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qban_flyer
11-21-2005, 08:50 AM
A friend of mine has a few 400XT outrunner motors, one he purchased from a private individual, the rest from Hobby Lobby.
I have eight of them so far, all of mine have been purchased from Hobby Lobby, six of which were purchased when they were on a $24.90 sale. Couldn't pass up on such a good deal :p.

The cogging effect on the one purchased from the private party is very strong, almost I.C. engine compression like, while the rest are rather smooth in their cogging action.

My E-Flite EFLA-1205 outrunner's cogging is similar to that of the motors purchased through Hobby Lobby. So are my two Himaxx. These motors were not connected to any ESCs when they were being so checked (felt?).

My question to you, motor gurus out there in E-Flight land is this: What causes some motors to have a different feel in their cogging? Is it the amount of magnets? Is it the spacing (gap) of magnets in relation to one another? Is it the windings? Is it the gap between the windings and the magnets? This enquiring mind would like to know why these motors behave this way.

I have e-mailed an electrical engineer friend of mine and hope he may have an answer for me regarding this issue, but i would also like to hear the opinions of many others here at Watt Flyer.

Thanks in advance for any and all opinions in this regard. :)

JustGoFly.com
11-21-2005, 05:19 PM
My question to you, motor gurus out there in E-Flight land is this: What causes some motors to have a different feel in their cogging?
A) Is it the amount of magnets?
B) Is it the spacing (gap) of magnets in relation to one another?
C) Is it the windings?
D) Is it the gap between the windings and the magnets? This enquiring mind would like to know why these motors behave this way.


A) Yes
B) Yes
C) No
D) Yes

and strength of the magnets and thickness of magnets, which will effect their strength.

But if your friend has a 400XT that is not the same as yours he's probably got one of the copy cats out there. Another manufacturer copied our line name, color and everything and didn't get the Kv dead on, but stated the same Kv as the copied motor. Not sure why they think that was the thing to do, but we're flattered.

Vinnie
JustGoFly.com

bz1mcr
11-21-2005, 08:33 PM
...

My question to you, motor gurus out there in E-Flight land is this:
What causes some motors to have a different feel in their cogging?
Is it the amount of magnets?
Is it the spacing (gap) of magnets in relation to one another?
Is it the windings?
Is it the gap between the windings and the magnets?

This enquiring mind would like to know why these motors behave this way.

I have e-mailed an electrical engineer friend of mine and hope he may have an answer for me regarding this issue, but i would also like to hear the opinions of many others here at Watt Flyer.

Thanks in advance for any and all opinions in this regard. :)

Yes, "the amount of magnets" effects the cogging. Stronger magnets increase cogging. Magnets can be stronger because of "N" rating or size.

Yes, magnet spacing is a factor. With 9 arm stators and 12 magnet poles, small variations in spaceing will reduce cogging. Precise magnet location will increase it. Also smaller spaces (wider magnets) and curved magnets increase cogging.

No, windings do not impact cogging.

Yes, well sort of: It is not the space between coil and magnet but the space between the stator tip and the magnets. Smaller space between the stator and magnet (commonly called the air gap) will increase cogging. That is also true of the other air gaps like the one between the magnets and can.


Now my turn to ask questions:
1) other things equal, is the cogging of a nine arm 12 magnet motor more, less, or about the same as a 12 arm 14 magnet motor?
2) Sticking with 9 arm 12 magnet pole motors, is stronger cogging always a good thing? Or said another way , Does the stronger cogging motor always perform the best?

qban_flyer
11-21-2005, 09:16 PM
But if your friend has a 400XT that is not the same as yours he's probably got one of the copy cats out there. Another manufacturer copied our line name, color and everything and didn't get the Kv dead on, but stated the same Kv as the copied motor. Not sure why they think that was the thing to do, but we're flattered.

Vinnie
JustGoFly.com

Hi Vinnie,

Thanks for your quick reply. Things now begin to make sense to me.

I always suspected his "other motor" was not a 400XT since it felt so different to the rest of them, though I could never have imagined or suspected there were copies of them out there!

He took the "odd one" and one of the H/Ls apart last night to see why wasn't it working. Part of his e-mail is found below, it's the reason I posted this question as I wanted to know for sure what was going on too.


I think I killed it!

What you may ask? The 400XT on my SS.

I cannot figure out what is broken. Everything looks good and seems to turn true.One other thing I noticed.

This one 400XT on my SS has yellow wire where the other three (H/L) have a blue wire.

Also, I took apart one of the other new motors so compare them to see if the one from the SS is damaged somehow. The stator in the others is thicker (that means more wire). So enquiring minds wanna know what's the deal.

Spooky.

Just need to figure out how to fix the crashed one.

The physical differences clearly supports what you have stated above Vinnie, he got himself a "copy" not an original 400XT. It also proves what I had suspected all along, they truly are different motors.

I do thank you for providing me with the answers I had about what makes these devices tick and why they gelt "different". I really appreciate it.

I also hope many people out there become aware of the shenanigan being perpetrated by unscrupulous individuals on unsuspecting buyers. Those claiming to be selling bogus merchandise as a legitimate one.

Do take care,

Bert (qban flyer) :)

qban_flyer
11-21-2005, 09:47 PM
Yes, "the amount of magnets" effects the cogging. Stronger magnets increase cogging. Magnets can be stronger because of "N" rating or size.

