How hot gets your muffler?

[ChapaWolf]

There I was dreaming about mufflers, soon enough I woke up and thought........... God I'm Exhausted!!!

[ChapaWolf]

Actually now that I think about it, different mufflers have different baffling, metallurgy, and back pressure. Add that to different ambient air conditions, altitude, a wide range of different fuel, wind speed, and compression ratio. Finally coming up with ?, or check your temp at the exact same place on the head for extremes, mostly over heating.

Once you have checked the temp enough times and compared it to the noises and performance, you'll get comfortable enough to leave the temp gauge where it should be, and that's in the box. I just got past the same stage you are in probably. I am not meaning any kind of disrespect by these statements. I just recently became somewhat proficient tuning by ear and I don't use the temp gauge but rarely.

I will tell you if your like me I was forced into the obsessive temp stage by what I call the three strikes and I'm a dumb-ass rule. I blew up three pistons in 2 different motors in less than 3 hours of flight. The temp gauge became my pacifier, I would shoot the mark I made on the head maybe 15 times per flight, but the second I put it down, the next flight i blew it again.

If you want some novice advice, novice being me, don't rely on the manufacturer to set any needle on the thing. ESPECIALLY THE LOW/IDLE NEEDLE SCREW. Setting mine to half way solved all my problems, if you have to rebuild order two pistons, two liners and three rings. If possible nothing, and for me I mean nothing, is worse than paying that $40 overnight-er getting down to engine business only to find out, post ring breaking, the piston has a pin that the ring gap sits on. Post all this slapping yourself for hammering the thing in. Or getting back in the air and pow, "maybe it was a glow plug" followed by "you must be high! that wasn't the glow plug dummy." Wondering on your way home if you can justify the overnight-er again. Once you've finally convinced yourself, you get online to find out that overnight means 2 weeks cause they just sold out.

Four was the lucky number for me hopefully nobody's temp gun stage was as drug out as mine. I love helicopters and that goes hand in hand with the old saying "easy come easy go." " I had $500 dollars yesterday but I get paid in 5 days thats when I plan on stocking up!! AM I the only one that thinks that way?

[RogerRabit]

It is not the ENGINE temperature or the liner, the piston or the ring i am worried about.

The reso holder piece is made ot of plastic and only isolated by a 1.5mm silicone end piece at the muffler from the temperature.

That plastic melts down, so there is a temperature of appox more than 200C at that point.

I have done some flights by doubling the silicone to 3mm thickness and not tightening the holder very.
It was ok if i richen the engine to the "four stroking point" and fly only 1400 RPM arround.

But yesterday the 800 blades got into some bad resonance in a 3d manouver so i decided to go to 1550 and -

now the piece failed again.

The engine temperature is max arround 105C from the telemetrie.

I definite will mill some aluminium holder part but the plastic part worked for long time so i am a little confused.

The liner, the ring, the piston all is looking perfect.

The engine nearly has no "smoke vane" after 1-2minutes of running but it is still little "four stroking".

Any ideas?

[ChapaWolf]

Has the pipe been involved recently in impact resulting from a crash, has the performance recently dropped, how many flight cycles has the engine muffler combo logged?

I am going out on a limb here but it sounds like you may have some baffling coming loose, causing increased back pressure and heat build up.

That sounds like a definete possibility since your still getting the 4 stroke out of the engine and no smoke after 2 minutes. The pipe is getting so hot because of a clogged baffle that it burns all the oil and fuel you normally see. This would also explain the burnt plastic if the exhaust has no where to go its gonna heat some stuff up.

I had a cyb mp-5 on my os 55 for about 5 flights. On the fifth flight the thing got extremely hot so hot in fact it blew the seam weld out and the pipe split in two.

[ChapaWolf]

This baffle problem could easily cause a piston cylinder to seize. Seizing would indicate that the mixture was not too lean and something else was causing the heat build up something so hot it expanded the head and the sleeve to the point of stopping the piston. All I can think of that would cause that is the engine not being able to exhaust the heat because of a blocked pipe.

[RogerRabit]

Originally Posted by ChapaWolf

Has the pipe been involved recently in impact resulting from a crash, has the performance recently dropped, how many flight cycles has the engine muffler combo logged?

I am going out on a limb here but it sounds like you may have some baffling coming loose, causing increased back pressure and heat build up.

That sounds like a definete possibility since your still getting the 4 stroke out of the engine and no smoke after 2 minutes. The pipe is getting so hot because of a clogged baffle that it burns all the oil and fuel you normally see. This would also explain the burnt plastic if the exhaust has no where to go its gonna heat some stuff up.

I had a cyb mp-5 on my os 55 for about 5 flights. On the fifth flight the thing got extremely hot so hot in fact it blew the seam weld out and the pipe split in two.

The bird never has been crashed, only two strut cracks from autos and a little bump in the tailtube from a low RPM auto.

If if shake the hatori there is nothing lose inside.
I will check if it has enough throughput and is not clogged.

I have a second unit so i will exchange. Didnt think that way.
Thanks for the tip.

The combo has approx 30 gallons and is running ok. Power is ok, not insane. If i lean it out the power is great but the temp increases over 120C very fast and then i land to not damage the engine.

I did mill a aluminium holder but that one is getting hot also and heats up the tailtube.

