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Old May 28, 2012, 09:43 AM
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Originally Posted by jk671 View Post
I thought you arent supposed to go past half throttle with no load on the motor,
The motor will spin faster than it's supposed to!
Yes, indeed. Thing is this happens around half throttle.

Edit. Got me thinking though. The esc throttle end points may not be set correctly.
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Old May 28, 2012, 10:25 AM
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I don't think there should be any issue running a motor with no load to full throttle.
It can only run as fast as the voltage supplied, and design (windings/stators) allow. (a mathematical result). It can't magically run "double the speed" and explode or something. At the higher no load speed what is going to happen detrimental? There is no aspect of it (??), bar the higher speed that the bearings will run at, that can wear or explode etc.
It won't run to infinite RPM..... The bell (outrunner) won't disintegrate.... the magnets will not break out of the glue (as they are inside the bell anyway).
I test all my motors at max RPM for KV testing and nothing untowards has happened so far ever.

KV rating is what the motor will do under no load, with it given max drive (throttle/esc). So to get a KV rating you have to run it at max 'throttle' - "max throttle" means telling the ESC to drive it to the max it can.
But you would just do it in the short time frame required to get the reading, because you are of course still taking it physically (bearings) to higher levels than it will more typically run at.
Mind you, running slower under real use load is still just another form of stress for it. eg heavy load on bearings, but at lower speed - versus no load being faster bearing speed but with less bearing load.

And because under no load the motor will run faster than in any use under load, then the timing advance does need to be larger (higher setting) IF you want it to run at its optimal maximum RPM. eg To get it to run the fastest it can.
It still has to be the "right" advance setting, or as best you can get it to right, but it will be a higher advance value than for a lower RPM when under load.
So...
I haven't read anything about this aspect - the two possible aspects it presents - but if you set it for optimal advance (timing) under no load then it will run X amount faster than if you used the lower advance timing that suits the real world load use better. I would expect that means for a KV test to be of real use you would want to use the timing advance that you expect the loaded motor RPM region to run at. Otherwise your KV 'rating' will become distorted when you go back to the lower timing advance that is optimal for the loaded operation.
And this will likely be why so many people test motors and come up with "The KV is a fair way away from the stated specs". Or one person says "this KV" and another person finds it to be another KV. The testing situation is not done the same (or correctly). And also bound to be some other erroneous reasons in some reported test cases too.

To recap: You would want to check KV using the timing advance setting that you use for real loaded operation. That is if you wanted to be able to use that derived "KV rating" to be more accurate for any mathematical calculations you wanted to make in your setup.
BUT.... all in all I actually see the true KV rating as not overly important other than as the initial guide as to what the motors area of operation will ROUGHLY be - to help you choose which to acquire/buy. Because if you overload the motor (which almost everyone does!) then it is not going to achieve its KV rating anyway. So in the end all that matters is what it did in THAT setup case you put it into.
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Old May 28, 2012, 10:41 AM
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Peter,

yes, but maybe the bearings are only rated at rpms achieved under load.
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Old May 28, 2012, 10:43 AM
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As for the "Higher timing uses more Amps.... often for no real benefit" common thoughts....
That is not strictly true... but does often end up the case. Whilst no one really ever seems to know the true reason why it is the case (the people saying it).

If your timing is too low, then the motor will not run as fast as it could. Thus it will run X amount slower which of course alters thrust (fan RPM) and it will use X amount less current too. Plus it will therefore run cooler too. In a way this is a way to de-tune a motor and run more 'efficiently' - not truly more efficiently, but the end result will be lower power output and less current used, thus more flight time (with that lower thrust possible).

As you advance the timing it will increase RPM - until you advance "too far" and start to be detrimental to optimal operation, due to powering a stator too soon and thus opposing the just passing magnet pole. As you increase the RPM the current draw will rise of course.
So up to the optimal maximum advance (and thus RPM) you were gaining RPM (except there are some other factors in play too which don't make that simplistic outline totally true) and are using more current to achieve that. But after that optimal timing point you continue to draw more current, but X amount of it is being used for detrimental 'reverse drive' result. So of course you don't want to go that far in timing advance and waste power (current) for that useless and wasteful drive result.

