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McCoy .35 RH ? Empty McCoy .35 RH ?

Post  oldguy on Mon Aug 13, 2018 3:46 pm

http://sceptreflight.com/Model%20Engine%20Tests/Index.html

   looking at this sight I see for the McCoy .35 RH breakdown illistration it shows a venturi insert.  What is the basis for this insert?  Would removing this insert cause the McCoy .35 rh not to do the 4-2 break because the McCoy 35 rh I have doesn't have the insert, and doesn't do the 4-2 break but the engines runs strong on the bench and on the plane.
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Post  Ken Cook on Mon Aug 13, 2018 5:04 pm

It's there to improve fuel draw. Removing it would make little difference in power but certainly could hamper fuel delivery. If one was to use a true Super Tiger spraybar then I would suggest not using it. Otherwise leave it in there as it will fundamentally assist fuel draw especially when needed the most.
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Post  oldguy on Mon Aug 13, 2018 5:16 pm

Ken Cook wrote:         It's there to improve fuel draw. Removing it would make little difference in power but certainly could hamper fuel delivery. If one was to use a true Super Tiger spraybar then I would suggest not using it. Otherwise leave it in there as it will fundamentally assist fuel draw especially when needed the most.


The nva i'm using is either an OS or a super tiger nva.  I know the McCoy is supposed to do  the 4-2 break but this one doesn't, any comments on why it doesn't? If the insert hampers fuel draw could it cause the engine not to the 4-2 break?
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Post  Ken Cook on Mon Aug 13, 2018 5:52 pm

The insert improves fuel draw and so does a oversized spraybar such as the Super Tiger. This is why I would remove it for a Super Tiger because the spraybar diameter is .156". A stock Mccoy spraybar is .134". A FP/LA spraybar measures .140". So you can see the Super Tiger is already taking up a lot of choke area which is why I would remove the insert due to the size. The ST unit can cause a loss of power with the insert. Why the engine isn't cycling is hard to diagnose. I have to ask, is the spraybar hole orientated correctly on the same angle as the venturi? That alone can be responsible. When the engine is running and your holding the plane, does it break lean when you point the nose up? What size prop are you using on the engine? Is this engine mounted upright or inverted or is it profile? The insert has very little impact on how the engine cycles back and forth. However, if the engine is running too lean it's not going to break into a fast 2 because your already running it there. The only reason I even mentioned this is because if your using the ST, to get the power out of the engine, you need to lean it further. A simple test is to just remove it and give it a try.
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Post  oldguy on Tue Aug 14, 2018 12:11 am

Ken Cook wrote:         The insert improves fuel draw and so does a oversized spraybar such as the Super Tiger. This is why I would remove it for a Super Tiger because the spraybar diameter is .156". A stock Mccoy spraybar is .134". A FP/LA spraybar measures .140". So you can see the Super Tiger is already taking up a lot of choke area which is why I would remove the insert due to the size. The ST unit can cause a loss of power with the insert. Why the engine isn't cycling is hard to diagnose. I have to ask, is the spraybar hole orientated correctly on the same angle as the venturi? That alone can be responsible. When the engine is running and your holding the plane, does it break lean when you point the nose up? What size prop are you using on the engine? Is this engine mounted upright or inverted or is it profile? The insert has very little impact on how the engine cycles back and forth. However, if the engine is running too lean it's not going to break into a fast 2 because your already running it there. The only reason I even mentioned this is because if your using the ST, to get the power out of the engine, you need to lean it further.    A simple test is to just remove it and give it a try.

The McCoy I have doesn't have the insert and i'm running it without one. The hole is oriented straight down the venturi. The engine is mounted on a profile R/M. I did try running it and then pitching the nose up but it didn't change rpms, I will try riching it up more and try it again. I'm running it with a 9 x 5 M/A prop. I haven't even gotten a chance to try and fly it yet. And already have noticed the wing has cracks and is loose at the leading edge where its glue to the fuselage. I have to come up with a way to stiffen and re glue this area before going forward. I'm thinking about some kind of L bracket setup that attaches to the L/ edge and to the fuselage, not sure still thinking of how I will tackle this. I used slow cure epoxy to attach the wing, but after just a few runs it has vibrated itself loose already. I have read since building this scratch built r/m that this was a problem area for the r/m. I wish I would have come across the article before hand. But that doesn't help me now. maybe the best thing to do is just remove the wing and start again and figure away to strengthen this area. I have never had a problem like this before, building all .15 size planes but this being my first 35 size plane and using the McCoy .35, I can see the same building technic I was using for them just isn't going to cut it. Oh well back to the drawing board. Oh well I really wasn't going to fly the McCoy in the 4-2 break anyway if I didn't have to.Thanks for your info Ken. Next time I run it I will try running it richer and see if I point the nose up if it goes to the 2 cycle mode.

