Von Ohain

A while a go HK launched a new series of motors named "Turnigy XK".
Its striking outward similarity, and similarity of specs, lead many (myself included) to believe these motors were rebranded Leopards, sold for a ridicilously low HK price.
Because of the low price I ordered a Turnigy XK3674-1650 Kv with the intent of running it in my freshly bought Genesis.
Just for the heck of it, I also included the stock Genesis motor in this comparison.
Since it coincidentally turned out to be exactly the same can dimensions, 3674, and actually has a slotted stator, just like the Leo!
Very rare for a cheapo inrunner, so I thought it might actually not be that bad afterall.

So, the motors I will be comparing is:
Leopard Red series 3674 2200Kv
Turnigy XK series 3674 1650Kv
Feisuda FSD 8Xl 3674 2075Kv (HK Genesis stock motor)

Mechanical Comparison.

End caps:

Both supports the same dimension bearings, and look similar. They are also interchangeable between the motors, but they are different, as shown in the picture.




Rotors:

The rotors of the two motors appear identical, and are also interchangeable.
The discoloration of the Leo is because its used, and has rust color. The wire wrapping around both rotors are the same gauge aswell.
The shorter length of the Leo rotor is because I had a fight with it and the angle grinder, I guess they were equal length as new.




Stators:

This is the killer blow for the Turnigy XK. Unlike the Leopard, It does not have a slotted stator.
I won't get too technical about why this is bad, but the design of this stator causes a large air gap between rotor and stator, and this is bad for the magnetic properties.
Its resistance for magnetic flux.
This also shows later on, when I compare efficiency of the motors.
The unslottet Turnigy XK suffers badly.
Leo on the left, Turnigy on the right.




Feisuda FSD 8Xl.
And lastly, the surprise from the underdog!
An unknown brand chinese motor which contains (some) quality components!
This motor does have a slotted stator!




But the downside is, it has a rubbish rotor.
Its a iron core rotor with magnets glued to the outside of it, and these magnets is not secured by any wrapping of any kind.
When this motor gets hot, and spins up to high rpm, these magnets will be guaranteed to separate from the rotor, and ruin the very neat stator of this one.
Plus, glued on magnets has worse heat dissipation than one piece magnets, so it overheats easier.




Some measurements.


I used a small propeller which I ran on each motor.
I spun them up to the same RPM, checking with a laser tachometer (16500 RPM).
Then I checked their power consumption.
Since all motors were running exactly the same load at the same speed.
Any differences is power consumption is a direct consequence of the motors efficiency, which in turn also means their heat generation.
Since the motors were of different Kv, a slightly lower efficiency is to be expected from the highest Kv motor (Leopard).

Leopard:




Turnigy:




Feisuda:




Not surprisingly, the Leopard came out on top, but just with a slight margin.
The real surprise here is the Genesis stock motor which is just marginally worse off than the Leopard.
The disappointment is the Turnigy XP which is just a Amp hog.
With a wind, and core, similar to a KB45 series motor, its outward similarity to a Leopard is just for show.
Its amp rating is probably optimistic. Its power ratings is probably achievable, if you double the rated voltage (which you can).

Each motors efficiency, compared to the Leopard.
(NOT ACTUAL EFFICIENCY!!! If you can find the actual efficiency of any of these motors, I can also calculate the actual efficiency of the rest)

Leopard (reference): 100%
Feisuda: 95.8%
Turnigy XK: 84.9%


Edit: Filled in the name of the Genesis motor, thanks to 785boats

785boats

Hi there
The stock motor in the Genesis is an FSD 8Xl motor. 2075kv. Made by Feisuda. As you can see from the rotor, it is a two pole motor & not a 4 pole like the other two.
I run these motors in my 4s Race boats. Both Mono & Hydro. I also tried both the Leopard & Turnigy 2200kv motors in the same boats with the same props & ESC's, but I found that the FSD 8Xl was faster. I was dissappointed in both the Leopard & the Turnigy motors, but they did both perform pretty much the same as each other. Just not as good as the 8Xl in my opinion. I run them in my sport boats now.
Here's a link to the FSD motors.
[link]http://www.fsd-motor.com/en_productview.asp?id=311[/link]
Cheers.
Paul.