But that is the reason why timing being too far advanced (high) uses more current, for more heat, and LOWER output anyway.

There is no real definitive information to tell the true best timing value for a particular motor and particular ESC (unless someone else tested it and reported that), so you just have to start at the lowest timing value and go through the timing steps, whilst testing the results. The aim being to plot out what Thrust (RPM) you get in that fan setup, for what Amps.... offset by what heat the motor had, and/or what the battery thought of your demands (lol), and you can choose what Timing suits your needs best.
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Old May 28, 2012, 10:51 AM
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For bearings....
They can't really tailor a narrow margin of accuracy. So they will pick a bearing with specs that are X amount tolerance over the expected usage area. Or, they might even pick bearings suited to the maximum RPM possibility too.
Seeing the bearing has to take a LOT more load in real use than at no load, it is likely that the bearings load ability means its RPM ability is way over the RPM the motor will even ever be capable of getting to anyway. We are not talking no load RPM being 100% more than loaded. A motor that 'should' do 50,000 rpm (for your used voltage supply) will usually be doing 40,000 rpm in a fan. (that can vary a lot case by case, but it is typical enough). eg Only 20% faster at no load.
So I expect that it is likely that bearings are no issue to no load maximum RPM at all anyway.
But I would still limit doing it to the shortest time you need to do it - which is pretty well only ever to test KV - so you aren't likely to ever do it again after testing that once anyway.
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Old May 28, 2012, 11:13 AM
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Quote:
Originally Posted by Tamjets View Post
Here is Parkzone Habu 7s 3300mAh TJ70 with CS rotor.

Sorry my camera out of focus.

http://www.youtube.com/watch?v=NzmADAPtXvA
hey what motor are you running?
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Old May 28, 2012, 11:58 AM
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Originally Posted by onefastxp View Post
hey what motor are you running?
That is E-flite BL32 2150kv motor.
This weeken my son put over 30 flights with his foam Habu. He love it with the upgrade I did for him.

Here is 6s BL 32 2150KV

TJ70 CS rotor (4 min 50 sec)
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Old May 28, 2012, 07:01 PM
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Quote:
Originally Posted by PeterVRC View Post
As for the "Higher timing uses more Amps.... often for no real benefit" common thoughts....
That is not strictly true... but does often end up the case. Whilst no one really ever seems to know the true reason why it is the case (the people saying it).
If your timing is too low, then the motor will not run as fast as it could. Thus it will run X amount slower which of course alters thrust (fan RPM) and it will use X amount less current too. Plus it will therefore run cooler too. In a way this is a way to de-tune a motor and run more 'efficiently' - not truly more efficiently, but the end result will be lower power output and less current used, thus more flight time (with that lower thrust possible).
Wrong, decreasing the timing will not decrease the RPM on every motor, and in the case of inrunners like HET with 6 pole magnet assemblies, increasing the timing will yield no increase in RPM at all, only an increase in amp draw. I know this from extensive bench testing over the past 6+ years. It has to do with the layout of the rotor, magnet gap, commutation frequency and how the ESC reads the back EM field of the running motor.

Slotted motors are pretty much all we deal with in daily rc life, these are high inductance motors and should be run on a low PWM frequency. Slotted inrunners like HET behave as I have described, and running them on "low" if you esc has 3 timing settings, or around 5-7 degrees yields the best balance.

However if you come across a slotless motor like the HYK1600 that we used years ago in the flyfly models, different rules apply. Its an ironless 2 pole inrunner and it benefits greatly in performance from a change in timing. It used to run at around 32K rpm in the Midifan, its commutation frequency calculates to 3.2Khz, well below the ESC's standard 8Khz and increasing the timing from low to high saw amp draw go from around 43 to around 53, and rpm climb from 27K to 32.5K.

If you calculate the commutation frequency of an HET motor running in the CS fan its around 9.9Khz so its over the 8Khz base setting of many standard ESC's and under the 12Khz of some others. A pattern emerges... A slightly higher commutation frequency wont be much concern but if it gets up around 2 times the PWM frequency then you will have timing issues. This is why "outrunner mode" was developed in ESC's, this mode will dynamically change PWM frequencies at high commutation frequencies, increasing outrunner torque at high rpm. Tradeoff is a lot of heat and you need plenty of headroom in the ESC.

