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Old 05-22-2009, 11:59 AM   #16
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Originally Posted by TeamTekin View Post
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.
Somebody tell me, bigger rotor produce higher temperature due to more watts to spin bigger rotor. Is this same as higher Kv ?

2ndly, bigger rotor means more magnetic strength ?
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Old 05-22-2009, 12:06 PM   #17
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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?
Under ROAR, page 44, 8.8.2.4.2 rule...max diameter of the rotor for stock motor (17.5) is 12.51mm, thats actuallly for all BL motor.

http://www.roarracing.com/downloads/..._Rule_Book.pdf
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Old 05-23-2009, 12:34 PM   #18
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Originally Posted by kn7671 View Post
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?
This is an ongoing sitution with the rotors being of different sizes and the internals of the can within the 1st batch of ths SP/Prince motors, whereas the 1st batch were very quick and had 12.5 rotors and had NO markings on the can to denote what turn they were, the second batch had 12.25 rotors, but the internals of the can had been altered, and had markings on the can showing that they were 13.5 but the frustrating thing is, that no one will own up to why they have changed the make up of the motor, why is this
TCCF
Oh and the strength of the magnets on the old batch of SP/Prince motors are varstly stronger than the new batch
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Old 05-23-2009, 07:29 PM   #19
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Somebody tell me, bigger rotor produce higher temperature due to more watts to spin bigger rotor. Is this same as higher Kv ?
A bigger rotor does not necessarily produce higher temperature. This is a function of thermal design. A bigger rotor could run cooler in some cases. The heat in a motor has a lot to do with whether it is powering a relatively heavy load (making more torque and drawing more current than it is designed to handle).

Kv is the air gap voltage constant in RPM/V. The motor coils absorb current and produce torque, but under commutation, other coils move through the air gap and generate reverse voltage. The maximum theoretical speed is:

nMax = Kv*Vs

where Vs is the source voltage. In practice Kv is given with +/- 15% or less precision and there's friction and windage, so nMax is a fairly rough estimate.
In a frictionless environment the motor cannot exceed nMax because Kv is a negative feedback source inside the air gap, limiting reverse voltage to no more than the battery voltage Vs at the steady state top speed.

Quote:
2ndly, bigger rotor means more magnetic strength ?
The type of magnetic materials determine strength, not the size of the rotor. A smaller diameter rotor can contain stonger magnets.

Larger overall machines of course make more power, generally with a lower value of Kv and greater torque, but the source of extra power is via absorbing more electrical power and distributing the magnetic flux linkage over greater surface area in the air gap. The magnets are not necessarily stronger, the heat not necessarily greater, the rotor size does not necessarily increase power, and Kv is a property of the magnet strength and number of turns.

Last edited by SystemTheory; 05-23-2009 at 07:39 PM. Reason: Add Last Paragragh
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Old 05-28-2009, 04:42 PM   #20
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Originally Posted by kn7671 View Post
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?
Tekin motors are well built and go fast! All the motors are pretty close because they are all built to the roar rules. However we machined our cans out of billet AL and used very high temp materials. We have had many customers literally melt the solder out of their motors and when cleaned up and soldered again they run fine. We also glue in the stacks and feel we have very good heat conduction to the surface to keep the motor color.

Timing is everything in spec motors and we do have a very nice adjustable timing instead of steps. We think we hold that whole assembly together better than most giving us a tight motor overall. We have a removeable sensor wire and use high grade sensors. Top it off with some precision bearings that cost more than double the standard China bearings and you have a long life motor.

I believe the rules require no mismatching of rotors to motors from different brands. Honestly I do not think any are interchangeable. We originally offered the motors with a 12.3mm and now all the motors except the 4.5 , 3.5 and 2.5 ship with a 12.5mm. Both are legal in roar races.

Motor design can be black magic and varies for each application. Full throttle 17.5 TC is not the same load as 2wd offroad. We have to find a happy middle in most cases.

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Last edited by Tekin Prez; 05-28-2009 at 05:04 PM.
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