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HomeAircraftHelicopterGasser Model RC HelicoptersOther › Gasser tuning
02-07-2010 01:31 PM  8 years agoPost 21
Fixit

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UK

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Are you using a prop?
You must use a prop to add load when breaking in on a bench.
Not sure why it happens but even with a prop I had a spark plug fail running it this way.

I only like to fly gassed up

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02-07-2010 04:21 PM  8 years agoPost 22
rbort

rrProfessor

Franklin, MA - USA

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I like it Gill
It looks REALLY nice!!! I'm sure it sounds much better too with a decent muffler

-=>Raja.

MA 1005 Hanson 280, 4210 flts
Spectra 27 3DMax, 3288 flts
Whiplash V1-2 Hanson 300, 1570 flts
Whiplash V2 Hanson 300, 402 flts

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02-07-2010 06:31 PM  8 years agoPost 23
gill4321

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Honaunau, Hawaii - USA

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Ohh yes that muffler makes it sound ohh so nice

Gill P

Gill P

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02-07-2010 10:39 PM  8 years agoPost 24
Justin Stuart (RIP)

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Plano, Texas

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Where are you taking the temperature at to arrive at this 240 degree mark? I guess the hottest part of the entire engine is right outside the exhaust port?

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02-08-2010 12:44 AM  8 years agoPost 25
gill4321

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Honaunau, Hawaii - USA

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yes that is exactly right. right next to the exhaust port.

Gill P

Gill P

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02-08-2010 12:46 AM  8 years agoPost 26
Justin Stuart (RIP)

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Plano, Texas

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So then the general consensus is that if the exhaust header is over 240 degrees Fahrenheit, then you are going to toast your motor?

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02-08-2010 01:33 AM  8 years agoPost 27
gill4321

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Honaunau, Hawaii - USA

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Well 240 is on the high side but its not deadly i dont think. ive look numerous times in my engine and I see the cylinder wall and every thing looks cool. I also live in a warm area where its normally around 80-85F so the engine will be a little warm.

Gill P

Gill P

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02-08-2010 01:54 AM  8 years agoPost 28
Justin Stuart (RIP)

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Plano, Texas

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I don't know if I can agree with these numbers.

In a full scale normally aspirated air cooled aircraft engine (such as a Piper or Cessna), you select an exhaust gas temperature around 1500F and a cylinder head temperature around 330F indicating the correct tuning (i.e. not too rich and not too lean). These numbers are based off of sensors embedded directly into the exhaust manifold and cylinder head, respectively.

The combustion temperature of gasoline in air is around 2000F.

So on a small air cooled heli engine, if you are running with an open exhaust, aiming an IR temp gauge directly at the exhaust port of the engine may give you a reading as high as 1300F. If you are running a very thin stainless steel header which is painted black and radiates heat very efficiently, you may have a reading as high as 400F. If you are running a thick aluminum exhaust like a Century V4, your exhaust temperature will be much lower. So what I'm saying is that there is just too much variability to be able to quantitatively ascribe a correct temperature to the "the exhaust side" of an engine to be of value from helicopter to helicopter. This says nothing of the problems with the emmisivity values of aluminum for an IR heat gun.

What I really think we need to do is base our temperature measurements on a location of the engine which is more predictable and more consistent from setup to setup and from engine to engine, such as the base of the crankcase.

Does't Raja do a "spit test" by placing his wet finger on the crankcase somewhere?

I don't know about you guys, but my temp gun comes with a thermocouple probe that has to be placed directly on the item being measured. Mounting something like this on the crankcase and taking measurements would probably be the most accurate. With all of the metal in the crankcase, and with the lack of cooling air flowing over the crankcase, I think taking measurements at this location would give us some real, applicable data.

I would think that taking the temperature directly off the bottom of the crankcase would be consistent regardless of how hot or cool the air was being blown by the fan, and since it probably takes a good 30 seconds for the crankcase to heat or cool to equilibrate with the cylinder head, taking the temperature here would give us way to tell how hot the engine was running before you landed.

For those of you familiar with diabetes, a measurement of the crankcase temperature would be, in my opinion, similar to taking a HGA1C measurement versus a finger stick blood glucose measurement.

I know there has been some talk about taking measurements at the "third fin on the left", but a measurement here is prone to so much error based upon the quantity of air being blown over the cooling fins and the temperature of the cooling air--not to mention the inherent inaccuracy of the IR temp gun itself.

Even better would be to place a thermocouple temperature probe directly into the exhaust flow, but this is not really practical.