Von Ohain

Thank you for the info about the Feisuda.
Do you know of any dealers for them, and how are they priced?
So far I know of only one descent chinese brand of inrunners, and thats Leopard.
Another option is definetly interesting, and I will be trying out these things too

A small detail:
Actually, the rotor of the Feisuda is a 4 pole, and the two other rotors is 2 pole.
But numbers of motor poles is not determined by the rotor alone, its also determided by stator.
For example, the Turnigy is a 2 pole motor while the Leo is a 4 pole motor, despite both have identical 2 pole rotors.
And if the Feisuda 4 pole rotor were to fit inside the Turnigy, then it would become a 4 pole aswell.
The reason the Feisuda rotor is a 4 pole, is because it has 4 magnets of alternating polarneity (N-S-N-S).
If it were to be a 2 pole, it should had just 2 magnets of alternating polarity(N-S). Or just one single magnet, utilizing both its N and its S side. Or 4 magnets with paired polarity (N-N-S-S).

To determine the motors total pole number is next to impossible just by visual inspection for a inrunner, because you need to know how its wound, and the windings is just a epoxy slob of copper wire.
But you can determine it by measuring the motors BackEMF on a oscilloscope.
If that has any interest, I can perform that test too, and upload scope pictures.

Diesel6401

My Feedback: (1)

Excellent Info. Makes me wonder about the Tacon motors. If they are the same as Leopards or similar to the XK series.

Von Ohain

Seems that Tacon is the same as Turnigy XK.

http://www.rc-monster.com/forum/showthread.php?t=30416

Someone has discovered that the Leos is pretty popular, so they make lookalikes, but with rubbish components inside.

785boats

I would be most interested to know if the Feisuda is really a 2 pole or 4 pole motor. I was under the impression it was a 2 pole.
The only place I've bought them is from Hi Model. They sell them under their own brand name but they are the FSD motors. They also sell some FSD motors as FSD motors too.
Here's the 8Xl I use. The picture shows blue bit the ones I've received are the magenta colour.

[link]http://www.himodel.com/electric/2075KV_Inrunner_Brushless_Motor_540_3674-8T.html[/link]

Here's a 9Xl with a great watering can that I also use. It's also an FSD motor.

[link]http://www.himodel.com/electric/1845KV_Inrunner_Brushless_Motor_W_Water-cooling_for_Boat_5403674-09.html[/link].

Cheers.
Paul.

*delete M i k e u p delete*

I dealt with neo magnets a few years ago.. I had a motor from fastelectrics of australaia ( andrewg ). I used a 05 motor can. I had power galore. the magnectics are like the Norway gentleman said. The N-N-S-S system was used. N #1 was placed at 12:00- N#2 was placed at 3:00 but was turned 180 degrees-S#1 was placed at 6:00 and turned 180 degrees-S#2 was placed at 9:00 and turned 180 degrees. I keep records and pictures. I had to quit as my wife had to had back surgery and that tied me up for 6 months. The 05 motor magnects had to be pulled and sanded inside and be smooth as a babies behind.

Von Ohain

Thanks for the links These motors is interesting, I will give them a try the next time i got some money to blow in the general direction of RC.

The motor pole number is determined by stator pole pairs multiplied by rotor pole pairs.
So, 2 poles = 1 pole pair, 4 poles = 2 pole pairs, etc.

This means that you can never have less poles than neither the rotor or stator alone.
This means that the Feisuda with a 4 pole rotor can not have less than 4 poles.
It can have more though, that depends on the stator.
If I were to drop the Feisuda rotor into the Leo, it would suddenly be an 8 pole motor.
Most likely the Feisuda is 4 pole, as making many poles in the stator is a bit of a headache with the wiring (within the realm of inrunners), so they ususally got just 2 poles in the stator.
I can verify this with my oscilloscope.

