right on with the standard cowl with no mods.- Otis
Thanks for the reminder! Already did the W&B. The new prop is about 10# heavier than the fixed pitch, and the W&B change with the extra weight farther forward was, surprisingly, insignificant. The RV-9A has a generous CG envelope.

After doing all the math and such, the constant speed prop moves the spinner aft by at least 1/4", measuring from the aft spinner bulkhead. The current solution is to get a 1.25" Saber Mfg spacer, the minimum thickness, and then build up the leading edge of the cowling with foam and fiberglass. The structural loads will be handled by the existing cowling. And I'd have to do some fiberglass work and paint work with a new cowling, also.

Measure four times, change your mind five times...
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