Yes, magnet spacing is a factor. With 9 arm stators and 12 magnet poles, small variations in spaceing will reduce cogging. Precise magnet location will increase it. Also smaller spaces (wider magnets) and curved magnets increase cogging.

No, windings do not impact cogging.

Yes, well sort of: It is not the space between coil and magnet but the space between the stator tip and the magnets. Smaller space between the stator and magnet (commonly called the air gap) will increase cogging. That is also true of the other air gaps like the one between the magnets and can.


Now my turn to ask questions:
1) other things equal, is the cogging of a nine arm 12 magnet motor more, less, or about the same as a 12 arm 14 magnet motor?
2) Sticking with 9 arm 12 magnet pole motors, is stronger cogging always a good thing? Or said another way , Does the stronger cogging motor always perform the best?

Hi Don,

Thanks for your reply too.

I haven't had a chance to compare the motors side by side so I have no clue as whether one has 12 or 14 magnets, though as you can see by the pasted text above that the stators are different on both motors that are "claimed" to be the same make and model.

The one obtained through a private individual has a much stiffer (for lack of a better term) cogging than the ones sold through Hobby Lobby. That's the one with the "thinner" stator meaning it has less wire as he explains it to me in his e-mail. There is also the wire color difference to consider. Different gauge?

Hopefully I will be able to inspect them side by side under a bright light source and a magnifying glass to check and see if there are other visible differences as well. Hope to do that before Saturday.

Thanks for your invaluable advice and two additional questions that I shall seek answers to. I know for a fact that the "odd one" behaved in a strange manner while under load (surging) while the rest have not. While the "odd one" made the WattMeter give out rather peculiar readings, the rest did not. The "odd one" has stronger cogging, does that make it better? I have no clue, that could turn out to be the $64K question.

While the rest of the motors spec out as expected, six amps WOT with a 7.4V T/P 900 mil Li-Pos, 1.5 amp at 50% throttle swinging a 10X3.8SF APC prop, and 9 amps with an 11.1V T/P pack spinning a 9X3.8SF APC propeller. The "odd one" sent the meter through the roof (current wise) with a 9.6V NIMH pack while spinning a 9X4.7SF APC prop. Voltage drop behavior as displayed on the Astro WattMeter was rather odd with that motor too! Not to mention the audible surging at WOT!

I find myself asking more questions just as I begin to get some answers, though as Vinnie states above, I can emphatically say that a copy may look like the real thing, but measurte and perform like one? Absolutely NOT!

Take care,

Bert (qban flyer) :)

ForestCam
11-21-2005, 10:34 PM
Does the stronger cogging motor always perform the best?

Definatly not. I have one of those Tower Pro BP-21 "can" outrunners and it's almost hard to turn by hand because of the "cogging", now my EP on the other hand is as smooth as a baby's butt and far out preforms the BP-21.

Twmaster
11-21-2005, 11:08 PM
Hi gang,

It's me with the motor issues. These two motors are obviously not the same. Practically everything on the oddball motor (purchased from a private seller on RCG) is different from the 3 identical motors purchased from Hobby-Lobby. I am beginning to suspect Vinnie is spot on. I saw his challenge to the fellow selling these other motors on RCU.

I just got in from work and will happily take detailed photos of both motoren (if anybody cares) later after I've had dinner and a short nap.

As for the motor I crashed I cannot figure out what is broken. Everything looks to be in good shape. The bell and shaft run true when placed in my drill press and spun at max rpm with a dial indicator against the bell and shaft. I am truely mystified. I have inspected the magnets, bearings, stator, you name it.

bz1mcr
11-22-2005, 12:33 AM
Mike, are we supposed to know something about the motor you crashed? I even did a search on your posts for the past week--- found nothing.

I would be glad to help, but you have to tell us something about what it does when you run it or try to. And what did you see when inspecting "the magnets, bearings, stator, you name it"

qban_flyer
11-22-2005, 12:43 AM
Mike, are we supposed to know something about the motor you crashed? I even did a search on your posts for the past week--- found nothing.

I would be glad to help, but you have to tell us something about what it does when you run it or try to. And what did you see when inspecting "the magnets, bearings, stator, you name it"

Hi Don,

As Mike has stated, he'll be photographing the innards of the motors later on this evening and posting them here.

You can't find any posts previous to mine since the motor stopped running late yesterday afternoon. I, myself am anxious to see the differences between them, so we'll see what if anything is wrong with the "odd" one. :o

qban_flyer
11-22-2005, 12:46 AM
Definatly not. I have one of those Tower Pro BP-21 "can" outrunners and it's almost hard to turn by hand because of the "cogging", now my EP on the other hand is as smooth as a baby's butt and far out preforms the BP-21.

I had a notion the ones with stronger (stiffer) cogging would not perform the same as the other ones since it measured so wierd under load and also had that "surging" problem.

Your post here convinces me of what I had suspected all along. More cogging won't make these motors as good much less better than the rest.

Thanks for sharing your experience with us.

Take care,

Bert

qban_flyer
11-22-2005, 12:49 AM
Hi gang,

It's me with the motor issues. These two motors are obviously not the same. Practically everything on the oddball motor (purchased from a private seller on RCG) is different from the 3 identical motors purchased from Hobby-Lobby. I am beginning to suspect Vinnie is spot on. I saw his challenge to the fellow selling these other motors on RCU.


