ALFIEV

Whoa Pontiac 40......... what's all that?

Pontiac_40

My Feedback: (3)

Looks like the same amount of parts as before or is it less parts?

http://www.hobbyking.com/hobbyking/s...strSearch=gf38

ALFIEV

Could be, I was comparing the list at Hobbyking to what I remembered from about 6 months ago. Hey.... you might want to edit post #799.

Alf

Pontiac_40

My Feedback: (3)

I just did, don't know what happened there...huh.

Pontiac_40

My Feedback: (3)

Got a reply from NGH:

Dear Zawar,

About your six questions, before email we had already gave your answers one by one.

1/ The muffler you can contact our USA official agent: Agape Racing and Hobby, LLC（ www.agaperacingandhobby.com）to buy the updated
parts (not standard).

2/Four-stroke engine vibration is larger than two-stroke, which is necessary. The advantage of four-stroke engine is large torque, low noise, high like real degrees,
energy conversation and environment protection.
NGH did s lot of researches on four-stroke engine vibration and we did more tests to reduce the compression ratio as well as the power did not decline.
For crankshaft counterweight you mentioned did not reduce the vibration, we have experiment proves it.

If you have a better way please let us know.

Share and grow together.

Have a good time.
Yours sincerely
Nancy

SrTelemaster150

The only way reducing compression could reduce vibration would be to reduce the power pulses. That would be by definition, reducing power.

A balanced crank nit reducing vibration? Sounds like BS to me.

PARDAL

Nancy, please,
You sayd:
""2/Four-stroke engine vibration is larger than two-stroke, which is necessary. The advantage of four-stroke engine is large torque, low noise, high like real degrees, ""

You do not know everybody knows: Only first degree vibrations are greater in four strokes than in 2S. We are claiming concerning 2° degres ones. first kind vibes are not ""necessary"", they are inevitables.
Sorry.

When I say 'first degree vibrations', please read torsional vibration.

ALFIEV

O.k.... So I finally got flight in on the corsair with 2 blade xoar 18x8 laminated prop. With the advanced valve timing (factory setting) and very slight advance (still retarded from factory setting) the engine made 7000rpm. Better take_off power/speed than previous. Flying very nice scale. Unfortunately I caught a gust of cross-wind, almost recovered but caught a wing-tip and that's that.... Broken wing spar and some other less serious damage (bah) :-SS :-SS
Anyway, the gf 38 went really well, the demise of the corsair was all my fault, I was definitely rusty:$ :$
Video will follow.
Alf

SrTelemaster150

How many ° BTDC did you end up with?

captinjohn

A video for what it is worth ! https://www.youtube.com/watch?v=NF3pLmut9FI


................................... https://www.youtube.com/watch?v=i2HCdUgmy8w

ALFIEV

Not sure, I hadn't bothered to use the timing gauge because earlier postings suggested to retard the ignition as far as you could by slotting the plastic sensor screw holes. This I did without removing too much plastic. I have moved it back just a tiny bit because the engine was not accelerating from idle to full power happily. Tuning did not assist so I tried to advance the ignition a tad and that seems to have worked. Very imprecise I know, but it is performing well.

ALFIEV

And here is anothe youtube link with today's flight. The video is better than my previous, but by no means perfect!! My wife did her best with her camera, at one point she tried to zoom and lost focus, but a large portion of the video is o.k.
You also get to see my "great" landing!!

http://youtu.be/z0p4jde160U

Alf

ALFIEV

Hey Tyor, have you flown your Val with the 3-blade Biela yet?

My Corsair is out of action for a while. Bad landing on my part, landing gear is broken and wing spar cracked. It will fly again....... one day.

The GF 38 ran really well and did not let me down.

Alf

Basil Yousif

My Feedback: (3)

I got the replacement manifold. After installing it I had a space in the carb mounting bracket. I installed some nuts to use up the space. This is why I think my last manifold broke. When I tightened the bracket screws it put too much tention on the manifold and it broke with the engine vibration. The engine still vibrates though so still trying to get that problem out of the way.

I like that cub in the video - smooth engine if that was my engine it would have shook loose and said good by to the plane and flew off on it's own!!

