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motor Numbers: I know I know

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Old 11-16-2012, 03:28 AM
  #1
OldNick
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Default motor Numbers: I know I know

Every time I think I have a handle on this there is some other factor that usually seems to mean nothing. ATM I am looking at the specs for a truck that has a 3000Kv motor (3000RPM/Volt, got that) then it says (3660). Now the 1/10th I have now has a 540 motor. I check out 540 motors and find that they can range from 380W to 1200W in power. So as far as I can see the 3660 could easily be less powerful than the most powerful 540 motor AND have different voltage handling capabilities: as in 2s, 3s 4s etc..in fact is the power directly related to the cell series rating of the motor?

I realise that the vendors will deliberately throw numbers around to sound good and say lttle, especially at my bottom-feeder level of buying. But is there a place where I can see what all this actually means, and try to dredge reality from the mirk they put out?.

That little piece of vent has made me feel better, but I would still apprecaite a guide.

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Nick
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Old 11-16-2012, 05:14 AM
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Default RE: motor Numbers: I know I know

There are a number of factors to consider when searching for a new motor and it's easy to get caught up in all the variables. The KVrating is typically the preferred way to measure a motor's power potential when comparing it to other brands and models. It's difficult, if not impossible, to put two 13.5 turn motors against each other and say that they will have the same or near similar performance. Apparently the turn ratings aren't standardized between the different manufacturers so, KV is used and wattage is a secondary consideration.

Also, among 540 motors, you can compare two 4000KV motors but they may have a different number of poles. If one is a 2-pole and the other is a 4-Pole then the 4-pole will put out more power. It will also consume more energy too. In most respects it's easier to ask, what type of vehicle will the motor be used in? What type of driving will you be doing, racing or bashing? Are you more interested straight line speed runs to impress your friends or do you want a solidly capable motor for off-road driving? Answering these questions will help steer you towards the right kind of motor. Most 540 motors can handle more than 3S LiPo power either. 550's can sometimes take 4S but are better suited to 4x4 vehicles as the increased power would be unmanageable in a 2WD vehicle.
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Old 11-16-2012, 06:09 AM
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Default RE: motor Numbers: I know I know

I am sorry, but your reply goes against all my feelings about "specs'. This is NOT to say you are wrong in your statements. It's just that it makes me feel that there is a whole set of numbers out there that are designed to sell, and to mislead and confuse rather than allow user comparison.
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Old 11-16-2012, 11:39 AM
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Default RE: motor Numbers: I know I know

Quote:
ORIGINAL: OldNick

I am sorry, but your reply goes against all my feelings about ''specs'. This is NOT to say you are wrong in your statements. It's just that it makes me feel that there is a whole set of numbers out there that are designed to sell, and to mislead and confuse rather than allow user comparison.
yes the Turn number on the motors is that one. Best ignore it(unless you are racing at a track) like Bkoz559 said as I find them t vary between manufacturer, hell even some of the same manufacturer motors it varies like the 540 it can be quite different from sensored to sensorless.
The KV rating you know approximately how many RPM's you will get(I'm sure there is a +/- tolerance but I've not seen it)

I don't understand why races say stuff like 17.5t when on the ROAR list I looked at motors from diff brands that are approved and their KVs were all over the place for the same class.
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Old 11-16-2012, 11:45 AM
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Default RE: motor Numbers: I know I know

You are probably right.  But learning WHICH number to pay attention to is what BKoz was trying to tell you.  That 3660 number is probably the manufacturer's model number for that motor.  540 and 550 refer to the motor "can size" (i.e. its physical size). It seems a lot of the confusion is in part due to manufacturers, and other people, still using terms that applied to brushed motors, and don't really have meaning in a brushless world.  Like for instance on my EXrun motor, it says "9T" on the can, but it is a 4300kv motor.  It's like they're trying to give oldsters used to brushed motors something to relate to when picking brushless motors. Problem is, whatever formula they use to make that comparison is not standard across the industry. 

