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Old Nov 13, 2012, 11:21 AM
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I think some people put the 9cc gas engine in some 30 size heli's already. I remember reading about it somewhere before. One company was experimenting with one in a .50 size heli. But they may have had to change the gear ratio and or rotor blade sizes too.

Years ago there was a short spurt of excitement in using model diesel engines in helicopters. But one needed to change the gear ratio to adjust for the higher torque of the diesel engines. Plus they could run different size rotor blades too. Getting model diesel fuel easily probably caused the diesel engines to fizzle out at heli engines in this case.

Oh yeah, one guy in Russia used four of the 9cc gas engines in a multi-rotor plane or heli. He had a video posted of his tests, but I don't remember if he had any flying videos posted yet or not. I think he mentioned it way back in this thread someplace.
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Old Nov 17, 2012, 08:56 AM
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Quote:
Originally Posted by earlwb View Post
I think some people put the 9cc gas engine in some 30 size heli's already.
it's not true, you will only find .50 size glow engines converted to gas.

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Originally Posted by gkamysz View Post
I'd expect a 9cc gas engine made to run 10-2kRPM to fall far short of the power made by glow engines for 50 size helicopters.
coming soon. http://www.infinity-hobby.com/main/n...ewsdesk_id=837
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Old Nov 17, 2012, 09:51 AM
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I'm aware of the GT-15HZ. Designed for heli by OS I expect it to perform. The NGH9 makes what kind of power and how will you adapt it to heli use? Converting a ringed glow engine to gas is far more practical than adapting the NGH9 don't you think?

Greg
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Old Nov 17, 2012, 10:23 AM
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You might have seen it before, but here is a Pentacopter with a NGH 9cc engine powering it.

Pentacopter with Gasoline engine. (7 min 16 sec)
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Old Nov 18, 2012, 06:00 AM
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I got myself an NGH 9cc for experimenting.

I have read the thread up to page 30 and then skipped to the end. About the ignition advance, let me state that a 1$ microcontroller is very well able to measure the time between two pulses, calculate the rpm, and advance / retard the spark accordingly.

According to Brutus1967 the pressure sensing hole on the front of the carb is the cause of the oscillating idle rpm's. Is there any confirmation for this? Is the idle better when the prop is replaced with a disk?
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Old Nov 18, 2012, 09:44 AM
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I don't beleive that diaphragm in the front of the carb does anything. It doesn't appear to block or open any orifices that I can see. Nor does it seem to obstruct or restrict any orifices either.

The inlet fuel passage leads directly to the main jet fuel passage. The two are recessed so even if the diaphragm closes off the top the fuel still flows freely.

Remember they took a Saito 4 stroke carb and modified it to clone it. In the process they split the carb from the pump/regulator part. Thus the front of the carb was probably the cavity for the regulator or the pump. So they simply made a gasket to close it off. The fuel only flows through that small recessed Tee shaped hole over near the side. It does look sort of stylish with all the screws on it, but they could have simply had left that part of the casting off and just have a small part to block off over the top of that recess for the fuel flow.







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Old Nov 18, 2012, 11:42 AM
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Thanks earlwb. The pictures show you are right. There is no pressure regulator in the carb. I did also disassemble my carb to be sure. Mine looks exactly like the pictures above. The whole pressure regulating thing is done int the "pump" device.

I did have a closer look at the NGH motor, and from the port and the timing it's clear that is a high performance device. The intake closes way after OT, that is the reason it spits gas from the carb at low rpm.

Btw a liter of glow fluel is 20$ here (17 swiss francs), a liter of gas is below 2$.

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Originally Posted by turk1 View Post
GT9 carb has much less suction at WOT than lower throttle ranges ... wonder if exhaust pressurized tank system will work better
Dont know if its outdated. After reading your sentence 10 times i finally did understand. I think you are partially right with your pressure analisis of the glow carb.