If you increase the PWM frequency you will increase the temperature in your ESC, as PWM increases controller losses increase. You will see little/no benefit of increasing the PWM in slotted motors unless your commutation frequency is very high.
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Old May 28, 2012, 07:49 PM
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Well the basic theory of WHY the timing alters things stands.
Whether or not a particular motors have other factors altering the Timing result outcome, is why you need to test them to see. (I didn't cover PWM aspects at all).

You would also need to test the motor under no load to tell what timings could really do to it THEN. Just as a theory test of these things because other than that it is a useless thing to do, as your real use of the motor will be in-situ under load anyway and under load the change that Timing could be trying to make can be masked by other factors too then. eg The fields ARE building/collapsing sooner, but you don't see any end result as the load demands make either end of the timing change end up at the same result anyway.

Advancing Timing will try to make it rotate faster (until excess advance is reached)... it is just a matter of whether the design (D, Y winding, stator design, magnet/pole count etc) and those other factors occuring in real-time make the end result any use, or even worse.
Thus... you test. Starting from low timing....

Another problem in ESC's is that most only have "Low" & "High" timing, or 4 quite wide steps.Etc. So the only available steps can be one side too low and the next too high, compared to what the true optimal timing value would be.
So you basically end up with "Low timing is best for this motor" - say 1degree - when truly 4 degrees would be better, but the next value is 7 degree and that is already into detrimental advance levels. "Low" actually means nothing.... only of use to someone with that same ESC and then uses that "low" setting too.

Plus that motor and ESC in YOUR setup... whatever FAN and thus load and thus RPM end result.... means it will operate in a certain RPM area.... and if someone else's is away from that RPM area then the timing for their setup could be better at another step higher or lower. So test results are somewhat specific to all the factors around the exact case you tested.
Throw the same motor from a 5 blade to a 6 blade fan, and thus different load/rpm area, and another timing value could be better.

Even though there are plainly defined maths etc in all the factors of a motor and thus what it could/should theoretically do, there are so many factors and variables that it would be futile to try to use the maths, except as a very rough guide as to what to expect.... you just have to go and test it to truly work things out. Which is also why advancing timing may not end up with the higher RPM that it theoretically would do (even if it had not reached an excessive advance amount yet).
But the general, theoretical, based rule is that higher timing advance will drive the motor to higher RPM, until the advance is too far.

I haven't read anything about it, but I expect that ESC's and the "Timing advance value" is not the true advance value it uses anyway. eg When it says 1 degree, that is not the advance it will be using. I expect they use a base advance - whatever that is... a few degrees at least? - and the timing setting is what they will append to that base value.
So 1 degree, or 0 (if any list that), just means no extra advance is added.
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Old May 28, 2012, 08:15 PM
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Quote:
Originally Posted by Extreme_RC View Post

Slotted motors are pretty much all we deal with in daily rc life, these are high inductance motors and should be run on a low PWM frequency. Slotted inrunners like HET behave as I have described, and running them on "low" if you esc has 3 timing settings, or around 5-7 degrees yields the best balance.
So 5-7 degrees timing on HET motors works best with the CS-10 Fan?
I have my 2W25/CS-10 combo set at the recommended 18 degrees(18.75 actually).

And one more Question for you...
My test numbers below are averaging Lower Amps numbers(around 10 Amps lower) & Lower Watt numbers in 4S & 5S tests than the other guys ("ravikoth" & "ViperViper") running the 2W25/CS-10 combo here.
The only other variable is I'm using the E-Flight Delta V-15 Housing instead of the CS-70. Also using Extreme RC 3.17 Shaft adapter & tested without spinner.

Could the E-Flight Delta-V housing account for the lower numbers??? The E-Flight Staters have more pitch or curvature than the CS-70 housing so it seems it would be more Amp hungry, not less!

*Tested without Intake Lip, numbers actually went down a little when tested with Intake Lip!
4S, 42-45 Amps @ 692-716 Watts w/ a Zippy 2650mAh/45C & a G-Force 3300mAh/35C respectively.

