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The vagueness of C/S to F/P conversion requirements

Bob Axsom

Well Known Member
I have been forced to admit that for racing one has to have a fixed pitch prop to win against competition with high performance fixed pitch props. Since I like to win I am forced to look into converting my O-360-A1A to fixed pitch prop operation and buy a high performance fixed pitch prop. With 6 more races to go in the season and being in 1st place by only 10 points the pressure to change is extreme. So I look at my full set of Lycoming Service Letter, Service Bulletins and Service Instructions and end up at SI no. 1435. I will not go into the details but the superficial treatment will assure inconsistent implementation across the fleet.

I researched the subject in this forum, I searched for part numbers in the Lycoming parts manual, I called the Lycoming Product Support line and I have consulted with friends and at this point I have to conclude that there is no single right way to make the complete conversion.

What I thought my attention would be focussed on was the inner crankshaft plug. Pierce or remove the rear crankshaft plug, install the front crankshaft plug is unambiguous but after that things get fuzzy. The word "should" is used with respect to removing the "propeller governor, adapter, oil line and fittings." Is that an all or nothing situation or can one pick and choose the implementation. Obviously in my immediate situation it would be easiest to remove the oil line and fittings, plug the ports and not deal with the inaccessible governor right now but I' was told I must remove the governor when I called the factory. I am also told that I can put a 72378 cover on the adapter or I can remove the adapter and shaftgear and install a different cover directly on the accessory case (remember SI 1435 said you "should" remove the adapter). I have to call a part specialist to get the hardware part numbers for that implementation method.

I attempted to get the port filling plugs identified but I'm not sure I have them yet. The best information I have is an AN814-6L with an MS29512-6 O-ring for the rear port and a Lycoming STD-700 for the front.

For the rear plug in the crankshaft I was told to make a very sharp punch by grinding a store bought tool. The steel is a soft steel and it will deform. If it deforms instead of piercing it can be removed entirely around the offset oil tube in the crankshaft. Either pierced or removed works - I like removed but will take what I get without damaging the oil tube in the crankshaft.

For installing the front Crankshaft plug I am told I can rent a 64681 tool from a Lycoming distributor or use a socket and a "dead blow hammer" to install it.I was advised to apply a Pematex sealing compound to the edge of the plug before installing it.(I believe it was #2 but I'm not absolutely sure of that).

I will work through this but it is not a simple clearly defined process without risk.

Bob Axsom
 
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While I don't know about the removal of the prop governors an lines, I have done the crankshaft operation on two different engines.

You are correct in that you do NOT want to drill the inner plug. Removing it is an option but I would be afraid of damaging the oil tube, as you mentioned.

My tool of choice is a long Phillips screwdriver and I punch two holes, just to make sure the outer chamber does not get pressurized.

To set the outer seal, I used a piece of oak that just fits inside the flange and a BFH. My BFH of choice for this operation is a handheld sledge hammer.

Keep an eye on that seal, it may weep, if it is not set properly.

For the prop extension, contact Sam at Saber. He will set you up with an extension that is a work of art and all the bolts and washers you will need.
 
Last year Mahlon posted an interesting explanation of how you can use a specially machined governor pad cover plate and leave the oil line and crankshaft rear plug intact to facilitate an easier conversion back to CS prop.

Here's the thread: http://www.vansairforce.com/community/showthread.php?p=662271#post662271

Of course, if you're after every last drop of speed, then removing the oil line will also remove a little bit of unneeded weight too.
 
Yes I saw that in my research

I believe that is the STD-784 cover mounted on the adapter. It is one of the two implementations that I am looking at. It still requires removal of the governor which is buried in there amongst my special lower cowl baffles behind the engine. My plan (oce I get the part numbers is to buy the parts for both options and be able to go either way if there is an "ah ha" or an "oh s" moment in the process.

Bob Axsom
 
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My Superior XP O-320-D1A as delivered from Aerosport, set up for fixed pitch as requested, came with governor adapter and cover plate installed with oil hose return line. I wasnt too keen on it at first but I guess i'll leave in tact for future switch to C/S if desired.

o875w8.jpg


2llksqv.jpg
 
Catto

This is the manufacturer that is beating me and from my research and personal contact I am convinced it has the fastest potential. I've gone through the original Hartzell C/S with 72" dia 7666 blades and the better B/A C/S with F7496 blades but there is no more to be had there. Hartzell engineering agrees that for my particular situation this is the right way to go. They say they cannot approve their props for operation above 2700 RPM where I need to go.

Bob Axsom
 
Bob
I wonder if this really the best option? It seems most finely tuned fixed pitch installations took many hours to get just right along with more than one prop. May I suggest that this is an after race season project. You may have to redesign all of your inlet baffling to account for the changes in airflow at the prop root and spinner area. As well you will need many hours of testing to document actual speeds.
May I be so bold to suggest a no filter ram air setup, or closing off the outsides of the inlets to bring temps up to the max you are comfortable with, or running over redline on rpm if not a BA hartzell? Besides the first time you go to a race with your new fixed pitch prop you will need massive altitude changes and wish you had that CS prop back.
Just my 2 cents.
Fly safe and have fun!
Dave
(This is experimental turn that thing up to race)
 
Thanks for the information and Photos

My Superior XP O-320-D1A as delivered from Aerosport, set up for fixed pitch as requested, came with governor adapter and cover plate installed with oil hose return line. I wasnt too keen on it at first but I guess i'll leave in tact for future switch to C/S if desired.

o875w8.jpg


2llksqv.jpg

It is a little like herding cats and it is good to see an actual supported implementation. This makes the cover designed for installation on the adapter and leaving the tube in place with no plugs poke its little furry head in the corral gate but what is the configuration of the rear plug in your hollow crankshaft? I have a guess but I do not want to influence your answer.

Bob Axsom
 
I am confident that it is the best option

Bob
I wonder if this really the best option? It seems most finely tuned fixed pitch installations took many hours to get just right along with more than one prop. May I suggest that this is an after race season project. You may have to redesign all of your inlet baffling to account for the changes in airflow at the prop root and spinner area. As well you will need many hours of testing to document actual speeds.
May I be so bold to suggest a no filter ram air setup, or closing off the outsides of the inlets to bring temps up to the max you are comfortable with, or running over redline on rpm if not a BA hartzell? Besides the first time you go to a race with your new fixed pitch prop you will need massive altitude changes and wish you had that CS prop back.
Just my 2 cents.
Fly safe and have fun!
Dave
(This is experimental turn that thing up to race)

I'm calling this the best option at this point. Tests and race results will tell for sure but after 50+ races my gut says it's time to leap in this very high potential direction. I am well aware of the loss of low pitch acceleration and climb potential everything is focused on level flight speed - like driving a stick shift car that only has high gear. At Pagosa Springs, Colorado on September 21st Jeff Barnes in his RV-6 was worried that he might loose to me because the density altitude at the 7.6K runway surface was approaching 10,000 ft and the minimum altitude you could clear the mountain ridges on the course was 9,000 ft MSL meaning ~ 1500 ft climb on course and operating in something like 11,500 ft density altitude. I flew it as smart as I could with careful consideration of the winds aloft forecast and the best I could do was 214.52 mph (186.54 kts) Jeff did 222.94 mph (193.86 kts). A very similar situation occurred in the Pappy Boyington race in Coeur d'Alene, Idaho where Brent Travis and I did 223.49 and 216.64 respectively with the same prop mix at high altitude. It is time!

Bob Axsom
 
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