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Old 10-15-2010, 04:35 PM   #1
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Default Brushless Motors, are there huge performance variations brand to brand?

I'm curious and haven't found much information online.

If you are looking to purchase a brushless motor there are several options available. Typically you have a specific turn motor you run for your class, 21.5, 17.5, 13.5 etc.

Between manufacturers are there big variations in performance in the same turn motor? If so has anyone compiled the data on the different brands and performance of their same turn motors?

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Old 10-15-2010, 07:11 PM   #2
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im curious as well
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Old 10-15-2010, 08:55 PM   #3
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I think it all comes down to gearing and tuning in your ESC.
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Old 10-16-2010, 12:32 AM   #4
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None of that has to do with the output of the actual motor...... I'm curious if certain motors turn more rpms,have a better torque curve, more punch etc.
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Old 10-16-2010, 01:01 AM   #5
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i bought a kv/rpm tester to test my castle motors. everyone i've tested: 9000kv, 7700kv, 6900kv, and the 5700kv is actually 300-400kv LOWER than labeled. my 9000 averaged 8700, the 7700 averaged 7400 and so on..

hook up my friends novak ballistic 3.5T which is rated @ 10500kv and it actually averaged 300-500kv OVER. close to 11000kv.
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Old 10-16-2010, 02:14 AM   #6
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Even between motors of the same brand but old and new type you have variations.
I got the old and new type GM Pro stock 13.5 motors and you can swap all parts between them but still the new type has more power due to that the rotor is 0.2mm bigger in diameter.
Windings are the same and if you put the new motor on the same timing it has still more power.
With LRP X12 13.5 this is the same case.
Motor has more power but less RPM but is still quicker on track.
Bad thing of the new motors is that with all the holes in the can to reduece heat buildup the maintenance interval of the motors is going up and the bearings wear a lot faster.

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Old 10-16-2010, 09:39 AM   #7
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When purchased new, there should be almost no variation among different brands of ROAR-approved, spec BL motors; these motors must be built, and approved, according to stringent ROAR guidelines. Motor timing adjustments, though, are not speced by ROAR and may figure into your purchasing decision.

When purchasing a spec motor, it is important to (also) consider the manufacturers' after market support---customer service policies (trade-ins), as well as availability of service items and accessories---rotors, bearings, stators, harnesses, etc. BL motors do require a certain amount of maintenance and occasional repair, so it is crucial that these spare parts are always available.
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Old 10-16-2010, 11:18 AM   #8
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Quote:
Originally Posted by NovakTwo View Post
BL motors do require a certain amount of maintenance and occasional repair, so it is crucial that these spare parts are always available.
So how often should this take place?
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Old 10-16-2010, 11:57 AM   #9
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Yes there is a massive difference sometimes. Winding wire thickness, winding style, cooper purity, quality of sensors and rotor strength all have an effect. I have tried a losi, Lrp X12, Speedpassion v3 and two GM with both the 1300guss rotor and the 1600.

Losi was smooth but was just 5 minutes of increasing fading as heat built up. Temperatures as little as 60c were enough to make it practically useless, for high traction at least.

Speedpassion is smooth and will feel the same when it finishes the race as when it started. Doesn't have out and out speed like some of the others and is a little over weight.

LRP x12 is very punchy and power comes in lumps. Didn't like that much as it makes getting on the power out of corners difficult. They over heat rotors and loss punch when hot, but for the first 3 minutes they are fast.

GM with 1300 rotor is a lot like the speed passion but has a little more top end and a very good motor with low traction.

GM with 1600 rotor is by far the best motor i have. It has very smooth power, incredible punch and the fasts motor i have used. Only fades if you really get the heat up with it. Even then i'm talking 95C.
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Old 10-16-2010, 01:37 PM   #10
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That's the info I'm looking for!

Anyone else have comparisons?
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Old 10-16-2010, 02:16 PM   #11
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Quote:
Originally Posted by liquidgenesis View Post
i bought a kv/rpm tester to test my castle motors. everyone i've tested: 9000kv, 7700kv, 6900kv, and the 5700kv is actually 300-400kv LOWER than labeled. my 9000 averaged 8700, the 7700 averaged 7400 and so on..

hook up my friends novak ballistic 3.5T which is rated @ 10500kv and it actually averaged 300-500kv OVER. close to 11000kv.
Where did you get this tester?
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Old 10-16-2010, 03:01 PM   #12
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Kv ratings only tell you how many rpm's you get per volt and nothing else.

More rpms per volt could simply mean that motor has quite a weak rotor or that it has more fixed timing as standard. For example you could have two motors rated at 2700kv. The first one has a weak rotor and 30dgress timing. The second has a very strong rotor and 10degrees timing. Obviously the second is a far superior motor but the Kv rating suggest they have the same performance.
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Old 10-16-2010, 03:58 PM   #13
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Motor KV is NOT a good way to compare motors, especially sensored 540 brushless motors. I can take a 10.5 motor, and test it at 7.2 volts, at 0 degrees of endbell timing, and make 3800KV. I can take the same motor, and bump timing to 10 degrees, and make 4150KV. Likewise, at 20 degrees, it become 4375KV. Unfortunately, many people look at KV ratings, and assume higher means it faster.

If you were to compare motors with equal torque, and one had a higher KV rating, the higher KV motor would be faster overall. However, KV ratings are easily cheated by advancing timing, bowever more timing ALWAYS means less torque. In KV ratings, torque is not calculated.

So, If you want to know how to calculate gear ratios for a speed run car, knowing the Voltage of your system and the KV of your motor is VERY IMPORTANT. However choosing Brand "A" over Brand "B" because of a higher KV rating is just silly. Unfortunately, in todays RC world, companies use "KV ratings" and "C Ratings" to sell products, even though they DO NOT accurately help the consumer choose a stronger option.

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