5S, 56-58 Amps @ 1042-1091 Watts w/ a Turnigy 3300mAh/30C and a FlightMax 3000mAh/40C respectively.

6/S, 72 Amps @ 1627.4 Watts w/ a Turnigy 2650mAh/ 30-40C (I don't think I'll be running this motor on 6S!)

Test numbers with & without INTAKE LIP: http://www.rcgroups.com/forums/showt...21248&page=260
Link with Pics: http://www.rcgroups.com/forums/showp...postcount=3865

The test numbers above are with the 2W-25/CS-10/E-Flight Delta V-15 Housing combo with a Turnigy 100A K-Force ESC set at 18.75 timing (the closest setting, recommended timing is18) on my PVC EDF test stand.

I can't begin to tell you how SMOOTH this thing sounds, so quite & effortless!
Didn't get Thrust #'s my scale suddenly stopped working, will try to get it up and running then I'll post some numbers up.

Thanks,

-Rick
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Old May 28, 2012, 10:42 PM
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Quote:
Originally Posted by Tamjets View Post
That is E-flite BL32 2150kv motor.
This weeken my son put over 30 flights with his foam Habu. He love it with the upgrade I did for him.

Here is 6s BL 32 2150KV

http://www.youtube.com/watch?v=eBJnhrBZIoE
Tam, is this the 2150 motor and the CS rotor in your shroud?

Sick...sick sounding, very impressive

Also, on the timing and PWM discussion...I've noticed that if I play with timing or PWM to safe settings you can get a high frequency whistle out of the motor at low RPM similar to what TAM got on take off in this vid...that whistle at taxing and landing RPMs is very realistic IMHO..you'll be asked if it's an EDF

I believe there's a vid of a 70mm F86 with the whistle (what I'm calling it) upthread
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Old May 28, 2012, 11:06 PM
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Originally Posted by erh7771 View Post
Tam, is this the 2150 motor and the CS rotor in your shroud?

Sick...sick sounding, very impressive

Also, on the timing and PWM discussion...I've noticed that if I play with timing or PWM to safe settings you can get a high frequency whistle out of the motor at low RPM similar to what TAM got on take off in this vid...that whistle at taxing and landing RPMs is very realistic IMHO..you'll be asked if it's an EDF

I believe there's a vid of a 70mm F86 with the whistle (what I'm calling it) upthread
Yes it is.
It sound even better live and it was fast. The 7s make the foam Habu fly the like the bandit. Even Doug Anderson love it. He flew very fast turbine jet and this Habu with the CS rotor on 7s is awesome and rock solid.


Parkzone Habu TJ70 CS rotor (3 min 0 sec)
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Old May 29, 2012, 12:34 AM
crashing build's character.
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Originally Posted by Tamjets View Post
Yes it is.
It sound even better live and it was fast. The 7s make the foam Habu fly the like the bandit. Even Doug Anderson love it. He flew very fast turbine jet and this Habu with the CS rotor on 7s is awesome and rock solid.


http://www.youtube.com/watch?v=NzmADAPtXvA
have you rader the habu on 7s yet?
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Old May 29, 2012, 01:26 AM
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Originally Posted by onefastxp View Post
have you rader the habu on 7s yet?
Not yet. This first time on 7s to see how much the motor can take. So far so good. Next weeken we get some speed run with it and doppler the speed.
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Old May 29, 2012, 03:37 AM
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Originally Posted by RugFlyer View Post
4S, 42-45 Amps @ 692-716 Watts w/ a Zippy 2650mAh/45C & a G-Force 3300mAh/35C respectively.
Thanks,
-Rick
I cannot comment on what other people get when testing various combos, but looking at your numbers they are all peak and not really indicative of a fan that has been running for 10-15 seconds and has stabilised.

42A and 692W = 16.47v, now the pack is 16.8v fully charged so this figure is not useful, you need to list up volts and amps after its been running for 10-15 seconds at WOT.

Seeing a drop in amp draw with an intake lip is something I have never seen! I would expect to see low 40's amps without a lip and 55-58A or so with a lip, its what I see when I am bench testing and balancing a 4s unit.
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