Now your idea of pressurizing the tank wont work. On the way to the carb there is a pump and a regulator making the pressure zero regardless of what it is in the tank. The point to pressurize is the reference pressure hole in the pump/regulator assembly. It's the sideways hole in the cover with the 4 screws. The pressure in this tiny hole determines the fuel pressure going to the carb. Connect this hole to the exhaust and you will have fuel squirting into the carb at full power.
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Old Nov 18, 2012, 10:43 PM
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Hi Cesco,You are right but I was meaning to remove regulator/pump unit and solely exhaust pressurized tank.Because that pump/regulator unit needs a venturi/bernoulli jet system carb.
PS:Here 1lt glow fuel(no nitro full castor) still costs about 2 $ (home brew) but 1 lt gasoline(without oil cost) is 2,8 $
So I still dont have any gas engine on plane.
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Old Nov 19, 2012, 09:25 AM
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PS:Here 1lt glow fuel(no nitro full castor) still costs about 2 $ (home brew) but 1 lt gasoline(without oil cost) is 2,8 $
So I still dont have any gas engine on plane.
Don't forget that the engine consumes about half the volume of fuel on gasoline vs. methanol.

Greg
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Old Nov 19, 2012, 11:58 PM
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Don't forget that the engine consumes about half the volume of fuel on gasoline vs. methanol.

Greg
Hi Greg,
Can't totally agree.Yes a little more consumption but mostly because supercharged alcohol which meaning more power on same volume.
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Old Nov 22, 2012, 04:36 AM
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Impressive numbers!

A comprehensive review for this engine appears in Christian Traders...

The RPM numbers they achieved dwarf the claimed HP numbers for this engine!

I calculated with the Reivers PropPower, Prop factor 1.23 for APC:

10 x 6 - 14,660 = 1.23 HP
11 x 6 - 12,987 = 1.39 HP (1.35 PF)
11 x 8 - 11,450 = 1.13 HP
12 x 4 - 12,615 = 1.16 HP
12 x 6 -10,893 = 1.08 HP
13 x 4 - 11,556 = 1.24 HP
13 x 6 - 10,128 = 1.19 HP
14 x 4 - 9,463 = 0.93 HP

What can I say!?
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Old Nov 22, 2012, 06:13 AM
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Quote:
Originally Posted by Cesco View Post
According to Brutus1967 the pressure sensing hole on the front of the carb is the cause of the oscillating idle rpm's. Is there any confirmation for this? Is the idle better when the prop is replaced with a disk?
I was not referring to the hole in the carb, I am assuming the pump has a pressure sensing hole, otherwise it could never function as a pressure regulator. It is that hole I was referring to, and the reason I was thinking about it, was because some people report the engine is running OK, others are reporting it is not, and that pump/regulator is subject to "owners view to correct installation" so it is possible, that results vary from owner to owner because of pressure fluctuations on this hole, caused by differences in installing it.

Brgds, Bert
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Old Nov 22, 2012, 07:55 AM
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Dar Zeelon, thanks for the article with the review for the little NGH 9cc gasoline engine. After figuring out how to run the engine, it is working good for me as well.

Here is a video of me flying the engine on my large .45 size pattern sport plane. It pulls it around quite well. I am using a 11x7 Master Airscrew prop on it. The plane is fairly large as it has a 59 inch wing span and is not much smaller than a Hangar 9 Phoenix classic pattern plane. So it should power the Phoenix acceptably, should one want to do it. I did three low passes so I could use a Doppler shift speed program to determine how fast it was going in the air. My program estimated that the plane was going just a hair under 58 mph in the air.

Flying my Low Wing Sport Pattern Plane with a NGH 9cc engine on it (10 min 7 sec)
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Old Nov 22, 2012, 02:14 PM
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To me it looks like it is doing more than 60 mph, Earl.
Probably closer to 80-85.
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Old Nov 22, 2012, 03:06 PM
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Yeah I think you may be correct. I was using the RCS Speed App on my iPhone at home through the speakers on my PC. It may not be working as expected.
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