HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Nov 11, 2011, 10:08 AM
3D Hack
JC Spohr's Avatar
United States, IL, Glen Carbon
Joined Jul 2010
1,891 Posts
Quote:
Originally Posted by Aeroplayin View Post
Also, the mechanical formula tells us the amount of power in Watts it takes to turn a 15x8 propeller with a 1.08 pK 5,760 RPMs, which was the APC's RPM reading at half-throttle from Lee's data. So it takes 338 Watts to do this, while it takes 1,100 more Watts to go from 5,760 RPMs to 8,560. That's 338W to produce the first 5,760 RPMs and 1,100W to generate the remaining 2800 RPMs.

So for the APC prop, that's 17 RPMs per Watt for the first half of the throttle curve and 2.5 RPMs per Watt for part-2. When I have some time, I'll run the numbers for the rest of the prop samples from Lee's data so we can compare to the reproduced data that should be coming soon.
This is a darned interesting subject and it just keeps getting more and more interesting.

Thanks again for the effort and sharing.

JC

ps - I hope Tom is going easy on your test (and personal) budget.
JC Spohr is offline Find More Posts by JC Spohr
RCG Plus Member
Last edited by JC Spohr; Nov 11, 2011 at 02:49 PM. Reason: I type faster than I proof read
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 12, 2011, 11:07 PM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
6,457 Posts
I will say that we do have some very interesting data coming, and we will be posting it as soon as we do some confirmation on a few things that seem to be creating a trend. Frank (FrankJP), Tom K and I completed a 14x7e APC vs. Xoar 14x7 PJN test on the Motrolfly 2820-750 with the custom 630 wind in order to form another comparison where APC and Xoar prop sizes were the same between the two options.

The preliminary results show the same type of trends as Lee’s data, where the Xoar generated an increase in load and power in comparison to the APC at both half and full throttle settings. Here are some preliminary results for the 14x7 comparison.

At half-throttle setting, the Xoar generated:

19.6% more Amps
23.8% more Watts
7.5% more Thrust

At full throttle settings, the Xoar generated:

9.3% more Amps
8.1% more Watts
5.2% more Thrust

In comparison, Lee’s data comparing the two at half-throttle settings, for the 15x8 props, showed that the Xoar generated:

4.7% more Amps
5.6% more Watts
1.0% more Thrust

At full throttle setting, the Xoar generated:

6.4% more Amps
7.1% more Watts
9.7% more Thrust

More detailed results will be coming soon when we have a chance to complete and compile the 16x8 comparisons on the Motrolfly 4315-680. I will say that this motor is an animal and at half throttle, the 16x8 APC on the Motrolfly generated 644 Watts at 5790 RPMs and 6.3 pounds of thrust.

We can compare this to Lee's data where the Torque swinging a 15x8 APC generated 338 Watts at 5760 RPMs and 4.5 pounds of thrust. These are interesting results considering the half throttle settings for all six samples in Lee’s data generates about 23% of the WOT Amps and 68% of the WOT RPMs.

We would have finished out the WOT test if we did not run into ESC timing issues, which is an interesting story in itself. Again, I need to verify a few things by reproducing what we found out about timing, load, and RPMs before I say anything, but I think this may be helpful information to those of us that never experienced this before.
Aeroplayin is offline Find More Posts by Aeroplayin
RCG Plus Member
Reply With Quote
Old Nov 13, 2011, 12:13 AM
Registered User
vienquach's Avatar
Chicago, IL
Joined Nov 2009
2,998 Posts
Quote:
Originally Posted by dead View Post
Well, there is also proportionally more drag on the prop just like the drag on a car increases...right Vien?
I am not so sure about that. Although they are both drag, but there're differences here. The flow above the prop is attached whereas the flow behind the car is fully separated, and more.

Also, you need to consider the increased friction, heat, and wire resistance of the power system as temperature increases as well.

Vien
vienquach is online now Find More Posts by vienquach
Reply With Quote
Old Nov 13, 2011, 12:28 AM
Registered User
vienquach's Avatar
Chicago, IL
Joined Nov 2009
2,998 Posts
Quote:
Originally Posted by Aeroplayin View Post
Also, the mechanical formula tells us the amount of power in Watts it takes to turn a 15x8 propeller with a 1.08 pK 5,760 RPMs, which was the APC's RPM reading at half-throttle from Lee's data. So it takes 338 Watts to do this, while it takes 1,100 more Watts to go from 5,760 RPMs to 8,560. That's 338W to produce the first 5,760 RPMs and 1,100W to generate the remaining 2800 RPMs.

