Wanted,Temperature operated cowl flaps

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Stuart Atwill
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Wanted,Temperature operated cowl flaps

Postby Stuart Atwill » June 3rd, 2020, 2:40 pm

Many years ago I bought a ThermaCowl from Oregon Scale Aviation in the USA. This little unit operates a servo according to the sensed temperature in the cowl. Does anybody know of a similar product?

Elliot Howells
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Re: Wanted,Temperature operated cowl flaps

Postby Elliot Howells » June 4th, 2020, 9:11 pm

easy to do these days with telemetry operated controls if your radio will allow :)

Stuart Atwill
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Re: Wanted,Temperature operated cowl flaps

Postby Stuart Atwill » June 5th, 2020, 6:53 pm

I'm sure my radio will allow, Futaba T14SG but I wouldn't have a clue how to go about it, I struggle with telemetry displays! Thanks for the post though. I'm 65 and more of a hammer and screwdriver man.

John McNamara
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Re: Wanted,Temperature operated cowl flaps

Postby John McNamara » June 6th, 2020, 8:58 am

Stuart, there is more to it than displaying telemetry on your screen. Of course you could do that and manually monitor temaperatures and adjust cowl flaps accordingly. However, to make this automatic you need, as Elliot eluded to, telemetry control. This is available on Jeti but I have no idea if its available in the Futaba range.
I will be doing exactly this on my Carf Corsair and the way I will go about that is as follows: I will use Jeti MT300 temparature sensors to read the temparature in the engine bay. This will be fed back to my transmitter and displayed, but that data will aslso be fed into telemetry control, which will have control of the cowl flap servo. Some expremintation will be needed to see what the alarm temparature will need to be set to, to open the cowl flaps.
I am a year older than you so If I can understand this stuff you can too. Yes it takes longer now (what doesn't? :D), but if its possible on Futaba then someone has already done it and can offer help.
John

Stuart Atwill
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Re: Wanted,Temperature operated cowl flaps

Postby Stuart Atwill » June 6th, 2020, 5:22 pm

Thanks for the reply John. I haven't heard of telemetry control on Futaba systems, but then again, I only heard of Jeti recently when there was an article in the LMA Journal. I must look into it.
Regards, Stu.

Arthur Fielding
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Re: Wanted,Temperature operated cowl flaps

Postby Arthur Fielding » June 6th, 2020, 7:05 pm

Hi Stuart
As I am even older than you perhaps it qualifies me to make a comment.So with due respect hear goes.
I have always believed in the keep it smiple idear
I can not help but wonder how many over heated engine runs you will get, and crashed models due to an engine stop or sieze before you get it right.
You could just fit a servo ( set servo to what ever speed you wont) to operate on a tx switch so you can open or close manually when the model is on the ground to give a scale effect, after all no one will see the any scale detail when the model is flying.
However good luck with you idea.
Perhaps you could do an artical on your progress .
Regards
Arthur

Glenn Masters
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Re: Wanted,Temperature operated cowl flaps

Postby Glenn Masters » June 6th, 2020, 10:06 pm

My advice , especially where radial engines are used, is to concentrate efforts to control air coming into the cowl rather than worrying about gill flaps and the like . . . use ducting and baffles to control the cooling air over the cylinders. If you use automatic devices to open the gill flaps, chances are you wont see the benefits of your handywork until after the engine is fried ! Arthurs servo idea is the way to go if bells and whistles are required . . . . .

John McNamara
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Re: Wanted,Temperature operated cowl flaps

Postby John McNamara » June 7th, 2020, 8:33 am

Glenn,
You are absolutely right about ducting the air inside the cowl to ensure proper cooling. That is fundemantal. I have assumed that Start has already taken care of this step. But having telemtetry that at least tells you what is going on in the air, that is progress. You do not need to look at the Tx screen whilst flying with a good quality radio, it will talk to you. Also you can look at and study logged data later. How can that be a bad thin?. Egress of hot air is of equal importance as ingress of cold air, so having cowl flaps open the whole time is the logical thing to do. But we are scale modellers and would like, if possible, to emulate the full size as closely as possible. Therefore, Arthur's suggestion means having manual control but no information. On which basis does one take a descision to close or open the cowl flaps?
John

Tony Collins 1073
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Re: Wanted,Temperature operated cowl flaps

Postby Tony Collins 1073 » June 7th, 2020, 10:04 am

John McNamara wrote:Glenn,
You are absolutely right about ducting the air inside the cowl to ensure proper cooling. That is fundemantal. I have assumed that Start has already taken care of this step. But having telemtetry that at least tells you what is going on in the air, that is progress. You do not need to look at the Tx screen whilst flying with a good quality radio, it will talk to you. Also you can look at and study logged data later. How can that be a bad thin?. Egress of hot air is of equal importance as ingress of cold air, so having cowl flaps open the whole time is the logical thing to do. But we are scale modellers and would like, if possible, to emulate the full size as closely as possible. Therefore, Arthur's suggestion means having manual control but no information. On which basis does one take a descision to close or open the cowl flaps?
John


John, full size aircraft which you are trying to emulate do not rely on a simple servo which as we all know can and do
fail. If you fitted a servo to do what you want and it failed in the closed position you could possibly do major damage to a
very expensive engine. True scale modelling is to be applauded absolutely but surely must be coupled with practicallity
and also with the knowledge that a seizure at the wrong moment could also cause the loss of the aircraft.

