250° F - is that too hot?
04-30-2009, 10:56 AM
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RE: 250° F - is that too hot?
ORIGINAL: Tired Old Man
Temperature redlining is something I've been in disagreement with some engineers over for a couple of years. Without the whole song and dance, you really never want to achieve redline or even close to it. To make it there means an engine tear down and rebuild or worse, a replacement. You should never have an engine running so hot, so loaded, or so undersized that it burns itself up trying to get the job done.
Temperature redlining is something I've been in disagreement with some engineers over for a couple of years. Without the whole song and dance, you really never want to achieve redline or even close to it. To make it there means an engine tear down and rebuild or worse, a replacement. You should never have an engine running so hot, so loaded, or so undersized that it burns itself up trying to get the job done.
As mentioned, I have had an engine hit a tad over 400* in flight multiple times with no adverse affects to date, 15 gallons or more.
04-30-2009, 11:14 AM
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RE: 250° F - is that too hot?
Not necessarily. You have warm ground temps rising off the surface that could impact outlet draw. Plus you don't have the forward motion that assists in moving air through the cowl. I had an engine that would warm up on the ground at idle rpm but would cool off some once the rpm was increased a little. Unless we elect to baffle our engines just like full scale opposed recips we will need to pay attention to things a little better than most do. Even full scalers try to keep the prop into the wind when on the ground as much as possible for better cooling.
04-30-2009, 04:20 PM
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RE: 250° F - is that too hot?
ORIGINAL: noahb
another thing that helped my temps alot was to make a low pressure lip on the cooling exit on my cowling. My temps dropped like 40 deg. when I did this mod. Could not believe that I was getting that much high pressure build up right there. I have mine baffled which helped, but man did the low pressure lip help out a bunch.
another thing that helped my temps alot was to make a low pressure lip on the cooling exit on my cowling. My temps dropped like 40 deg. when I did this mod. Could not believe that I was getting that much high pressure build up right there. I have mine baffled which helped, but man did the low pressure lip help out a bunch.
04-30-2009, 04:44 PM
#29
RE: 250° F - is that too hot?
Joe,
It's an easy thing to do. On a fiberglass cowl on the bottom of the cowl you just use an exacto to cut a score into the fiberglass (not all the way through) the cowl about 1/4 to 1/2 inch back from the front of the opening towards the front of the cowl which is the same width of the opening, use a dremel to cut the sides of the score all the way through from the opening to the score line, bend the fiberglass down so that it's at least at a 30 degree angle into the airflow, add a little CA to the area you cut to make it hold shapea nd there ya go. This creates turbulence at that point and draws air from the cowl.
On canister cutouts with wood planes, I use 1/8 tri-stock at the front of the cutout to get the same effect to help vent the heat from the fuselage
If no one posts a pic, I'll go out to my C-Arf and get you some
It's an easy thing to do. On a fiberglass cowl on the bottom of the cowl you just use an exacto to cut a score into the fiberglass (not all the way through) the cowl about 1/4 to 1/2 inch back from the front of the opening towards the front of the cowl which is the same width of the opening, use a dremel to cut the sides of the score all the way through from the opening to the score line, bend the fiberglass down so that it's at least at a 30 degree angle into the airflow, add a little CA to the area you cut to make it hold shapea nd there ya go. This creates turbulence at that point and draws air from the cowl.
On canister cutouts with wood planes, I use 1/8 tri-stock at the front of the cutout to get the same effect to help vent the heat from the fuselage
If no one posts a pic, I'll go out to my C-Arf and get you some
04-30-2009, 06:21 PM
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RE: 250° F - is that too hot?
ORIGINAL: bubbagates
Joe,
It's an easy thing to do. On a fiberglass cowl on the bottom of the cowl you just use an exacto to cut a score into the fiberglass (not all the way through) the cowl about 1/4 to 1/2 inch back from the front of the opening towards the front of the cowl which is the same width of the opening, use a dremel to cut the sides of the score all the way through from the opening to the score line, bend the fiberglass down so that it's at least at a 30 degree angle into the airflow, add a little CA to the area you cut to make it hold shapea nd there ya go. This creates turbulence at that point and draws air from the cowl.
