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05-07-2005 07:36 AM  12 years agoPost 61
nivlek

rrProfessor

Norfolk England

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I am convinced that engine overheating is down to poor design of the cooling system in our helis . I have a couple of late eighties Kalt Omega Pro helis and they have a superb cooling fan design . The fan is larger than modern fans with large curved blades . I purchased them all second hand , two of them were fitted with aero engines . On of the aero engines is a Y.S. 60 fitted with an Hatori pipe . I have flown this particular one quite a lot and only use 5% nitro fuel , originally useing a
fuel with only 15% oil . I now use a fuel with 20% oil , but that heli/engine
combination has never even hinted at running hot . I have just bought a HT cooling fan to fit to my Raptor 50 before I even fly it . It has ten blades instead of the standard fans six . Why did TT think that a fan originally intended for a thirty size engine , is good enough for a fifty size engine producing more power/heat and also with the fan turning slower due to the different gearing ratio ? I run loads of engines in fixed wing models on 5% or straight with no overheating , so if the cooling systems in the helis were good enough there would be no problem .
Using high nitro so that you can run the engine rich to keep it cool just seems like you are masking the cooling problems by wasting some of the power boosting potential of the nitro . I have also fitted a Bellwood head to my OS 5OSXH after first trying the head on an aero engine .
The head did increase the top end rpm quite a bit . This must mean that the engine is running more efficiently as it produces more power without using more fuel . This must also mean that the engine will run cooler as less of the fuels energy will become wasted as heat . I am also going to do some testing on my OS aero engines by running them without the shim under the head . This will narrow the squish band and slightly raise the compression , so will also hopefully work better with low/no nitro fuel .

At the end of the day , it gets dark .

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05-07-2005 11:11 AM  12 years agoPost 62
wouter

rrApprentice

Belgium

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hehe, if been thinking about that radiator from RCmarket also for quite some time...
the way i figured it is to hang it under the heli (mounting on the landinggear)
only thing i don't know yet is how to bring the water in contact with the
engine... fuel tubing isn't gonna work because is much too isolating...
direct contact with the engine housing would be ideal...


a simpler solution could be to add some thin, extending aluminium sheeting to the head of the engine. Sorta like extra cooling fins...
i think it could be done by using some light welds...

anyways,
i'm gonna try some stuff this summer
first need a new engine (Hyper or the 55, still haven't figured it out yet)

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05-07-2005 11:11 AM  12 years agoPost 63
wouter

rrApprentice

Belgium

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hehe, if been thinking about that radiator from RCmarket also for quite some time...
the way i figured it is to hang it under the heli (mounting on the landinggear)
only thing i don't know yet is how to bring the water in contact with the
engine... fuel tubing isn't gonna work because is much to isolating...
direct contact with the engine housing would be ideal...


a simpler solution could be to add some thin, extending aluminium sheeting to the head of the engine. Sorta like extra cooling fins...
i think it could be done by using some light welds...

anyways,
i'm gonna try some stuff this summer
first need a new engine (Hyper or the 55, still haven't figured it out yet)

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05-07-2005 12:46 PM  12 years agoPost 64
nivlek

rrProfessor

Norfolk England

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If somethings worth saying , it's worth saying twice .

At the end of the day , it gets dark .

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05-07-2005 02:54 PM  12 years agoPost 65
gremlins2g

rrNovice

New York,NY

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Does anyone know if the 52 and the 55 have the same carb diameter, for mounting ? It was mentioned that the 55 is 13mm

Thanks all

Stock Evo 50,hyper50,401/9253

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05-07-2005 04:45 PM  12 years agoPost 66
Hendrix

rrNovice

Piraeus Greece

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Probably they didn't wanted to completely redesign the frames in order to fit a biger fan (for cost reduction).
Now about this HT cooling fan do you think that it is working well?
I am thinking of puting one.
Chris

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05-07-2005 05:12 PM  12 years agoPost 67
nivlek

rrProfessor

Norfolk England

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Now about this HT cooling fan do you think that it is working well?
I'll let you know in a couple of weeks , I haven't fitted it yet . It looks similar to the Quick UK design but has two advantages . Firstly it has ten blades to the Quick UK fans nine , secondly it's half the price . It is very nicely made , and comes with collets to fit either a 36 or 50 size engine . I can't see how it could fail to shift more air than the standard fan .