So for the APC prop, that's 17 RPMs per Watt for the first half of the throttle curve and 2.5 RPMs per Watt for part-2. When I have some time, I'll run the numbers for the rest of the prop samples from Lee's data so we can compare to the reproduced data that should be coming soon.
I prefer to have the thrust, watt, and RPM data for the whole throttle range instead of just 50% and WOT. Also, you need to consider prop stall (flow seperation) as well when you run close to WOT static.

From my own experience, the thrust / watt curve is very close to linear, so I need about 55% of max watt to get about 50% of max thrust. One professor at my school also did several static thrust measurements with expensive sensor and transducer also observed close to linear behavior of thrust vs. watt.

In your data, the relation is pretty much different from linear, well, you only have 2 data points. Would be much better if you have at least 5-6 data points to predict the relation.

338 W gives 5760 RPM ...

Vien
vienquach is online now Find More Posts by vienquach
Reply With Quote
Old Nov 13, 2011, 08:59 AM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
6,457 Posts
Quote:
Originally Posted by vienquach View Post
I prefer to have the thrust, watt, and RPM data for the whole throttle range instead of just 50% and WOT. Also, you need to consider prop stall (flow seperation) as well when you run close to WOT static.

From my own experience, the thrust / watt curve is very close to linear, so I need about 55% of max watt to get about 50% of max thrust. One professor at my school also did several static thrust measurements with expensive sensor and transducer also observed close to linear behavior of thrust vs. watt.

In your data, the relation is pretty much different from linear, well, you only have 2 data points. Would be much better if you have at least 5-6 data points to predict the relation.

338 W gives 5760 RPM ...

Vien
Remember two things about this data.... throttle is a setting and not a measure instance, as Lee’s readings may have come from, but the near-exact reading (5760 and 5790) were coincidental only, but speak volumes.

Second, my data is an ad hoc field collection as opposed to Lee's controlled system method. As you know, to complete this analysis, we wanted to take the subjectively observed comments from contributors, who were providing conflicting, or actually contradictory interpretations, and put the Xoar and APC props to the test in the field. The final information that I will provide is video evidence so that the reader can look at the data, and the hover-to-punch-out visual and come to their own conclusions.

Additionally, prop stall, or the pitch distortion, is something we cannot measure or observe, but can be (possibly) interpreted from the data.

Lee and I have both challenges everyone to contribute in a productive way, and if you feel there is contrary evidence, either measured or visual, here is the place to provide it. I'd love to see a near-linear curve from real-time data since it seems you have access to the tools to provide it. Unfortunately, the currently collected data "is what it is" unless Lee can run the numbers again at more data points, but for now, my data seems to support his non-linear performance.

The best I can do is have two other people there to observe the readings, so even if the tools are poorly calibrated, a relative relationship should be acceptable since I doubt three of us made a mistake reading and documenting the data.

We invite everyone’s contradicting data, or contradictory analysis, but I prefer that we don’t become dismissive about this data’s relevancy, or contradict it by referring to data collected by someone else for other purposes, as we cannot satisfy the need for trust and accuracy of everyone, or prepare results with tools that you feel are more accurate. I’m not challenging people to engage, but I do request it if someone fees there is significant cognitive dissonance in our findings.

So this begs the question… can you use the tools at your disposal to prepare a cure like this using these props, and these prop sizes, on these motors?
Aeroplayin is offline Find More Posts by Aeroplayin
RCG Plus Member
Reply With Quote
Old Nov 13, 2011, 11:49 AM
Registered User
vienquach's Avatar
Chicago, IL
Joined Nov 2009
2,998 Posts
We have scheduled for several thrust measurements in the wind tunnel under different flow conditions (static vs. non static, this should be interesting), but there are still many experiments to run before that one could be done.

I agree with you that the thrust vs. watt data is not linear, but more data points (if you have a chance to acquire them) would give us a much better analysis. Then we would know, relatively, when the prop starts to flex/stall.

For example, the APC produced 4660g of thrust consuming 1431W of power @ WOT --> that looks like the whole power system was really suffering in efficiency (3.26 g/W), although it was doing very good at 50% throttle setting (6.1 g/W). I am curious to see what happened in between those two points.

Vien
vienquach is online now Find More Posts by vienquach
Reply With Quote
Old Nov 13, 2011, 07:33 PM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
6,457 Posts
Quote:
Originally Posted by vienquach View Post
For example, the APC produced 4660g of thrust consuming 1431W of power @ WOT --> that looks like the whole power system was really suffering in efficiency (3.26 g/W), although it was doing very good at 50% throttle setting (6.1 g/W). I am curious to see what happened in between those two points.

Vien
We may be able to run additional throttle points for at least the Torque this week. I gave the props to Frank to try because he has a Torque setup on his 60 inch Extra. Let's see what happens this week. For now, we already have the situation where two people who never met each other, from as far away from each other as humanly possible in the lower 48, came up with results that say that the Xoar does indeed produce more Amps, Watts and Thrust at half and full throttle settings than the APC.