On canister cutouts with wood planes, I use 1/8 tri-stock at the front of the cutout to get the same effect to help vent the heat from the fuselage
If no one posts a pic, I'll go out to my C-Arf and get you some
Joe,
It's an easy thing to do. On a fiberglass cowl on the bottom of the cowl you just use an exacto to cut a score into the fiberglass (not all the way through) the cowl about 1/4 to 1/2 inch back from the front of the opening towards the front of the cowl which is the same width of the opening, use a dremel to cut the sides of the score all the way through from the opening to the score line, bend the fiberglass down so that it's at least at a 30 degree angle into the airflow, add a little CA to the area you cut to make it hold shapea nd there ya go. This creates turbulence at that point and draws air from the cowl.
On canister cutouts with wood planes, I use 1/8 tri-stock at the front of the cutout to get the same effect to help vent the heat from the fuselage
If no one posts a pic, I'll go out to my C-Arf and get you some
04-30-2009, 07:42 PM
#34
RE: 250° F - is that too hot?
ORIGINAL: Josey Wales
Thanks! That helps alot. Seems pretty easy so I'll give it a try on my 110" EF
ORIGINAL: bubbagates
Joe,
It's an easy thing to do. On a fiberglass cowl on the bottom of the cowl you just use an exacto to cut a score into the fiberglass (not all the way through) the cowl about 1/4 to 1/2 inch back from the front of the opening towards the front of the cowl which is the same width of the opening, use a dremel to cut the sides of the score all the way through from the opening to the score line, bend the fiberglass down so that it's at least at a 30 degree angle into the airflow, add a little CA to the area you cut to make it hold shapea nd there ya go. This creates turbulence at that point and draws air from the cowl.
On canister cutouts with wood planes, I use 1/8 tri-stock at the front of the cutout to get the same effect to help vent the heat from the fuselage
If no one posts a pic, I'll go out to my C-Arf and get you some
Joe,
It's an easy thing to do. On a fiberglass cowl on the bottom of the cowl you just use an exacto to cut a score into the fiberglass (not all the way through) the cowl about 1/4 to 1/2 inch back from the front of the opening towards the front of the cowl which is the same width of the opening, use a dremel to cut the sides of the score all the way through from the opening to the score line, bend the fiberglass down so that it's at least at a 30 degree angle into the airflow, add a little CA to the area you cut to make it hold shapea nd there ya go. This creates turbulence at that point and draws air from the cowl.
On canister cutouts with wood planes, I use 1/8 tri-stock at the front of the cutout to get the same effect to help vent the heat from the fuselage
If no one posts a pic, I'll go out to my C-Arf and get you some
05-01-2009, 11:55 PM
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RE: 250° F - is that too hot?
Hi Josey,
I have the 110 EF Yak with the BME 116 no fin motor.
With the cowl on and no baffling, the motor hit 310 in about 15 seconds at full throttle on the ground with a Mejzlik 28-10.
With baffling, and the pipe tunnel open, with a second light firewall in the pipe tunnel just before the landing gear, and the covering opened up between the scale oil cooler and the landing gear, the motor runs at 225 under the same circumstances.
On another note, it was 92 degrees the other day and the plane became hard to start. As soon as the choke prime was gone, it would quit.
Given the carb between the mufflers and all the incoming air forced over the fins I assumed a heat related issue.
I cut another hole in the scale louvers just in front of the carb and siliconed a 1/4 thick bit of lawn mower filter foam inside. The idea was to let cool air in and not in a turbulent way. Haven't had any problems since.
Branwell
I have the 110 EF Yak with the BME 116 no fin motor.