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02-08-2010 01:27 PM  8 years agoPost 29
AceBird

rrElite Veteran

Utica, NY USA

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I would think that taking the temperature directly off the bottom of the crankcase would be consistent regardless of how hot or cool the air was being blown by the fan,
Because of the time lag you would not be able to measure what is happening to the engine under full load, the most likely critical temperature.

If you are looking for accurate measurements the readings need to be instantaneous. So in my mind the only way to measure if the combustion is optimized is using exhaust gas analysis, either oxygen or carbon dioxide.

That being said, I do think you could use a measure of temperature as a way to keep you safe but it wouldn't be optimized. However, with an IR gun I would not read a fin. I would paint the exhaust manifold black with a radiator paint and fix it on that spot. This should be the hottest spot that you can read and fluctuate more with loadings.

Ace
What could be more fun?

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02-08-2010 01:58 PM  8 years agoPost 30
jschenck

rrProfessor

La Vista, NE.

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I try to get IR temp gun readings on the case between the muffler flange and the bottom head fin. My intention is to look for relative changes and also to look for not exceeding a max of around 250F

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02-10-2010 02:06 AM  8 years agoPost 31
gill4321

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Honaunau, Hawaii - USA

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That is also what I do. I always check in the same place all the time to ensure consistency. So far Its all good. I just need to put my heli back together and keep tuning on.

Gill P

Gill P

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02-10-2010 07:34 AM  8 years agoPost 32
1275mini

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Wirral North West U.K.

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sounds good to me !

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02-18-2010 07:51 PM  8 years agoPost 33
gill4321

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Honaunau, Hawaii - USA

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found that i have a exhaust leak so I ordered a Copper exhaust gasket. I also noticed it ran hotter with the leak so im not flying it till i get it fixed and then its on to the proper tuning.

Gill P

Gill P

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02-18-2010 07:54 PM  8 years agoPost 34
1275mini

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Wirral North West U.K.

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02-18-2010 10:38 PM  8 years agoPost 35
Fixit

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UK

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I’ve tried all the gaskets including copper and found the best way to fit the muffler is to use RTV silicon on the flange, let it skin over first then nip the bolts up, I’ve never had one fall off or leak doing it this way.

Edit
You can also use some RTV on the threads to stop them vibrating loose

Good Luck

I only like to fly gassed up

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02-18-2010 10:55 PM  8 years agoPost 36
zorba

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Montreal, Quebec, Canada

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What motor are you running Gill?
You have to reduce the vibrations and you don't need any gaskets.
I took emery cloth doubled it up and matched sanded the muffler to the exaust port. Of course you have to dismantel the engine first and then wash it real good. The other thing you can use is laping compound, we used that to lap valves is has some kind of fine sand in it and by rubbing the two surfaces together they will match.The other downside is that you have to use that muffler with that engine only.

I hope this helps.

Cheers

PS hi ya Pete.

3-450's,rex500ESP,rex600G,Rex700G,Raptor60G,FreyaCW-EXII, VarioEC155, Logo20, Cessna310,CL-415,

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02-18-2010 11:26 PM  8 years agoPost 37
Fixit

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UK

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Hi Bill
It must be twenty year since I used lapping paste; does anyone still use it when building a head up?

I only like to fly gassed up

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02-18-2010 11:29 PM  8 years agoPost 38
zorba

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Montreal, Quebec, Canada

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Well as a backyard mechanic I do. I don't have the fancy equipment they do plus is easier for them to replace the head than lap it. How've been healthwise?

Cheers

3-450's,rex500ESP,rex600G,Rex700G,Raptor60G,FreyaCW-EXII, VarioEC155, Logo20, Cessna310,CL-415,

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02-18-2010 11:43 PM  8 years agoPost 39
Fixit

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UK

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How've been healthwise?
On the up M8 thanks.
Looking forward to the summer so we can fly in comfort

I only like to fly gassed up

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02-19-2010 12:03 AM  8 years agoPost 40
zorba

rrApprentice

Montreal, Quebec, Canada

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good to hear. Are you all setup and ready to fly or you are still building?
Mine is on hold firstly the weather and after a new engine.
The CY just don't cut it. Too many vibs. So I ordered the Max 3D pro from Hanson should be here next week.

anyway I'll keep you posted.

Cheers

3-450's,rex500ESP,rex600G,Rex700G,Raptor60G,FreyaCW-EXII, VarioEC155, Logo20, Cessna310,CL-415,

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