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  #1  
Old 12-29-2018, 05:40 PM
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AX-O AX-O is offline
 
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Default Please read if converting from Fixed pitch to Constant Speed prop

All,
In the process of changing from a fixed pitched prop to a constant speed prop, I have ran into one major issue. Hoping to have a thread that folks can view and use to make a decision before heading down this road.

If you are a moderator, please consider making this a sticky. It will save someone thousands of dollars and many weeks of troubleshooting and backtracking.

STOP!!!! before you even think about doing this conversion, some very costly advice i had to learn on my own (even though the info is out on VAF on various threads if you look around).

All engine cases are not crated equal. Make sure you know what type of case you have and how it has been configured. Just because you have a hallow crank does not mean you can convert to constant speed by adding a governor and associated line, gasket, pad, etc.

Some engine cases have a port/hole on the left engine case half. (Example picture, not my engine)



Some do not. (Example picture, not my engine)


That little hole not being plugged with an NPT plug will allow the pressure created by the prop governor to escape into the engine case. NOT GOOD for constant speed operations.

This topic has been discuss here previously but I missed it. Below are a few links:
click
Click

After reinstalling my engine and being ready to fly, my prop was taking a long time to cycle. At some point during the ground check the prop stopped cycling. Oil temp was at approx 170 deg. After reading, researching and trouble shooting I came up with a plan.

I used the 90 deg fitting on the nose of the engine and put air pressure to it vice oil pressure from the prop governor. The result was air immediately rushing out of the case vent and the oil dip stick (if I opened it), the prop would not move. Since the plug inside of the crank is in place and did not have a hole (correct for constant speed configuration); either the NPT plug is not in, the front bearing is not installed correctly or the inner crank plug is leaking.

At this point the best case scenario is I remove the prop and the inner crank plug is not on right. but it looks like the engine is coming off again and going to an engine shop to get tore down. Pics below of the set up used to put air pressure in the 90 deg fitting.



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The information that I post is just that; information and my own personal experiences. You need to weigh out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk. Further more, these are my opinions and not those of my employer.

Last edited by AX-O : 12-30-2018 at 11:23 AM. Reason: added clarification on the first 2 pics posted.
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  #2  
Old 12-29-2018, 06:26 PM
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Mike S Mike S is offline
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Quote:
Originally Posted by AX-O View Post
If you are a moderator, please consider making this a sticky.
Done, and thanks for posting this.
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  #3  
Old 12-29-2018, 07:39 PM
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I thought that little hole was how oil actually got into the crankshaft and thence to the prop hub?
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  #4  
Old 12-29-2018, 08:11 PM
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Is this a factor for cases with a front gov mount also?

Do you know if there is any way to determine if the case has the hole, other than the air leakage test??
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VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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  #5  
Old 12-30-2018, 01:25 AM
Jetj01 Jetj01 is offline
 
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Default Yup, that sucks!

Back in 2009 I thought I?d be taking the first flight in April until same unfortunate scenario. Had to remove and split motor and get that hole plugged. Flying commenced in May. The rebuilder assumed the engine was going into a Cherokee 180 with fixed pitch and so removed the plug. They did ?fix? it at no charge but I did have to remove the engine and re-install. Bright side? I did a ?cleaner? install the last time👍
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  #6  
Old 12-30-2018, 10:18 AM
chevelle000 chevelle000 is offline
 
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Default Engine

Please be careful when building an engine for the first time. Ask for advice before assembly.

The crankcase you have pictured is for an A4 type solid crankshaft engine. Check crankcase part numbers before use.

Also, I see on your assembly of the engine you used black paste on the camshaft lobes. "DO NOT" do this for roller engines.
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  #7  
Old 12-30-2018, 11:30 AM
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Just to clarify. The 2 pictures of the engine cases are not of my engine. They were examples I found online that showed what I was trying to convey.

The engine will be sent to an engine shop as I don't have the tools or expertise to take it apart and put it back together.
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The information that I post is just that; information and my own personal experiences. You need to weigh out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk. Further more, these are my opinions and not those of my employer.
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  #8  
Old 12-30-2018, 07:48 PM
Boyd Birchler Boyd Birchler is offline
 
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Default

Converted a 0-360 A4M to a hollow crank from it's original solid crank.

I found out about this by due diligence research and good luck before I built the engine back up. The mod was quite easy to do, drill, tap threads and use an internal wrenching pipe plug.

Have not always been lucky: had a C90 Continental that would not get oil pressure, had the engine off the plane twice before finding the culprit: 6 little #10 machine screws were left out on the front of the camshaft....
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  #9  
Old 12-31-2018, 11:35 AM
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The photos in the 1st post got me looking at what I have laying around in my hangar.

The second photo will work with Constant Speed IF there is a hole and pipe fitting on the outside of the case to connect the constant speed governor line.

The first photo may work if there is a hole and pipe fitting in the right case AND the plug that Axel is talking about is installed in the LEFT case half with a hollow crank and correct crankshaft plug. IF going constant speed, the hole shown in the first photo must be plugged.

I have one cranked crankcase that was used with constant speed prop for 2,800 hours and it looks like the 2nd photo with NO hole in the left case half. The hole without a plug in the left case half is the reason why constant speed did not work with Axle's engine.

I read the original post several times and did not understand. Looking at actual hardware that worked allowed me to understand the post. This is my attempt to help others understand and not have the same issue in the future.
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Last edited by RV6_flyer : 12-31-2018 at 06:46 PM. Reason: spelling
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  #10  
Old 12-31-2018, 04:48 PM
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Default Additional info....

Since it didn't look like either of threads that Axle linked to have the information I am adding it here......
There is a Lycoming service instruction (don't remember the # right now) that documents a specific procedure for testing the nose section of a constant speed engine.
There will always be a certain amount of leakage (there has to bee since the oil feeding the main bearing has to go somewhere). There is a specification for the amount of leakage allowed. The test is done using a Cyl differential pressure tester just like is done when checking cylinders. If pressure delta is outside of the allowed range, it is a sure indication that something in the nose section is not right (excessive bearing clearance, missing plug, etc.)
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