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RE: ... - 7/13/2008 2:48:31 AM   
diamondave



Posts: 1636
Joined: 9/2/2004
From: marana, AZ, USA
Status: offline 		didnt have a chance to mess with my servo yet, was at the field with another plane i just got done, but i have a question for any of you formula junkies, dealing with a prop, ever heard of this?
DxDxDxP=?
a guy was doing that saying you can compare the load 2 different props will put on a motor, for example;
22x22x22x10=106480
23x23x23x8=97336
so according to him, the 23-8 will put less load then the 22-10, the bigger final number is more load, any body ever hear of that? do the numbers maean anything? he didnt really explain much about it just said its a rough way to calculate the load like that, just curious

(in reply to exakta777)
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RE: ... - 7/13/2008 3:05:52 AM   
JoeAirPort



Posts: 6971
Joined: 8/11/2003
From: Milwaukee, WI, USA
Status: offline 		22x10=220
23x8=184

The math is way easier.

The two numbers do effect engine load but not sure if the relationship is as we have in our math. Any prop PHD's out there?

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(in reply to diamondave)
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RE: ... - 7/13/2008 3:07:22 AM   
rcbill


 

Posts: 447
Joined: 2/13/2003
From: pleasant prairie, WI, USA
Status: offline 		Dave,
I'm no expert, but it sounds complicated to me. I used something similar but it was like 22x10=220 and 23x8=184 for prop load comparisons. Not an exact science but just to give you an idea if you are in the same ball park.... Bill

(in reply to diamondave)
       Post #: 6178

RE: ... - 7/13/2008 3:09:57 AM   
rcbill


 

Posts: 447
Joined: 2/13/2003
From: pleasant prairie, WI, USA
Status: offline 		How about that??? Almost sounds like a double post..... Bill

(in reply to JoeAirPort)
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RE: ... - 7/13/2008 1:59:26 PM   
diamondave



Posts: 1636
Joined: 9/2/2004
From: marana, AZ, USA
Status: offline 		i thought it was alot of math to do, when he explained it to me, i used my calculator on my phone and just went 22x3, then x10, he said you cant do it that way it had to be 22x22x22x10, so i dont know, thats why i was asking more about it with all you smart fellows , plus i was a little suprised that the 23-8 was less load then a 22-10, i know the pitch is higher but i thought the more mass of the 23 would equal to more load but i guess not, you easier way says the same thing too

(in reply to rcbill)
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RE: ... - 7/13/2008 3:06:41 PM   
xtraflyr


 

Posts: 1595
Joined: 3/10/2002
From: Chester, NJ, USA
Status: offline 		We need Mr. Vess to answer this!! He is after all a Propologist

Cya,
Frank


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RE: ... - 7/13/2008 3:16:23 PM   
rcbill


 

Posts: 447
Joined: 2/13/2003
From: pleasant prairie, WI, USA
Status: offline 		Dave,
I have a tendancy to think that the 23x8 would put a bigger load than the 22x10. The extra diameter plus the extra weight of the prop and drag etc makes me think that way. Like I had mentioned perhaps it's just to see if you are in the ball park on load when changing from something like a 21x12 to a 23x6....???? I duno.... Anyone else with the proper math is welcome to join in.... I'm sure Dick Hanson or Pat Roy or TKG would have a more appropriate explaination.... Bill

(in reply to diamondave)
       Post #: 6182

RE: ... - 7/13/2008 3:44:33 PM   
JoeAirPort



Posts: 6971
Joined: 8/11/2003
From: Milwaukee, WI, USA
Status: offline 		You prolly get more (static) thrust out of the 23x8 but more (dynamic) air speed out of the 22x10. I wonder if one loads the engine more at both static and dynamic conditions.

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Joe AP

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RE: ... - 7/13/2008 4:19:38 PM   
rcbill


 

Posts: 447
Joined: 2/13/2003
From: pleasant prairie, WI, USA
Status: offline 		Joe,
I'm gonna stick with "I dunno"..... Bill

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RE: ... - 7/13/2008 6:55:40 PM   
JoeAirPort



Posts: 6971
Joined: 8/11/2003
From: Milwaukee, WI, USA
Status: offline
quote:

ORIGINAL: rcbill

Joe,
I'm gonna stick with "I dunno"..... Bill


Well at least you're smart enough to stick with that....I think I'll follow suit.

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Joe AP

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RE: ... - 7/13/2008 10:31:52 PM   
Richard D Bahmann aka/Wrongway



Posts: 2014
Joined: 1/7/2004
From: Ormond Beach, FL, USA
Status: offline 		How about the one that loads the engine the most is the one with the lesser RPM?

Check out the prop calculator of Pei Reivers at www.mvvs.nl or ask him in my opinion, a real expert.

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Gonna kick the tire and light up my
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RE: ... - 7/14/2008 1:25:24 PM   
Flyin Hawaiian


 

Posts: 815
Joined: 4/28/2005
From: Orlando, FL, USA
Status: offline 		I know that this Engine / Prop Load Calculation makes for great discussion, but totally unecessary. Most of us already know that works for most 50cc applications, the 22-8 to 22-10 and 23-8 props will work. But if you do not factor in the atmospheric conditions (altitude) it really is a moot point. What it really boils down to is performance you can feel through your thumbs: Engine RPM's, Engine Temperatures, aircraft selection, and aircraft weight, still needs to be factored in. No I am not a formula junkie, (even though I deal with formulas with my Job every day) but I know what works and what does not work. Formulas are a good way to find a good starting point, but real world results that is shared here amoungst ourselves, is what matters!


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