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Old 03-06-2011, 03:36 AM   #346
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In normal operation the brushless motor stator coils are subjected to high mechanical forces due to torque reaction and vibration as the motor coils are driven by alternating current. This constant pulling and pushing of current through the coils causes the coils to move in sync with the drive frequency and this force increases as the motor load increases.

Novak 17.5 turn brushless motor has a Kt value of approximately 0.7 oz-in. So, if during acceleration, the motor draws 100 amps, which is quite typical, the motor produces about 66 oz-in of torque (95% efficient motor) and there is equal and opposite reaction force in the coils ( Newton’s third law of motion).

Imagine 5.5 lb-in of force pushing on the coils, this small amount of movement will (over time) cause some damage. In order to improve the motor's reliability, the windings are epoxy impregnated.

The epoxy provides a degree of mechanical strength to the windings, particularly in the unsupported end wind. Where the coils enter the slot of the stator they are also strengthened in order to resist the forces caused by the torque reaction.

This coating prevents vibration caused by the changing magnetic fields. It prevents wires rubbing against one another which will eventually wear the insulating coating, causing a short in the coil.

Epoxy also displaces air (which is a thermal barrier) from inside the coil and replaces it with resin. This improves the thermal conductivity of heat from the inside of the the windings to the lamination on the outside. Since the laminations are on the outside, they are able to conduct heat to the ambient air.

Thermal Conductivity in W/m degree C ( 1W/m C = 0.5779 Btu/(ft hr F))

Air 0.024
Standard Epoxy 0.188
Epoxy with additive 1.7

As you can see, plain epoxy is 7.8 times better in heat conductivity than air; epoxy with thermal additives is 73 times better. This coating also provides a degree of environmental protection against the ingress of moisture, and also improves the electrical insulation between the winding and the stator.
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Our factory pre-set motor timing is 29-30 degrees. If you would like your motor checked or re-timed, you can PM me for assistance.
is this vibration affect the same on balistic mod and 1S ?
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Old 03-06-2011, 08:57 AM   #347
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In regards to this new thermal epoxy stators, I was wondering how much this has added to the weight of the stator?


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About 1 gram.
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Old 03-06-2011, 09:29 AM   #348
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is this vibration affect the same on balistic mod and 1S ?
We have not seen this type of damage with mod wind motors; 1S Spec racing seems to be particularly hard on motors (all mfgs' motors, not just Ballistics). Extreme coil vibration is caused by excessive bursts of current from timing/boost escs; if you are not using this type of controller, you probably don't need an epoxied stator.

Oval racers, using timing escs (1S), probably experience the most damage to their motors from this excessive current (resulting in burnt stators). An additional benefit of epoxying the stators is making them tamper-proof. No re-winding the stators to remove wire. I have read reports of this sort of motor tampering, but we have no hard evidence---just hearsay.
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Old 03-06-2011, 09:46 AM   #349
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About 1 gram.

Thank you.


Shawn.
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Old 03-08-2011, 06:27 PM   #350
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Default Epoxied Stators

I would recommend if your running the epoxied stators to trail fit the can assembly, you will probably find that you may have to run without the paper gasket on the pinion side of the motor. You should also check the amount of slack in the rotor, more shims are required.
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Old 04-07-2011, 11:18 AM   #351
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Our epoxied, Ballistic 540, replacement wound stators are now in available in our store. Available winds are from 6.5T through 25.5T.
I read this after just picking up a Ballstic 17.5. So, is this new stator not in the new motors being sold? If not why wouldn't it be if it is more reliable?
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Old 04-07-2011, 11:26 AM   #352
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I have heard of no testing on comparative heat differences; in our tech note above, we are not claiming they will run cooler. Our main reason for the epoxy coating is to prevent excessive coil vibration due to repeated bursts of timing/boost currents.

For example, we are not increasing our motor temp guidance numbers. The stator epoxy coating will not prevent your rotors from weakening from repeated over-heating. I re-read our store listing and I cannot find any claim (by us) that your motor will run cooler with this stator.
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I read this after just picking up a Ballstic 17.5. So, is this new stator not in the new motors being sold? If not why wouldn't it be if it is more reliable?
you won't be running timing/boost not to worry.
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Old 04-07-2011, 11:42 AM   #353
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you won't be running timing/boost not to worry.
At least not until someone changes their mind again. So this is pretty much a non issue without boost?
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Old 04-07-2011, 03:44 PM   #354
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I read this after just picking up a Ballstic 17.5. So, is this new stator not in the new motors being sold? If not why wouldn't it be if it is more reliable?
We won't be selling our B 540s with the epoxied stators through distribution; the epoxying procedure is labor-intensive and the additional costs cannot be passed through because of the ROAR MSRP cap on brushless motors.

In the next couple of weeks, we will be updating our Build-A-Ballistic™ 540 program to add several epoxied winds as options. Novak customers who want to purchase the motor customized with one of these stators, can order one.

We will be offering several epoxied 540 winds through distribution, along with one 550 wind, the 4.5T.
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Old 04-14-2011, 10:23 PM   #355
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I was at a race back in feburary and had my 17.5 apart because a fellow racer told me to make sure my bearigs were free. So when I got done checking, I started to put the motor together, till I had a mis-hap. I accidently dropped the motor and lost one of the shims that goes on the output shaft side. So I ended up taking my 13.5 apart (both are Ballistic motors) and taking the shim out of it just to get me by till the end of my race day. I would like to know if Novak sells those shims seperately or part of the rotor or part of something else. I have a 13.5 that I would like to use sometime soon and just would like to know where to get some just for this instance ever happen again. Right now I have a couple of CRC's axle shim 5mm or 5.5 mm in its place. Also what is the procedure to re-align the rotor properly so it not affect the power band of the motor. Is it like the way we use to center the armature in the brushed motors?
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Old 04-14-2011, 11:49 PM   #356
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I use the CRC front axle shims interchangeably with the rotor shims. I think they are 3/16 ID. The method explained to me by Novak CS was to use 1 shim on the sensor board end of the rotor always for consistent distance between the sensor board and rotor, and then shim all but a small amount of rotor play out using the 3/16 shims on the other end.
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Old 04-15-2011, 11:50 AM   #357
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Might sound off topic but read thru and u will see the light.
A few days ago I was doing some welding with a Lincoln gas powered stick welded. It has about 100' of both stinger and lead wire. Each was coiled around the steel tube wire racks. After welding for 10-15 min I noticed something strange about my stinger it kept popiing off my work. Strange I thought what it was when it arked the wire on the role would draw up about 3" ! Basically the current goin thru the raped wired was makin a magnet and it was pulling the wire inward and yanking my stinger off. Lol with this new light of how it works. I can def say epoxy wires r a must for long term high current vrsts. Current makes a magnet. And as wires heat up they r softer and eventual will bend then have a short eventualy. Never could grasp the concept till I seen it in larger scale.
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Old 04-18-2011, 02:03 PM   #358
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We include motor shims in our hardware kit for the Ballistic.
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Old 04-20-2011, 01:35 AM   #359
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Anyone try the epoxied stators?
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Old 04-20-2011, 11:03 AM   #360
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Anyone try the epoxied stators?
Yes in 17.5 and 13.5. Best to trial fit your motor when replacing the exp stator. I see no differences in motor performance on a dyno or track. The motor temp is slightly less, but on track to many variables to really know if that's the cause. The exp coating makes the motors about 1 gram heavier.
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