Von Ohain

Determining pole count of the Feisuda.

Here is a picture from of my scope. The trace is the backEMF of the Feisuda motor, spinning it at 532.5 RPM with my power drill.



This gives us a lot of information, a lot more than we need in fact.
But note that it takes 56 mS for one period of the backEMF.
You can tell that by counting squares that the signals travels over, and in the bottom of the screen, it says "20mS/Div". It means each square is 20mS in time for the signal.

From motor theory 101, I also learned that the motors pole pair number will determine the relationship between electromagnetic rpms, and mechanical rpms.
That is, the more pole pairs your motor has, the slower will your motor spin if the same frequency power is applied to it.

The relationship is Electrical RPM/Mechanical RPM = Pole pair number.

So, a little numbercrunching:

56mS is the period time for the signal.
56mS/1000=0.056S
1/0.056S = 17.86 Hz

It has a frequency of 17.86Hz.

So, the RPMS. The motor was spun at 532.5 RPM.

532.5 RPM / 60S = 8.875 RPS.
Hz means "per second", so to be able to compare, we have to divide RPM with 60 seconds, to get RPS. Revolutions per second.


17.86Hz / 8.875 RPS = 2.012 (thats 2, inaccuracy is blamed on cheap measuring equippment)

BackEMF frequency divided by Mechanical rotation speed (measured in revolutions per second) tells us that the motor has 2 pole pairs.
Its a 4 pole motor.

Edit: messed up my numbers.

785boats

But it has the same magnetic compression as a Feigao 8Xl. That is to say it cogs over (by hand) at the same intervals, every 180 degrees . And the Feigao is a 2 pole motor for sure. Perplexing.

785boats

It's also been pointed out on other forums that, unfortunately, the Turnigy motor you used is a 2 pole motor too. Not a 4 pole like the Leopard. That's probably why there is no slotted stator in it.
Cheers.
Paul.

Von Ohain

How the motor turns over gives no clue as to how many poles it has.
The Leopard has about 1 million cogs before it has completed 1 revolution, but it is most definetly a 4 pole.
However, if it cogs only 2 times, it makes little sense to have a 4 pole rotor, as I would believe a 4 pole rotor would cog 4 times in an unslotted stator?
Maybe its not so simple as Feisuda = Feisuda? Maybe there is several variants of it.
As we see from the pictures, the Turnigy XK and the Leopard has identical rotors, despite the stator being very different.
So there is some kind of connection between the motors.
Maybe its the same for Feisuda and its derivates too. Maybe yours has a 2 pole rotor, while mine has a 4?


By the way, doing 1 million cogs when you turn it is a typical porperty for slotted stators.
Doing 0 cogs, or a small number of very soft cogs is typical for ring core stators.
My Feisuda is a million cog motor, and yours is doing 2?
It would be interesting to do an autopsy of your Feisuda aswell.
There must be major differences between them.

Snowride

As mentioned you are comparing a 4 pole Leopard to a 2 pole Turnigy. For sure you will see a difference in efficiency. The test is rather useless IMHO. Kinda like comparing 2 identical cars with one having a four cyl and the other a 6, of course the 6 is going to out perform the 4. This is the 4 pole version of the XK3674 Turnigy with 12 segment stator you should have compared it with. http://www.hobbyking.com/hobbyking/s...dProduct=17701

Here are some pics of my Turnigy XK4082 4 pole

Von Ohain

Snowride, you are missing the point.
The point wasn't to test the two motors up against each other.
The point was to determine wether or not the Turnigys are rebranded Leopards, or if they are lookalikes.
And they are lookalikes.

