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Old Dec 04, 2011, 09:48 PM
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vienquach's Avatar
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I think I will give the 2815 a try. It should have more than enough power, IMO.
You had it for such a good deal .

Vien
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Old Dec 04, 2011, 10:03 PM
They Call him Dead!
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United States, SC, Pawleys Island
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Yes, I did. Remember that my version was a custom wind! That will be required to swing the big prop.
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Old Dec 04, 2011, 10:26 PM
c/f
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There is a major differance of how the various meters and recorders get their info, some are raw from battery side while others are at differant pickup points within the circuitry.

Heres a thing that makes me go Hmmm, why is it some feel the ESC 3 legs to motor, need to match in gauge that of the ESC battery gauge wire?Hmm

Reality is the 3 legs see half that of the battery legs. Hmmm......
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Old Dec 05, 2011, 01:15 PM
Not as Good as The Kid
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South Pasadena, FL
Joined Sep 2009
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Here’s the data from Saturday. It is important to remember that the Thrust data was measured using a digital scale that is not accurately calibrated, but from a statistical perspective, it can be accepted that the values are relative in comparison.

For all graphs other than the Efficiency graph, RPMs are illustrated along the x-axis. Before I use some of the Excel tools to prepare a linear extrapolation, I would rather represent the real values first in order to open the raw findings up to independent examination to those who wish to participate or prepare their own analysis. We welcome all valid comments and interpretations.

Now that Frank, Tom, and I, have established a standard operating procedure for this type of field data collection, I intend to re-take the 14x7 Xoar and APC comparisons for the 48 inch EXP, on the Motrolfly 2820-750 (683Kv) and I will do a 12x6 comparison on the Torque 820kv motor as soon as I can.

The one final part of this analysis is the subjective pilot reporting from Tom, and videos. Although Tom is flying in the wind, I prefer to not have it influencing the visual comparisons.

Amps
Volts
Watts
Thrust
Efficiency
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Old Dec 05, 2011, 01:22 PM
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United States, NJ, Millville
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Quote:
Originally Posted by c/f View Post
There is a major differance of how the various meters and recorders get their info, some are raw from battery side while others are at differant pickup points within the circuitry.

Heres a thing that makes me go Hmmm, why is it some feel the ESC 3 legs to motor, need to match in gauge that of the ESC battery gauge wire?Hmm

Reality is the 3 legs see half that of the battery legs. Hmmm......

Maybe this is the cheapest option? Stock one wire size instead of two? Just a thought. You would think they are manufacturing more than one ESC so they would have various wire sizes anyway. But it does make i simpler.
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Old Dec 05, 2011, 01:35 PM
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When you say "lower RPM" in the graphs, I assume you mean relative to the other props, not a lower RPM in the graph as in 5100 vs. 7100. I thought by lower, you meant the lower RPM's (left) side of the graph, but I don't think this is true.
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Old Dec 05, 2011, 01:49 PM
VOLTS > AMPS
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This suggests that over 200 Watts of energy was diverted from kinetic energy to heat versus the Xoar results.

any ideas on why this happened?
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Old Dec 05, 2011, 02:04 PM
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United States, SC, Pawleys Island
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Very interesting to see that the Xoar seems to be the perfect prop. Even though it is the same 16 x 8 size as the APC it is much more efficient and produces way more thrust for way less amps. Using the Xoar Tom could get rid of his throttle end point adjustments and still keep using the same amount of amps he is currently using AND get way more thrust.

If I am missing something please let me know, but this is really amazing!
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Old Dec 05, 2011, 02:15 PM
Facts, Logic, 3D
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Originally Posted by dead View Post
...Xoar Tom could get rid of his throttle end point adjustments and still keep using the same amount of amps he is currently using AND get way more thrust.
I am currently and have been using the Xoar.

--Tom K.
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Old Dec 05, 2011, 02:55 PM
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Quote:
Originally Posted by Tom K. View Post
I am currently and have been using the Xoar.

--Tom K.
Are you using the Xoar with the throttle pulled back? I thought you were doing that with the APC? If you were using the APC, when did you switch?
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Old Dec 05, 2011, 03:19 PM
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I'd like to address all the questions so nothing slips through the cracks, so let's take this one at a time:

Quote:
Originally Posted by rborn View Post
When you say "lower RPM" in the graphs, I assume you mean relative to the other props, not a lower RPM in the graph as in 5100 vs. 7100. I thought by lower, you meant the lower RPM's (left) side of the graph, but I don't think this is true.
My reference to “Lower RPMs” was a comparison to where the other two props topped-out. The APC, at WOT (wide open throttle) was registering a lower RPM reading compared to the other two at WOT.

Quote:
Originally Posted by stgdz View Post
This suggests that over 200 Watts of energy was diverted from kinetic energy to heat versus the Xoar results. any ideas on why this happened?
I can speculate, from past experience, that when we see voltage sag that is significant in comparison to other props on the same power setup (motor, ESC, and battery), that the load resistance causes a higher current draw.

