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Sayer

Can someone explain brushless motors to me

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I've been trying to wrap my head around how these things are rated and it just seems to be completely arbitrary.

I thought I had it figured out, but just stumbled across a forum where someone was being lauded for upgrading(?) a 4000kv motor to a 2800kv motor. Isn't that the opposite of an upgrade? and how do T ratings map to Kv? Is a 5T brushless motor better than a 2000Kv motor? Is a 2000Kv 4 pole better than a 2000Kv 2pole? If you have 4 pencils and I have 7 apples, how many pancakes will fit on the roof?

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The higher the kV the faster the motor for a like for like rotor and can size. Similarly the lower the T rating the faster the motor. Stupidly brushless T ratings are not aligned to the brushed motor T ratings, typically a 13.5t/16.5t brushless will be equivalent to a stock silver can 27t motor.

4 pole motors are torquier than 2 pole, so potentially could make better use of certain gear ratio options.

Longer motor can lengths equal greater torque too, so a 65mm long 1/8th buggy motor won't perform as well in a truggy as a 70mm long version.

You can only compare kV for a set motor size - a 10kv 1/18th motor is fast but only in its scale application.

KV ratings are only an indication, one companies 3900kv could be a faster/torquier motor than someone else's 4300kv one.

Hope that helps a bit

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**** electrical mumbo jumbo. Why can't they just use a simple type of measurement, like o.5kw / 2,000rpm @7.2v. Or atleast agree on something that everone uses.

All I know is if it's got a shiney red anodised coating, it's faster than a silver chromed one. If it's green it uses less power and battery lasts longer. If it's orange and got fins it's for a crawler. And yellow one's with fans on top are for drifting.

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Thanks Percymon, that's the best explanation I've seen.

So what would make a good torquey crawler brushless motor? And what difference does sensored make?

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I've been using two types of brushless motors in the past.

One is a Carson Brushless Black Shooter (true 540-sized) 16 Turns or 2500 kV motor in a DT-01 Mad Bull, and my impression is that this motor easily beats closed 27 Turns brushed RS-540 silvercans and even rebuildable brushed 27 Turns stock motors (e.g. GM Racing Pinnacle Brillant 27T). Torque and topspeed are quite high, but with a battery consumption equal to a RS-540, so the efficiency seems to be quite good.

The other one is a Carson Brushless Black Shooter (true 540-sized) 12 Turns or 3400 kV motor in a DT-02 Sand Viper. This is just mental. Bypassing people gaze in amazement when I'm pushing full throttle on the transmitter. Often they ask "this is a nitro car, isn't it?", since they won't believe their eyes that a battery powered car can go this fast.

Keep in mind the Sand Viper is a rather lightweight 2WD buggy.

For tapping full performance of these motors, I'm using 2s (7.4V) LiPo batteries. When using NiMHs, the topspeed starts suffering right after the first minutes, but what remains is the energy efficiency of the brushless vs brushed motors.

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The "upgrade" I was talking about is here http://www.ultimaterc.com/forums/showthread.php?t=162758&page=2 where a poster swaps out the stock RTR motor for a 4 pole 2400kv ( I was wrong in the OP) The problem being that while it's probably got more torque, that still seems like a lot of work to lower your top speed as the stock motor is 4000kv - and the very next guy is all "wow, that must fly now" and I'm thinking nope

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The "upgrade" I was talking about is here http://www.ultimaterc.com/forums/showthread.php?t=162758&page=2 where a poster swaps out the stock RTR motor for a 4 pole 2400kv ( I was wrong in the OP) The problem being that while it's probably got more torque, that still seems like a lot of work to lower your top speed as the stock motor is 4000kv - and the very next guy is all "wow, that must fly now" and I'm thinking nope

The motor is looks like it's larger than a stock 540 size brushless, possibly a 1/8 motor. It'll certainly accelerate better, but I can't see it being any faster either, as the car is relatively light anyhow. Even if it gets run on 3S, in theory it will still be slower than the 4000KV motor originally installed.

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Yeah, clear as mud.:-D I still prefer the brush motor. It has mor character with the brushes sticking out, the diodes and easier to understand. the brushless are the engine bay of new cars...everything is covered up. too tidy not mechincal enough. i rest my case.

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Motors cannot be measured just by kV or T or size.

Same goes for brushed, a stock 27T and a super-mega-sport-tuned-hand-wound-mumbo-jumbo 27T are not the same

kV means thousands of rotation if powered with 1Volt. It gives you an ideea if you can properly gear it on your car and your batteries.

T does not map to kV (same as brushed). Because it also depends on magnet strenght and other things. It just gives you an ideea if you will blow the esc immediately (since escs are rated in T) or you have a chance. But it does not guarantee anything.

4-pole have more power than 2-pole because you have more windings energized at the same time, attracting poles from the rotor magnets. Like, more man rowing the same boat.

That's the point on which you give up and just look what others use on the same type / class of car and the same cell count.

To give a _very_ rough ideea, examples from my bashing cars. But I am no expert and not looking after extreme speeds (like, on the verge of airborne).