One interesting thing that happened today is that at least four of us at MCRC that own and fly Torque and Motrolfly motors on Extreme Flight Edge and Extra 48 and 60 inch EXP airframes are convinced from the visual tests that the Xoar is, hands down, producing more thrust and load than the APC at the 14x7, 15x8, and 16x8 sizes. We will continue to work on the video so that everyone can see what we are seeing, but that will have to wait for another week.

Another thing to consider is this: If we are generating 23% of the Amps and 68% of the total RPM's at half throttle in two separate test environments, then the probability of achieving a scenario where we have half the Amps and half the RPMs, or ever having a linear relationship between the two at any point setting, seems more and more remote.
Aeroplayin is offline Find More Posts by Aeroplayin
RCG Plus Member
Reply With Quote
Old Nov 13, 2011, 07:59 PM
Team Twisted!
cbriggs11's Avatar
United States, SC, Greenville
Joined Nov 2009
224 Posts
If any of u guys interested in getting a good deal on a power combo, I've got a 2814/820 torque and a 45 amp airboss esc for sale. Great condition maybe flown 20 times. $100 shipped. Pm me if u have any questions. Thanks
cbriggs11 is offline Find More Posts by cbriggs11
Reply With Quote
Old Nov 13, 2011, 09:34 PM
VOLTS > AMPS
stgdz's Avatar
United States, MN, Buffalo
Joined Jul 2011
3,866 Posts
AP, if you are producing more watts and amps the battery drain is higher correct?

Have you tried comparing flight times at all, I know you guys are kinda at a subjective thing with this. Its one of the things that always bugs me and makes me dig deeper when doing analysis, do I go faster and run out of gas but cover more ground in a shorter amount of time or do I pace myself and cover the same amount of ground but take a longer time.
stgdz is offline Find More Posts by stgdz
Reply With Quote
Old Nov 13, 2011, 10:24 PM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
6,457 Posts
Quote:
Originally Posted by stgdz View Post
AP, if you are producing more watts and amps the battery drain is higher correct?

Have you tried comparing flight times at all, I know you guys are kinda at a subjective thing with this. Its one of the things that always bugs me and makes me dig deeper when doing analysis, do I go faster and run out of gas but cover more ground in a shorter amount of time or do I pace myself and cover the same amount of ground but take a longer time.
We calculate flight time individually. Tom will fly the same plane with the same battery for a shorter period of time than I will. The current (Amps) you use is directly proportional to the flight time, so this is what we do...

Charge your battery
Set your timer for 2 minutes
Go fly normally for the full 2 minutes
Recharge your battery and read the mA that you returned to the battery before you disconnect the battery from the charger - most chargers will display this.
Take the mAh rating of your battery and multiply it by 0.8, so if you have a 3000mAh battery, then 0.8 x 3000 = 2400. This is 80% of capacity because you don't want to completely drain your battery.
Divide the mA you put back and divide 2400 by this number
Take that number and multiply by the 2 minutes to get your projected flight time

So if I flew for 2 minutes and put 800mA back into the 3000mAh battery, then 0.8 times 3000 is 2400, and 2400mAh divided by 800mA is 3.
3 time 2 minutes is a projected flight time of 6 minutes.

The safe thing to do is try flying for 5 minutes, and check the numbers. Also check the voltage after each test, and after all flights as the value should not be less than 3.7 volts per cell after the battery had a few minutes to recover after the flight.
Aeroplayin is offline Find More Posts by Aeroplayin
RCG Plus Member
Reply With Quote
Old Nov 14, 2011, 03:53 PM
Facts, Logic, 3D
Tom K.'s Avatar
Florida
Joined Nov 2010
3,582 Posts
Quote:
Originally Posted by Aeroplayin View Post
Charge your battery
Set your timer for 2 minutes
Go fly normally for the full 2 minutes
Recharge your battery and read the mA that you returned to the battery before you disconnect the battery from the charger - most chargers will display this.
Take the mAh rating of your battery and multiply it by 0.8, so if you have a 3000mAh battery, then 0.8 x 3000 = 2400. This is 80% of capacity because you don't want to completely drain your battery.
Divide the mA you put back and divide 2400 by this number
Take that number and multiply by the 2 minutes to get your projected flight time

So if I flew for 2 minutes and put 800mA back into the 3000mAh battery, then 0.8 times 3000 is 2400, and 2400mAh divided by 800mA is 3.
3 time 2 minutes is a projected flight time of 6 minutes.
Heyy... that's my line! Also, when you come down, check your voltage. If you have 3.7 volts per cell, that's borderline. Try and adjust your flightime (using 75% capacity instead of 80% mentioned above works best, I've found) so you land with about 3.75-3.8 volts per cell. This will extend battery life (life as in number of cycles).