Since there is a finite amount of energy, and the conservation of energy concept is part of the process, if the energy is not going to kinetic energy and causing at least the same RPMs as the other props on the same power system, it must be going to some other form or energy. All of the other forms of energy, such as internal resistance, reverse voltage, magnetic field, etc, will add to either current or resistance, and the formula for Heat is (Current^2 x Resistance). Therefore, heat would be a good guess, but just a guess.
Quote:
Originally Posted by dead View Post
Using the Xoar Tom could get rid of his throttle end point adjustments and still keep using the same amount of amps he is currently using AND get way more thrust. If I am missing something please let me know, but this is really amazing!
Possible, but the endpoints were still programmed as not to damage the motor and the ESC. A good thing too, considering how the APC Amped-out so quickly. I don’t think we would consider the APC 16x8 for this power system ever again.
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Old Dec 05, 2011, 03:32 PM
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Sorry so taxing AP. I really appreciate all your work. I know it is a lot! But I do want to make the best of your findings. So to be clear, Tom WAS using the 16 x 8 APC with throttle settings a week or two ago right? He was pulling around 60 to 65 amps I believe right?

So, when you did this test, you performed it with the same throttle settings right? If so, did you do any testing of the Vox 16 x 6 with out the throttle settings so as to get a true WOT reading? That is the one I am most interested in. Again, I prefer to run a set up that does not require any throttle mod on the end points. In order to do this I need a system that will run at 60 to 70 amps wot and still operates efficiently.

If my above assumptions about your tests are correct, then I am guessing that I will be happier either with a Xoar 16 x 7 (not 16 x 6) or with one more turn on my motrofly so as to achieve lower KV. But it all depends on what a true WOT is for this set up. If the xoar is only pulling 62 static amps at the augmented WOT, then it would probably be safe to run it without the throttle settings to see what you get, no?

Thoughts? Again, thanks for all this work. I am riveted.....
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Old Dec 05, 2011, 03:44 PM
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leespaddock's Avatar
USA, WA, Redmond
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Quote:
Originally Posted by Aeroplayin View Post
Here’s the data from Saturday. It is important to remember that the Thrust data was measured using a digital scale that is not accurately calibrated, but from a statistical perspective, it can be accepted that the values are relative in comparison.

For all graphs other than the Efficiency graph, RPMs are illustrated along the x-axis. Before I use some of the Excel tools to prepare a linear extrapolation, I would rather represent the real values first in order to open the raw findings up to independent examination to those who wish to participate or prepare their own analysis. We welcome all valid comments and interpretations.

Now that Frank, Tom, and I, have established a standard operating procedure for this type of field data collection, I intend to re-take the 14x7 Xoar and APC comparisons for the 48 inch EXP, on the Motrolfly 2820-750 (683Kv) and I will do a 12x6 comparison on the Torque 820kv motor as soon as I can.

The one final part of this analysis is the subjective pilot reporting from Tom, and videos. Although Tom is flying in the wind, I prefer to not have it influencing the visual comparisons.

Amps
Volts
Watts
Thrust
Efficiency
Most Excellent work.

I was surprised at the siginificant amp draw on the APC, but that is why multiple independent tests are a necessity and can be so revealing. I can't help but wonder how a electric Xoar 16x7 would perform in this power system test and if it would yield the best prop performance. However how these puppies fly is the really important the question.

I can't wait to see the flight test results as that is where the proof really is in the puddin. Thank you again Tom, Frank and Jim for all your effort and for seeing this interesting test thru completion. I only wish I lived a bit closer so I could play right along side you.

To complement your stellar results, attached is my compiled test comparisons results for the APC vs Xoar (14x7 / 15x8 / 16x8) show down. Slightly different data but the end result is the same Xoar is the top prop at least on the bench.

System Constants Used in Test
Motor Torque 4016T-500 (Turns 16/ KV 500)
Battery Turnigy nano-tech 3300mah 6S 45~90C Lipo
ESC Airboss 80 Elite (80A)


Lee
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Old Dec 05, 2011, 03:50 PM
Facts, Logic, 3D
Tom K.'s Avatar
Florida
Joined Nov 2010
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Quote:
Originally Posted by dead View Post
So to be clear, Tom WAS using the 16 x 8 APC with throttle settings a week or two ago right? He was pulling around 60 to 65 amps I believe right?
No, I've been using the Xoar ever since the second or third flight. The APC was over amping too much (over 75) even with restrictions without adequate power, so I decided to go with the Xoar. The Xoar pulled better with slightly less restriction (still at 88%) and less amps at 60-65 amps.


--Tom K.
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Old Dec 05, 2011, 05:00 PM
They Call him Dead!
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Thanks Tom. Just trying to keep my facts straight.
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