And as for efficiency comparison, number of poles is not what determines efficiency.
In this case, its stator construction. Please note that your Turnigy has a SLOTTED STATOR, and that will make it much better than my Turnigy, with a RING CORE STATOR.
So yes, yours is much more likely to be competative with the Leo. But it has nothing to do with pole count.
And since there apparently is Turnigys out there with both stator contructions, I will still be buying Leopards until there is a certain way of telling the slotted stator Turnigys apart from the ring core stators.
Because as long as that is not included in the specs, you are buying the Turnigys on hit and miss. Its just pure luck if you get a slotted stator or not.

And as for the analogy with car engines, there is neither any universal truth that more cylinders is more performance. Because it isn't.
Car engine performance is determined by BMEP (break mean effective pressure) times Displacement times Revs.
The reason why multi cylinders tend to be more powerful is because they usually got bigger displacement.
But if you theoretically were to build a single cylinder 7.2 litre, it wouldn't stand back for a V8 7.2 litre In terms of performance.
The reason they don't do that is because vibrations would be unbearable, and the design wouldn't be compact enough to fit in any practical cars engine bay.

Snowride

No not missing the point. If you want to find out how close they actually are in build design or if they are actually rebranded clones, you should have taken apart similar model numbers which you did not.

The 3674-B-XXXX in the leopard would be comparable inside to a XK3674-B-XXXX in the Turnigy which is supposed to be the equivalent at least in terms of poles and size. Instead you used the 3674-XXXX (notice there is no B in that part number) which makes it a 27% cheaper 2 pole motor which will have different parts and cannot be compared for similarities.

If you would have actually used a B model in your comparison you would see it also has a slotted stator just like the leopard and we would not be having this discussion.

Von Ohain

I see no "B" I'n the case of your motor, but still it has a slotted stator.
That looks to me like its not the B that determines what stator it has?

Dan S

although the equivalent HK motor was not used to compare with the Leopard motor, I still believe that some very nice work and effort was put into this thread.

Von Ohain, if you can get your hands on this motor: http://www.hobbyking.com/hobbyking/s...dProduct=17701,
more than likely that one would be an exact equivalent to the Leopard used.

Dan.

Von Ohain

Thanks for the interest Dan, I see by the activity on other forums that this tread causing a bit of a fuzz.

Whether or not its a "B" series is not interesting in my opinion, as Snowride's motor also has a slotted stator, but it does definetly not have a "B" in its name.
So we know that there is good and bad Turnigy XK's out there, but no consistent way of telling one apart from the other.

I have no personal interest in investing time and money to convince know-it-alls one or the another way.
I will not buy Turnigy XK motors for hit-or-miss chance on slotted stator units.
I have found the answer that I was looking for, and I thought I share it just because I know many wonder about the same.

Also the fact that uneducated people is doing their best to discredit the information I'm sharing with you for free is not encouraging me to continue my work,
and definetly not share it even if I were to continue it.
Constructive critisism, that is fine. Jumping to conclusions and judging from preconcieved notions is not.
And I'm not about to invest time and money to do anything about other peoples preconcieved notions.
I got my personal curiousity satisfied, and I'm done here.

And finally, this has nothing to do with you Dan. It has to do with all the trolls whos discrediting this thread on other forums, but none of them actually having what it takes to come here and take the discussion with a professional.

By the way, if you are happy about looking inside of a XK3674-B-1900Kv, take a look here:
http://www.rcgroups.com/forums/showthread.php?t=1612069

Diesel6401

My Feedback: (1)

I think their is a common misconception that pole count effects effciency (like mentioned) and quality. The way I was informed (which may be wrong) about pole count is that the higher poles (say 4) are more "forgiving" then say a 2 pole motor and so on. What I mean by forgiving is if you over-prop a 2 pole you may see a large spike in amp draw and heat as if you over-prop a 4 pole (all things being equal beside pole count of motor) then you might not see such an aggressive spike. Now I am sure their is a lot more of a technical answer with that, but that's what I've read and it's worked in my rc experience. As far as the quality Lehner comes to mind as I believe they maybe 2 pole motors (at least that's what I've read numerous times on different sites, but I don't (and won't) have one of those to check myself anytime soon) and they are Bad A motors.