[ChapaWolf]

Did you ever get any resolution to the Overheat problem

[RogerRabit]

Yes

The story continued as follows

I changed the plastic part another two times and the preassure line did even come off with JB Weld glued in.
I only could solve the preassure line by mechanically using a securing system ( folding copper between two countered nuts )

Then the teflon piece had a hole burned in so hot it got still the engines temp was ok, no wear on liner or ring or piston.

I was so pi**ed off from constantly changing things that i ordered new teflon pieces and stainless reso clamps
I then used some high strength alu and milled a reso clamp for the tailboom and mounted that.
It worked ok for some flights but the tailboom started to pick up temperature as the clamp is no thermal isulation

So i did put some high temperature silicone under it where it clamps and also did shorten the reso length a little.

Big mistake. First few flights where ok. Mostly idle 1, only short sessions in idle 2

When i went to to the field on the weekend and my buddies where there i noticed a dent in the muffler and was wandering where i did damage it.
I thought it must have been from handling so i did not worry too much
Second big mistake

First flight ok

Second flight i wanted to do some "show offs" you know that "boys and toys" stuff you do to brag in front of your buddies

Third big mistake

I was nearly most time in idle 2 and inside a rolling circle the noise level increased tremendous.

I just instinctly autoed the bird down not knowing what happened.

The muffler broke in two pieces.

It was bended in between like a accordion.

My error was that the room between the front end of the muffler and the manifold was no longer there due to the shortening to lower the reso length and the high force aluminium at the end did not give way.
You can calculate yourself how many mm's Aluminium expands between 25 and 200 degrees celsius at a rate of 26mikron per degree per meter
It is 175 x 26 / 1000 / 2 = 3 mm approximate

The thin aluminium of the muffler could not handle that tension at the temperature and vibration level and gave up.

So that was the final dead of the HATORI reso.

I did buy a Zimmermann stainless steel muffler ( no reso ) and attached it.
It was totally different to put on the needles but after tuning it the machine is now running like a dream again.

The system is cooler ( as i think, i cannot really meassure as the polished stainless steel does not work with my IR gauge ) and the biggest advantges are

The overpressure connector is long and stainless and laser welded into the muffler
There is no need for a manifold and a teflon piece longer.
And the engine has no " special " tuning spots, you just can use all rpms like you want.

[ChapaWolf]

Man that sounds completely frustrating I can relate to that. I have had some luck with engines since I started flying helis. I started getting real comfortable with keeping things in the air. This was about a year ago when I started with no help really. I wanted more power so I bought a ys56 here on the freak used. I was upgrading from the os50. The 50 has one needle the ys56 has 3. When I got the 50 it was already tuned so I knew nothing. 2nd flight pow the piston blew. I got an os 55 brand new. 1st flight no smoke POW no joke! I ordered a ring and a piston overnight shipping. Started putting it back together and who knew the piston had a tab on it to align the ring.... broke the ring forcing it in. I went to order a knew ring..... out of stock. 2weeks later got a new ring. Had it so rich it would barely take off. So I leaned it up a bit put the canopy back on and somehow cut the pressure line off the muffler. I was in a hurry to lift off because I was on a road and a car was in sight. I wasn't looking for smoke and that's good because there wasn't any... POW!!! I almost shit my pants. More like started crying like a little Sissie. Don't repeat that last part to anybody.

Anyway I am on the 112th successful flight since and the moral of both stories I think is you'll know what to look for next time and I'll never run lean again. Sometimes lessons are hard learned.

Great to hear your back to enjoying your hobby (more like obsession if you're like me) and finally cooled off.

Happy flying from the USA sir.

[ChapaWolf]

Hey bud I forgot I had problems getting my pressure nipple staying in too. Nothing worked not JB weld silicone nothing. So I got the next sized nipple and drilled a small hole in one of the corners in the nut portion. I then drilled a small hole in the corner of the flange part on the muffler and used a trash bag twist tie to safety wire from the one hole to the other in a tightening direction. If you are not familiar with safety wire its a method of securing bolts and nuts similar to cotter pins. I will provide a picture of what I'm talking about. My camera isn't here so I can't show you the actual job I did.

[RogerRabit]

I used mechanical securing at last also

I put in a tank nipple with a flat flange from the inside
Put a thin ( i think it was 5mm ) nut on it, then the security copper, aother 5 mm nut tightened against the first one.
Then the copper is bent alternating up and down.

I do not know if it is holding long term but the idea is that the copper is expanding on heat and presses both nuts against the thread and locks them against motion with the alternating bend up/down geometry.

http://www.google.de/imgres?q=sicher...w=1024&bih=672

I used a copper sheet , cut it coarse , just drilled the inside and did the bendings.

Thanks for the interest and a nice day to the USA !

[npttm76]

Don't worry about hot muffler

[ChapaWolf]

If you really want to measure the muffler temp drip a piece of plastic on it so its not reflective. I just thought about that figured I would share.

[VortechZ230]

I really enjoy a HOT MUFF!....

[RogerRabit]

Originally Posted by ChapaWolf

If you really want to measure the muffler temp drip a piece of plastic on it so its not reflective. I just thought about that figured I would share.

The plastic allways melted, so that gives an idea of the temp.