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Old 11-29-2016, 04:19 PM   #21
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Poor "RockinRush" Chad you will get a whole show dedicated to your woes.....
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Old 11-29-2016, 04:22 PM   #22
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Da bad chad
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Old 11-29-2016, 07:57 PM   #23
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Quote:
Originally Posted by HELI_FUN View Post
"pack of 10 at Storables for $5.99"



Walmart special?


http://www.storables.com/small-shoe-...ack-of-10.html

Storables is an actual store online and locally. I got a good deal now that I see them at $18 for 10...must have been Black Friday sale.
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Old 11-29-2016, 08:06 PM   #24
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Quote:
Originally Posted by Michaelinpr View Post
Justin? Can you make a post when you have time about how you use your drill press to calculate actual motor Kv? I am very interested to know how to do this.


Yep! I'll do a tech tip for you. I think I can do that one relatively quickly...
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Old 11-29-2016, 08:16 PM   #25
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Quote:
Originally Posted by Justin Pucci View Post
http://www.storables.com/small-shoe-...ack-of-10.html

Storables is an actual store online and locally. I got a good deal now that I see them at $18 for 10...must have been Black Friday sale.
oh sorry didn't catch that it was a site.
walmart has something like that too. 30 for $25 but out of stock right now

https://www.walmart.com/ip/Sterilite...-Unit/44787644

also interested in how to calculate actual motor Kv tech tip, cant wait
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Old 11-29-2016, 08:32 PM   #26
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Quote:
Originally Posted by Justin Pucci View Post
Yep! I'll do a tech tip for you. I think I can do that one relatively quickly...
Thanks. Rob, KiloXray, sent me the steps to do it. But I am sure there are many people that will want to try this.
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Old 11-29-2016, 11:14 PM   #27
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Quote:
Originally Posted by DUCDOC View Post
Poor "RockinRush" Chad you will get a whole show dedicated to your woes.....
Hey! I am completely open to it being my fault if I'm doing something wrong! I can't see what that could possibly be but I'm open to it. My wiring is pristine, have had chaffing back when but those were always easy fixes and never caused a servo to go out. Since thise 2.times i sand all edges and cover them in CA so theres no way off it chaffing. I've only had a gear failure once. Almost every time its something related to the board and and a solder joint. Over volt?.... i dont know? How can that happen? I always run a 2s lipo, never a bec. The servos are designed to run on everything a 2s can put out. Majority of failures have been on Nitroooooooooo! Because thats how I roll. However, its been on both electric and Nitrooooooooooo! List of failures ( or atleast thats what il call them ) : servo case screws not loctited so the case fell apart on second flight, multiple times wires came unsoldered from board, motor unsoldered from board, cap unsoldered from board, tail wag and found servo acting up and then just quit, servo just started spinning and found tiny gear on motor rounded off just enough to not grab. Most of all..... dudes..... i specifically pointed out lubing shafts out of nowhere and not a single one of you caught it!!! Hahahaha. My favorite episode by far. I can listen to " All about lube " over and over and die laughing every damn time.

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Old 11-30-2016, 10:48 AM   #28
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Here's a quick write-up that I've given others in the past who have contacted me individually on the motor kv method:

1. Put the motor on a drill or drill press.

2. Spin it up to whatever speed your drill is capable of.

3. With a hand held digital multimeter, first measure the ac rms voltage read between any two phases of the motor. Write it down.

4. With the same DMM, measure the frequency between any two phases and write it down.


5. Calculate peak voltage by multiplying the RMS value you wrote down by 1.343. Record this as Vp.

6. Calculate your speed in rpm by multiplying the frequency you wrote down by 120 and then dividing that number by the number of motor poles (usually 8, 10, or 14).

7. Divide your rpm by your peak voltage to get Kv in rpm/V.

I use a 3000rpm drill press and get very consisted numbers. I do it for every motor I own before I put them in a heli and keep it all in a database. Don't be surprised if you see as much as a +/-5% variation from the nameplate value.

