exocet-RCU

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Hi all. I picked up a twin that looks like a Skylark 56 bash but the wing is shorter. Anyway, it appears to be set up for 2 .09 - .10 engines. I have a couple of NIB Enya .09 IVs that I want to put on. Can you tell me what props you would recommend for this application? I know the older Enyas like to swing larger props than their counterparts so I was thinking a 7x4 or a 7x4 cut down to 6.5x4. Thoughts?

Thanks in advance

Tim

Mr Cox

I think they run best with a 7x4-7x5 or slightly larger loads. Should spin around 14500rpm on the 7x4 as I remember it.

exocet-RCU

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Thanks for the info, Mr. Cox.

fritzke

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I noticed Tower is listing a batch of new (?) APC props in good sizes for us: 4.2", 5.5" 5.7" 6x2, 6x3 " and some new 7" and 8" ones that would be good
for an 09...well 8" may be a bit much for an Enya 09...
Dave

http://www3.towerhobbies.com/cgi-bin/WTI0052P

1QwkSport2.5r

I was recommended using an 8x3 MA combat prop for my .15-IVs, I imagine an .09 would be fine turning a 7x3-7x5 or maybe a 6x5-6x6? I also noticed my .15's gained almost or slightly more than 2,000rpm using 15% nitro from using 0% nitro so if you need more power, run a bit more nitro.

gcb

Tim, remember these are iron/steel engines and will perform best if broken-in with heat cycles. They should swing 7x4's easily. I would not cut them down. Once the Enyas are fully broken-in don't exclude trying an 8x3 or 8x4.

Good luck.

George

hfenn

I had good luck with Master Airscrew 8X3. Heed the break in procedure and it will last a long time.

exocet-RCU

My Feedback: (1)

So gentlemen, remind me of the break in process. If I remember correctly, I run the first tank in '4 cycle' extra rich mode. Let it cool down. Then run again, leaning it out so it alternates between 2-cycle and 4-cycle. Let it cool down. Then run again, leaning out a little more so it is now fully in 2-cycle but NOT fully peaked out. Let it cool down again and then run it again leaner but not quite at full. Does this sound correct?

1QwkSport2.5r

I run my lapped iron/steel engines as rich as it will run without glow support for the first start. Run 2 minutes and cool off. I run one full tank doing 2 minute intervals at the sloppy wet rich setting. For subsequent tanks I lean it out 500rpm at a time for a half dozen 2 minute intervals each. After a half hour I run a couple tanks at the 2/4 break where it occasionally hits a 2-stroke run. After about 45-50min I'll peak it and Richen to about 800-1000rpm off peak and run it there for awhile. Once the piston will roll to BDC on its own, I consider that pretty close to broke in. If that makes sense. I'm known to go overboard with things, so you may consider my method extreme.

I usually use 0% nitro and 20-25% castor oil fuel. After break-in, I'll use 10-15% nitro 22-25% castor oil.

gcb

That pretty much covers it. The first "extra rich" run is to get any manufacturing junk, polish, etc. out of the engine. After that, it pretty much depends on how tight your engine is. If at any time the engine starts to "sag" or slow down, shut it down immediately. That means it is over-heating and needs to cool. After it cools, richen the needle a few clicks and run it again.
Some engines you can run right up to peak for a couple of minutes, then pull or pinch the fuel line to shut it down. Let it cool to ambient temperature. That completes one heat cycle. Other engines need to be run very rich for two minutes then pull the fuel line and let it cool. These engines are leaned a couple of clicks every other heat cycle. When it runs well at peak it is ready for a plane.
Oh, another point, break-in is best accomplished on a bench where you have full control at all times. At no time should you run the engine over lean.

Of course there are other ways to accomplish break-in but I like and use this method.

George

exocet-RCU

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Thanks, guys. I know what I'll be doing at the field tomorrow night. Bench Runs!

Mr Cox

Excessive long and rich runs of these engines will only wear out the engine prematurely, so there has to be a bit of a "feeling" for the engine involved. The initial rich run is there to mate all the surfaces and after that you want to do heat cycles in order for the iron surface to harden and also to get a nice protective castor film on both the piston and liner. This is done by ending each run by running lean, pinch the line until the engine stops and let it cool down.

There is a good description of the break in process on a diesel site somewhere, can't find it now though...

Edit; Found the link I was thinking of now; http://www3.bc.sympatico.ca/dieselco...ut_diesels.htm

Mr Cox

This sounds more like an old-school ringed engine break in to me.

exocet-RCU

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The link on the diesel site was interesting. Thanks for sharing it.

