Re: .09/.15 NVA at last

Ken Cook Sat Dec 03, 2022 7:55 am

Jim, I might have mentioned this before as you had told us what engines you had at hand. Both the Medallion .09 and .15 are not very common. Sadly, kit manufacturers never produced a lot of kits around this engine size. Essentially, you received a kit claiming this size engine to the max size engine. For the record, whenever you see engine sizes on the kit box, ALWAYS use the largest engine as it will generally fly the model the best. The .09's especially because in my opinion they were just not popular vs the .049's. This is my observation over the years.based on what I've seen at meets and contest not too mention hobby shop support. I've used the .15 on the Akromaster and Midwest series planes. The Midwest planes fly poorly and the Akro is not far behind it. It's in my opinion that Midwest used the heaviest wood on the planet. In truth if the Akro was designed properly a modern .061 should fly it. However, Sig designed it like a Mack truck and it flies like one. The medallion .15 is a noisemaker, and it's noise is not to be mistaken for power. This is a very moderate engine with a very flat torque curve.

Over the years one thing that I noticed is that .15 engines generally are unlike smaller mills and certainly turn up vs .35's. In control line, you need to drive the plane at a constant speed. This means that you want the prop to slip but at the same time, you want the plane to maintain speed. What I generally see is a over propped .15. The 8" props are commonly used and this is where the engine is bogged down. Yes, it may work fine for the roundy round fliers but when you pull the trigger into the maneuvers is where it will bite you. This is where the Medallion doesn't exactly fit the bill, most would think if the Medallion .049 works so well, the .15 should be much better and powerful. Bigger is better theory so to speak.Well , in my opinion it's somewhat of a dud. Most .15's I've ever used I put a 7x6 prop on them and turn them up. This doesn't have much impact on the Medallion due to it's rather flat curve and it's power seems to fade into the higher rpm range. A 8x4 tends to work better on this engine but I like to use wide blade props on it even in the 7x6 range. When the Medallion is mounted profile, this engine likes to catch fire more than any other engine, I've experienced. However, this is also depends on the type of cylinder you have. I've noticed the fire issue with the thin cylinders when mounted profile. The thick wall doesn't seem to be impacted by this. What I've also encountered which I've seen more than once is the piston rocking in the thin walled cylinder .15's. The crown of the piston catches the exhaust port on it's travel back up when running and stops the engine abruptly ruining the engine.

Hopefully , none of this deters you from building what you desire, just some things I've noted in regards to this engine. Glow plugs for these are practically unobtainable unless you want to pay the king's ransom on EBAY. Therefore, if you have stock plugs, I highly recommend you adding a additional head shim and keep your nitro low to prevent premature plug failure. This does come with somewhat of a loss of power though. Kamtechnik does make the turbo head which is nice for both engines the .09 and the .15. This head will certainly take some adjusting with head shims for ease of starting. Another thing I noted with the .15 is the carb body, it tends to flare out when tightened causing a air leak. I'm not certain if it's the wall thickness or just the size of the part but it doesn't take much to bulge this part when the retaining collet is snugged. The Medallion I believe was introduced in the late 60's, one thing I never understood is that when you design and offer a engine, one would think you would excel your competition in every aspect. Not true with this engine, while the Fox .15 was offered about 5 years earlier, it had many aspects that even today make it worthwhile. Next to the GHQ and slag engines, the Fox .15x is probably one of the most undesired engines. I find it intriguing that the Medallion.15 weighs almost the same as the Fox and that the bolt pattern is identical. One major advantage of the Fox is it's exhaust stack is off to one side vs the Cox with it's exhaust exiting wherever the cylinder is indexed. This means that in a full body plane your exhaust could be hitting straight back into your firewall or fuse side.

And after all this, someday I will figure out why my paragraphs are indented when I type but everything is stacked when I send.

