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Old Feb 16, 2012, 10:50 PM
Double Naught Spy
iamplanecrazy2's Avatar
USA, TX, Waxahachie
Joined Aug 2004
379 Posts
Thanks Rusty, I'm doing ok. Just way behind. I do have a torn rotator cuff in
my right shoulder that is irritating the out of me but its really not
slowing me down. I guess I just have to many irons in the fire and need to
rearrange them to get back on this project!
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Old Feb 16, 2012, 11:05 PM
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RknRusty's Avatar
United States, SC, Columbia
Joined May 2010
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Oooo, ouch! I can sympathize, I have a disintegrated cuff in mine too. This is the time of year when I make it flair up. Either of my shoulders can put me out of business, then clear right up as suddenly as it came.

Anyway, we're looking forward to you tinkering again. I saw a 7 cylinder radial configured much like yours on another forum. It runs with an OS carb and an impeller. It didn't say anything about the firing order though.
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Old Feb 19, 2012, 10:12 PM
I am 5' 8" the Taube is 7' 4"
Clancy Arnold's Avatar
USA, IN, Indianapolis
Joined Jan 2008
617 Posts
IamPlaneCrazy2

I just got to thinking about the firing order I recommended and still do.

For an output shaft RPM of 5,000 will require each Sure-Start to run at 12,500, RPM. 5,000 x 2.5 gear ratio.
12,500 power pulses from each Sure Start times 9 engines is 112,500 power pules to generate the 5,000 RPM.
112,500 PPM / by 60 = 1,875 Pulses per second! That sound is going to HURT!

Wish I could be there!!
Clancy
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Old Feb 20, 2012, 01:02 PM
I am 5' 8" the Taube is 7' 4"
Clancy Arnold's Avatar
USA, IN, Indianapolis
Joined Jan 2008
617 Posts
IAmPlaneCrazy2
One additional calculation!

9 engines times 2.5 gear ratio equals 22.5 power pulses per revolution of the prop.

Rated Horse Power of a Cox Sure-Start? Guestimate 0.1 HP times 22.5 equals 2.25 HP!! My OS FS91 is rated at 1.6 HP and pulls a 14 x 6 at 9,000 RPM easily.

The low RPM would dictate a high pitch prop and the HP would say a big prop so my recommendation would be a 14 x 12 prop to start.

Any one else have a recommendation / suggestion?
Do you disagree with my calculations?

I still would like to be there for that first run!
Clancy
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Old Feb 20, 2012, 02:01 PM
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greyflight390's Avatar
United States, TX, League City
Joined Feb 2009
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Quote:
Originally Posted by Clancy Arnold View Post
IamPlaneCrazy2

I just got to thinking about the firing order I recommended and still do.

For an output shaft RPM of 5,000 will require each Sure-Start to run at 12,500, RPM. 5,000 x 2.5 gear ratio.
12,500 power pulses from each Sure Start times 9 engines is 112,500 power pules to generate the 5,000 RPM.
112,500 PPM / by 60 = 1,875 Pulses per second! That sound is going to HURT!

Wish I could be there!!
Clancy
My ears are ringing just thinking about it. But I agree with you Clancey. I sure would love to hear that little beastie scream.
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Old Feb 20, 2012, 03:03 PM
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gkamysz's Avatar
Chicagoland
Joined Feb 2000
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I think we'll have to see how much power it makes. A sure start doesn't make 0.1HP. I estimated less than 1/2HP total output a while back in the thread.

Silently waiting for the outcome. I'm trying to decide what kind of multi-cylinder Cox to build myself.

Greg
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Old Feb 20, 2012, 03:15 PM
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dogshome's Avatar
Joined Dec 2006
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Quote:
Originally Posted by gkamysz View Post
I think we'll have to see how much power it makes. A sure start doesn't make 0.1HP. I estimated less than 1/2HP total output a while back in the thread.

Silently waiting for the outcome. I'm trying to decide what kind of multi-cylinder Cox to build myself.

Greg
W12?
Inline 12!!!

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Old Feb 20, 2012, 05:54 PM
I am 5' 8" the Taube is 7' 4"
Clancy Arnold's Avatar
USA, IN, Indianapolis
Joined Jan 2008
617 Posts
Gkamysz
I tried to consider the displacement to HP of other relative mild engines. Fox 35 stunt at 0.5 HP (1.42 HP / Cu In) and the OS 25 FP at 0.6 HP (2.4 HP / Cu In).

With the gears and all it is going to be interesting to see how much of the generated HP actually gets to the prop. I used 2/3 for efficiency so about 0.1 HP x 22.5 = 2.25 HP output. Should we refigure it at 6000 RPM output with each Sure-Start turning 15,000? That would be 2,250 power (NOISE) pules per second!

I am reconsidering being there. LOL
Clancy
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Old Feb 20, 2012, 05:56 PM
I am 5' 8" the Taube is 7' 4"
Clancy Arnold's Avatar
USA, IN, Indianapolis
Joined Jan 2008
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Duplicate post! How do you delete a duplicate post?
Clancy
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Last edited by Clancy Arnold; Feb 20, 2012 at 06:09 PM.
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Old Feb 20, 2012, 06:17 PM
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greyflight390's Avatar
United States, TX, League City
Joined Feb 2009
925 Posts
Just stick your fingers in your ears
It could not be as bad as the Republic xf-84h Thunderscreech
http://en.wikipedia.org/wiki/XF-84H_Thunderscreech
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Old Feb 21, 2012, 04:01 PM
Registered User
Joined Oct 2004
1,079 Posts
I'd go with about 1/2 hp net after going through the gears, induction losses etc.
However, this is an interesting project with someone using basic tools. Let's hope it gets finished so we can hear how it sounds!
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Old Feb 21, 2012, 06:03 PM
I am 5' 8" the Taube is 7' 4"
Clancy Arnold's Avatar
USA, IN, Indianapolis
Joined Jan 2008
617 Posts
706jim
I am with you, I hope someone has a video camera running when that thing starts. I know we all want to see and HEAR it run.
Clancy
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Old Feb 21, 2012, 11:15 PM
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surfer_kris's Avatar
Sweden
Joined Jan 2008
961 Posts
Quote:
Originally Posted by Clancy Arnold View Post
Gkamysz

With the gears and all it is going to be interesting to see how much of the generated HP actually gets to the prop. I used 2/3 for efficiency so about 0.1 HP x 22.5 = 2.25 HP output.
It sounds like you are confusing momentum and power here. The gears can only change the momentum not the power.

9 engines x 0.1 hp x 0.6 efficiency ≈ 0.5 hp
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Old Feb 22, 2012, 04:43 AM
Oxford Panic
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United Kingdom, Oxford
Joined Feb 2003
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Old Feb 22, 2012, 06:13 PM
I am 5' 8" the Taube is 7' 4"
Clancy Arnold's Avatar
USA, IN, Indianapolis
Joined Jan 2008
617 Posts
Surfer_kris
I see what I did wrong. Yes 0.5 HP.
The gears will not generate power but they will loose (consume) power. It takes power to operate the gears. I revise my recomedation, a 9 x 7 prop might work.
Clancy
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