Tim

MJD

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But it's an old school iron/steel lapped glow engine.. what's wrong with that process?

Mr Cox

A lapped engine needs to stay tight, you don't want to have any excessive wear, it should only be just enough for a tight seal and then heat and work harden the surface to keep that fit. The piston may even grow a little during the heat cycling and give an even better seal. It is all in the link above.

Leaning out an extra 500 rpm per tank, never reaching a full 2-stroke, serves no purpose for a lapped engine without piston rings. It may well work on a ringed engine were the ring should seat against the cylinder while the spring action can take up wear, especially in dykes ringed engines.

MJD

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Okay gotcha.. I wasn't being controversial, actually was curious about the difference in approach.

Mr Cox

No problem, no offense taken. It just seems to often become a rather heated topic...

The link explains it quite well I think, and it should be a trustworthy source too.

1QwkSport2.5r

The method I outlined is the routine I was taught for lapped engines, and I use a similar regimen for ringed engines. It was explained to me to keep the lapped piston cool initially as to not make it overly tight in an engine that already has a tight p/l fit. I have treated most of my new lapped engines this way and they have a fit that rivals an ABC. I will read the link you posted, Mr. Cox. I'm always looking to learn something new and can appreciate different viewpoints.

Cross Check

Hi All,

Enjoying lapped engines, is fun.
Break them in nice,
Let them enjoy flying...
Till the 'Varnish Ring' wears out..
Only worn out a McCoy.35, Fox.36R/C so far...

I have some Enyas, that keep going and going !
I'll bet Ken Enya knows Samorai metallurgy !

Got a Enya .09, Left side exhaust, tiny R/C carb, nice spinner nut,
And no kidding, A NV assembly that will fit on an Enya.45 carb!


My Enyas enjoy chugging nice size props.
The small bore carbs, are very nice, for idle and throttle response.

Want more power?
Get a bigger Enya !

Cheers,

Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team

gcb

I have used that process for diesel break-in for years and have recommended it to other diesel users.
Remember the part where steel is removed from the liner and gets imbedded in the porous iron piston and is then used to smooth the liner. I think part of the process relies on the castor and lubricating qualities of kerosene to accomplish this. It may not work so well with the much thinner alcohol and castor, especially for those who use part synthetic lube which will prevent the castor varnish buildup.
Runs starting rich and leaning out a little every other time lessens the chances of overheating and causing excessive wear, with the worst case being thermal runaway where the heat breaks down the lube and sometimes causes severe wear.
As I mentioned in my previous post, there is seldom only one way. Your engine, your choices.

George

exocet-RCU

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Well, I ran each one 8 times yesterday at 4 minutes each run. I started in full rich, sloppy mode and gradually leaned each engine out with each successive run. I used a Master Airscrew Simitar prop, 7 x 4. The 9th run on each, I ran at normal operating settings for an entire tank(2 ounce - 7 minutes). They seem to run pretty well. Both idle and transition from idle to full throttle without significant lag time. I guess now the only thing left to do is mount them in the plane, connect everything up and have the maiden flight. I do think I'm going to get medium heat plugs for them instead of the hot ones I currently have as I prefer to run 15% nitro fuel and I think the combination might be too hot. Thoughts?

Tim

1QwkSport2.5r

I run Enya 3 or Fox idle bar plugs in my 15-IVs and have used 0, 5, and 15% nitro in them (20-25% castor oil lube) and didn't have any issues with any of the fuels I used. Provided you set them a few ticks rich, hot plugs should be fine.

exocet-RCU

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Success! Did the maiden flight last night with Master Airscrew Scimitar props (7X4). It doesn't fly fast but it definitely has enough power to keep it in the air. I had the engines slightly rich (just breaking into the 2-cycle sound) and actually one went more rich as the flight went on. Flew for 5 minutes and brought it in for a perfect landing on the runway. Then I was able to breathe........

I needed to have the elevator trim all the way down and then it still wanted to climb so I need to do some adjustment. It wasn't twitchy at all, though, so I don't think its tail heavy. It balances 3 and 3/8 inches back from the leading edge, which is in the range is should be (3 and 1/4 to 3 and 1/2)

I'm thinking of putting on wood 7X3.5 props instead of the 7X4s. Thoughts?

MJD

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My only thought is that I have yet to see a wood prop under about 10" diameter that is equal or more efficient than a decent molded prop - most of them have grotesque airfoils towards the tips. YMMV.