GallopingGhostler Sat Dec 03, 2022 9:56 am

Ken, you have some enlightening experiences with the Medallion .15 engine. To me, it has always been a curiosity but not enough to buy one. I used to see them on display in Pete's Model Hobbycraft's glass display counter, particularly their store in Kailua on the other side of the Pali Tunnel from Honolulu. This was in the 1970's. Then, I bought their Medallion .09 R/C with exhaust throttle ring, which I gave to my brother as a birthday present.

**944_Jim** Sat Dec 03, 2022 1:38 pm

Ken,
What you posted has been duly noted. I thank you for sharing your insight, knowledge and experience. Your wisdom keeps my pipe-dreams from turning into nightmares. In short, I now know not to expect much more from Miss Mossie II than I got from the first one. Any better performance will be icing on the cake.

The .09/.15 engines were purchased for the sake of building planes around an engine this forum is all about. While Admin allows us to share all sorts of builds around all sorts of engines, I just think building unusual models around Cox engines is what this forum is all about. Building around anything else just means the plane is an orphan here, and possibly more appreciated on RCG or SH. As I indicated above here this is the COX engine forum.

I love reading build logs, and enjoyed sharing the completed builds of the BHM Mossie and Scientific P-40. It brought me joy to share their flights and (my) failures too! Building is the passion, getting better at building and flying is the dream, and reliving a childhood (but with disposable income) is what gets me excited. In short, I'm learning all the stuff a lot of guys got to learn 25-40 years ago.

Since I'm a sucker for twins, beginning with the B-25 and later the Mosquito, I always wanted to build one. The BHM Mossie was a quick "in," and was quite useful as a training ground with respect to twin operations-despite its inherent bloat as flying slabs of heavy balsa. What was learned will make the Frog a much better plane...I hope. I don't really expect it to do loops or fly inverted. Your described shortcomings may not be an issue with this plane. But at least I know NOT to expect a whole lot more than I initially hoped. This is all part of learning.

Since I didn't know the "Big Medallions" are as limited as you describe, this does disappoint me. I hoped to build an Akromaster around a Medallion .15 if I ever got the engine squared away. But I had already acquired a couple of OS .15s for the job.The Akro has been traced for future copies just for the sake of trying different engines and props...if I ever learn the airframe well enough to quickly build copies. An alternative may be to build the engine bearers wider apart, and use aluminum brackets so I can switch engines on one airframe. I expect that this solution will add a bit of excess weight,.but it does present a good experimental platform with little investment of time.

I know I need to fly something that can actually fly better than I can, so I can grow my flight experience. We've discussed this before, and Fred has graciously provided me with cookbook answers that CAN and WILL allow for my growth as a pilot. The last couple of years have been spent working full-time and growing two boys into men while collecting the tools, engines, and kits to satisfy my desire to build neat examples of kits I dreamed of building/flying in my youth. The boys still need their Dad, so being Dad is my priority. My time is not disposable yet.

Soon enough, my wife and I will be empty-nesters, with the big adult responsibilities met. Once that happens I'll be full-time playing with my planes, trains and automobiles. But this is still a few years away.

In short, please know I value your input and am grateful for it! Please don't take any of the above to mean you should stop providing feedback.

Thank you.

**944_Jim** Sat Dec 03, 2022 2:00 pm

Ok...Thread drift happens, and this one took a few turns. I suspect I'm one of the community's "premier drifters." Since this one took a turn towards Chinese engines, I wanted to go in that direction for a moment. This morning I dusted off the storage box marked "AP" for "Kiwi-Chris" as he mentioned wanting some AP .09 details.

What shocked me is I forgot how many APs I had! This happened because I originally believed they share the same mounting pattern as the beam-mounted Cox .049s, and (I suspect) Norvel .049/.061 engines. They were cheap enough that I could ignore their initial cost.

Shown are the .061 engines with OEM carbs (second picture, top three), and Jan Haluzko venturies (second picture, bottom two) and my single NIB .09 with OEM venturi. The .061 with Cox spinner was used on the Scientific P-40. It sports a drilled/threaded Cox spinner and barrel on the nose. I used my Craftsman drill press to jig up, drill and tap the Cox spinner barrel.

