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CanoMod . Futaba-RC . A Main Hobbies

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HIROBO Freya - Sceadu - Shuttle > BIG mistake
 
 
clueless
Senior Heliman
Location: somewhere in between

gREETINGS,
Re sceadu cooling problems I just looked at the supplied cooling fan --IT'S WRONG-- IT HAS BEEN DESIGNED FOR OPPOSSITE ROTATION. its supposed to be a centrifugal outwards flow but when fitted to a regular engine its backwards
how dyall miss that ?
04-10-2002 Over year old.
 
 
Ken B
Elite Veteran
Location: Phoenix, AZ

hmmm.

As I recall that the blades on my fan are unidirectional. They are just straight off center. I don't have the fan in my hand and I am not looking right down at it...

If I'm wrong it wouldn't be the first time

I don't have cooling problems! I use a home made shroud, works GREAT!

Ken B
04-10-2002 Over year old.
HOMEPAGE  
 
 
Doug
Elite Veteran
Location: Naples Florida....

I can tell you the direction of the "scroll" on a low pressure ratio radial outflow "fan" makes only a slight difference, in fact the blades being backwards will increase the airflow at the expense of pressure rise.(increase in velosity,decrease in static pressure) ( I learned a lot about this while building a "home built turbine").
04-10-2002 Over year old.
 
 
Hockeytown
Veteran
Location: Pontiac, Mi. U.S.A.

He may be right!

Here is a pic I took when I was building my Sceadu 50:

http://www.westmug.org/djg/Sceadu_5...ly/DSC01987.JPG

I never gave it much thought, but it IS pitched in reverse for a CCW engine on a CW main rotor system.

Let us know what you all think.

Thanks

Darin[color=red]
Hockeytown[/color]
04-10-2002 Over year old.
 
 
heliraptor
Key Veteran
Location: Colchester, Essex, UK

Metal fan

Hi

After the reports of cooling problems I went straight for a quick uk metal fan, supposed to be 30% more efficient (their quote) and the blades go the right way ;-)

Went for the NHP carbon cooling duct too, it runs real cool, very cool in fact and I have had no overheating problems at all.

Lee
04-10-2002 Over year old.
HOMEPAGE  
 
 
Hockeytown
Veteran
Location: Pontiac, Mi. U.S.A.

Quick UK

Go here:

http://www.quickuk.co.uk/acatalog/r_index.htm

then go to the Hirobo parts for the Sceadu.......

Jeff, are you out there?

I find it hard to believe that no one noticed this before now......but it makes sense to me.

Thanks

Darin[color=red]
Hockeytown[/color]
04-10-2002 Over year old.
 
 
Hockeytown
Veteran
Location: Pontiac, Mi. U.S.A.

Side by side.....

Here is mine, and the Quick UK fan:

Looks like it's wrong to me!
[BREAK]




Darin[color=red]
Hockeytown[/color]
04-10-2002 Over year old.
 
 
Hockeytown
Veteran
Location: Pontiac, Mi. U.S.A.

Look Up

I posted 2 messages in a row......my first has the link to Quick UK.

Darin[color=red]
Hockeytown[/color]
04-10-2002 Over year old.
 
 
Doug
Elite Veteran
Location: Naples Florida....

Hey guys take a look at a squirrel cage fan and notice that the blades are "backwards". As I posted before the "correct" direction depends on the required pressure rise which in our case is nil.
04-10-2002 Over year old.
 
 
Hockeytown
Veteran
Location: Pontiac, Mi. U.S.A.

Then it doesn't matter?

Does that mean that the direction of a cooling fans blades don't matter?

It just doesn't make sense to me......the direction of the stock blades would lead you to believe that air is being drawn into the center of the fan....where it then has no place to go. The blades on the QuickUK fan will force air away from the center and down across the head.

So with the direction being imaterial, is all we are looking for in a fan is one that moves air, no matter what the direction.......and then we rely on the cooling shroud to direct it where it needs to go?

Sorry if it seems like I'm beating a dead horse here, but a fans direction has always had purpose and logic.........and this one still isn't sitting right

Thanks

Darin[color=red]
Hockeytown[/color]
04-10-2002 Over year old.
 
 
Doug
Elite Veteran
Location: Naples Florida....

The air flow will be greater with the "backward" blades (with identical blade sizes) but the clearance and blade "size" of the AL fan is likly a greater factor.
04-10-2002 Over year old.
 
 
fitenfyr
rrProfessor
Location: Port Orchard, Washington

Uhhhhhh....

Ok I guess I don't get this either. What does pressure rise have to do with moving air across the head? This is not a close tolerance compressor application so the fan is really just "grabbing" air and forcing it in another direction right?
I know air moves from high pressure to a lower pressure, but in this case it would appear to have no outlet if the "low" pressure point is being created in the center of the fan and not the outside as would appear to be the case here.

