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Old 05-14-2009, 12:14 PM   #1
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Default Brushless Motor Rotor Differences

Hi.

Has anyone else noticed, how the magnetic strength is different between rotors of different manufacturers, and different rotor strength even between the same manufacturers for the same model motor. Some are notchy which have a strong magnet, yet some are not notchy at all.

Thanks Ya`All
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Old 05-14-2009, 01:08 PM   #2
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Notchy or 'cog torque' is not neccessarily just from a strong magnet or a good thing in a motor design. It is simply the attraction of the magnet to the stack teeth when the motor is not being powered. That same 'drag' is present when the motor is running which is not a good thing overall.

Slotless motors have almost no cog torque, but can have very strong magnets. So you cannot really judge a motor by how hard it is to turn the shaft with your fingers. Some people go to great lengths in the designs to reduce the cog torque.

Our slotted 1/10 and 1/8 motors have very little cog torque and very strong magnets. Smooth low end and plenty of power.

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Old 05-14-2009, 01:19 PM   #3
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Originally Posted by TeamTekin View Post
Our slotted 1/10 and 1/8 motors have very little cog torque and very strong magnets. Smooth low end and plenty of power.

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I've not owned a Tekin motor, but I can tell you that the Tekin motors are very smooth.

Can you tell us what motor characteristic is preferred for different types of conditions? In on-road 1/12 Stock class, would a smooth, low-cog motor be preferred to a motor that cog's more for a more natural drag brake? What about mod classes, or off-road, smooth, cog, etc...
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Old 05-14-2009, 01:29 PM   #4
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Less cog torque is always good, but sometimes you have to accept it in order to get other factors where you want them. Some applications need all the torque at certain point on the performance curve like spec racing onroad or oval where top end rules. We are running some horribly inefficient setups in spec, but they go fast

In hammer down applications where most time is spent at high rpm the low speed advantages are not as important. In 2wd offroad or 1/8 electric the smoothness entering and feathering corners is very nice. Even in TC the drag from the cog torque can upset the car entering a corner. We have a Push control feature to soften this effect on motors with a lot of cog torque. Our motors are pretty free rolling and most add Drag Brake instead.
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Old 05-14-2009, 01:31 PM   #5
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Quote:
Originally Posted by TeamTekin View Post
Slotless motors have almost no cog torque, but can have very strong magnets. So you cannot really judge a motor by how hard it is to turn the shaft with your fingers. Some people go to great lengths in the designs to reduce the cog torque.

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I have a few Asian made Slotless motors where the attraction of the magnet to the coil windings makes it feel like a Slotted motor. Now, this motors have a very high Io which makes them run very hot.

Jim are your motor's stator skewed to reduce the cogging?

Regards.
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Old 05-14-2009, 01:36 PM   #6
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Nope, and no I cannot tell you what we have done

Looking forward to this discussion, but we are headed out of the office for the Rock Crawler Scale Nationals in MT. I will check back on this thread since we do like people to understand. Many think a strong cog torque is good, which means our motors are not good... which is simply not true. Our motors may be the most engineered of the bunch for specific applications.
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Old 05-14-2009, 04:18 PM   #7
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Quote:
Originally Posted by TeamTekin View Post
Nope, and no I cannot tell you what we have done

Looking forward to this discussion, but we are headed out of the office for the Rock Crawler Scale Nationals in MT. I will check back on this thread since we do like people to understand. Many think a strong cog torque is good, which means our motors are not good... which is simply not true. Our motors may be the most engineered of the bunch for specific applications.
lol We all have tricks up our sleeves lol. I like the fact that your brought back a sensored style 4 pole motor. I've been able to modify my old sensored Aveox to work with one of my hybrid sensored/sensoreless ESC and it's freakish powerful. I love how it doesn't strain a bit to get the motor moving.
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Old 05-14-2009, 07:17 PM   #8
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Quote:
Originally Posted by TeamTekin View Post
Notchy or 'cog torque' is not neccessarily just from a strong magnet or a good thing in a motor design. It is simply the attraction of the magnet to the stack teeth when the motor is not being powered. That same 'drag' is present when the motor is running which is not a good thing overall.

Slotless motors have almost no cog torque, but can have very strong magnets. So you cannot really judge a motor by how hard it is to turn the shaft with your fingers. Some people go to great lengths in the designs to reduce the cog torque.

Our slotted 1/10 and 1/8 motors have very little cog torque and very strong magnets. Smooth low end and plenty of power.

Tekin Prez
I switched to BL systems because of cog-torque from brushed motors. My
EX motors (bonded rotor) is what I was looking for. It runs so smooth,
relieving stress from drivetrain off power (coasting). Problem is it lacks
power so I bought a Vector X11 and was overly dissapointed. It has so
much drag off power that it made the car very unnatural to drive. I think
that motor is for racing. I cant complain about the power, it's fast but it
doesnt seem right. My LRP Sphere broke and had it exchanged for a new
Novak XBR system, I changed the EX Motor's stock rotor to a sintered
rotor from a Velocity Light motor. 40% improvement in power, efficiency
and braking, there is some low cog-torque but bearable.

