RE: Prop pitch cooling - the final word  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> RE: Prop pitch cooling - the final word
Page: <<   < prev  1 2 3 4 5 [6] 7 8   next >   >>  

Login
Message << Older Topic   Newer Topic >>
RE: Prop pitch cooling - the final word - 2/20/2007 2:51:03 PM   
wjvail



Posts: 375
Joined: 9/5/2002
From: Meridian, MS, USA
Status: offline 		Wow has this thread come a long way. I'd like to get in but I'm not sure what the topic is any more!

Bill Vail
www.RCScreenProtectors.com

< Message edited by wjvail -- 2/20/2007 2:53:49 PM >

_____________________________

"Well, Nothing bad can happen now."

(in reply to Sport_Pilot)
       Post #: 126

RE: Prop pitch cooling - the final word - 2/20/2007 2:54:35 PM   
Sport_Pilot



Posts: 7728
Joined: 1/21/2002
From: Acworth, GA, USA
Status: offline
quote:

ORIGINAL: Jim Thomerson

A genera truism, not directed at anyone in particular.

Before you can learn something new, you have to accept that your present understanding of the subject is somewhere between incomplete and totally wrong.


Which it always is, unless totally wrong.

_____________________________

“I Saw Elvis at 1000 Feet” John Force

(in reply to Jim Thomerson)
       Post #: 127

RE: Prop pitch cooling - the final word - 2/20/2007 2:54:41 PM   
Hobbsy



Posts: 10686
Joined: 12/2/2001
From: Colonial Beach, VA, USA
Status: online 		It's about falling objects, flying people and involves a lot of hot air.

_____________________________

"I have gone faster backwards, upside down and on fire than most people have gone at all" Don Garlits

(in reply to wjvail)
       Post #: 128

RE: Prop pitch cooling - the final word - 2/20/2007 2:56:38 PM   
Sport_Pilot



Posts: 7728
Joined: 1/21/2002
From: Acworth, GA, USA
Status: offline 		Flying people, or frying people?

_____________________________

“I Saw Elvis at 1000 Feet” John Force

(in reply to Hobbsy)
       Post #: 129

RE: Prop pitch cooling - the final word - 2/20/2007 3:14:07 PM   
yallaair



Posts: 215
Joined: 1/1/2006
From: Floro, NORWAY
Status: online 		I've got It!!!!

Fast movin air is cooling better??? Nope! What about the tip of the nose on the supersonic CONCORDE??? It's **** hot from the air friction!!! Maybe the fast moving air of a high pitch prop is just "heating the engine"

....

_____________________________

Darn the ground..... and the jumping trees

(in reply to Sport_Pilot)
       Post #: 130

RE: Prop pitch cooling - the final word - 2/20/2007 3:57:05 PM   
Sport_Pilot



Posts: 7728
Joined: 1/21/2002
From: Acworth, GA, USA
Status: offline
quote:

Nope! What about the tip of the nose on the supersonic CONCORDE??? It's **** hot from the air friction!!
.


This has been discussed; you have to go supersonic for friction to be significant.

_____________________________

“I Saw Elvis at 1000 Feet” John Force

(in reply to yallaair)
       Post #: 131

RE: Prop pitch cooling - the final word - 2/20/2007 4:20:43 PM   
proptop



Posts: 4509
Joined: 10/18/2002
From: Rome, NY, USA
Status: offline 		Well...
If a person were to flap his gums fast enough...the hot air could go supersonic? Just talkin' about myself here, ya know!

_____________________________

It's bad luck to be superstitious...
Revver Bro #77

(in reply to Sport_Pilot)
       Post #: 132

RE: Prop pitch cooling - the final word - 2/20/2007 4:21:00 PM   
MJD


 

Posts: 1705
Joined: 5/27/2003
From: Orangeville, ON, CANADA
Status: offline
quote:

ORIGINAL: JNorton

MJD
quote:

Those that are mentioning they are engineers would identify with the credo that if the results do not match the model, go back and check your assumptions.
I get so tired of that same old saw. I spent 15 years working on the floor. The last 15 as an electric controls engineer. No engineer worth his salt would make the results match the model. PERIOD END OF STORY.
John


Where on earth did I say to make the results match the model? I only said check the assumptions, they may be flawed, i.e. redesign the experiment if necessary.

What I implied was that if the results are confusing or seem illogical, go back and look at the path that lead to the results, i.e. review the experiment or analysis and see if the assumptions led you down an erronous path. That is not the same thing as making the results match the model. Testing two variables where there are actually five might be an example. In such an experiment, results that match the model would likely result in erronous conclusions and in the end nothing is learned.

(in reply to JNorton)
       Post #: 133

RE: Prop pitch cooling - the final word - 2/20/2007 4:31:32 PM   
Sport_Pilot



Posts: 7728
Joined: 1/21/2002
From: Acworth, GA, USA
Status: offline
quote:

Well...
If a person were to flap his gums fast enough...the hot air could go supersonic? Just talkin' about myself here, ya know!


Well if most participating in this thread are present during the engine test, this could indeed be a factor. Something I did not consider.

< Message edited by Sport_Pilot -- 2/20/2007 4:33:03 PM >

_____________________________

“I Saw Elvis at 1000 Feet” John Force

(in reply to MJD)
       Post #: 134

RE: Prop pitch cooling - the final word - 2/20/2007 4:33:04 PM   
proptop



Posts: 4509
Joined: 10/18/2002
From: Rome, NY, USA
Status: offline

_____________________________

It's bad luck to be superstitious...
Revver Bro #77

(in reply to Sport_Pilot)
       Post #: 135

RE: Prop pitch cooling - the final word - 2/20/2007 5:55:16 PM   
KC36330


 

Posts: 2528
Joined: 4/19/2006
From: Enterprise, AL, USA
Status: offline
quote:

ORIGINAL: Sport_Pilot

Do I correctly understand the airflow in this device?


