What makes cdrom motors different from commercial ones?

[FredericG]

The CastleCreation ECS's seem to have difficulties with cdrom motors, especially the newest software versions. I am wondering, what makes cdrom motors so different from commercial ones? Is it because they are handwound or is it the overall construction of these motors?

Do other esc brands also have more difficulties with cdrom motors?

Thanks,
Frederic

[jskrebs]

I have done a lot of work with CD rom motors and found very little problems with the CC ESC's. Could you be more specific on what issues you have experienced.

Jeff

[FredericG]

At ¼ throttle, there are short interruptions, hiccups. At higher throttle, the motor looses power, turns slower, makes a strange noise but consumption does not drop. I think this is sync loss. After retrograding to the oldest version, 1.021 I think, it works more or less but not very reliable. With two other, commercial motors, the esc works very well (with the different SW versions)

Other people are also complaining about it: http://www.rcgroups.com/forums/showthread.php?t=388646

So, it seems to be linked to cd-rom motors

Thanks,
Frederic

[jskrebs]

Wierd,

I have not had any of those problems, But I have not bought a new ESC for a year or so. All of mine worked fine right out of the bag. I even run 2 motors off of one ESC.

Do you see this with or without the prop? I can duplicate these symptoms by over propping.

Jeff

[Ward]

Is this a CDROM motor you've built yourself? Is it a 3-phase motor?

[FredericG]

I have not had any of those problems Do you know what SW version you have? Perhaps you have one of the older versions where it works. With the newer versions you hear a short (intentional) screeching noise when starting. This is because it uses low frequencies during the startup procedure.

Do you see this with or without the prop? No issues without prop.

Frederic

[FredericG]

Is this a CDROM motor you've built yourself? Is it a 3-phase motor? I do not know. It is a motor somebody at our club has built. He has some experience with it and several people at the club use motors he made. I did not have the opportunity to talk to him about it.
I presume he tested the motor and nothing is fundamentally wrong with it. On the other hand the esc has proved to work well with commercial motors. In addition other people are also reporting issues with CC and cdrom motors.

I have lots of questions like:
Is it difficult to wind a motor?
Is it easy to do something wrong so that the esc has problems with it?
Or is the construction of a cdrom motor such that it is harder for an esc to keep in sync with it (weaker magnets for example?)
?)
Do you expect an esc should use another algorithm for a cdrom motor than for a regular outrunner?

Thanks,
Frederic

[ecologito]

Is this a CDROM motor you've built yourself? Is it a 3-phase motor?

For what I know all CD rom motors (brushless) are 3-phase motors. That is why for a brushless use your stators must have an arm number multiple of 3.

[E-Challenged]

Make sure that your wire connections to from the speed control to motor are good ( low resistance) and that one or more of the solid strand stator wires is not cracked inside the shrink tubing. A poor connection or broken wire is often mistaken for an esc problem.

[Ward]

For what I know all CD rom motors (brushless) are 3-phase motors. That is why for a brushless use your stators must have an arm number multiple of 3.

I thought I had read somewhere that some CDROM stators had odd numbers, like 7 or 11 arms. I figured it was worth a shot at least.

[ki0qm]

The PHX controllers had issues with some of the lower KV motors. This had nothing to do with homebrew or commercially made. They provided some firmware updates to the ESCs (either via mail in or PHX-Link) that fixed the issues. I believe the fix was to allow selectable switching frequencies.

[shadow sst]

with my experience, winding cd rom and go brushless motors. when you over prop cc speed controls
tend to loose phase when at hi speed. go down in dia. or pitch.

[Phlygaren]

Is the shaft fixed properly? So can and shaft rotate at the same rpm? It happened to me when testing a floppymotor, at higher revs rpm drops, the shaft was not fixed properly. The ESC can handle motors if they are correctly built. My floppymotor is a little bit stronger than Nippy 080898 and about the same Amps.
jskrebs, that was interesting with two motors on one ESC. Are they homemade? I tried to build two exactly the same but it did not work with them on the same ESC.//K

[FredericG]

Is the shaft fixed properly? I had a close look at and I think this cannot be the problem...

when you over prop cc speed controls Well, perhaps I am abit overpropping. According to guy who built it, I should consume around 8A with a 7x3.5 prop. This prop was not available at the shop; a 6x5 consumes 10A and a 8x4 clipped down to a 7x4 consumes 10A. Perhaps the kv is a bit higher than anticipated.


What strikes me is that the motor performs better when cool and that misfires happen as I proceed with testing. Perhaps the connectors between ESC and motor are warming up?

Thanks,
Frederic

[jbatch]

See Post #11: "The PHX controllers had issues with some of the lower KV motors. This had nothing to do with homebrew or commercially made. They provided some firmware updates to the ESCs (either via mail in or PHX-Link) that fixed the issues. I believe the fix was to allow selectable switching frequencies."

Bingo!!!

I had exactly the same screeching, like dry bearings screaming out for oil, traced
problem to updated CC PHX software. Tried reloading earlier version into ESC and
fiddled with parameters. Trouble disappeared and motors ran smoothly thereafter.

[HarleyDog]

I had similar problems with my first CD rom motors. I found that the CC-10 seamed to work better with them when the timing was set to advanced.
The A-10 and A-12 does not seam to suffer from those problems and I have found the I can usually start a bigger prop with that esc. However if your having problems with the motor starting with the CC-10 and going to full throttle ,than you are pushing the prop size already.
I have also found that the battery has allot to do with it. My e-tec 1000 and 1250's and will not hold up the voltage above 10 volts at full throttle even though they are within there load capacity. My kokam 910 and Dualsky 1050's don't have any problem holding ten to eleven volts. So my first motors that would runs at a high kv would not run at full throttle or false start with the better battery's, and to big a prop.
The biggest help in my motors seemed to come from installing curved magnets. This lowered the amp draw and improved torque just enough to make the motors run really well with there maximum size prop. This particular motor in these pic's are built from a combination of parts from strong rc (http://www.strongrcmotors.com/) and slofly (http://slofly.com/cart/index.php?cPath=0_23&osCsid=f5515a8498b2abc62476033431094adf).
Total retail cost in parts for this motor not counting the motor mounts and prop saver, is $16.00. It takes me about an hour to assemble one.
I think that is big difference between manufactured motors and homemade is weight, cost and performance. I don't think manufactures want to take the chance to build them to run that hard and be that fragile. The stock can and no back plate is as light as it gets, but they don't take much abuse.

But for $16.00 , at 19 grams you get over 18 oz's of thrust. And by the way. The GWS 7x3.5 can not run faster than what this motor will spin on the down hill run! It makes a beautiful howling noise as it as the blade tips start to cavitate or stall , whatever there doing, but they won't spin faster.

[wjbite]

I just read an Application Note from Microchip about controlling brushless motors.
After reading it I am supprised that there aren't more problems with lots of combinations of motors and ESCs. We seldon buy motors and ESCs in matched pairs. It seems that a problem is expected for certain combinations that cause an RPM limitation. Exceeding that RPM limit imposed by a combination of motor perameters and ESC perameters causes a "loss of phase lock" for sensorless motors. Varying the PWM frequency is one adjustment to prevent loss of lock.
www.microchip.com AN857
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en012037

[FredericG]

Thank you all for your input so far.

I decided that it would useful to know the Kv of the motor. For that I need to know the speed of the motor under no load.
Without load at full throttle I see a sinus of 1.81 kHz on the scope. I am now wondering, what is the (fixed) factor between this frequency and the RPM of the motor? There are 9 coils and 12 magnets....

Thanks,
Frederic