Also, there's a lot of theory embedded in those numbers, but rather than giving you the derivation, I just combined it all into simple constant values. We'll leave the deeper details to the formal tech tip if anyone is interested...

Enjoy!
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Old 11-30-2016, 10:54 AM   #29
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Awesome Justin, thanks for that! I would be interested in the theory also 👍
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Old 11-30-2016, 11:33 AM   #30
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Quote:
Originally Posted by ChadCarlin View Post
Hey! I am completely open to it being my fault if I'm doing something wrong! I can't see what that could possibly be but I'm open to it. My wiring is pristine, have had chaffing back when but those were always easy fixes and never caused a servo to go out. Since thise 2.times i sand all edges and cover them in CA so theres no way off it chaffing. I've only had a gear failure once. Almost every time its something related to the board and and a solder joint. Over volt?.... i dont know? How can that happen? I always run a 2s lipo, never a bec. The servos are designed to run on everything a 2s can put out. Majority of failures have been on Nitroooooooooo! Because thats how I roll. However, its been on both electric and Nitrooooooooooo! List of failures ( or atleast thats what il call them ) : servo case screws not loctited so the case fell apart on second flight, multiple times wires came unsoldered from board, motor unsoldered from board, cap unsoldered from board, tail wag and found servo acting up and then just quit, servo just started spinning and found tiny gear on motor rounded off just enough to not grab. Most of all..... dudes..... i specifically pointed out lubing shafts out of nowhere and not a single one of you caught it!!! Hahahaha. My favorite episode by far. I can listen to " All about lube " over and over and die laughing every damn time.

Sent from my SM-N910V using Tapatalk

Only failure for me so far was with a lead coming unsoldered from the board on a voltage step down for my Throttle servo. 1 full tank of WFO Throttle which was a funtask of trying to keep the headspeed down to a comfortable level.
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Old 11-30-2016, 11:59 AM   #31
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I had a servo come with the motor not soldered to the PCB. Failed in hover on the 5th flight or so. Took it apart, soldered it back on, worked fine, but I never trusted it. Sold it a while later. That same servo had a defect on the gear, basically was missing one tooth. It was not crashed and had been there, presumably, since I got it. The missing tooth was in a spot that never actually came into contact with another gear... it was one on the output shaft gear.

That servo happened to be from the same brand that Chad has had issues with.
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Old 11-30-2016, 12:31 PM   #32
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Anyone else interested to see how the Graupner system works out for Saje?

I've been interested in Graupner since they hit the states...seems like really good value and good quality as well. Plus built in telemetry to virtually everything they make is a bonus.
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Old 11-30-2016, 01:59 PM   #33
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Default Measuring motor kV

Thanks, Justin! A cool and interesting technique.

One question - How do you verify the RPM of your drill? There is probably a good answer, but I can't think of it. Optical tach maybe? Or are quality drills accurate enough to use the printed value?

I have done this with a CC ESC by simply spinning a motor with no load and then using the logged values for RPM and voltage. It definitely showed me that I had a big delta from the name plate on a couple of motors. I wonder if using the logs from VBar control flight analyzer would work as well.

DC is fascinating, and I don't know enough about it yet. So, what are the pros and cons of using a drill vs. ESC? Which would be more accurate? Is there a circular logic problem with using the ESC to measure?

Or should I wait for the tech tip.
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Old 11-30-2016, 03:12 PM   #34
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Quote:
Originally Posted by K2Freak View Post
Thanks, Justin! A cool and interesting technique.

One question - How do you verify the RPM of your drill? There is probably a good answer, but I can't think of it. Optical tach maybe? Or are quality drills accurate enough to use the printed value?

I have done this with a CC ESC by simply spinning a motor with no load and then using the logged values for RPM and voltage. It definitely showed me that I had a big delta from the name plate on a couple of motors. I wonder if using the logs from VBar control flight analyzer would work as well.

