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Oct 24, 2018, 10:32 PM
Did I make the A Main?
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REVIEW: NOVAK NX4-3900KV 4-Pole 540 Motor

So I recently bought a TEKNO ET410 and ran into thermal issues with a generic 2-Pole 5.5T motor in the truck, after swapping out a spare 7.5T motor, I just wasn't impressed with the torque and decided that I wanted to try a 4-Pole motor, however I did not want to use a HobbyWing motor because they come with a 5mm shaft and are designed for 4WD SCT's. I have spoken with a TEKNO team driver in my area and he cautioned that 4WD SCT motors would tend to generate too much torque and cause on-power push in the corners. I first tried a 2WD SCT motor (SC211-4400KV) from TenShock, but would later discover that TenShock motors are not compatible with HobbyWing ESC's, doh!

In my quest to find a 4-Pole 2WD SCT motor to help hit the sweet spot of slightly more torque than traditional 2-Pole motors but not as much torque as 4WD SCT motors, I came across a batch of discontinued Novak NX4-3900KV 4-Pole 540 motors on eBay for $35 shipped:

There were 10 of these motors available at the time I made the purchase 3 days ago (talk about fast shipping!), but only 5 available now at the time of this writing. Who knows if any more of these motors will pop up elsewhere on the net because Novak went out of business a couple of year ago:

With no warranty support or spare parts, I'm only looking at this as a disposable motor, and for $35, I'm willing to take the risk!

Full specs of the motor are listed here:

Box Opening:

So the first thing I did was drop the NX4 onto my motor analyzer just to get some baseline numbers:

The next thing I did was check the shim, but couldn't help but notice that 2 of the screws on the endbell did not have any thread lock on them!

Holy mother of monster gap, I don't think I've ever seen a rotor spaced this far away from a sensor board. I suppose this can be a good thing for the design of the ET410 which has the sensor board facing the front of the chassis, if you take a hard crash, then you risk having the weight of the rotor hit the sensor board which can easily damage it. Anyway, there were 2 shims and I played around with various combinations where I left the smaller shim on the sensor board side and moved the larger shim to the opposite side to get the best results, which I will show later.

Although the specs provide the diameter of the rotor at 18mm, I decided to measure the length of the magnets, I did not include the length of the metal plates used to secure the magnets and measured 24mm total:

After final tuning the shim, this was the optimal performance that I was able to get out of the motor, note that there is no mechanical timing adjustment, the motor started out with a reading of 18 average timing and I wound up with 20 average timing when I was done I actually got the current draw to drop 0.2A which tells me this is the most efficient setting, kinda helps to see both the RPM and KV jump up showing a little more power after tuning the shim of the rotor:

Look for updates after this weekend which is when I plan to get some run time with this motor and I will share more of my thoughts then, wish me luck!

Check out more stuff on My Bookmarks page!
Last edited by bill_delong; Jan 18, 2019 at 04:31 PM.
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Oct 25, 2018, 12:04 AM
Did I make the A Main?
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So I just took apart my TenShock SC211-4400KV motor and measured the magnets on the rotor, I got 21mm long and 15mm diameter, the rotor was physically longer, but I only measured the visible tape which is where the magnet is located.

Here is the formula for the volume of a cylinder:
V = π r^2h

3.14 * 7.5^2 * 21 = 3709 = TenShock magnetic volume

3.14 * 9^2 * 24 = 6104 = Novak magnetic volume

Tenshock / Novak = 3709 / 6104 = 61% or Novak has roughly 39% more magnet mass!

*** This doesn't take into consideration of the quality of the magnets, but I am interested in comparing the volume of magnet used between both motors

*** Also worth noting that the TenShock motor had no spacers/shims on the rotor which left no tuning for shim, I am very disappointed in the overall quality of TenShock, that is a brand that I probably won't buy again
Last edited by bill_delong; Oct 25, 2018 at 12:33 PM.
Oct 25, 2018, 09:04 AM
Did I make the A Main?
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I have not had the chance to run the Novak motor on the track yet, but I did experiment with a few short WOT bursts from a dead stop on my carpet at home. With the SC211 motor, the front wheels would stay flat, in fact it felt very similar to the power of the 7.5T motor I had installed. With the NX4 motor, the ET410 does a quick wheelie, actually a little more aggressive of a wheelie when compared to the 5.5T that I have. I definitely need to turn down the punch, hopefully I can find the sweet spot for this weekend's race!
Oct 30, 2018, 06:10 PM
Did I make the A Main?
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Happy to report that I have a full day of practice and a full race day on the NX4 in my ET410... I started out with am 18T pinion for practice without the cooling fan hooked up and I was averaging 110 after coming off the track at LVC. Acceleration was great, but top speed was lacking so I geared up to a 20T pinion for race day which was the perfect gearing for my ET410, temps came off the track around 130 with the cooling fan enabled and a 5 min run with close to 2 min of warmup each round. Top speed was perfect and my car was very competitive, I would highly recommend the NX4 for anyone looking for a decent 4 pole motor to put in the ET410!

Here's a clip with my ET410 in action to get an idea of what to expect from the motor, where my truck is pictured here, I'm the 3rd car to start at the beginning of the race:

Mod 4wd Truck (Heat 1/1) [Q3 Race #7] :: 10/27/2018 :: Thornhill Racing Circuit (5 min 37 sec)
Jan 18, 2019, 04:26 PM
Did I make the A Main?
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Quick update, I have just logged 15 race days on the Novak motor and it's been working very well for me. If for any reason that I should have any problems, I don't think I will be able to buy another as they are discontinued and sold out now, I will probably consider the Rocket Racing 540 4-Pole 3900KV Sensored motor as a suitable replacement.

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