Could you share the seller's name (or user ID) with us so that we won't make the same mistake? Or just e-mail it to me?

L8R

Twmaster
11-22-2005, 12:56 AM
Mike, are we supposed to know something about the motor you crashed? I even did a search on your posts for the past week--- found nothing.

This is because the motor was crashed yesterday. I am the fellow to whom Qban_flyer is referring in the original post to this thread. I was merely filling in a few details as to what I observed thus far. Vinnie brought up a point about knock off motors. Perhaps the situation I am in ATM will satisfy some curiousity on Vinnie (and my) parts. Additionally I'd like to determine what exactly is wrong with the motor and repair it if possible. Otherwise I don't understand -your- post.

I would be glad to help, but you have to tell us something about what it does when you run it or try to. And what did you see when inspecting "the magnets, bearings, stator, you name it"

Here is what happened, The plane impacted a building. The shaft of the motor was pushed back through the bell by about 2.5 to 3MM. I repressed the shaft back into it's original position. The repositioning of the shaft has had no effect on the issues described below.

What I found is nothing wrong. All bits spin freely (without bell), appear to be in place (although I do not have an identical motor to compare to). I am not willing to take a chance and smoke my speed control just yet. Basically what is happening is the motor now cogs very strongly. Almost as if it is binding or comming into contact with something. Visual inspection (with a magnifying glass too) reveals no scoring on either the magnets or stator which I would expect to see if coming in contact somehow, no fractured or misaligned magnets, the bearings run true and freely with a plain 3MM shaft inserted through the motor base.

When the bell from the H-L supplied motor is installed onto the base/stator of the 'questionable' motor the same very hard cogging is experienced.

Also as I said in my previous email all of the parts are different. However I will correct myself here. The ball bearings appear to be identical.

It seems we (I) am/are trying to solve two mysteries. :)

JustGoFly.com
11-22-2005, 01:21 AM
Could you share the seller's name (or user ID) with us so that we won't make the same mistake? Or just e-mail it to me?
L8R

Guys - it is NOT the sellers fault. There are dealers out there that don't know they are selling product that is copy cat. So please don't take it out on the poor guy who sold the motor. I'm sure the motor worked well - my point is you should measure the KV and not go based on the data you might find posted for 400XT motors.

Vinnie

JustGoFly.com
11-22-2005, 01:24 AM
Mike,

Check the bearing - you might have wrecked it which could be causing the harder turning. You're right not to try it with your ESC unless you measure the amp draw while running the motor. Your motor and ESC can handle short spikes so if you have an amp - measure the draw to see if anything is binding.

Vinnie

Twmaster
11-22-2005, 01:30 AM
OK, here are some comparative photos.

First photo is the packaging. The only difference I see here is the foam packing. Otherwise even the photo copied page from MTM is the same.

http://www.twmaster.com/motoren/motor014.JPG

Second photo shows the thickness of the stator. Motor in question on the left, SK400XT purchased from H-L on the right.

Although looking at this photo I see what looks like a separation of the plates of the stator. Hmmm.

http://www.twmaster.com/motoren/motor015.JPG

Third photo shows the top of the stator where it sits on the end of the base. Again, questionable motor on left, Genuine 400XT on right.

http://www.twmaster.com/motoren/motor016.JPG

Fourth photo shows the inside of the bells. Note the different color magnets. Same as above, ? on left, 400XT on right.

http://www.twmaster.com/motoren/motor017.JPG

Fifth photo shows the bells side-by-side. Note the differing shape/sixe of the hub on the front of the bells. Also note the bell on the left is about .75 to 1MM longer than the bell on the right. Again same orientation. ? L 400XT R.

http://www.twmaster.com/motoren/motor018.JPG

So Vinnie, do I have a knock off here? Don and Vinnie, see anything wrong with the motor on the left?

JustGoFly.com
11-22-2005, 01:40 AM
Nice pictures.

The motor on the left is the knock off - but should work fine. The winding's may not be the same and amp max may not be the same. Email me and I'll explain how to measue KV so you can determine the ideal prop to use on your motor.

Vinnie

Twmaster
11-22-2005, 01:45 AM
Mike,

Check the bearing - you might have wrecked it which could be causing the harder turning. You're right not to try it with your ESC unless you measure the amp draw while running the motor. Your motor and ESC can handle short spikes so if you have an amp - measure the draw to see if anything is binding.

Vinnie

Vinnie, thanks for the tips. As an FYI I replaced both bearings with known good ones from a failed CD-ROM motor building project. It is still behaving like it is in a bind. One other thing. If I put a prop on the end of the shaft and hold the base while turning the shaft the motor gets harder to turn the faster you try to turn it. This is without an ESC connected.

I'm completely puzzled as to why it feels fubared at this point.

*sigh*

--
Mike N

qban_flyer
11-22-2005, 01:46 AM
Guys - it is NOT the sellers fault. There are dealers out there that don't know they are selling product that is copy cat. So please don't take it out on the poor guy who sold the motor. I'm sure the motor worked well - my point is you should measure the KV and not go based on the data you might find posted for 400XT motors.

Vinnie

I am not faulting the seller.

I have always suspected that motor as not being a 400XT and expressed my feelings to Mike when I compared it to one of mine installed in a similar model. Mike replied by showing me the plastic case it came in, which was labeled exactly the same as mine.