DC is fascinating, and I don't know enough about it yet. So, what are the pros and cons of using a drill vs. ESC? Which would be more accurate? Is there a circular logic problem with using the ESC to measure?

Or should I wait for the tech tip.

Good questions!

1. The beauty of this method is that you don't need to know how fast you drill is going...the multimeter and some simple math with tell you.

Measuring the frequency of the voltage waveform across any two phases tells you the so-called magnetic frequency at which the motor is moving in Hertz (rotations per second). Multiplying that by 60 gives you RPM. Then, dividing that by half of your motor's pole count gives you the rotor rotational speed in RPM. The 1/2 factor in the magnet pole count in the denominator causes the 60 to be multiplied by 2, which gives the 120 factor I mentioned in the method above.

The faster you can spin the motor with your drill, the more accurate the measurement because the voltage you'll read is directly proportional to the RPM it's moving (via the Kv) and the measurement error on your multimeter will then become a smaller proportion of the overall measurement.

2. ESC versus Drill: It all depends on what your objective is...

ESC's all do PWM drive slightly differently, so the effective Kv of a motor will depend on the ESC to which it's paired. If all you use is one brand of ESC, then it's fine to do it that way.

I use multiple brands of ESC, so I'm not so concerned about the specifics as I am about getting a universal measurement that can be compared across platforms and with others.

For example, if you and I want to compare motors, we can't do so consistently if we're comparing between methods or ESC's. Neither are more/less accurate per se...just depends on the telemetry accuracy of the ESC versus the multimeter.

Does that help?
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Old 11-30-2016, 03:27 PM   #35
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Quote:
Originally Posted by Justin Pucci View Post
2. ESC versus Drill: It all depends on what your objective is...

ESC's all do PWM drive slightly differently, so the effective Kv of a motor will depend on the ESC to which it's paired. If all you use is one brand of ESC, then it's fine to do it that way.

I use multiple brands of ESC, so I'm not so concerned about the specifics as I am about getting a universal measurement that can be compared across platforms and with others.

For example, if you and I want to compare motors, we can't do so consistently if we're comparing between methods or ESC's. Neither are more/less accurate per se...just depends on the telemetry accuracy of the ESC versus the multimeter.

Does that help?

Also, it bears mentioning on the ESC method, the telemetry that you're getting for voltage is not clearly described to be the peak or the RMS. Maybe it is, maybe it isn't, but if you don't know, then you don't know what math to do to get your kv calculated correctly.
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Old 11-30-2016, 03:38 PM   #36
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Thanks!.

That's exactly what I was wondering - you have cancelled out the rpm of the drill by measuring frequency. Perfect. Wish I'd figured that out myself.

Yeah, in the motor rewind forum kv values are often given with ESC pairings, so I guess I was wondering whether an ESC is really "objective," or if you get a specific result due to the operation of the device. Sounds like it's at least partially the later...

Good stuff. Thanks again...
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Old 11-30-2016, 03:55 PM   #37
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Yes, the ESC measurements are objective relative to that model of ESC as long as you're doing the correct math.
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Old 11-30-2016, 06:21 PM   #38
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"Anyone else interested to see how the Graupner system works out for Saje?
I've been interested in Graupner since they hit the states...seems like really good value and good quality as well. Plus built in telemetry to virtually everything they make is a bonus."

Yes i've been flying Graupner or several months now. Using the ESC telemetry for a "Fuel Gauge" also flew their gyro receivers too. Just recently got my hands on another 3DIGI. Looking forward to hearing his experiences and findings.

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Old 12-01-2016, 02:52 PM   #39
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Oh my gosh. I'm currently listening to the episode and I almost pee'd myself laughing at the Align translations
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Old 12-01-2016, 03:03 PM   #40
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the helicopter has more excellent stability Sex and manipulation.

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