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Old Oct 07, 2007, 12:43 PM
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Static thrust:RPM charts for APCE props?

Does anyone know of any charts for various sizes of APC electric props, showing Static Thrust produced throughout the RPM range?

This would be SO helpful when working out suitable power setups for new models.

(Don't understand why the prop manufacturers don't supply a chart like this on the packet for each prop they sell).
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Old Oct 07, 2007, 01:16 PM
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Quote:
Originally Posted by Flyer88
Does anyone know of any charts for various sizes of APC electric props, showing Static Thrust produced throughout the RPM range?

This would be SO helpful when working out suitable power setups for new models.

(Don't understand why the prop manufacturers don't supply a chart like this on the packet for each prop they sell).
Hi Flyer88,

Contact RC Groups member FliesLikeABeagle. He's written a free program that does exactly what you're looking for. It's called "WebOCalc" and most of the prop selections are in fact APC props with a sprinkling of GWS DD props as well.

You can reach him by clicking on my username. His address is listed on my blog page.

Chuck
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Old Oct 08, 2007, 04:31 PM
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Thanks Chuck
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Old Oct 08, 2007, 04:57 PM
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Or

http://brantuas.com/ezcalc/dma1.asp
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Old Oct 08, 2007, 05:37 PM
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This one might help also, although I use Brantuas more,

http://www.adamone.rchomepage.com/calc_motor.htm

Challenger413
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Old Oct 08, 2007, 06:21 PM
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Have a look at peakeff.com. It is probably the best site I have seen for comparing props for a given power setup.

Doug
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Old Oct 08, 2007, 06:53 PM
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Quote:
Originally Posted by Flyer88
Does anyone know of any charts for various sizes of APC electric props, showing Static Thrust produced throughout the RPM range?

This would be SO helpful when working out suitable power setups for new models.

(Don't understand why the prop manufacturers don't supply a chart like this on the packet for each prop they sell).
This is old stuff, but it will give you some idea. I will redo the graphs for all these using new data (I have it all in my Spreadsheet) when I get a chance.

Cheers, Phil

This program of Rod's does a pretty good job: http://www.badcock.net/cgi-bin/powertrain/propconst.cgi


as does our simple one: http://www.gobrushless.com/testing/t...calculator.php
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Old Oct 09, 2007, 01:39 AM
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I've been comparing some thrust values with different calculators and noticed that Rod Badcock's calculator follows Dr. Kiwi's charts, but their thrust values are much lower than those calculated by http://www.drivecalc.de/

For example, APC 7x5 at 7283 RPM, 50 meters altitude:
thrust 222.07g with http://www.gobrushless.com/testing/t...calculator.php.
thrust 228.5g with Rod Badcock's calculator http://www.badcock.net/cgi-bin/powertrain/propconst.cgi.
thrust 243g with www.drivecalc.de calculator.

Wonder which one is right…
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Old Oct 11, 2007, 04:16 AM
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Quote:
Originally Posted by funfly2
I've been comparing some thrust values with different calculators and noticed that Rod Badcock's calculator follows Dr. Kiwi's charts, but their thrust values are much lower than those calculated by http://www.drivecalc.de/

For example, APC 7x5 at 7283 RPM, 50 meters altitude:
thrust 222.07g with http://www.gobrushless.com/testing/t...calculator.php.
thrust 228.5g with Rod Badcock's calculator http://www.badcock.net/cgi-bin/powertrain/propconst.cgi.
thrust 243g with www.drivecalc.de calculator.

Wonder which one is right…
The difference between 222 and 243 grams is only 21 grams. On top of roughly 220 grams, that is a pretty small error - less than 10%.

Keep in mind that the variation in thrust you get from your model due to daily changes in temperature, humidity, state of battery charge, number of cycles on the battery, ESC timing advance, wear and tear on the prop, all add up to far more than 10%.

-Flieslikeabeagle
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Old Oct 11, 2007, 06:42 AM
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I think Rod used some of my early Tractor Stand data to generate his equations (as we did with the gobrushless calculator) - those thrust figures were perhaps 5% low for larger props, as much as 10% low with tiny props... that may be the answer! Morris M and Jay were working on an new version of the gobrushless, but I don't know what stage that is at.
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Old Oct 11, 2007, 12:05 PM
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Quote:
Originally Posted by Dr Kiwi
I think Rod used some of my early Tractor Stand data to generate his equations (as we did with the gobrushless calculator) - those thrust figures were perhaps 5% low for larger props, as much as 10% low with tiny props... that may be the answer! Morris M and Jay were working on an new version of the gobrushless, but I don't know what stage that is at.
A couple of years ago I was in contact with Rod, and at that time he was also using some of the Hyperion data (gathered mostly by Phil Maur, IIRC, and later used in Rod's E-meter software).

Dr. Kiwi, as a man who's done a lot of prop testing, how much variation do you find between two supposedly identical props (same manufacturer and nominal prop size), say two APC 9x7.5 "E" props?

-Flieslikeabeagle
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Old Oct 11, 2007, 12:18 PM
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Quote:
Originally Posted by flieslikeabeagl
The difference between 222 and 243 grams is only 21 grams. On top of roughly 220 grams, that is a pretty small error - less than 10%.

Keep in mind that the variation in thrust you get from your model due to daily changes in temperature, humidity, state of battery charge, number of cycles on the battery, ESC timing advance, wear and tear on the prop, all add up to far more than 10%.

-Flieslikeabeagle
I agree that 10% difference might not be a big deal, but what drew my attention was that the values shown on www.drivecalc.de calculator were always higher than those shown on http://www.badcock.net/.

But I guess that the answer is on Dr Kiwi's post:
Quote:
Originally Posted by Dr Kiwi
I think Rod used some of my early Tractor Stand data to generate his equations (as we did with the gobrushless calculator) - those thrust figures were perhaps 5% low for larger props, as much as 10% low with tiny props... that may be the answer! Morris M and Jay were working on an new version of the gobrushless, but I don't know what stage that is at.
I would greatly appreciate a link to Dr Kiwi's gathered data from static testing using his new Pusher Stand...
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Old Oct 11, 2007, 12:46 PM
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Originally Posted by funfly2
<snip>what drew my attention was that the values shown on www.drivecalc.de calculator were always higher than those shown on http://www.badcock.net/.
Now that you mention it, I wonder where Christian Persson got the prop thrust data he wrote into his program, Drivecalc?

-Flieslikeabeagle
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Old Oct 11, 2007, 01:44 PM
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Originally Posted by flieslikeabeagl
Now that you mention it, I wonder where Christian Persson got the prop thrust data he wrote into his program, Drivecalc?

-Flieslikeabeagle
See below:
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Old Oct 11, 2007, 05:00 PM
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Thanks for the screenshot.

I don't use Windows or Mac OS, so I've never seen Drivecalc run...the recently released Linux version had some problems on my Linux box.

-Flieslikeabeagle
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