I don't want anybody else to fall in the same trap he did. Matter of fact, I know I won't since all of mine have been purchased from H/L and have performed flawlessly in every respect. The odd one has presented us with "issues" from the get go, something the other ones have not.

I won't be buying any 400XTs from other suppliers than either justgofly.com (been to your site quite a few times though I haven't seen the 400XT there) or H/L. So far these motors fit my e-needs perfectly. I don't need anytning more powerful than the 400XT since all the models I fly are supposed to be powered by 280 sized geared motors. I also like to get items at bargain prices if I can :D.

Twmaster
11-22-2005, 01:58 AM
One thing I keep forgetting to comment on. While the motor shown in the left side of my photos may be a knock-off I have to say the quality of the manufacture seems to be good. Not the usual cruddy fare put out by the typical knock-off makers.

I should also point out that the 'knock-off' motor flew my Slow Stick quite well for the most part. I did have two issues that may be related to some sort of inferior quality of assembly. First, on two separate occasions the motor failed to start when plugged in and powered on. Also, in flight at high power settings (i.e. WOT) it would make a pulsating sound and seem to be slowing down and speeding back up in time to the pulsations.

qban_flyer
11-22-2005, 02:15 AM
First, on two separate occasions the motor failed to start when plugged in and powered on. Also, in flight at high power settings (i.e. WOT) it would make a pulsating sound and seem to be slowing down and speeding back up in time to the pulsations.

These are the two issues I spoke of above. Seems to me the magnet type of the one on the left are quite different than those of the one on the right.

They appear a bit rougher, while the magnets of the one on the right are rather smooth all around, especially around the ends and edges. I know this has nothing to do with the failure of the motor, but it is worth mentioning that the internal composition and finish of the magnets (I am assuming them to be ceramic types) do not appear to be even close.

Then there is also the issue I have read about @ the other site, one about some 400XTs being rather noisy and to emit a loud whinning, only to become quiet after some usage. None of the ones I have ever come in contact with have ever sounded noisy or emit any loud whinnig noises, so what gives? Are the noisy ones copies also? :confused:

Twmaster
11-22-2005, 02:22 AM
Well just to satisfy a curious itch I went here:

http://www.rcgroups.com/forums/showthread.php?t=429130

And wouldn't ya know it. The motor I crashed and the packaging is identical to those shown there. :mad:

Unless I can solve the issues with it being in a bind I think it is going in the trash bucket.

qban_flyer
11-22-2005, 02:25 AM
So did I and here are a couple of posts on the 400XT. One mentioning the "noise". The other one propeller sizes for them.

http://www.rcgroups.com/forums/showpost.php?p=4620034&postcount=419

http://www.rcgroups.com/forums/showpost.php?p=4554774&postcount=351

:confused:

:confused:

:confused:

ForestCam
11-22-2005, 02:30 AM
This is just a wild stab in the dark but... Could it be possible that you screwed up one or more of the windings on the stator? I would think that a stator with a short could act as a load so by turning the can the load is causing the cogging.
Is there any difference in resistance across the three windings? Is there a major difference in resistance between the good stator and the one in question?


:edit:

And if it does end up being in the stator don't trash it re-wind it!

bz1mcr
11-22-2005, 02:32 AM
Your pictures are very nice and clear. You do have a mystery going. I have two suggestions for getting more information about what is going on with the bad acting motor.

1) blacken the stator tips and magnet faces with a sharpie type marker. That makes it a lot easier to se any contact areas. They are typically very small. So look very carefully after reassembly a short runup. Mechanical contact is usually easy to hear also. Listen carefully and compare to a good motor if in doubt.

2) with a prop installed watch for any sign of the can moving in an axial direction when the surging occures. If thrust is pulling the magnets away from the stator that can cause hunting or sagging rpm.

Finaly, you mentioned the different shape of the inside of the can hub. In the picture it looks like it may be showing signs of wear. If it does, what is it rubbing on? The bearing and end of the bearing tube look clean? Is there a washer or something missing or just not shown?

EDIT if you are going to trash it-- I am courious enough to pay the shipping to have you send it to me. I'll let you know what I find and you can have it back when I'm done if you pay the shipping back to you. How's that?

Twmaster
11-22-2005, 02:35 AM
This is just a wild stab in the dark but... Could it be possible that you screwed up one or more of the windings on the stator? I would think that a stator with a short could act as a load so by turning the can the load is causing the cogging.
Is there any difference in resistance across the three windings? Is there a major difference in resistance between the good stator and the one in question?

Forest you bring up a good point. I should also check the windings. If I read an earlier reply in this thread correctly the windings should have no effect on power off cogging as it is a function of magnetism and copper is not magnetic.

I will be checking the windings for shorts just to be safe. Or I may just pitch the motor as it is not the genuine article and I'm a bit mad about getting hoodwinked.

ForestCam
11-22-2005, 02:42 AM
If you end up pitching it I'll send you $3.95, put it in a Priority Mail box and ship it to me!:p

qban_flyer
11-22-2005, 02:46 AM
This is just a wild stab in the dark but... Could it be possible that you screwed up one or more of the windings on the stator?

I am a witness as to the tender loving care this motor has received since Mike has had it. It has had issues from the get go, and unless it was defective from the beginning, I don't think Mike has done anyting to harm it. Quote below by TW.