--Tom K.
Tom K. is offline Find More Posts by Tom K.
RCG Plus Member
Latest blog entry: 12S on the 3DHS 74" Edge 540
Reply With Quote
Old Nov 14, 2011, 04:52 PM
Registered User
leespaddock's Avatar
USA, WA, Redmond
Joined Aug 2010
231 Posts
Propeller Pondery / Pitch & Dia Effects / Tweeks with one propeller brand

Just to demonstrate the effects of playing with the pitch and diameter of one propeller brand. This test keeps the propeller brand constant (Vox), the Lipo constant at 6s and changes with the C value (45/90C) and Mah (3300), but varies the prop pitch and diameter. Vox was chosen for demonstration only because I was able to obtain the broadest range of electric prop pitches and diameters.

The data/results are attached below. Again what becomes obvious is the fact that if you change the propeller parameters or pretty much any component in the power system for that matter it can significantly change the load and output of the system.

What is interesting at least with the VOX brand and this power set up (Torque 4016T-500 / Battery Turnigy nano-tech 3300mah 6S 45~90C Lipo / ESC Airboss 80 Elite (80A) is that the 15x7 provides more thrust than the 15x8 and it was more efficient doing so.

What can be learned from this experiment? Once you have selected a propeller brand of your liking, you may find some unexpected gains from experimenting with slight pitch or diameter changes.

Next is the my last bench test: a APC vs. Xoar bench test show down.
This data will complement Aeroplayin, Frank and Tom’s APC vs Xoar test results. I have tested both the 14x7 and 15x8 APC and Xoar. I am just waiting for the 16x8 to arrive to complete the test and post the results most likely by the end of November.

Lee
leespaddock is offline Find More Posts by leespaddock
Last edited by leespaddock; Dec 01, 2011 at 11:53 AM.
Reply With Quote
Old Nov 14, 2011, 05:41 PM
Registered User
USA, FL, Casselberry
Joined Jan 2010
107 Posts
Looking for help on an Airboss 80a esc.

I know the current model will run 6s. The one I have says "2s-5s Lipo" on the case. Does anyone know if I can manually set this older Airboss to 6s?

Thanks,
Dave
dave102269 is online now Find More Posts by dave102269
Reply With Quote
Old Nov 14, 2011, 05:58 PM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
6,457 Posts
Quote:
Originally Posted by leespaddock View Post
Just to demonstrate the effects of playing with the pitch and diameter of one propeller brand. This test keeps the propeller brand constant (Vox), the Lipo constant at 6s and changes with the C value (45/90C) and Mah (3300), but varies the prop pitch and diameter. Vox was chosen for demonstration only because I was able to obtain the broadest range of electric prop pitches and diameters.

Lee
Good stuff as always, Lee. Thanks. Frank has been hard at work with the props you sent and we should have some additional comparison sets available by the end of the week. I'm hoping to have the APC and Xoar video comparisons soon. I took a few this weekend of the 14x7 Xoar but it was a windy and the sky was too clear so once the plane cleared the horizon, there was no cloud reference to help illustrate the vertical velocity. We'll try again next weekend when we will have time to fly again.
Aeroplayin is offline Find More Posts by Aeroplayin
RCG Plus Member
Reply With Quote
Old Nov 14, 2011, 08:18 PM
TEAM EXTREME / HORIZON HOBBY
mxcop's Avatar
United States, NJ, Tuckerton
Joined Oct 2006
601 Posts
Quote:
Originally Posted by dave102269 View Post
Looking for help on an Airboss 80a esc.

I know the current model will run 6s. The one I have says "2s-5s Lipo" on the case. Does anyone know if I can manually set this older Airboss to 6s?

Thanks,
Dave
Call E.F. tomorrow and check, I don't know if the older Airboss 80's are good for 6s, but I do remeber hearing Chris saying something about Airboss controls being labeled wrong at one point too, play it safe and make the call. One thing I can say for sure is the BEC is better on the newer controls, they're all 6v now.

Lee
mxcop is offline Find More Posts by mxcop
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question RC kits for experimenting with flight control systems SubZer0 DIY Electronics 11 Oct 12, 2011 08:58 AM
Wanted left wing for extreme flight yellow and black 74 yak hondaboy92hatch Aircraft - Fuel - Airplanes (FS/W) 0 Sep 29, 2011 10:18 AM
Discussion Extreme power systems & Royal Evo 12 rbehrends Radios 5 Oct 11, 2007 05:55 PM
Discussion Battery for Logo 10 - Thunder Power "eXtreme" 5S 4600 or Flight Power 5S 3700? WeatherB Electric Heli Talk 6 Jan 25, 2007 10:29 PM