With the cowl on and no baffling, the motor hit 310 in about 15 seconds at full throttle on the ground with a Mejzlik 28-10.
With baffling, and the pipe tunnel open, with a second light firewall in the pipe tunnel just before the landing gear, and the covering opened up between the scale oil cooler and the landing gear, the motor runs at 225 under the same circumstances.
On another note, it was 92 degrees the other day and the plane became hard to start. As soon as the choke prime was gone, it would quit.
Given the carb between the mufflers and all the incoming air forced over the fins I assumed a heat related issue.
I cut another hole in the scale louvers just in front of the carb and siliconed a 1/4 thick bit of lawn mower filter foam inside. The idea was to let cool air in and not in a turbulent way. Haven't had any problems since.
Branwell
05-02-2009, 01:54 PM
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RE: 250° F - is that too hot?
It was vapor locking, I've had it happen to me before. Rcexell, 3W, and other ignitions can also crap out on you from heat. CH seems to be the best at tolerating heat.
Most people don't understand how well baffling really works with any engine, especially the light power house BME's. You have proven this true, but most people still won't believe you, very few ever believed me.
Most people don't understand how well baffling really works with any engine, especially the light power house BME's. You have proven this true, but most people still won't believe you, very few ever believed me.
05-02-2009, 03:52 PM
#37
RE: 250° F - is that too hot?
I have a sort of a similar setup as branwell on my 88" EF Yak. The pipe tunnel entrance is open but the tunnel is empty. The tunnel exit opening has the covering removed on the bottom. Question: Does my oil pan create that negative pressure like the modification you guys were talking about doing? If not I was thinking of cutting the trailing edge of the oil pan on both bottom corners and curving the FG down to create that lip needed to draw air out of the cowling. I also wonder if doing this at the pipe tunnel exit would help. I have no temp readings to share. The engine runs great but more cooling is more power.
05-02-2009, 07:28 PM
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RE: 250° F - is that too hot?
Put a couple of good sized lips, louvers, etc., in front of those back cut outs and it should increase draw. More air flow is always better.
05-02-2009, 07:36 PM
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RE: 250° F - is that too hot?
Im going to try and make some baffles out of 1/4 balsa sheets for the front. It seems like it is plenty strong but I will use some light glass for added strength. I already have the bottom of my oil pan cut so I cant do the lip unless I glue an extra piece on the end. I also cut out the louver vents on the sides of the cowl not sure if it will help but it was pretty easy to do.
05-02-2009, 07:50 PM
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RE: 250° F - is that too hot?
Hi Joe,
Yes, your oil cooler will create a vacuum directly behind it.
I am not sure it will create a vacuum as far back as you have your tunnel opened. If you are getting too hot, I would close up the tunnel covering back there and open it right behind the cooler to the landing gear.
How much vacuum is created you might ask?
Enough that on my plane, its sucking the oil from the exhausts back up and into the cowl leaving a nasty mess. While I will keep an eye on the temperature, I am going to close off some of the exit area so my cowl is closer to neutral pressure.
Branwell
Yes, your oil cooler will create a vacuum directly behind it.
I am not sure it will create a vacuum as far back as you have your tunnel opened. If you are getting too hot, I would close up the tunnel covering back there and open it right behind the cooler to the landing gear.
How much vacuum is created you might ask?
Enough that on my plane, its sucking the oil from the exhausts back up and into the cowl leaving a nasty mess. While I will keep an eye on the temperature, I am going to close off some of the exit area so my cowl is closer to neutral pressure.
Branwell
05-02-2009, 07:55 PM
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RE: 250° F - is that too hot?
Hmmm, if it is sucking it back into the cowl the the flow seems to be going the wrong way....................
I've cut louvers before with a dremel and a small carbide coated tip, go slow and be careful of slips
I've cut louvers before with a dremel and a small carbide coated tip, go slow and be careful of slips
05-02-2009, 08:00 PM
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RE: 250° F - is that too hot?