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Post  Cribbs74 on Tue Aug 14, 2018 1:16 am

I think you are onto the fix. Sounds to me like you are just running it too lean.

The first time I used a Fox .35 I had no idea how it should sound and I kept running it too rich and it would never break out of 4 cycling.

If this helps the proper needle setting on the ground should have the engine running at a fast 4 cycle with occasional breaks into 2 cycle. Nose up it should break into a clean strong 2 cycle. Upon release and assuming your tank is plumbed correctly it should richen up a little after the first lap and stay in a strong 4 cycle. Once you start manouvering it will do the 2 and then back to 4 on level laps.

The 4-2-4 is really a misnomer, it’s actually just rich/lean. It’s a 2 stroke engine and that’s all it can ever be.

You can run it in 2 stroke if that’s what you prefer, you just have to get the needle to a point where it is slightly rich so it doesn’t go overlean during flight.

Personally I like the 4-2-4 as it allows me to take my time between stunts and usually ensures I won’t ever go too lean. It also sounds good too... Eyebrows

Ron
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Post  Ken Cook on Tue Aug 14, 2018 4:30 am

A 9x5 is light for pitch on the red head. Based on what I mentioned, it sounds to me that the engine is already running too fast. If you were to use a 9x6 or 9x7 it would break back and forth. The Mccoy like the Fox likes a bit of a load on it. If the engine is vibrating , a bit more pitch could certainly stop that. One thing I noted about the redheads, they don't mind 10x6 props and they swing them quite well. The Fox .35 usually has a hard time with the 10x6 due to it overheating and sagging through the manuevers. This is mainly due to the stock muffler. The redhead not having one seems quite happy.
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Post  GallopingGhostler on Wed Aug 15, 2018 2:04 am

oldguy, Ken's propeller advice is spot on. Here's the original Testors McCoy .35 Red Head engine manual as 3 jpeg captures:

McCoy .35 RH ? Mccoy_10
McCoy .35 RH ? Mccoy_11
McCoy .35 RH ? Mccoy_12

It states,

Propeller Recommendations
  • Free Flight - 10x6
  • P.A.A. or R.C. - 12x5
  • Stunt - 10x6
  • Speed - 7x10

3. Use a 9/5, 9/6 or 10/5 propeller for break-in and for flying with your engine runs without stopping when the needle valve is adjusted for peak speed. After the break-in period, you may use a 10/6 propeller for best performance.

Prop size 9x5 was only for break in. (Not sure why the instructions substituted a "/" for "x" in the numbered instructions.)
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Post  Oldenginerod on Wed Aug 15, 2018 5:39 am

Interestingly, the instructions George posted don't show a venturi insert.
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Post  GallopingGhostler on Wed Aug 15, 2018 9:16 am

Oldenginerod wrote:Interestingly, the instructions George posted don't show a venturi insert.

The .35 RH on my Ringmaster has the venturi insert. My other two, a parts engine and a runner do not have the venturi insert. But they appear to have more taper in the venturi narrowing down to about the same cross sectional area whereas the other appears to have a straighter venturi downshaft with the venturi insert reducing it to about the same cross sectional area.

Of course this is using my naked eye without pulling the venturi NVA and again comparing. Could it be possible there are several different permutations of the earlier non-lightning bolt depended on what year produced?
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Post  oldguy on Wed Aug 15, 2018 9:48 am

GallopingGhostler wrote:
Oldenginerod wrote:Interestingly, the instructions George posted don't show a venturi insert.

The .35 RH on my Ringmaster has the venturi insert. My other two, a parts engine and a runner do not have the venturi insert. But they appear to have more taper in the venturi narrowing down to about the same cross sectional area whereas the other appears to have a straighter venturi downshaft with the venturi insert reducing it to about the same cross sectional area.