First, on two separate occasions the motor failed to start when plugged in and powered on. Also, in flight at high power settings (i.e. WOT) it would make a pulsating sound and seem to be slowing down and speeding back up in time to the pulsations.

Twmaster
11-22-2005, 02:48 AM
If you end up pitching it I'll send you $3.95, put it in a Priority Mail box and ship it to me!:p

I'll keep that in mind. I do have a burned up 400T coming to me from Canada. I wanted to experiment on moving the propshafts to point out the bottom of these motors like the AXi's do. However I just might be able to make one good motor out of the two. :cool:

timocharis
11-22-2005, 11:35 PM
Mike,

Unless my eyes deceive me, the knockoff stator is shorter (front to back) than the 400XT. This can cause some trouble.

For one thing, even with the same winding count, the Kv will be higher. Even more troubling, if the magnets have the same rating N(x), the smaller stator could get saturated by the oversize magnets. That would not be good from an efficiency standpoint and may even cause stumbling.

Since so many people like the 400XT, let's assume Vinnie got it right (and that should be no surprise, since he seems to put more work into getting motors right than just about anyone else around). This would imply a good chance that, using the same specs, the knockoff is a fry candidate. Might not be real good for your batteries either -- run an amp test and find out what the puppy is slurping before using it with anything good.

Just my 2 cents.


Dave North

bc-slowflyer
11-23-2005, 03:47 AM
I'll keep that in mind. I do have a burned up 400T coming to me from Canada. I wanted to experiment on moving the propshafts to point out the bottom of these motors like the AXi's do. However I just might be able to make one good motor out of the two. :cool:

Mike did you get my 400T yet?

Thanks;
Rod

Twmaster
11-23-2005, 02:32 PM
Mike did you get my 400T yet?

Thanks;
Rod

Not yet.

birdleggs
11-25-2005, 03:47 AM
Has anyone measured the constants on the HL 400XT? (KV, I, R)

Twmaster
11-25-2005, 03:54 AM
According to the paper included with the H-L shipped 400XT the kV is 950 Can the other numbers be measured with a DVM?

birdleggs
11-25-2005, 04:29 AM
Mike
Thanks for response. Yes the "R" & "I" can be measured, I just have not done those yet, Hopoed someone else had.
Cheers J.

Twmaster
11-25-2005, 04:36 AM
Say there 'leggs.....

What is the definition of R and I? I'd be happy to measure these if I have the equipment to do so.

Twmaster
11-25-2005, 05:24 AM
And I forgot to mention. I fired up the 'oddball' 400XT today. It runs but does not sound like it is hitting full power. At this point I am getting the feeling that it is somehow ruined. I suppose it will go in the parts bucket for future experimentation. :(

ForestCam
11-25-2005, 05:51 AM
Say there 'leggs.....

What is the definition of R and I? I'd be happy to measure these if I have the equipment to do so.
Resistance and Impedence? You'll need a DVOM.
But what do I know.:D

Oh and if it's still not running right it'd be a perfect motor to run into the side of a building with. :p

qban_flyer
11-25-2005, 06:31 AM
And I forgot to mention. I fired up the 'oddball' 400XT today. It runs but does not sound like it is hitting full power. At this point I am getting the feeling that it is somehow ruined. I suppose it will go in the parts bucket for future experimentation. :(

Me thinks your oddball motoren be dead as a door nail, Tw! :eek:

birdleggs
11-25-2005, 04:21 PM
Say there 'leggs.....

What is the definition of R and I? I'd be happy to measure these if I have the equipment to do so.

Twmaster
Thanks for reply.
"I" is the no load current which measures the current (amps) with the shaft running free.
"R" is motor resistance and is measure with the motor securely mounted and the shaft clamped to keep from turning. I usually use a large prop to restrain the shaft. With this motor I would apply about 6 to 8 amps then take a reading on the voltage. (R=Volts/Amps) With the motor constants you can determine useful infomation concerning the motor and it useage parameters. Its proberly best to use a digital multi-meter to do these reading.
Also you can determine the "Kv" for a motor by using a drill with known rpm ; clamping the shaft in the drill; running the drill and measuring the voltage produced by the motor. (Kv = rpm/voltage)

J

qban_flyer
12-02-2005, 01:30 AM
Nice pictures.

The motor on the left is the knock off - but should work fine. The winding's may not be the same and amp max may not be the same. Email me and I'll explain how to measue KV so you can determine the ideal prop to use on your motor.

Vinnie
Well Vinnie, it appears that the "motor" on the left has made another debut at Watt Flyer.

It is being sold here now from an old revived thread.

:eek: :eek: :eek:

bz1mcr
12-02-2005, 03:58 AM
Can you post a link so can all go give our opinion to the guy.

qban_flyer
12-02-2005, 01:17 PM
Can you post a link so can all go give our opinion to the guy.

It's in the For Sale section of Watt Flyer. It also is the only advertising the 400XT "On Sale" from China and it includes "performance" charts as well.

I don't think the Forum rules would allow me to specifically say who he is and or give his thread number, otherwise I would have done so already. I'd like to abide by the Forum rules, though I also like to warn others of potential pitfalls. I confronted him on the "other site". His reply was to attack me and then close the thread there and list the "400XTs" as "SOLD". He has now come here to try and sell the same stuff he had for sale there.

