Question about Motors
 

Hi, I am reading the booklet that came with my AXi motor and have some questions.


I would like a picture of a brushless outrunner motor that points out all the parts. I figure out what the 5 pole armature is. Thats where the windings are. But where is the commutator, and how does it work?

Also, it talks about using SMT technology? What is that, surface-mount-technology? I dont see any electronic components on the motors, so I am not sure what they mean by SMT???

Thanks,

Cyrus

RE: Question about Motors
 

Oh yeah, and they say you can adjust the timing. How do you adjust that on an e-motor??? I wonder if they could have possibly printed the information in a smaller font.....:eek: This is what you get for buying something made in the czeck republic......pffft......[&o]

RE: Question about Motors
 

Hello Cyrus-

It sounds like that brochure may be describing products other than brushless motors. A brushless motor does not contain any surface mount parts, nor does it contain a commutator. In a brushless motor, commutation is performed electronically by the speed controller.

The company that makes Axi motors, Model Motors Ltd., also makes speed controllers and brushed motors, so perhaps the brochure is referring to those products.

The outer, rotating part of a brushless outrunner motor is known variously as the can, rotor, bell, and perhaps other names. The magnets are affixed to the inside of the can.

The inner, non-rotating part with the wires wrapped on it is usually called the stator.

You can adjust the timing of a brushed motor, but for a brushless motor, the timing can be adjusted only with the speed controller, assuming the controller has adjustable timing.

- Jeff

RE: Question about Motors
 

I agree with jdetray, sounds like you read the ESC-manuals.
I have a lot of AXI`es, love them because you get a lot of motor for the money. Propably the most popular brand in Europe...

I also love other products made in Czechkia! Their high-end sailplanes are next to nothing, the best I have bought. And I have a dozen Czech sailplanes now, from 1,5 meter up to 6 meter VS.

The "timing" is set when you program the controller. Low timing on motors which have few poles, and higher timing on outrunners with a lot of poles.

RE: Question about Motors
 

Hmm, well, I just read their booklet that had all their products. Still dont like their instructions though, they suck. Who reads font 05? This isnt the 1800's anymore!

Anyways. Can you explain the timing some more?

Thanks!

Cyrus

RE: Question about Motors
 

On a brush type motor, the commutator in on the end of the armature. It's the copper bars where the brushes run on. SMT is surface mount technology in the speed controller, either brushed or brushless.

RE: Question about Motors
 

Hi Cyrus-

Timing in either a brushed or brushless motor refers to when the switching between windings occurs with respect to their angular position relative to the magnets. By energizing the windings when they are in the correct position relative to the magnets, you can optimize the operation of the motor. If the timing is off, the motor may operate inefficiently or in extreme cases, not operate at all.

Brushed motors are timed at the factory to operate best when rotating in one direction. If you operate the motor in the opposite direction, such as in a gearbox, you may get better performance if you re-time it. This is done by rotating the end bell. Some brushed motors even have markings on them to indicate where to set the end bell for best performance in either direction. "Better performance" typically shows up as lower current consumption for the same power out.

In a brushless motor, you change the timing via settings in the ESC.

That's about all I know. If I've said anything incorrect, I hope someone more knowledgeable will correct me.

- Jeff

RE: Question about Motors
 

Thanks, this is slowly making more sense. I finally got my ESC and AXI hooked up. Turned out nice I think.

Question for you all, my battery goes to my ESC and to the throttle as normal. Now, I do I need a futaba battery as well, or can I fly like this? What will happen when the battery cuts out when it gets low?

Also, How do I determine how many pole my Axi motor is? It's a 2814/10 motor. I counted what looked to be 12 coils inside through the holes, but I dont know if thats the same thing or not. I thought it would be like 10 or something, since its a /10 in its name?

BTW, the ESC is a jetti advance 30 plus, and the battery is a thunder power 2100mAH/7.4V. Do you think this battery is sufficient? The airplane is a flitron Quiet Storm

The airplane weighs 20-22 oz

RE: Question about Motors
 

As for needing another battery for your receiver (if I understood your question), no you don't need it, since the ESC usually provides power to the other components (receiver, servos) if it has a BEC (it reduces the battery's power down to 4.8v to 6.0v so it can power the receiver and stuff safely). And when you're battery gets low, you will notice your motor stopping or losing power, but the ESC reserves power for the receiver so you can still control your servos and hence glide the airplane for a safe landing.

With a Lipo battery, you want to be careful and make sure you don't fly too long and discharge it too much I believe 3.2v per cell is a "safe-safe" low voltage limit. Usually if your ESC is lipo compatible it should automatically detect and set the appropriate low voltage cuttoff setting for your 3 cell pack. Check your manual for details.

RE: Question about Motors
 

Hi slo,

Yes, I checked it and it said what you wrote. Actually, Thunder power recomends 3.3V per cell. It said to program my cutoff voltage at 6.6Volts, but my Jeti has auto-detection, so I cant even play arround with that setting.

Another question, what does "BEC" stand for, and what does it do.

Also, what does "OPTO" stand for, and what does it do?