At the end of the day , it gets dark .

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05-07-2005 05:24 PM  12 years agoPost 68
Hendrix

rrNovice

Piraeus Greece

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a simpler solution could be to add some thin, extending aluminium sheeting to the head of the engine. Sorta like extra cooling fins...
I have been thinking of an aluminium shroud around the head held with
HT silicone not welding as i dont want to mesh with the engine.
I dont know i will try the tubing first and then decide what to do next.
I just dont know if there is enough space between the frames for that thin aluminum shroud. 2 mm clearance will be needed for that.
There of course the option of an open cirquit water cooling system which does not need a water cooler.
As the water boils it evaporates and it can cool the engine 400 times more efficient than non boiling cirqulating water.
Only a minimum amount of water is needed in each flight.
I am thinking as i program Microcomputers a temp sensor and a couple
water injectors on the outside of the motor.
Nivlec I just read your reply about the fan.
We were both typing at the same time
Chris

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05-07-2005 06:48 PM  12 years agoPost 69
wouter

rrApprentice

Belgium

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If somethings worth saying , it's worth saying twice .
sorry, connection timed out for a sec there
There of course the option of an open cirquit water cooling system which does not need a water cooler. As the water boils it evaporates and it can cool the engine 400 times more efficient than non boiling cirqulating water. Only a minimum amount of water is needed in each flight.
Yep that's also an option.
But i wouldn't underestimate the amount of water you will need.
It also has to be a fairly steady "flow" on the engine in that case to
avoid thermal shocks...
A sort of spray or haze would be good.

Hendrix,
what exacty are those water injectors?
how big are they? have any links?
sounds cool...

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05-07-2005 07:48 PM  12 years agoPost 70
Hendrix

rrNovice

Piraeus Greece

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Just high pressure jets.
A pump and a small orifice.
Basicaly small burst of atomized water should be enough
With the help of a microcontroller and a Dallas temperature sensor,
accurate to 0,1 degrees the temperature should be kept within
a 10 degrees Celsius range by controlling the jet bursts.
I havent found anything particular i am just thinking loud.
I am in the stage of considering some alternatives in case that the
liquid cooled system i am preparing does not work well.
Chris

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05-07-2005 09:29 PM  12 years agoPost 71
Hendrix

rrNovice

Piraeus Greece

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Just a clarification.
I intend to use thin copper tubing like the ones found inside refrigerators,
not fuel tubing.
Copper should make good contact with the help of a collar.
Chris

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05-08-2005 07:17 AM  12 years agoPost 72
nivlek

rrProfessor

Norfolk England

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But i wouldn't underestimate the amount of water you will need.
Exactly . If you consider that our engines are around 25% efficient and they can produce around 2bhp, 1.5Kw , they create upto 4.5 Kw in heat , roughly twice the power of a kitchen kettle . If you intend to pipe fuel through the head , it would need to be cooled again before entering the engine . If it is not cooled after going through the head , you would loose the cooling effect of cold fuel entering the carb cooling the engine in the process , and end up back at square one . Improving heat loss through better heatsinks and improved airflow is probably the way to go . A back plate cooler , like on the West 50 , would help a little and some extra cooling through the engine mount might be possible. Also the fact that my HT fan is alluminium may help to disipate a little heat from the front of the engine .

At the end of the day , it gets dark .

