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Old 01-27-2018, 06:18 PM
Fletch88 is offline
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I have ran a tank of gas through the Os 40 on the bench and remembered reading about the user who said the rockers wore out quickly due to poor lubrication up top. So I removed the rocker cover to see for myself. Everything is well lubed and nice and tight. Running Redline 40-1 with engine upright on bench.
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Last edited by Fletch88; 01-28-2018 at 03:59 PM.
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Old 01-28-2018, 12:39 AM
birdbrain is offline
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If I remember correctly it was a guy akouzmit or similar name who is on here as well and his problem was that his engine was running a too small a prop and the pcv valve wouldnt open and shut as it should as a result and this led to these issues . I think once he propped it up a bit his probs. went away .I.I.R.C.
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Old 01-28-2018, 02:49 PM
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Hi,
Well, yes the rocker extensive wearing (actually rocker axle wearing) came in this conditions:
1) Engine mounted cylinder up.
2) Prop as recommended for braking or one step up.
3) 7 min moderate RPM in the air and then ~10 min non-stop full throttle in the air.
4) At the end of such cycle I immediately seen that engine is loosing power in hovering mode an in order to maintaine fixed altitude I was forced to advance throttle stick almost 20-25% up at the end of the same 20min flight.
5) After the flight inspection shown that one rocker was absolutely dry and rocker axle was wear out quite extensively.
6) I also found that plane was cowered in a lot of oil on the fuselage although the muffler was pointing in absolutely different direction.

I realized that engine was runnin at or above recommended RPM in the air while running for ~10 min at full throttle.
Initially I thought it is a rocker axle hardening process issue, and replace it twice, but every time after about 7-10 min flight at full throttle I was getting extensive rocker axle wearing.
Then based on fuselage oiling observation and searching about ball based valves on the engines I decided to reduce RPM by mounting larger prop, which in the air at full throttle will not exceed max recommended RPM.
At the same time I also learned about special lubricant, which work well at very high temperature and applied it on both rocker axles.
Since then I do not see much oil on the valve output and running engine for 5 min at full throttle do not cause rocker axle wearing.
I also believe that mounting engine with cylinder down may help to improve rocker lubrication because valve position on crankcase will be up, which may reduce oil loss during engine operation.
——
Interestingly I also have SAITO FG36 for many years and run it quite a lot at full throttle, but never ever experienced any issue with that engine except I replaced ignition by different brand right away after purchasing.
The only thing .. in all my planes FG36 was mounted horizontally due to cowl configuration.

This short video clip show how bad rocker axle wearing is after a single 20 min flight with engine running at full throttle about 10 min.
OS GF40 Rocker support wear (0 min 32 sec)
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Old 01-28-2018, 03:07 PM
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... This is how bad rocker axle wearing was in one flight.
Look for the gap between calliper upper arm and axle.
Now compare with no space between calliper bottom arm and axle
.
The axle wear is about 17% of its diameter !
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Old 01-28-2018, 03:58 PM
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Cont

I added a throttle servo and ibec kill switch to GF 40 bench setup. Ran for 10 mins at varied throttle with no more than 3-4 seconds WOT at any time. Liking the way this engine sounds and the tremendous low end torque it carries. Everything up top still nice and oily.

I think this will go in a balsa USA Smoothie XL.
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Old 01-28-2018, 06:41 PM
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Just be aware that max RPM in the air is 1500-2000 RPM higher compare to bench max RPM.
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Old 04-28-2019, 09:44 PM
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I have one flying the Hangar 9 DHC-2 Beaver 30cc. Flies it well, but have to say it transfers a good amount of vibration until about 2,000 RPM. Once in the air, it smooths out, but when the wheels are on the ground, the vibration transfers to airframe.

Like others have said, electric start only.
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Old 07-25-2019, 08:22 AM
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Hi,
Let me tell you my experience with this engine.
As in the previous post, I bought it for a Hangar 9 DHC-2 Beaver.
I admit I was probably lucky avoiding the problems mentioned in this forum. First, the engine is mounted inverted and the rockers are very well lubricated. Secondly, I always use an electric starter and, finally, I work with big props: initially a 20x8 two blade Biela (~ 6000 rpm on the ground), afterwards a 20x8 three blade Biela (~ 5000 rpm on the ground). The muffler is a custom Zimermann from Germany.
I now have about 50 flights and consider the GF40 is one of my best engines: easy start, quite acceptable vibration and only one dead stick (for an unknown reason). For this kind of airplane obviously the right choice!
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Old 07-25-2019, 08:32 AM
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Rene - thanks for sharing!

I suspect the increased mass of the 3-blade smooths out the engine. What make prop are you using?

Cheers
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Old 07-25-2019, 01:12 PM
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Biela. He mentioned it in his post, Mark.
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Old 07-26-2019, 09:57 AM
Kiva Flyer is offline
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Quote:
Originally Posted by RENE MEYS View Post
a 20x8 two blade Biela ([FONT=Times New Roman, serif]~ 6000 rpm on the ground)
That seems very low for that prop. Is the muffler restrictive? I run a straight pipe and pull ~1000 rpm more than you using an APC 20x8.
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Old 09-30-2019, 08:26 AM
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Hi,
Sorry for this late response. The low rpm is due, in my view, to the wide blades of the Biela prop (whereas the APC generally have narrow blades). The Zimmermann muffler produces about the same rpm as the stock muffler.
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