- drift car (<2kg), 2S: 3300-4600kV, 2-pole, 540 size

- 1/10 sct-like (~3kg), 2S: 4000-4600kV, 4-pole, 540-550 size; 3S: lower kV, not sure how much, 3800kV or lower

- 1/8 monster truck (~6kg), 4S: 2000-2200kV, 4-pole, big can, like 4074 or around; 6S: not sure

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I went with a 3656 (36x54) 4000Kv 2 pole motor in my gravel hound. Fairly rapid on 2S, very nearly achieving flight on 3S (50mph plus).

I'm using a 4274 1/8 2000KV 4 pole running 3S in my txt-1, giving the same sort of speed as a silver can running on 3S, maybe a bit quicker, but a lot more torque, and I haven't advanced the timing or geared it up yet

I've got a 5674 800KV 4 pole turnigy motor in my 1/10 grapple skidder (I think these are primarily intended for model ships, as they are massive in comparison with a 540). On 3S, Massive torque but very slow. Doesn't notice the 7Kg weight of the model and accelerates and stop very quickly. The motor is capable of 6S, but I haven't got room in the model to fit a 6S battery, and haven't yet been able to locate a speedo capable of handling it at that voltage.

@Sayer, If you're thinking of something for Jugg2, just get a 3S LiPo and run on silver cans, this will as much as the chassis can handle. A lot cheaper than going brushless. Mine is capable of standing backflips in this setup :)

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I went with a 3656 (36x54) 4000Kv 2 pole motor in my gravel hound. Fairly rapid on 2S, very nearly achieving flight on 3S (50mph plus).

I'm using a 4274 1/8 2000KV 4 pole running 3S in my txt-1, giving the same sort of speed as a silver can running on 3S, maybe a bit quicker, but a lot more torque, and I haven't advanced the timing or geared it up yet

I've got a 5674 800KV 4 pole turnigy motor in my 1/10 grapple skidder (I think these are primarily intended for model ships, as they are massive in comparison with a 540). On 3S, Massive torque but very slow. Doesn't notice the 7Kg weight of the model and accelerates and stop very quickly. The motor is capable of 6S, but I haven't got room in the model to fit a 6S battery, and haven't yet been able to locate a speedo capable of handling it at that voltage.

@Sayer, If you're thinking of something for Jugg2, just get a 3S LiPo and run on silver cans, this will as much as the chassis can handle. A lot cheaper than going brushless. Mine is capable of standing backflips in this setup :)

Don't worry, the Jugg2 essentially became a shelf queen after I rolled it and snapped off one of the side mirrors (since replaced) - I was running it on 2s at the time lol

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Yeah, clear as mud.:-D I still prefer the brush motor. It has mor character with the brushes sticking out, the diodes and easier to understand. the brushless are the engine bay of new cars...everything is covered up. too tidy not mechincal enough. i rest my case.

I agree, the brushless motors just look too plain. It's a bit like the new cars (real ones) , they make really nice technical looking engine then put stupid plastic cover over it, that's spose to look better. <_<

I love the old Tamiya brushed motors. :wub:

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Brushless motor has just a spinning rotor, not much to see. Some of them look more "tech" than others.

Brushed is fine as long as you drive nice old slow cars. It's quiet, it has nice startup. But try to backflip a 6kg 1/8 monster truck with a brushed motor.

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Brushless motor has just a spinning rotor, not much to see. Some of them look more "tech" than others.

Brushed is fine as long as you drive nice old slow cars. It's quiet, it has nice startup. But try to backflip a 6kg 1/8 monster truck with a brushed motor.

Use 2 and gear it like the pumpkin, lunchbox, willy etc....:-D I can wheelie my XC with Tamiya standard silver stock motor. I just reverse it and full forward...and i have wheelie with my XC. Not very good for the drive shaft.

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Yes you can wheelie with a cw-01 (mp/lb/willy/montero) with silver can. Have one, nice for a little low speed fun, with minimal damage. My now favourite backyard car.

But if you have ever driven a savage flux on 6S which can backflip (not just wheelie, but do a complete backflip in the air) at half throttle and reach 5 times the speed of the cw-01... you'll understand brushless power. I tried one, it's power scared me. We're talking of motors in excess of 2000Watts, compared to the... how much has a silver can? 50-somethings Watts?

Again, is not that you cannot have fun with brushed motors, but you cannot have the same power and torque as brushless, not by a long shot

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The higher the kV the faster the motor for a like for like rotor and can size. Similarly the lower the T rating the faster the motor. Stupidly brushless T ratings are not aligned to the brushed motor T ratings, typically a 13.5t/16.5t brushless will be equivalent to a stock silver can 27t motor.

4 pole motors are torquier than 2 pole, so potentially could make better use of certain gear ratio options.

Longer motor can lengths equal greater torque too, so a 65mm long 1/8th buggy motor won't perform as well in a truggy as a 70mm long version.

You can only compare kV for a set motor size - a 10kv 1/18th motor is fast but only in its scale application.

KV ratings are only an indication, one companies 3900kv could be a faster/torquier motor than someone else's 4300kv one.

Hope that helps a bit

Make this a sticky thread in the all electric thread I say !

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