Of course this is using my naked eye without pulling the venturi NVA and again comparing. Could it be possible there are several different permutations of the earlier non-lightning bolt depended on what year produced?


The RH on your R/M, is the glow plug centered or off set?  The RH I have has the off set plug.   I will be trying different props to see which gives the best performance.
Thanks.
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Post  GallopingGhostler on Wed Aug 15, 2018 10:15 am

oldguy wrote:The RH on your R/M, is the glow plug centered or off set? The RH I have has the off set plug. I will be trying different props  to see which gives the best performance. Thanks.

The instructions appear to be for the earlier RH with glow plug centered in the head. My RM RH has the offset plug. My other runner RH has the same offset plug. Parts engine has the centered plug.
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Post  oldguy on Wed Aug 15, 2018 10:27 am

GallopingGhostler wrote:
oldguy wrote:The RH on your R/M, is the glow plug centered or off set? The RH I have has the off set plug. I will be trying different props  to see which gives the best performance. Thanks.

The instructions appear to be for the earlier RH with glow plug centered in the head. My RM RH has the offset plug. My other runner RH has the same offset plug. Parts engine has the centered plug.

The illustration here shows the insert. On the first RH listed. Looks to be the centered plug, advertising on these seem to be all over the place, it's hard to go by what ads you see.

http://sceptreflight.com/Model%20Engine%20Tests/McCoy%2035%20Red%20Head%20Stunt%20%281%29.html
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Post  GallopingGhostler on Wed Aug 15, 2018 12:48 pm

oldguy, I looked at several Sceptre Flight engine test articles. Of interest is that those showing the centered plug were 1960 or earlier.

HR Warring's May 1960 Aeromodeller issue (1) shows a centered plug head and venturi insert sleeve.

EC Martin's October 1957 Model Airplane News article shows a centered plug head and explains that the original brass crankshaft sleeve bearing has been replaced by a sintered steel sleeve bearing. A brass insert spacer pad (crank throw spacer) cushions the con rod bottom end from rubbing the aluminum back plate. This was later replaced by a nylon one. As a test case, I have one of my runners with this replaced by a simple 1/8" aluminum pop rivet, which fits perfectly. I filed and polished the end that contacts the backplate.

(I surmise that even though pop rivets are of a harder grade of aluminum than the cast aluminum backplate, it is softer than brass. Please note, I hand start my engines. I would not use an electric starter, as it will quickly wear down the nylon one. Also this is a reason why one would not want to use an RH to power an aircraft as a pusher engine. I noticed during tear down of one of my previously received as used that the nylon crank spacer head was completely worn down with noticeable backplate scratch wear. Previous user must have employed an electric starter. My parts engine provides an extra back, in case I notice additional wear on my refurbed (polished) backplate on my second runner.)

Peter Chinn's evaluation of the .19/.29/.35, testing only the .29 (3) does not reveal the date or issue, but shows tear down parts of the .35 with centered plug head and no venturi insert sleeve. It may be a late 1950's article.

Peter Chinn's 4th May 1969 Aeromodeller .35/.40 RH article reflects the later improved lightning bolt case and cylinder assembly with strengthening webs exposed in the exhaust port opening. I am told that with some additional modifications, a later Black Head much more durable Dyke's ringed piston can be fitted to this cylinder. It doesn't show a venturi insert sleeve but has the offset plug head and nylon crank throw spacer.

Also of interest is this RH engine article, which reflects a modeler machinist's improvements to the RH that improved their longevity and usefulness for a CL modeling club.

http://www.flyinglines.org/kb.mccoy.html
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Post  GallopingGhostler on Wed Aug 15, 2018 1:26 pm

Here's an interesting Stunt Hangar forums discussion on the McCoy's from various posters (Membership - free may be required to view):

stunthanger.com - open-forum - so-what-about-mccoy-engines
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Post  oldguy on Sat Aug 18, 2018 5:46 pm

GallopingGhostler wrote:Here's an interesting Stunt Hangar forums discussion on the McCoy's from various posters (Membership - free may be required to view):

stunthanger.com - open-forum - so-what-about-mccoy-engines


Yea thanks, that's agood discussion.
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