No, not at all. Byron jets do not use ducting on their intake side, they use what we jet fliers call a 'cheater hole' air isn't drawn in and directed across the engine. the fan unit is drawing air in from the bottom of the fuse with the only directed/ducted air being out the thrust tube. installation into the jet naturally causes air to be drawn in through the cheater hole and across the engine but very inefficiently, forward air speed also allows ram air in through the non ducted 'scale' intake and this helps in cooling because the tuned pipe is installed here as well as air is blown across the engine. it's no different then the use of different pitched props causing less cooling with their slower/less volume air flow (prop wash)


on the comments about the fuel foaming or sucking in air bubbles being the cause of the overheating in a hover, YS makes an all foam clunk for the 160DZ, it costs 13 bucks but well worth it and it will eliminate all bubbles from being drawn into the fuel line and giving a lean setting, it'll also allow the engine to draw fuel for a few seconds with the clunk exposed to air without drawing air into the fuel line (it's drawing the fuel from the foam), while that may or may not be the cause of the overheating, it can defiantly be eliminated with a simple clunk change. pumped engines (gassers) tend to overheat in hover as well so to me that eliminates tank location as the cause. elimination of 'suspected' causes is the quickest way to find the answer to the problem, not debating who has what degree and worked with what for how many yrs.

kc

(in reply to Sport_Pilot)
       Post #: 136

RE: Prop pitch cooling - the final word - 7/24/2007 4:26:47 PM   
yallaair



Posts: 215
Joined: 1/1/2006
From: Floro, NORWAY
Status: online 		I' have started on a prop test project. I'm testing various props and loggs static thust, RPM on grond, ambient temp, cyl. head temp, and prop wash airspeed. Later on I will also fly those props and logg aispeed, RPM, engine temp. Here are some readings:

Engine used: ASP 91 FS, 15/15 fuel, fully synth.
APC 13x8, 7,1lbf static, 9600RPM, Cyl. head:120 deg.C, 55 knot propwash
Dynathrust 14x8, 7,3lbf static, 8400RPM, Cyl. head:115 deg.C, 45 knot propwash
APC 14x6, 9,1lbf static, 9300RPM, Cyl. head:121 deg.C, 50 knot propwash
APC 12x8, 7,3lbf static, 10300RPM, Cyl. head:115 deg.C, 60 knot propwash
Volk 14x6, 9,1lbf static, 9000RPM, Cyl. head:118 deg.C, 50 knot propwash

I'm really looking foreward to see the airborne results. Eagletree logger already installed in airplane.
Picture of test airplane and engine:
http://www.anzjon.net/joomla/index.php?option=com_rsgallery2&Itemid=48&page=inline&id=242&catid=18&limitstart=0

Edited picture link.

< Message edited by yallaair -- 7/25/2007 10:27:31 PM >

_____________________________

Darn the ground..... and the jumping trees

(in reply to KC36330)
       Post #: 137

RE: Prop pitch cooling - the final word - 7/25/2007 2:21:11 AM   
Jazzy



Posts: 1106
Joined: 1/8/2002
From: Erie, PA, USA
Status: offline 		OMG!! I just read through all seven pages of this drivel.

Who is Bogarting that darn bowl! (of popcorn that is)

I don't recall anyone mentioning that an engine in level flight does not need to work nearly as hard as an engine in a hover. Is it ok to say that in a hover the props load on the engine (essentially a static load) is the greatest?
So we have a hard-working engine pointed straight up (or nearly so) that has to draw it's fuel from a clunk that is 10-14" below the carb. Right?

I think that the main issue here is the load on the engine. Do you all think that the RPMs will be higher in WOT level flight as opposed to WOT hover? If the RPMs are higher in level flight that would indicate less load on the engine... right? Less load - less work - less heat?

Now change WOT to a set RPM. As the aircraft moves forward there is less load on the engine to maintain the set RPM. Less work required. Less Power needed. Less heat.

I can hover (when I burn off a few oz of fuel) my magic with an old plain bearing TT .40 (NOT the .42) and an APC 12.25 X 3.75. Does it overheat? Not that I know of. It is set quite rich at level though.

A static comparison, should produce similar loads. Fuel draw? If the needle is set to provide slight rich running vertically then it should hover slightly rich too. Static test: slightly rich.

Was it Dar that did the original testing?... I found the temps to be quite interesting. Personally, I think the load of the 10X8 is greater than the load of the 12X3.75 at 11000 RPM and should produce a higher engine temp. BUt it is moving more air... Strange how both temps were the same...

Can someone put real butter in the popcorn... Hey! the bowl just passed me in freefall... Who put lead (Pb) in the bottom of the bowl!?

Oh, Look! there's Sylvester... and Tweety! Daffy and Speedy too!

< Message edited by Jazzy -- 7/25/2007 4:11:25 AM >

_____________________________

Aww $#!^.... I left the )@#& transmitter at home!

(in reply to yallaair)
       Post #: 138

RE: Prop pitch cooling - the final word - 7/25/2007 2:23:38 AM   
gkamysz


 

Posts: 1603
Joined: 6/24/2003
From: Crystal Lake, IL, USA
Status: offline
quote:

Is it ok to say that in a hover the props load on the engine (essentially a static load) is the greatest?


Define "load".
How does it relate to engine temperature?

_____________________________

Greg

(in reply to Jazzy)