Thanks,

Cyrus

RE: Question about Motors
 

BEC = Battery Eliminator Circuit. This is the portion of the ESC that routes and regulates power to your receiver and servos, so you can use a single battery in your plane. If your ESC has a BEC, you don't need a separate receiver battery.

OPTO = Optoelectronic. Circuits utilizing optoelectronics use light impulses instead of wires (or printed circuits) to make some connections. By eliminating the "hard-wired" connections, they reduce or eliminate some types of electrical interference.

- Jeff

RE: Question about Motors
 

Ahhh great thanks for the clarification Jeff!

I guess my Jeti has a BEC, although it is not very clearly stated. I thought they would put something like ESC w/BEC on the label or something, you know? :)

Cheers,

-Cyrus

RE: Question about Motors
 

It would be unusual if it did NOT have a BEC. Most ESCs intended for small planes have BECs.

- Jeff

RE: Question about Motors
 

Usually there are a BEC on the ESC`s if they are not the "Opto" type. These have not BEC.
The one thing to remember when using BEC is the max number of servoes it can handle. On 2S you get the most from the BEC, on 3S you get less and on 4S it often can`t be used at all.
Your motor could take as much as 40 Amp, but propably it is most efficient at max 30A.
You could use quite high timing on this. (15-25`)

Here is a table, very useful to select prop, but the language might be difficult for you: http://www.mft.nu/elmotortest/axi_2814-10.htm

RE: Question about Motors
 

Crap good looking out! I read that my ESC is made for 3 servos and my airplane uses 4! Why dident I realize that! You saved my butt Norway, thanks!! :D

RE: Question about Motors
 

Now to add some confusion.

Many flyers routinely exceed the recommended number of servos. The limiting factor is actually not the number of servos, it is the amount of current the servos require. You can often exceed the recommended number of servos by one with no problems.

You might be voiding the manufacturer's warranty if you do this, but it is being done by many flyers every day. I imagine the ESC manufacturers want to be conservative in their recommendations, and I don't blame them.

- Jeff

RE: Question about Motors
 

Another question, I just got the Jeti advanced programming card. It says I can change the Brake on or Brake off, what is this?

RE: Question about Motors
 

Cyrus,
The brake function is mainly for powered sailplanes, it stops the prop from windmilling so that it can fold, assuming you have a folding prop;), normally brake should be off. Also as to the number of servos that the ESC can handle is very much determined by the number of cells that you will be using with 2 cell lipo not much problem but if you go 3 cell watch out, the number of servos you can power goes down as the linear regulator that they use gets hotter as the voltage it has to drop increases, if your ESCs BEC won't cut it, a good choice is to add a separate BEC such as the ParkBEC http://www.dimensionengineering.com/ParkBEC.htm

Good luck,
Pete

RE: Question about Motors
 

Thanks for the info pete!

RE: Question about Motors
 

Hey Guyz,
k
I gota another one. This Castle Creasions ESC I have says you can change the frequency ie. 8Khz.....what do they mean by this??

Thanks!

RE: Question about Motors
 

Well, it's kinda complicated, but I'll do my best. The 8khz frequency is the operating frequency of the ESC. I believe that's how many times a second (8kHz = 8000 times a second) the ESC sends electrical pulses to the motor (or something happens that makes the motor work). Generally brushed mode ESC (like normal motors use) operate from 1kHz to 2kHz, which is lower than most brushless ESC. Basically the higher the kHz rating for the ESC, the more efficiently the power is used to drive the motor = usually more runtime, and I think somehow slightly lower motor temperatures.

RE: Question about Motors
 

Hi Cyrus,
Which Castle Creations controller do you have? most of the CC ESCs seem to have 11Khz as their lowest PMW switching rate, usually they recommend the default setting of 11Khz for most brushless motors, the higher settings are for higher inductance motors, damned if I know which ones they are:D. Good luck.
Pete

RE: Question about Motors
 

Hey, I gota another problem.

I have an axi 2814/10 motor, and a 2s Thunder power and a 30A Jeti turning a 10x4.5". When I spool up to full throttle, the motor quits on me. I am reviewing it with a medusa power pro analyizer and I have found that the reason is that the battery voltage keeps dipping below 3V/cell..... I tried using a 3s battery, and it still falls below 9V.......what does this thing need, a 5s? This is getting absurd. Too much current draw is NOT the issue.

RE: Question about Motors
 

Hi Cyrus-

What makes you think too much current draw is not the issue?

When battery voltage drops like that under load, it is because the battery can't maintain its voltage under the current load you are asking of it. You need a battery that can supply the required current without a large voltage drop. Either you need a battery with a higher C rating or one with a larger capacity (mAh).

How much current does your power system draw? What is the mAh and C rating of your battery packs?

- Jeff

RE: Question about Motors
 

My Power pro, (which is like labview), only see's a current of about 20 or so amps before the motor quits. The ESC can do up to 30A, so this should not happen. It is because the voltage dips below 3V/cell. 2s -2100mAh. 10x4.7e prop. It -should-be able to spin a 10x7, I dont know why it's not.