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05-08-2005 09:29 AM  12 years agoPost 73
Hendrix

rrNovice

Piraeus Greece

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Improving heat loss through better heatsinks and improved airflow is probably the way to go
I totally agree.
Thats what i am trying to do by fitting a water cooler different fan etc.
I also agree that cooling the engine by evaporating excess high nitro content
fuel is not a solution but a workaround, masking the problem.
Chris

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05-08-2005 09:47 AM  12 years agoPost 74
nivlek

rrProfessor

Norfolk England

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A composite headsink head might be better than all alluminium . Copper conducts heat twice as welll as ali , so if we had a copper block to conduct the heat from the engine and then an ali heatsink to dissipate the heat away from the copper block , maybe we would have some joy .

At the end of the day , it gets dark .

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05-08-2005 10:56 AM  12 years agoPost 75
Hendrix

rrNovice

Piraeus Greece

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Yes copper is a fine material for heat transfer but unfortunately here in Greece
is impossible to machine something for the head without selling my house.
I am afraid we are far behind as machining shops are concerned.
Anyway i am almost done here.
Next week should be the first flight with watercooling and 0% nitro.
I am waiting for the cooler now.
We will see.......
If it doesn't work at all i will proceed to plan B, but if only minor modifications
are needed like materials etc. i will make it work.
I am also thinking an electric ducted fan unit blowing air directly on the head.
I know that i will need a bigger battery but i think it is a good idea to try
in case of failure.
Chris

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05-08-2005 12:53 PM  12 years agoPost 76
PaulH-MA

rrVeteran

Boston, MA

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Remember, copper absorbs heat better than aluminum, but aluminum disapates the heat back to the environment better than copper. This is why they heat sinks in your computer have a copper core inside of the aluminum fins

--Paul

TREX 450
Bergen Intrepid Gasser x2

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05-08-2005 01:08 PM  12 years agoPost 77
nivlek

rrProfessor

Norfolk England

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I know , that's why I suggested a composite head with an aluminium section to disipate the heat away from the copper block .

At the end of the day , it gets dark .

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05-08-2005 08:42 PM  12 years agoPost 78
Hendrix

rrNovice

Piraeus Greece

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Well i will try the copper tubing first wound on the top of the head where the glow plug is and then if the test are promishing i will think of something in order to make a true water cooled head like a marine engine.
Plan B is to mount the better fan, a nice shroud for guiding the air and if needed
an electric ducted fun from GWS blowing directly on the head.
With lipo packs weighting almost nothing it is not a big problem to mount a 3Ah
lipo pack for both the rx and the motor.
I am an electronics engineer and i have desighned and built a
microcontroller controlled 12V to 5V 10A switching converter which can supply enough power to the Rx and servos.
I think that even the Ubec that is capable of supplying 3 to 5 amps should be enough for the job.
The difference of my design is the safety features in case of a failure.
I dont think that passing the 12V directly to the Rx , servos and gyro will be
very good.
For those who know about switching regulators the Ubec is a non isolating converter where mine is of the isolating type.
I have to minimize the size and weight though because it is not as small as i want it to be for the job.
Chris

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05-08-2005 08:51 PM  12 years agoPost 79
nivlek

rrProfessor

Norfolk England

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I spent seven years testing and repairing switch mode power supplies , so I do have some idea of what you are saying .

At the end of the day , it gets dark .

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05-08-2005 09:48 PM  12 years agoPost 80
Hendrix

rrNovice

Piraeus Greece

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Thats why i havent fit a smps yet on the heli and i tend to trust the batteries better.
You never know when they will fail but after many years in this area i know one thing, they will fail eventualy so i dont trust them on a killer like the Raptor.
When i say killer i dont speak performance wise but literaly.
I hate to think what will happen if this thing fail in mid air
with people around.
To tell you the trouth i have nightmares when i think of those things.
Thats why i always seek isolated places but in our times those places are
located further away every day so it not practical for me to travel
200 km to find a suitable spot.
If you think that official flying sites are an option you probably haven't visit Greece lately. Last time i counted the helicopter flyers here we were under
100 persons(realy active).
Chris

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