Ken Cook Sat Dec 03, 2022 4:09 pm

Jim, just don't take my post as something that would deter you from trying it. This is what I experienced in using the Medallion .15 on my Akromaster and Midwest series planes. I had a old article from the late 70's on the Akromaster and the Medallion .15. It had listed certain changes to enhance performance on the plane and I can't find it anywhere. It was a very helpful article which had many details that I've long forgotten. I think it might have been either American Modeler or possibly Model Aviation. This article is what set my goal to build it and use the Medallion. The thing is that if I did it today, it would be a lot different. I fly a lot better now then I did then. One thing I always noted is that when a new flyer flies, he prefers speed over a plane just lugging around. I think it boosts confidence that the plane will fly through the maneuver due to speed. I was that way years back. Nowadays, it doesn't impact my flying. I know if the plane is capable or what to do if it isn't .

I had the AP Hornet on the Akro and I liked it. However, the Hornet is a lot of weight but it just required a slight bit of tail weight and it was great. I liked the ease of starting but I hated the rear exhaust. The muffler is worthless and the shims they offer is ridiculous. To have the exhaust slam into the rear and take a hard 90 out through too small of a pipe is just poor. It robs a fair amount of rpm's and I discovered almost 1000k. The noise level isn't even all that much louder when the engine had the muffler removed. I also owned the Yellow Jacket .15 which was not a good engine for me. We wanted a inexpensive engine for .15 combat. This engine wouldn't turn up enough to do what we were asking of it. At the time, we were using AME Norvel's , FP.15's and Fox .15 BB's and LA .15's. The FP would hit 20K+ on a Master Airscrew 7x4. This is not shabby for a bushed sport engine. The Norvel came in second at around the same rpm. We were getting about 18K with the Yellow Jacket but we were using the APC 6.3x4 on the engine. I never used the same prop because of that shaft size AP uses would result in me drilling out the prop and then it's committed to that engine whereas the larger hole in the APC worked well enough.

ffkiwi Sat Dec 03, 2022 7:38 pm

944 Jim-thanks for posting those AP pics...the 09 venturi is roughly what I was thinking of...in fact I was going to do a Cox Conquest venturi, suitably scaled. In two minds whether to use a tangential feed NVA-thru the cinch bar location, or a conventional cross the venturi one...or a K&B 7738 two sided setup. Anyway I can certainly do some scaling from the photo....and when you get around to measuring the venturi ID feel free to post that info. Fortunately I DO have a lathe...so venturis are not a big issue.

Just back (2pm) from the flying field after a fairly intensive morning trimming-flew/trimmed/checked 5 power models -all diesel, then went on to rubber...unfortunately the wind blew up SWerly about 12.30pm out of nowhere which put paid to things.....so only got one flight in in rubber-and it was a flyaway....fortunately I found it....didn't want t have to explain to my wife 4 weeks out from the Nats that I'd lost her Coupe on a quick trim check flight...

ChrisM
'ffkiwi'

aspeed Sun Dec 04, 2022 4:41 pm

On my AP .15, I made a tangent venturi at 4mm dia. because that is what the F2D max is, and I wanted to use a hard tank. I used it like that with good luck on another plane, but the F2D plane would not work well with a hard tank, or for other reasons even a bladder. I was told by a trusted source that it needs a smaller prop to work on a bladder. I had a small F2D prop on it at it revved up nice at about 24,000 rpm, but I noticed the rod bearing getting a bit sloppy after one test run. When it runs it flies well, a bit slower than the Fora which is good for an old fart like me, it has to be remembered that it is only a .135 for comparison. I did like the ASP .15 / Magnum XLS blue head. I made up a Turbo head for it and it did very well. It was matching the revs of the Fora with a 7-5 prop. I know the Fora uses a smaller prop, but I think the ASP might break with the chinesium materials. The LA is pretty hard to beat, and the FP is similar. The Norvel is a beast with a bigger venturi and no muffler too.

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