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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › O.S. GT15HZ Gasser
06-03-2014 02:42 PM  4 years agoPost 61
Jamovich

rrVeteran

Bangalore, India

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If I do not want to use a separate battery for the ignition module what sort of regulator must I use to protect the electronics (from arcing) if I wish to plug it into the main battery?

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06-04-2014 11:10 PM  4 years agoPost 62
dkm

rrNovice

sydney, Australia

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I use a RCEXL Opto Ignition Kill Switch and a ferrite ring on the power lead to the ignition module.

"Ignition Kill Switch manufactured by RCEXL Ver 2

Allows you to kill engine remotely from transmitter
Optically Isolated circuit
Will kill engine on loss of radio signal or receiver power.
Plugs into spare RX channel (ie gear channel or similar)
Remote bright LED with Bezel to show when ignition is ON.
Reverse Polarity Protection
Surface Mount Components
Weight = 11 Gram"

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06-05-2014 04:09 AM  4 years agoPost 63
Jamovich

rrVeteran

Bangalore, India

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Thanks for your input. I already use something similar. Are you saying that the ferrite ring itself is enough to cancel possible interference due to arcing?

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06-05-2014 05:05 AM  4 years agoPost 64
dkm

rrNovice

sydney, Australia

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To be sure I ended up using a seperate battery and have the engine and ignition unit bonded.

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06-07-2014 11:25 AM  4 years agoPost 65
Jamovich

rrVeteran

Bangalore, India

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Problems continue
I replaced my battery with a 2s lipo and put an x2 reactor regulator on it.

The problem with all the electronics seeming to shutdown for a moment may come from the fact that if one uses a LiFe with a regulator it will cause a 2.4 ghz receiver module to go into fail safe when there is load on the system. This does not happen with a PCM or FM receiver as they have a lower cutoff threshold. I was told that this is a known issue.

However I seem to have another problem. When I was hovering today The heli seemed to abruptly bank to the right. This happened on 3 occasions. I was able to correct immediately twice but the third ended up with broken blades (hopefully that's all!)

All other control surfaces were responsive at all times

What the hell is happening?!? I'm told that if it is interference then the whole system would be locked out not just 1 servo badly behaving (s9255 controlling the aerilon)

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06-07-2014 09:29 PM  4 years agoPost 66
dkm

rrNovice

sydney, Australia

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Are you running FBL or Flybar?
The GT15 has been a big learning curve for me, origionally 36mhz - changed to 2.4, then I killed two 701 gov/gyro units with vibration.
Upgraded to two batterys with ferrite coils and bonding.
Replaced the ignition module due to plug lead fit.
Replaced the cooling fan and fitted airflow shrouds.
The Freya is now flying with flybar SZ-5 head, GV1 gov and 520 gyro,
2000mah radio and 1500mah ignition NiMh, 9255servos with BLS251 tail.
All seems well....

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06-08-2014 08:57 AM  4 years agoPost 67
Jamovich

rrVeteran

Bangalore, India

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I'm using the engine in a eagle 3. So it has a fly bar.

Vibration does not seem better or worse than a nitro. Gt 15 runs at the same rpm and has similar mass to a 90 size nitro. The zenoahs obviously would differ as they are completely different both in mass and rpms. Why should the gt 15 be more or less vibration prone than the equivalent nitro?

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06-08-2014 04:57 PM  4 years agoPost 68
rexxigpilot

rrProfessor

Florida

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Higher vibration in a gas engine is caused by higher peak cylinder pressure for gas (gas has a greater energy density) compared to nitro. This causes stronger power pulses, which causes stronger vibrations.

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06-08-2014 07:38 PM  4 years agoPost 69
Jamovich

rrVeteran

Bangalore, India

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Thanks for clearing that up.

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06-13-2014 02:20 PM  4 years agoPost 70
GMPheli

rrElite Veteran

W. Bridgewater, MA USA

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"Higher vibration in a gas engine is caused by higher peak cylinder pressure for gas (gas has a greater energy density) compared to nitro. This causes stronger power pulses, which causes stronger vibrations."

Then why do gassers make less power than an equivalent sized nitro? Higher peak cylinder pressure should mean more power, should it not?

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06-14-2014 05:55 PM  4 years agoPost 71
rexxigpilot

rrProfessor

Florida

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The "nitro" engine makes more power than a gasoline engine because it burns much more (about 3 times more) fuel. Nitromethane (CH3NO2) is both a fuel (CH3, methyl, part of molecule) and oxidizer (the O2 part). Nitromethane doesn't rely only on the oxygen in the air like gasoline does.

The optimum air/fuel ratio in lbs. of air/lb. of fuel for gasoline is 12.8, 6.0 for methanol and 1.7 for nitromethane. The energy densities of the fuels in MJ/L are 34.8, 17.9 and 11.3 for gasoline, methanol and nitromethane, respectively. Therefore, with a 30% "nitro" fuel with 20% oil and 50% methanol, the total power is 1.07 times the energy per unit power cycle or engine revolution compared to gasoline (assuming same combustion efficiency for both).

Now, 1.07 times doesn't seem like a lot, but since "nitro" engines are typically run about 15% to 20% faster rpm than a typical gasoline engine, the total available energy per unit of time (power) is closer to 25% to 30% more.

The combustion efficiency issue is important too. An inefficient or poorly tuned "nitro" engine can make less power than a properly tuned gasoline engine. Many "nitro" engine users don't have their engines properly tuned. Many "nitro" flyers generally have them too rich to avoid a lean run. So, the difference in power between a typical "nitro" and gas engine is closer to 10% to 20%, with "nitro" having the power advantage.

These differences in how much of each fuel is consumed and the energy densities provide for a "nitro" powered engine having a higher average cylinder pressure than a gasoline engine, but the peak cylinder pressure of the gasoline engine is still much higher.

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07-18-2014 05:19 PM  4 years agoPost 72
Jamovich

rrVeteran

Bangalore, India

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Installed the backplate cooling fins (which is found on the .91 f3c engine). Drop in fit. Let's see if that helps to cool the engine a couple of degrees

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