I am thinking of trying a 3 blade propeller and a cone to reduce the vibration.

tyor

yes I have flown with the biela. it worked very good. It fly like with the master prop i use in this video. But run a little smoother because of hevier prop.
http://youtu.be/4OHXPzCsR3Q

Pontiac_40

My Feedback: (3)

Looking good Alf, Tyor.

Yesterday I got 7200 rpm on the bench for the first time.I was using a Mejzlik 18x10 prop which to my surprise gave me 400-500 more rpm then the wood Menz 18x8 prop, it could also be that the engine is breaking in. I got a tad over 7200 with the timing advanced (close to factory), with it fully retarded, I got a tad over7100, so not a huge difference on the top end.I noticed the engine shaking a lot just above idle, I checked the valve clearance and found them to be off, the exhaust gap had widened while the intake gap had tightened, I adjusted the clearances and that tamed the shaking quite a bit.

SrTelemaster150

Don't you find it a bit odd that the intake lash became less? The only way I could see that happening is for the valve to be recessing itself into the seat.

Pontiac_40

My Feedback: (3)

Sr Telemaster,

I do find that very odd, and this is the second time I’m adjusting theses valves within a little over of gallon through the engine.I’m going to investigate it if this persists.

ALFIEV

Looks great Tyor, you seem to have the Val dialed in. Great to see you have a similiar landing style to me

Your Biela 3-blade looks to be a different profile to mine. Mine is a WWll replica style. I may be incorrect, but yours looks more sports syle. Not sure of this because I couldn't get a close up from your video. It could explain a little of the difference in RPM you are getting compared to what I was getting. The WWll style blades look like big rounded paddles!!!! I will fly with the 2-blade XOAR I think.

Thanks for the video and reply.

Alf

P.S I have just edited this post! I have re-read your text above the video and realise now that the prop in the video is the masterairscrew, not the Biela. No problems, a great video thanks!!

ALFIEV

Interesting you didn't get much of an RPM drop with retarding the ignition. I dropped about 500-600 rpm. I should have set up the ignition timing gauge and been more accurate with my adjustment. I got lazy and just moved it as far as I could as this seemed the best advice at the time. No doubt it smoothed out my engine and made it easier to start, but with a loss of performance. I am happy with how the engine runs now, you should find your engine improves with further running.

stevelesl

A long time since i posted on the NGH38 topic (although my Mid West AT-6 in very nearly ready now) so I was reading through the threads again and particularly on the ignition timing I can say that mine is a Pro version, it is serial number is 0004, I guess this is early (you never know with serial numbers) and my timing checked out right at 30 deg using RCXEL timing tool, when i ran it last year preparing for my AT-6 build I got it running very well and hope this is the case when I run it on the plane which will be a week or two from now.
It amazes me that some folks saw as much as 40 deg from new and that the guy who apparently designed or was part of the design of this engine Michael Chow (I think?,) stated earlier in the thread that 40 deg was standard.
Everything about this engine now worries me, cam timing reportedly out, spares availability, ignition timing debate etc etc. Blows me away that an engine like this that just had to take some seriously clever folks to design (and in fact kinda clone the OS 40 that came out way after the NGH 38) could have so many serious issues.
Just hope mine runs like it did when I ran it in and tuned it origionally. Wish I had waited for the OS 40 and paid the extra money, not usually just looking for a bargain, just bought a new Saito FA 325 radial and when you look at the engineering on that thing it makes it clear that these cut price clones are just not worth it.
Oh well, we will see what happens.

ALFIEV

It's not so bad stevelesl! SJN and Tyor have had good success and I'm sure others have as well. I'm actually quite happy with my engine now. Played around with some things I thought might improve it, some things worked, some were unsuccessful. Give it a go, I think you will enjoy the engine. I know I'm looking forward to flying again when my airframe is worthy of carrying my engine!

HERB

Just a couple of questions. 1) What oil are you fellows using for break in mineral or synthetic.
2) What ratio are you using. I see the instructions call for 25:1 for break in and then 35:1 after break in. To me this oil ratio seems very high.

Pontiac_40

My Feedback: (3)

I'm using Stihl 2 stroke synthetic. By "very high"do you mean too much oil or too little oil?

ALFIEV

I've been using Klotz oil. It's synthetic but has a small amount of castor oil I believe. I like the smell of burning castor oil......