Also note that the 2 pole Turnigy can indeed be a re-badged Lepard motor, many people don't know that Leopard does actually make 2 pole motors: http://www.leopardhobby.com/product/...ionID=01020805


Comparing top end motors: which is the more effcient and the betterchoice the 2 pole lehner or the 4 pole Neu?!? I'm clueless, just a question and may be a little off topic.


About the car motor things, check out the video ford has called (6 vs 8) in which it's 6cyc eco-boost motor competes against popular 8cyc motors in numerous test. It's a pretty cool video. I'm not a Ford fan (Gm guy), but it's a cool vid nontheless.

Von Ohain

Thats a good question Diesel, I can not give you an absolute answer.
At high revs, a 2 pole is better because the 4 pole requires 2 times the frequency of the applied power, which causes higher inductance in the windings.
At low revs, a 4 pole (or more) is better because it keeps the electrical RPM (or frequency of applied power, if you want to call it that) high, and thats better to work with for a sensorless ESC.
But at which RPM the crossover between whats best will happend is for me impossible to say with the incomplete datasheets of our hobby grade motors.
To say that would require knowing the inductance of the motor coils, and some nasty fourier mathematics that I refuse to even try.

Also thanks for pointing out that Leo makes 2 poles, I was one of those who didn't know :O

Diesel6401

My Feedback: (1)

So if im reading your response right is it safe to say that two like motors for example the 2 pole Leopard and the 4 pole leopard same size, same kv same wind type the 2 pole would be more effcient at higher rpm then the 4 pole and vise versa? Is that a safe line of thinking comparing same brand/quality type, but without Einstein math we do not know what that rpm number actually is?!? Close or I'm in left field?

Rather interesting....


Plan on getting a 2 pole Leopard anytime soon to check the stators 

Von Ohain

Miserable double post, please delete

Von Ohain

In the case of the Turnigys, it appears that the 2 poles has ring core stator and the 4 poles has slotted stator, so they wouldn't be comparable.
Whats the case for 2 pole vs 4 pole Leopard I wouldn't know, I have never seen a 2 pole Leopard inside.

Given that all other factors is the same, yes that would be the right way to read my response.
And, what you say about 4 poles being more forgiving about overloading sounds reasonable, given the higher impedance. Although I never tried.

Without proper datasheets we never know. If you compare the datasheet of even the most expensive hobby grade motors, versus commercial/industrial grade motors, its obvious that we are left tumbling in the dark. Without the data of the motors, you need Einstein-math to re-engineer what the engineers behind the motors has not written in the datasheets.
Im not about to do that, its a pain!

Heres an example:

This is Siemens "Motor ABC". It roughly summarizes the characteristics of an electric motor, and how to read it out of a datasheet.

http://www.google.no/url?sa=t&rct=j&...SwCEWVr9ZLdwfA

Here is an actual datasheet for some high end hobby grade motors. See how many of the characteristics described in the link above you can actually find:
http://www.neumotors.com/Site/1100_series.html

Siemens describes, literally, a book of characteristics for an electric motor. Even high-end hobby grade motors summarize the characteristics of one particular motor with a single line.
Needless to say, how can absolute answers be given when nobody outside the manufacturers design office knows. (Or do even they?)

Snowride

I have seen that as a few of the guys in the office have Ford f-150 trucks. One guys got the new V6 eco boost and the comparisons were not far behind. The eco boost is more powerful, has higher tow capacity and has better economy however, I seriously doubt it will have the longevity of a non turbo V8. Really nice engine and if it were me I would opt for the eco boost. Like I said, apples to apples, you would need to compare a turbo V8 to a turbo V6 all things being equal. Lets give the V8 2 turbos if you want to compare. How about 1500hp. http://www.bankspower.com/techarticl...facts-of-life-

7500rpm

Remember, the old saying.....There is No Replacement for Displacement !       

So much for the V6- V8 comparisons, with all things being equal.