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Timing Test
By Ken Myers
Orginally appeared in the August 2007 Ampeer
Modified for viewing on tablets and smart phones 08/10/2015
Newsletter of the Electric Flyers Only of Southeastern MI, USA
EFO Site

     For a long time now, the correct timing to use for brushless outrunner motors has been a problem because of all of the conflicting information available in both the print media (magazines & instruction sheets packed with ESCs) and the Internet.

     Advanced timing was used on some brushed motors for "Sparkless Commutation". On high performance brushed motors, like the Astro Flight cobalt FAI motors, timing was advanced for an application where high amperages were to be drawn for most of the time when the motor was on, and partial throttle was not going to be used. F5b and LMR (limited motor run events) were two common aircraft applications, while car and boat drag racing were another. Advanced timing was used in these high amperage applications because as the power increased beyond a certain point, trailing edge "fire" appeared along the trailing edge of the brush and caused burning on the trailing edge of the commutator. This "fire" caused the positive brush to wear twice as fast as the negative brush.

     According to Bob Boucher in his Electric Motor Handbook Chapter 3 "Timing for Sparkless Commutation", "Over advancing motors is commonly done in racing motors where maximum power and maximum speed are all important. Over advancing a sport motor will cause excessive heating and failure if the motor is run at half throttle or less. Don't over advance the motor in a sport model where you intend to fly at half power much of the time."
     Please carefully read and think about those three very important sentences!

     With brushless motors, all of the commutation, including the timing, is done in the electronic speed control (ESC) not the motor. The brushless ESC manufacturers SHOULD be the ones to know how to best use their products with different types of motors, but...

     Castle Creations appears to have no information on their Web site about timing, other than what is in the instruction manuals for each brushless controller. Here is what is in the manual today for the Phoenix-45. (It wasn't always this recommendation!).

     Carefully read the last sentence in the Low Advance section.

     The FAQ (frequently asked questions) on the Castle Creation site contains no information about timing. It is actually hidden here under Special Note on Timing Advance.

     The following is my edited version of the paragraphs that Castle Creations has on the Web page noted above.

"Special Note on Timing Advance:
Timing advance in brushless is controlled within the ESC itself instead of rotating the endbell on a brushed motor.

What you'll find when you experiment with timing advance settings, is that going up or down from the normal setting will cause two reactions. With each step down from normal, your motor temp will go down and the top speed will go down about the same as dropping a tooth on the pinion. Going up, it's just the opposite - it's like adding a pinion tooth, but the motor temp will go up. (Obviously aimed at the car guys. KM)

Over time with testing, we've found it's best to use a lower setting in order to keep motor temps in check, especially with very, very fast setups.

Higher advance makes the motor run hotter, and the higher the Kv of the motor, the hotter it will get! Too high of an advance setting will give the same results as too much advance on a brushed motor - you will actually LOSE power and speed while the motor cooks itself!"

     It would be really nice if Castle Creations added a FAQ about the effects of timing on inner-runner and outrunner motors, high and low Kv, winds and types of motors.

     Here is a link to some timing information for a Hacker ESC.

     Note that the Timing Mode 1 is most likely referring to the B Series inner runner Hacker brushless. You can see they are recommending 30-degrees on outrunners.

     And still another link to the Welgard 65-amp instructions in .pdf format.

A quick review is in order;
Castle Creations - low advance
Hacker reference - 30-deg
Welgard - 15-deg or maybe 30-deg

     Searching the Web will provide even more confusing information. Many times I've seen that outrunners should be timed with 30-deg advance, and equally as many times a 15-deg advance.
     So what is it? There was only one real way to answer that question, and that was a test.

     I still had my BP/TowerPro 3520-7 on the test stand, along with the Welgard 65-amp (now discontinued and replaced by the BP 60A Brushless ESC for only $24.95!).

     On Monday, June 25, 2007 I ran a series of tests to answer the following questions.
What happens to the Io when the timing is changed?
What happens to the Kv when the timing is changed?
What happens to the Rm when the timing is changed?
What happens to the current when the timing is changed?
What happens to the RPM when the timing is changed?
What is the best timing for me to use with a BP/TowerPro 3520-7 outrunner?

     The timings available on the Welgard 65A in degrees are 1/7/15/30. The temperature through the 5-hour testing period ranged from 84F to 90F, with the barometric pressure about 30.15 in. and humidity in the mid-40% range.

     The testing was done just inside of my garage at the garage door opening facing north, while the rear entry door of the garage was left open for some airflow. The battery for the prop testing was my 6S1P M1 A123 LiFePO4 pack from bigerc.com. It was used at ambient temperature and recharged after each round of testing, as described in the August 2007 Ampeer.

     Io, the no load current, has always been considered a constant, but is it?
10-cell Sanyo RC 1700 NiCad
1-deg Average: 12.808v, 1.76 amps, 7836 RPM
7-deg Average: 12.864v, 1.76 amps, 7908 RPM
15-deg Average: 12.946v, 1.88 amps, 8064 RPM
30-deg Average: 12.966v, 2.42 amps, 8568 RPM

4S1P Skyshark 4000mAh 10C Li-Po
1-deg Average: 16.122v, 2.00 amps, 9864 RPM
7-deg Average: 16.115v, 2.075 amps, 9900 RPM
15-deg Average: 16.145v, 2.125 amps, 10050 RPM
30-deg Average: 16.112v, 2.66 amps, 10584 RPM

     Io goes up with the timing advancement. This was NOT an unexpected result, as it also does with brushed motors when the timing is advanced! Conclusion, Io cannot be given for a brushless outrunner as part of the "motor" data as it is dependent on the ESC design and manufacturing and how the end user sets the timing.