Suffice it to say that it was originally posted here on 10-16-05 and that it was revived yesterday. It should not be that difficult to find him and his motors. Twmaster gave a link to the "other" site's thread by him. His user ID there is the same as in here!

I haven't mentioned his name, but I have provided all the resources you need to seek him out. :o

ForestCam
12-02-2005, 06:46 PM
It's in the For Sale section of Watt Flyer. It also is the only advertising the 400XT "On Sale" from China and it includes "performance" charts as well.


The sale prices don't seem very spectacular either.:rolleyes:

qban_flyer
12-02-2005, 09:34 PM
The sale prices don't seem very spectacular either.:rolleyes:

Glad you found him and his motors! :p

Worse yet, they are copies, not the real thing!!! :mad:

At the "other site", when I challenged him he castigated me then closed the "Blowout Sale" thread so that I could not rebut him with facts. He declared all the 400XT motors as "SOLD". :confused:

He is gonna have a hard time trying to sell them here, where everyone knows about the difference between them, and the bargain price the "real thing" can be had at Hobby Lobby! :D

JustGoFly.com
12-02-2005, 11:55 PM
I just don't understand why they insist on posting MTM and using the same names as the MTM motors. There may be nothing wrong with the motors, but they are NOT MTM motors. I've asked Dan to stop calling them MTM motors, since I'm sure he's just caught in the middle of a pile of motors he bought for resale. MTM has stated that those are NOT their motors. I came up with the name Motor Max, since MTM is less memorable and sure enough this copy uses Motor Max on all of their motors.

Anyway - I have plenty to do without being distracted by these guys. I will simply ignore them and not add any more press to their threads. I may PM Dan to ask him to stop claiming they are MTM motors and the same as my motors. Dan has purchased many motors from me and I'm sure he thought they were a good price on the same line and is just tired of all this. I am tired of supporting these products and have a difficult time first discovering that they are not my motors, then explaining to customers who come to me for support that they are not mine. It sure doesn't make me look good and lack of support and false claims of them being the same upsets anyone who buys them. We may just have to redesign our whole line to get away from this.

Vinnie

Twmaster
12-03-2005, 12:42 AM
Vinnie, not only are they using the MTM brand name but they include a photo copy of the MTM 'manual' sheet that comes with the genuine article. (or at least comes with the Esskay motors I bought from H-L.

As for the motor I had it worked fine. In fact I think my Slow Stick was faster with the 'copy' motor. Although I am sure this is due to differing KV ratings.

qban_flyer
12-03-2005, 02:54 AM
As for the motor I had it worked fine. In fact I think my Slow Stick was faster with the 'copy' motor. Although I am sure this is due to differing KV ratings.
Mike, to my knowledge, we never had the opportunity to compare the two motors side by side on that plane on the same day with the same ESC and battery pack. Any brushless motor will make the Slow Stick faster. You saw mine leap off the ground in less than six inches and go straight up with the Hobby Lobby motor.

Then there was the "surging" problem that you had with the copy motor when you were flying it WOT. It was not caused by ESC overload since you were using an 18A unit. Add to that the way the entire affair behaved when we tried to measure it with your WhattMeter, the fact that it failed to run a couple of times and it becomes obvious the product you were using is inferior when compared to the ones obtained through Hobby Lobby.

The most plausible explanation for the surging is that it might have been caused by saturation. Let us also not forget that the magnets on the copy motor extended well beyond the coils of the stator. What caused it to misbehave when the WhattMeter was inserted in the circuit is beyond the scope of my limited knowledge of electrical devices.

I will address Vinnie's post separately as I wll be quoting what the man said on the "other site" when I confronted him with the facts and what his reaction to me was. He claims his motors to be "superior" to the original ones (?). :confused:

qban_flyer
12-03-2005, 03:58 AM
Sold - Brushless motor BLOW OUT

I have decided that rather than quote posts from the "other site", I'll let the individual reader go there and see for himself/herself. The header above is the way it reads there. The SOLD was added when he closed after being confronted by yours truly.

I've been told that posting the link to the original sale is OK to do, so by going to the link below you can determine for yourself what's going on. The same motors are being offered for sale here in Watt Flyer.

The only reason I am raising this red flag is because I have been exposed to the product in question, and know how frustrating using them can be. I'm just trying to warn others about potential pitfalls.


http://www.rcgroups.com/forums/showthread.php?t=429130

Twmaster
12-03-2005, 04:58 PM
Twmaster
Thanks for reply.
"I" is the no load current which measures the current (amps) with the shaft running free.
"R" is motor resistance and is measure with the motor securely mounted and the shaft clamped to keep from turning. I usually use a large prop to restrain the shaft. With this motor I would apply about 6 to 8 amps then take a reading on the voltage. (R=Volts/Amps) With the motor constants you can determine useful infomation concerning the motor and it useage parameters. Its proberly best to use a digital multi-meter to do these reading.
Also you can determine the "Kv" for a motor by using a drill with known rpm ; clamping the shaft in the drill; running the drill and measuring the voltage produced by the motor. (Kv = rpm/voltage)

J

Say Leggs! See here:

http://www.rcgroups.com/forums/showpost.php?p=4677549&postcount=441

Twmaster
12-03-2005, 05:07 PM
Mike, to my knowledge, we never had the opportunity to compare the two motors side by side on that plane on the same day with the same ESC and battery pack. Any brushless motor will make the Slow Stick faster. You saw mine leap off the ground in less than six inches and go straight up with the Hobby Lobby motor.