I have not had any cooling problems at all with mine. However I live in the Pacific NW where the mean temp has been about 40 deg since I got mine. I did take it down to Las Vegas where it was about 60 and didn't have an overheating problem there.

Interesting
Jason

Jason Stiffey
Fly Fast....Live Slow...
04-10-2002 Over year old.
HOMEPAGE  
 
 
Doug
Elite Veteran
Location: Naples Florida....

Think of yourself as an air molecule, as it enters the impeller it is accelerated radially outward, its path describes an arc with ever increasing velocity. With blades angled away from center the path will describe a gentle arc and the resulting exit velocity will, as a result, be the lowest for a given RPM. Straight bladed impellers will force the molecule to describe a steeper arc (greater acceleration) and the resulting velocity will be greater. The reverse blades impeller forces the air to follow a very steep arc and as a result the exit velocity will be the highest for a given RPM. But it the system has any resistance (pressure rise) then the straight bladed or "angled away" blades will perform better. In our case the "rise" is less than 1" of water (03 PSI) rise. The reverse angled fan has the greatest potential for air flow. The shape and size is of equal importance.
04-11-2002 Over year old.
 
 
moose
Senior Heliman
Location: Somerset UK

I also run the Quick UK fan and NHP cooling shroud and have no overheating problems at all.
04-11-2002 Over year old.
 
 
Carps
Veteran
Location: Caterham, Surrey, England

Ditto the Quick fan and NHP shroud. But then I had no overheating problems in the first place.
Just made myself paranoid by reading all the overheating posts on the net
04-11-2002 Over year old.
HOMEPAGE  
 
 
ed vega
Key Veteran
Location: nyc, queens

take a look at the other hirobo systems. why does it look backwards?. nothing wrong with it. I got the same fan on my hirobo dauphin. and looking at earlier versions they have the same pitch , when did hirobo start making fans for clockwise rotation , the fan and shroud needs to be a match.
hopefuly your not leaning out an engine to the point of overheating .



04-11-2002 Over year old.
 
 
ampex456
Senior Heliman
Location: Bayville, NJ

Cooling Fan

Hello,

I am not an engineer for cooling fans, but Hirobo has staff with this type of experience. Are they perfect, no they are human like everyone else therefore they are fallible. However they spend countless hours designing and testing their components. Just because someone else makes one a little different or completely different does not make Hirobo wrong and the other guy completely right. How many aftermarket components never work and we find that the stock units ran just fine. This is in general for all things we buy. Maybe a free speech thing. ) Anyway, the stock fans have always worked for me regardless of the design and I get to play with mine flight after flight. If you are overheating or are worried about it, look elsewhere for the problem.

.02

Jeff G
04-11-2002 Over year old.
 
 
G. Williams
Heliman
Location: North Carolina

I am not an engineer, but I have worked with liquid handling pumps for a lot of years. The direction of rotation on these pumps is vital to get proper performance out of them. Most of them use an impeller similar to the one in question. I have never seen an impeller rotate in this direction. Air handlers may be different and high speeds may change things. I simply don't know. My best guess is that the impeller (fan) running in this configuration will be trying to move air into (from the exaust side) and out of ( from the inlet side) simultaneously resulting in decreased air flow. I am going to vote for the gentleman who noticed this. I will also going out on a limb and say that I don't think anyone can produce another example of a fan turning in this direction. Gerald.
04-11-2002 Over year old.
 
 
ampex456
Senior Heliman
Location: Bayville, NJ

What did you expect him to say?

Enough in the "subject". Hirobo knows what they are doing.

Jeff G
04-11-2002 Over year old.
 
 
Hockeytown
Veteran
Location: Pontiac, Mi. U.S.A.

It's just perception

I am in the engineering software business. We sell software to do 3D Solid modeling, FEA, CFD (computational fluid dynamics) and a whole host of other things.

I assume that these guys use this type of software to test things, it just makes sense. I have seen things that your eyes say won't work, but the software says will. In almost every case......the software was right!!

This is one of those things that your eyes and physics of fluids don't agree........but the only one that really matters IS physics in this case.

I'm not saying the design is wrong....I really just want to know the in's and out's of why things do what they do................just like when I was 6 and I took my brothers walkman apart.....I JUST WANTED TO KNOW HOW IT WORKS The cool thing is that now, at least I can put them back together too!!

I got a couple of tanks thru my Sceadu 50 yesterday and it certainly is an amazing machine!!! I have a couple of fresh gallons I'll be taping into in about 25 minutes.......so wish me luck, and happy flying. (the second won't be a problem )

Thanks

Darin[color=red]
Hockeytown[/color]
04-11-2002 Over year old.
 
 
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HIROBO Freya - Sceadu - Shuttle > BIG mistake
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