     Please note that the real system power out is a very "iffy" calculation without a dyno. The number indicated here for system Power Out (Pout) is based on my best guess using my spreadsheet data and some prop data. Please don't assume that power system is as efficient as it appears here, but since the same type of calculation was used to figure the system Pout, the relative numbers will remain pretty much the same

APC 10x7E
1-deg Average: 18.242v, 22.32 amps, 10176 RPM, Pin 407, Pout 332, eff. 81.6%
7-deg Average: 18.280v, 23.20 amps, 10224 RPM, Pin 424, Pout 337, eff. 79.5%
15-deg Average: 18.242v, 23.74 amps, 10302 RPM, Pin 433, Pout 344, eff. 79.4%
30-deg Average: 17.898v, 27.02 amps, 10572 RPM, Pin 484, Pout 372, eff. 76.9%

APC 11x7E
1-deg Average: 17.936v, 29.00 amps, 9708 RPM, Pin 520, Pout 422, eff. 81.2%
7-deg Average: 17.916v, 29.18 amps, 9726 RPM, Pin 523, Pout 424, eff. 81.1%
15-deg Average: 17.906v, 30.06 amps, 9810 RPM, Pin 538, Pout 435, eff. 80.9%
30-deg Average: 17.488v, 33.58 amps, 9996 RPM, Pin 587, Pout 461, eff. 78.5%

APC 12x6E
1-deg Average: 17.824v, 31.80 amps, 9516 RPM, Pin 567, Pout 457, eff. 80.6%
7-deg Average: 17.796v, 31.80 amps, 9546 RPM, Pin 566, Pout 461, eff. 81.4%
15-deg Average: 17.746v, 32.86 amps, 9594 RPM, Pin 583, Pout 468, eff. 80.3%
30-deg Average: 17.256v, 35.92 amps, 9738 RPM, Pin 620, Pout 489, eff. 78.9%

APC 13x6.5E
1-deg Average: 17.376v, 39.96 amps, 8886 RPM, Pin 694, Pout 550, eff. 79.3%
7-deg Average: 17.230v, 40.18 amps, 8850 RPM, Pin 692, Pout 543, eff. 78.5%
15-deg Average: 17.238v, 40.98 amps, 8940 RPM, Pin 707, Pout 560, eff. 79.2%
30-deg Average: 16.444v, 43.96 amps, 8886 RPM, Pin 723, Pout 550, eff. 76.1%

     If Kv were a constant, then the highest voltage in with the lowest amp draw should produce the highest RPM, but actually, when the timing is advanced, the highest advance produces the highest RPM with the lowest input voltage; therefore the Kv must be relative and not absolute. Relative Kv is changing with the timing. Therefore, the Kv number given by a motor manufacture is a relative number and once again will be determined by the specific ESC and timing chosen by the end user.

     What happens to the Rm (apparent motor resistance)? Unlike a brushed motor, the brushless motor will not run without the ESC to do the commutation. Thus, the ESC is actually a part of the motor and any Rm number given by a motor manufacture is pretty useless as it is only one part of the actual brushless motor system.

     While the motor Kv can be derived using the drill press method, once the ESC is factored into the motor equation, everything changes. One way to find out how the Rm, which I now like to call the motor/ESC relative resistance (Rme) is affected by the relative Kv is to do a quick and dirty relative Kv calculation.

     Using the no load data from above, here are the quick and dirty relative Kv calculations. Note that these numbers are all slightly higher than the real Kv, but close enough for a comparison.
1-deg 7836 RPM /12.808v=611.8 relative Kv
1-deg 9864 RPM /16.122v=611.8 relative Kv
7-deg 7908 RPM /12.864v=614.7 relative Kv
7-deg 9900 RPM /16.115v=614.3 relative Kv
15-deg 8064 RPM /12.946v=622.9 relative Kv
15-deg 10050 RPM /16.145v=622.5 relative Kv
30-deg 8568 RPM /12.966v=660.8 relative Kv
30-deg 10584 RPM /16.112v=656.9 relative Kv

     Using the relative Kv the output volts can be estimated, and that voltage can be used to calculate the relative Rme using the voltage drop and amp draw for the various prop runs. When this is done, (I'm not showing it here, but I'll be happy to provide my spreadsheet to anyone interested) it can be seen that the relative Rme goes down as the amps go up within any timing setting and that the relative Rme also goes down as the timing is advanced.

     Since the simple and most used way to predicted brushed motor performance is based on the Io, Kv and Rm being constant, it is easy to see why those constants fail when predicting outrunner brushless performance.

     I have been advocating the use of Drive Calculator for predicting motor/battery/prop performance, because it is NOT based on Io, Kv and Rm being constants!

     Here is why I believe in the performance predictions of Drive Calculator. The following shows my measured data compared to the information output by Drive Calculator. Remember that Drive Calculator has to take into account all of the changing "constants" of the motor and ESC, as well as what is going on with the power supply, in this instance a 6S1P M1 pack and manipulate the prop data and arrive at a prediction. You be the judge. (avg is my actual measured average and DC indicates the Drive Calculator Prediction. The numbers are presented in this order; volts in, amps, RPM and Watts In)

     Low timing should provide the power and efficiency I want when I use this motor and help keep all parts of the power system quite "happy."

     Link to the FREE Drive Calculator program for the Windows, Mac and Linux operating systems.

To Reach Ken Myers, you can land mail to the address at the top of the page. My E-mail address is: KMyersEFO@theampeer.org