If you say you have a powerful motor with low cog-torque, I would
most likely buy one to upgrade some of my aging but still smooth
Novak EX motors. Problem is Tekin products are not carried by our
LHS in the Philippines. Tekin's distributor here closed down some 4 or
5 years ago. Based from reviews and recommendations, Tekin products
are at the fore-front of brushless techs, so I would like to see and buy
your products IF it's available locally.
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Old 05-14-2009, 08:02 PM   #9
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Quote:
Originally Posted by TeamTekin View Post
Nope, and no I cannot tell you what we have done

Looking forward to this discussion, but we are headed out of the office for the Rock Crawler Scale Nationals in MT. I will check back on this thread since we do like people to understand. Many think a strong cog torque is good, which means our motors are not good... which is simply not true. Our motors may be the most engineered of the bunch for specific applications.
I notice most of the team drivers at a national race using a new rotor in there motor everytime they raced.

What makes a motor faster a balanced rotor or a stronger rotor or both?
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Old 05-15-2009, 06:18 AM   #10
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I did a bit of testing back in this area a while ago. I prefer running one brand speedy/motors as you don't have silly problems that you sometimes have when you mix and match brands. Since the LRP TC spec was the gun speedy I ran their motors too. I did a back to back test to compare motors a while ago now to see if I had gone in the wrong direction with the motors. I tested 3 motors back to back with the same gearing to directly compare them (LRP, Novak & SP 3.5t). The LRP was the slowest and the hottest but most importantly it felt like it had way less grip than the other two motors. The LRP also had way more torque cog than the other two motors. As a result I changed to SP as it was equal best but had better varitety for 5cell (4.5, 4.0 & 3.5).
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Old 05-15-2009, 07:21 AM   #11
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Quote:
Originally Posted by Dragonfire View Post
IThe LRP was the slowest and the hottest but most importantly it felt like it had way less grip than the other two motors. The LRP also had way more torque cog than the other two motors.
Very interesting... I also run LRP ESC's and LRP motors, and I found the motors run hotter than practically everyone else on the track. I don't think they are any slower in the stock 17.5 or SS 13.5 range, but I think Tekin may be on to something.
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Old 05-16-2009, 01:40 AM   #12
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Questions?? DIFFERENCES??

I've tried the 4 most popular motors at our track, Novak,LRP, SP.& Orion.( ALL 17.5's)
Novak to me seems to have more torque and rpm than the rest. LRP to me has less torque but more RPM and the SP also appears to have more RPM.
Novak seems to run coolest out of the four, next would be the SP,ORION and then LRP,which seems to run about 20 degrees hotter than the other three.
ESC's and gearing seems to make a difference in temp depending on how aggressive the profiles are. The more aggressive gearing the hotter the motors appear to get, regard less of brand!
Then there's the Orion 17.5 it seems to be closest to Novak, good torque and rpm combo and not a lot of heat afterwards.
Another variable is driving styles, a racer who uses a lot of brake and is off and on the throttle will generate a lot more heat in the motors regardless of Mfg. brand. So, now you get into what motor works best with your driving style!

After saying all this now you get into the batteries! A strong battery will make a big difference across the whole power curve with a motor regardless of brand but in saying this it seems to increase motor temps as the power increases as well.
O.k. bottom line! It's a lot of variable to determine the exact differences in motors! Best to leave the motor characteristics to the experts, and I'm not one of them. It's getting late! Discussion,,,,, to be [email protected]#*

Last edited by maxepower; 05-16-2009 at 01:51 AM.
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Old 05-16-2009, 02:13 AM   #13
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Quote:
Originally Posted by kn7671 View Post
I think Tekin may be on to something.
I don't doubt it. I have never tried their motors or speedies mainly because they have limited motors around the 4.0 range for tuning. The lack of a 4.0 meant I didn't consider them. As it stands racing 2s mod a 4.0 is generally the gun motor.

Just a not with spec motors. They tend to have different characteristics than their modified cousins. LRP mods use large rotors while their spec motors are much smaller. Other brands like SP run a 12.5mm rotor in almost everything.
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Old 05-19-2009, 12:47 PM   #14
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Quote:
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I notice most of the team drivers at a national race using a new rotor in there motor everytime they raced.

What makes a motor faster a balanced rotor or a stronger rotor or both?
Not sure why you would need a new rotor every run. We rarely see a rotor that has changed.

A balanced rotor is always a good thing. Stronger magnets give lower KV and more torque. Weaker magnets give more rpm and less torque. Somewhere between the highest rpms with the lowest gearing and the lowest rpms with the highest gearing is a sweet spot for each application and motor. There is not a single and answer for all.
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Old 05-22-2009, 11:10 AM   #15
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Tekin - tell us why you would recommend a Tekin brushless motor over a competitor's.

So according to ROAR's Rules, the largest a rotor can be in Stock and Super Stock is 12.5mm, which should mean that it would be LEGAL to swap from a 12.3mm rotor to a 12.5mm rotor if offered as an option.

At a ROAR race, can you swap to a 12.5mm rotor in a Stock motor if originially equipped with a 12.3mm rotor?
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