Hi RTK,
It sucking up and into the cowl from the exhaust cut outs. From there, its traveling back and out where the oil cooler is creating a vacuum. Never seen anything like it, but I have never had a plane with a round cowl and scale oil cooler acting as a dam. All I can say is DAMMM :-)
Branwell
It sucking up and into the cowl from the exhaust cut outs. From there, its traveling back and out where the oil cooler is creating a vacuum. Never seen anything like it, but I have never had a plane with a round cowl and scale oil cooler acting as a dam. All I can say is DAMMM :-)
Branwell
05-02-2009, 08:11 PM
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RE: 250° F - is that too hot?
OK, I understand. You are pulling from the exhaust pipe (s) (stock) back up and out the back. I ASSumed you were pulling from the back forward, duh..........I'm a little slow sometimes.
05-02-2009, 08:45 PM
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RE: 250° F - is that too hot?
ORIGINAL: branwell
Joe,
What tool did you use to cut out the louver vents? Do you have a pic or two?
Thanks,
Branwell
Joe,
What tool did you use to cut out the louver vents? Do you have a pic or two?
Thanks,
Branwell
I will go back and clean up the slots tomorrow
05-02-2009, 08:52 PM
#46
RE: 250° F - is that too hot?
Actually I was thinking that I would do both the oil cooler dam AND the pipe tunnel exit dam. That way I could draw more air through the front baffling. The more the marrier.
You branwell's you are probably right....maybe doing both of these is not going to work. Maybe it will end up drawing air backwards through the pipe tunnel instead of through the front of the cowling where I want it. It might actually be better to block my pipe tunnel like you said. Then make the dam on my oil pan with a bigger opening there? Hmmm.
You branwell's you are probably right....maybe doing both of these is not going to work. Maybe it will end up drawing air backwards through the pipe tunnel instead of through the front of the cowling where I want it. It might actually be better to block my pipe tunnel like you said. Then make the dam on my oil pan with a bigger opening there? Hmmm.
05-02-2009, 09:11 PM
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RE: 250° F - is that too hot?
Hi Joe,
I think I am going to try that, and maybe a few other things. I have a spare cowl as the Brake Clean I sprayed inside the cowl to clean it out had an altercation with the paint. :-)
Branwell
I think I am going to try that, and maybe a few other things. I have a spare cowl as the Brake Clean I sprayed inside the cowl to clean it out had an altercation with the paint. :-)
Branwell
05-09-2009, 05:53 PM
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RE: 250° F - is that too hot?
ORIGINAL: branwell
Hi Joe,
I think I am going to try that, and maybe a few other things. I have a spare cowl as the Brake Clean I sprayed inside the cowl to clean it out had an altercation with the paint. :-)
Branwell
Hi Joe,
I think I am going to try that, and maybe a few other things. I have a spare cowl as the Brake Clean I sprayed inside the cowl to clean it out had an altercation with the paint. :-)
Branwell
05-09-2009, 09:51 PM
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RE: 250° F - is that too hot?
ORIGINAL: RTK
Put a couple of good sized lips, louvers, etc., in front of those back cut outs and it should increase draw. More air flow is always better.
Put a couple of good sized lips, louvers, etc., in front of those back cut outs and it should increase draw. More air flow is always better.
05-10-2009, 09:50 AM
#50
RE: 250° F - is that too hot?
ORIGINAL: Josey Wales
Sounds good..I got my baffle glued in today..didnt get to fly but I ran the engine to make sure the clearances were good....Im going to add a lip as well.
ORIGINAL: branwell
Hi Joe,
I think I am going to try that, and maybe a few other things. I have a spare cowl as the Brake Clean I sprayed inside the cowl to clean it out had an altercation with the paint. :-)
Branwell
Hi Joe,
I think I am going to try that, and maybe a few other things. I have a spare cowl as the Brake Clean I sprayed inside the cowl to clean it out had an altercation with the paint. :-)
Branwell