My SS seems to be slower and less powerful with the H-L supplied 400XT in my observations. Comparing my SS to yours is not a good comparison due ot mine being a porker at 18.5 ounces.

Then there was the "surging" problem that you had with the copy motor when you were flying it WOT. It was not caused by ESC overload since you were using an 18A unit. Add to that the way the entire affair behaved when we tried to measure it with your WhattMeter, the fact that it failed to run a couple of times and it becomes obvious the product you were using is inferior when compared to the ones obtained through Hobby Lobby.

I will agree that the real 400XT seems to not have this surging issue. However I believe the problem with not starting is the ESC becoming confused at power up due to power connection foul ups on my part.

The most plausible explanation for the surging is that it might have been caused by saturation. Let us also not forget that the magnets on the copy motor extended well beyond the coils of the stator. What caused it to misbehave when the WhattMeter was inserted in the circuit is beyond the scope of my limited knowledge of electrical devices. This is likely what is going on IMHO.

I will address Vinnie's post separately as I wll be quoting what the man said on the "other site" when I confronted him with the facts and what his reaction to me was. He claims his motors to be "superior" to the original ones (?). :confused:

He also claims them to be identical which is obviously not true as evidenced by my photos.

birdleggs
12-04-2005, 10:20 PM
Twmaster
Thanks for the heads up on the thread. Using the constants in the thread with standard motor calculations, I come up with almost the same using 3 cell lipos: max eff = 77%; amps @ max eff = 6.7; Kt = 1.322; Km=2.96 (Km is a figure of merit for all motors, that quickley tells you how "good" the motor is. the larger the number, the better the motor. Km = Kt/ Sqrt R) 2.94 is a "good" number for such an inexpensive motor.:)
J.

HLINDRUD
12-17-2005, 04:18 PM
If a Motor has high cogging does it effect the operation for that motor in RC flying? The reason I ask is that LightFlight RC Sells Light weight 20 MM Motor 4100KV that is 29G Compared to Eflite 370 which is 48G. This Motor is only 4G heavier than the 130 Brushed motor that comes with Cox Micro Warbirds. I have Already Built the Cox P40 That has 370 5400KV It weighs out at 6.1 OZ HS 55 730 2S. Im in the process of setting up Cox P47 Thunderbolt. Going to use 29G Motor and Micro cirrus Servos Keep wt under 5 OZ.

Have a good Day

THE Electric Guy

cyclops2
12-17-2005, 04:29 PM
Cogging is eliminated in quality industrial servo motors by " skewed " armature slots or segments. It is that simple. Yes it cost a lot more money to make a skewed motor. I do not know about cheaper rotating 1 piece magnetic rotors. I could find out. But who would pay the extra money?

TRASHBUG
12-22-2005, 01:16 PM
I have one of the knockoffs with the yellow lead and strong cogging. It flys a Sig Rascal with authority. It's my understanding that stronger cogging will also result in more torque and more amp draw. I know this one is hard to start with any speed control. You need a hard start to get it going. It whines when under power. It also SCREECHES with power off and a freewheeling prop. It always gets the attention of the other flyers:) I've never heard anything like this in another electric. Weird! Otherwise power is ok. Biggest problem is the hard to start thing. If I go too low on throttle when landing the motor sometimes quits and is hard to restart. A little inconvient;)

qban_flyer
12-22-2005, 01:41 PM
I have one of the knockoffs with the yellow lead and strong cogging. It flys a Sig Rascal with authority. It's my understanding that stronger cogging will also result in more torque and more amp draw. I know this one is hard to start with any speed control. You need a hard start to get it going. It whines when under power. It also SCREECHES with power off and a freewheeling prop. It always gets the attention of the other flyers:) I've never heard anything like this in another electric. Weird! Otherwise power is ok. Biggest problem is the hard to start thing. If I go too low on throttle when landing the motor sometimes quits and is hard to restart. A little inconvient;)

Photos posted by Twmaster above (#15) clearly shows the two motors to be different in many ways. The one with hard cogging he had failed to start on many occasions. The Hobby Lobby one would always start on command. You jave confirmed the problem with starting, one I thought might have been caused by the ESC. The same brand ESC is being used with the one from H/L and there have been no issues with it.

The copy also draws quite a bit more current, and the voltage drop on start up as measured with a Whattmeter was substantial as compared to the legitimate 400XT. Then there was the "surging" of the motor at WOT.:confused:

cyclops2
12-22-2005, 09:40 PM
You are right about the high and wastefull power to break loose from a dead stop.
That is why they are never used in servos. Which need torque.

ForestCam
12-22-2005, 09:56 PM
he castigated me
Had to look that one up! LOL
I guess GEICO is easier then Watt Flyer too.:D

qban_flyer
12-23-2005, 01:39 AM
Had to look that one up! LOL
I guess GEICO is easier then Watt Flyer too.:D

I was pulling a Howard Cossell on you guys on that post.:D

qban_flyer
12-23-2005, 01:40 AM
You are right about the high and wastefull power to break loose from a dead stop.
That is why they are never used in servos. Which need torque.

DITTO!