Here's another spec to put in yer bonnet: What is the vehicle weight a given motor is intended to be run in? THAT is probably more important than any other rating.  You wouldn't want to put a 380-size motor like my EZrun in a Slash.  My motor is intended for vehicles weighing less than five pounds. (An Evader weighs 3.5lbs)  A Slash is a good deal heavier than that, maybe eight pounds. Putting my motor in a slash would burn up that little thing.  So, what does all this mean? What is important?  1) Start with vehicle weight, look for a motor designed for loads compatible with the given vehicle. 1/10 to 1/12 and less than 5lbs, you could probably get away with a 380-size motor. Over 5lbs, a 540 would be good. Pushing 8lbs, a 550-sized motor would be good.  2) What TYPE of vehicle is it? On-road? Off road?  Bashing or racing?  High-speed on-road cars like higher KV motors, off-road cars usually like slightly lower KV ratings, as they produce more torque by way of gearing.

If you're just looking thru catalogs looking at various motors, they may not list all the info you need to make an informed decision.  But the generalities I listed should get you going in the right direction.  (Providing that MY understanding of this topic is correct....)

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Old 11-16-2012, 06:59 PM
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Default RE: motor Numbers: I know I know

The 3660 you asked about is the physical size of the motor can, 36mm diameter by 60mm long. The power ratings in watts are kind of confusing, they're usually a peak power handling rating. Meaning they don't indicate what the motor is putting out power wise, only what it can consume for a few seconds without burning up.
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Old 11-16-2012, 07:15 PM
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Default RE: motor Numbers: I know I know

a 3650 is pretty much a 540 can
and a 3660 is a 550 can

Maj you beat me to the explanation I was double checking what I typed to make sure I was 100% correct [:@]
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Old 11-16-2012, 08:14 PM
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Default RE: motor Numbers: I know I know

Thanks for all the input guys. The 3660 being a sort-of 550 makes sense.

I think the problem is not with the actual motor specs, but the way the vendors describe them, just throwing numbers around without really providing any true useful figures.

I am actually looking at a generic (HSP)1/8 4WD offroad truck. Its specs have only the 3660 and the 3000Kv for the motor. No weight either. Not much use. I have found a review of the beast that says the stock motor can take 3S, the ESC can take 4S, but you need a new motor to use 4S.

Actually places that sell motorsd and stuff usually seem to have half-useful motor specs. IT's just the new RTR vehicles that are minimal, at best.
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Old 11-16-2012, 09:20 PM
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Default RE: motor Numbers: I know I know


Quote:
ORIGINAL: OldNick

Thanks for all the input guys. The 3660 being a sort-of 550 makes sense.

I think the problem is not with the actual motor specs, but the way the vendors describe them, just throwing numbers around without really providing any true useful figures.

I am actually looking at a generic (HSP) 1/8 4WD offroad truck. Its specs have only the 3660 and the 3000Kv for the motor. No weight either. Not much use. I have found a review of the beast that says the stock motor can take 3S, the ESC can take 4S, but you need a new motor to use 4S.

Actually places that sell motorsd and stuff usually seem to have half-useful motor specs. IT's just the new RTR vehicles that are minimal, at best.
what isn't useful about those specs?
the motors RPM's is 21600 @ 2S, and 33300 at 3S way more useful than the Turns. If you have the gear ratio, and tire size you could approximate the speed with some calculations(something you cannot do with the number of turns)
Only thing missing is the amperage the motor can pull max
As for the RC knowing HSP they took a 1/10th and just stretched it to 1/8th scale so using 1/10th electronics is a possibility. Hell I made a 1/8th scale buggy that flies on 2s out of a 1/12th scale truggy(and some SCT parts).

Now if you REALLY want to see useless specs look at castle creations MM's The one I got says for 1/8th truck, no amp rating only KV. Had to go find some sub contracting site for CC to get the actual rating of the electronics.
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Old 11-16-2012, 10:25 PM
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Default RE: motor Numbers: I know I know

Yes I know how the Kv works. But I would have thought that amperage was pretty basic oiece of info and it's not there. And the weight of the truck would be nice, so you can compare with other vehicles for acceleration.

You could calculate some speeds, except that for, say, a 1/10 model they give no Kv rating, then for this one they do not give other specs to help...actually it looks as if this would do 45KPH on a 2S LiPo. 12.95:1 gearing (I assume that includes the diffs), 150mm tyres, 3000Kv motor. But again no acceleration.

For their 1/10 Bronto Pro they keep muttering about up to 70KPH and figures like that. You can't check that as you do not get the KV of the motor.

My point is that if they do not show all the figures, they can claim anything (or nothing and let youthful foolishness do their job for them) and we can not know or compare.
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