Glenn Masters
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Re: Wanted,Temperature operated cowl flaps

Postby Glenn Masters » June 7th, 2020, 10:12 am

I cant argue with your using whatever info one can get with modern radio gear John.
I am exposing my luddite self here - not really moving with technology that is available to us these days . . . In my defence, I will say that when my aircraft is strafing past myself at a pace with the engine singing back to me with a joyious snarl, you can bet i'll be planning my next big scale manouvre rather than listening out for any computer messages . . .
Like yourself, I'm a scale modeller too (albeit old-school) and when a corsair is taxiing with cowl flaps open and displayed, then its a fine sight indeed, but whether they need to be vital for proper cooling - well the jury's out on that . . . .
regards. Glenn

John McNamara
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Re: Wanted,Temperature operated cowl flaps

Postby John McNamara » June 7th, 2020, 10:30 am

Glenn,
You are absolutely right about ducting the air inside the cowl to ensure proper cooling. That is fundemantal. I have assumed that Stuart has already taken care of this step. But having telemtetry that at least tells you what is going on in the air, that is progress. You do not need to look at the Tx screen whilst flying with a good quality radio, it will talk to you. Also you can look at and study logged data later. How can that be a bad thing? Egress of hot air is of equal importance as ingress of cold air, so having cowl flaps open the whole time is the logical thing to do. But we are scale modellers and would like, if possible, to emulate the full size as closely as possible. Therefore, Arthur's suggestion means having manual control but no information. On which basis does one take a descision to close or open the cowl flaps?
John

Glenn Masters
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Re: Wanted,Temperature operated cowl flaps

Postby Glenn Masters » June 7th, 2020, 1:30 pm

. . . you can say that again ! :D

Tony Collins 1073
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Re: Wanted,Temperature operated cowl flaps

Postby Tony Collins 1073 » June 7th, 2020, 3:06 pm

déjà vu :? :? :?

Stuart Atwill
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Re: Wanted,Temperature operated cowl flaps

Postby Stuart Atwill » June 7th, 2020, 4:47 pm

Thanks for all your comments guys, very interesting. My Corsair has done over 200 flights without any problems. The cowl flaps start to open as the engine warms up and are fully open well before takeoff. They only close again after the engine has cooled and radio gear switched on, looks better static when they are closed and they don't catch on anything when handling the fuselage.
I wanted to do the same for my P40 which at the moment is switch operated. I open them fully before engine start and don't close them until the engine has cooled. If they are automatic I don't have to remember to do this.
Safe and fun flying guys,
Stu.

Steve Perry
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Re: Wanted,Temperature operated cowl flaps

Postby Steve Perry » June 9th, 2020, 9:42 am

There is a simple way to do this with a cheap servo tester, replace the potentiometer with a NTC thermistor of the same value.
It's a little more complicated as the pot is 3 wires and the thermistor is 2 wires, simply connect a a 1k resistor in series with the thermistor to give the 3 connections required :)

Servo tester 2 quid from China, thermistor 2 quid for a pack of 5, resistor a quid for 20.

I am not sure if it work "straight out of the box" with the temperature range required, but for a fiver it's worth playing with :)

Cary Bailey
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Re: Wanted,Temperature operated cowl flaps

Postby Cary Bailey » June 9th, 2020, 3:14 pm

For your information, I run my radiator flap on my P-51 tied in with the throttle. I have mixed it in such a way that at low throttle the flap is open (taxying) and at full throttle for take off and climbing. At flying speed it closes (not fully) because the airspeed forces the air through the engine compartment. My cooling arrangement is that the heated air from the cylinders travel through the fuselage and exit out of the scale radiator exit.
Cary

Stuart Atwill
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Re: Wanted,Temperature operated cowl flaps

Postby Stuart Atwill » June 9th, 2020, 4:49 pm

Thanks Steve and Cary, I will look into both methods.
Stu.

Steve Perry
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Re: Wanted,Temperature operated cowl flaps

Postby Steve Perry » June 11th, 2020, 6:53 am

I have ordered a servo tester and will have a play with it, I have also ordered an Arduino as a backup plan.
I suspect that the mention of Arduino witchcraft might sound horribly complicated, it's not but gives an easy way of setting the fully open and fully closed temperatures. With the simple servo tester modification the closed position of the servo will vary between summer and winter due to the ambient temperature.
I am guessing that fully closed at 20c and fully open at 100c would be a good starting point.
Both methods look like costing about a fiver to make :)

Stuart Atwill
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Re: Wanted,Temperature operated cowl flaps

Postby Stuart Atwill » June 12th, 2020, 3:41 pm

Thanks Steve, I found out about Arduino and have joined up. I still don't really know where to start. Would the 'bread board' have to be in the aircraft? I would be happy to purchase a working solution from you, electronics is not my strong point!
I think perhaps the upper temperature should be much lower, maybe around 50 - 60, I'm guessing that's about how mine operates.
I'm not really looking for anything too sophisticated, just open when the engine is warm and closed when its not.
I really appreciate your help.
Stu.

Steve Perry
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Re: Wanted,Temperature operated cowl flaps

Postby Steve Perry » June 12th, 2020, 4:41 pm

Nothing as crude as a breadboard, just something the size of a matchbox using an Arduino nano :)
I am not an Arduino expert but I can tweek other folks code to get it to do what is needed :)

Something along the lines of experiment 2 but with a thermistor instead of a potentiometer https://www.allaboutcircuits.com/projects/servo-motor-control-with-an-arduino/
Probably with 2 screwdriver adjusters for servo travel and fully open temperature :)

The servo tester has arrived and I have ordered a suitable thermistor.


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