My Electrifly AMMO 4300 motor has imperceptible cogging and it is an extremely efficient one.:)

Twmaster
12-23-2005, 01:41 AM
Trashbug,

I rarely had the non-start problem with the motor although it happened enough to be annoying. I thought it had more power than the 'real' 400XT. At least it seemed to have more power.

What current is the motor you have pulling WOT on your Rascal? What size prop are you swinging?

Thanks.

frvrngn
02-09-2006, 08:26 PM
I just got one of these "knockoffs". It was the one advertised in the for sale forum as a HL Esskay. It has VERY stiff cogging, even way more than my cheap Tower Pro outrunners which I thought were stiff. I havent had a chance to run it yet, my bullet connectors are all too large on my ESC's. I guess I should have looked at this thread first, the pic shows the yellow wire vs. blue:o

Anything I should look out for? It looks to be in good condition. I was going to try it on my Slow Stick (have a BM-08 Tower Pro now) or use it on a lightweight Stryker build up for something slower than my speedy wings.

What props are you guys using? I am running 8cell or 10cell NiMh on my planes...

Thanks

qban_flyer
02-10-2006, 01:13 AM
I just got one of these "knockoffs". It was the one advertised in the for sale forum as a HL Esskay. It has VERY stiff cogging, even way more than my cheap Tower Pro outrunners which I thought were stiff. I havent had a chance to run it yet, my bullet connectors are all too large on my ESC's. I guess I should have looked at this thread first, the pic shows the yellow wire vs. blue:o

Anything I should look out for? It looks to be in good condition. I was going to try it on my Slow Stick (have a BM-08 Tower Pro now) or use it on a lightweight Stryker build up for something slower than my speedy wings.

What props are you guys using? I am running 8cell or 10cell NiMh on my planes...

Thanks

User Twmaster was one of the first ones to get one of "these", and though it is a copy of the original and presented him with some ESC issues, plus surging (using 8 cell NiMH packs), he claims it was not a bad motor after all.

Matter of fact, he even told me he found it to be a bit more powerful than H/L's version. He should know as he has several of those as well.

For a ten cell NiMH I would recommed a 9X3.8SF or 8X6E APC propeller. I use a 10X3.8SF on two cell Li-Pos on mine. :)

JustGoFly.com
02-10-2006, 01:26 AM
I just got one of these "knockoffs". It was the one advertised in the for sale forum as a HL Esskay.

The HL Esskays are not knock off's. They are the real deal. Use an 8x4 or 7x6 on a 10 cell battery. I'm sure you'll enjoy the motor.

Use bigger than 8x4 on the 400T and you run the risk of frying the motor.

Vinnie

frvrngn
02-10-2006, 02:55 AM
The HL Esskays are not knock off's. They are the real deal. Use an 8x4 or 7x6 on a 10 cell battery. I'm sure you'll enjoy the motor.

Use bigger than 8x4 on the 400T and you run the risk of frying the motor.

Vinnie

I dont think its an Esskay, its one of the others with super stiff cogging and a yellow wire vs. blue. The new ones are supposed to be smoother in cogging with the blue wire. This motor feels like spinning a 4stroke! He said he bought it HL a long while back, so who knows. I'm going to try it regardless.

Twmaster
02-10-2006, 03:10 AM
frvrngn, I was flying my Slow Stick on one of those motors (yellow wire) I too bought it from a seller claiming it to be a H-L supplied motor. In all fairness I have not a clue who is making them, whether they are geniune or bogus or what. I will say that I liked the one I had. In my opinion it flew my SS better/faster etc than a genuine 400XT as supplied by H-L (BTW I have 10 of these motors, the HL ones I mean).

I used a 9x6 APC SF prop and 8 1000mA NiMH cells. It flew like a bat with it's tail on fire. I would like to get another one of the yellow wire motors.

If you put 10 cells on it I'd also suggest following Vinnie's wise advise on prop size.

frvrngn
02-10-2006, 02:57 PM
Thanks for the tips! I need to go out and pick up some props at lunch. One last question before I try something I shouldnt. Can I swap the shaft around to make this a pusher?

ron_van_sommeren
02-10-2006, 03:02 PM
Cogging, or the lack of it, is not a good indicator for quality, power or efficiency. Strong cogging may give a problem during startup, more current is needed to get it over the first 'bump'. So if your controller or battery is not up to it ... Once the motor runs, it's no problem anymore.

Stronger cogging also makes for more noise.

Twmaster
02-11-2006, 12:30 AM
Thanks for the tips! I need to go out and pick up some props at lunch. One last question before I try something I shouldnt. Can I swap the shaft around to make this a pusher?

Yes you can. However you need to do this carefully and support the inside of the bell when you press the shaft through. Do not attempt to press the thing back later as the press fit may become loose from too many pushes.

Save the clip. You won't need it while in the other direction as the magnets will keep the bell where it needs to be.

timocharis
02-12-2006, 12:06 AM
Ron,

What causes harsh cogging? I've been wondering about the relationship between it and noise (some coggy motors _kill_ my ears).


Dave

ron_van_sommeren
02-12-2006, 11:47 AM
Stronger magnets, smaller airgap between magnets and stator, better magnetic circuit, magnet shape, magnet coverage,

#magnetpole/#statorpole ratio If the closser to 1, the less cogging. A ratio of 1 would give the most cogging but that motor of course would not run at all.

Prop speed is not constant due to cogging, that's what produces the noise.