Basic Motor Considerations

[Thx1326]

Looking through the variety of motors, there are literally hundreds of choices with subtle differences.  I am currently using an Alpha 400 which seems to be a very popular motor with 3500KV.  With an 11 tooth pinion giving a gear ratio of 12.73 means with 11.1 volts it "should" give a max head speed of 3051.  That would be a 100% throttle pulling max amps.

I see motors that are listed in forums,  and other sites that are:

Lighter in weight - a good thing
more efficient - up to 98%
and draw less amps.

One motor in particular seems to stand out in the spec's in that it weighs only 36g, pulls a max of 25-30 amps and is rated at 5250KV.  Using the same setup, this motor would give a max head speed of 4577 while pulling less amps.  This would allow you to run the motor at a max throttle of 66% to reach the same speed as the alpha 400.

This would allow the ESC and motor to run cooler, draw less amps and give you longer battery run times.

Is there something missing here?  What other considerations need to be considered?  Obviously, the construction of the motors will effect their longevity - but the truth is that most of these motors come out of the same factory and are re-branded and re-labled for different suppliers.  These no-name motors seem to be whole lot less money and truth be known, the number of blatant motor failures as a percentage to other malfunctions is a very small percentage.  Like so many other things in the hobby, you seem to pay a very hefty premium for the name brands which don't really add more value (there are exceptions - I'm speaking in generalities here).

Thanks in advance.

All input is welcome.

[kloner]

To start with, read this pdf, this is my general knowledge of what normal kv motors and sizes do

http://innov8tivedesigns.com/Software/ScorpionHeliMotors.pdf

read page 2 & 3, that is for the 450's

then read about the bottom motor. That where the 450 is supposedly heading, i dunno, don't have one never seen one but bet it is bad ass

http://www.innov8tivedesigns.com/#P1

Now i'm not saying this is the only motor, but it has the best explanation of how the different kv motors come into play



You have some head speed calculations. Because of variances i don't know how to manually figure these things out, but if you want a calculator to see what different battery/motor kv equates to headspeed, use this

http://heli.dacsa.net/CalculatorV2/

Every video you see of mine is scorpion motors on 30c and 40c 3s and 6s batteries using throttle curves that look like 0,65,80,90,100 and 100,80,100...... all of em. You see 2221-8, 3026-1400 and 4035-800

[dditch66]

most motor specs I see, the only useful parts are the Kv and Max watts. Often they post max amps and such but from what i've been told, the max watts is what you have to look at. I've run motors that say 4s max but used 6s and so long as I don't go over the max watts I was fine.  Efficiency can also be misleading cause it changes with load. The alpha 400 is popular cause it's cheap and compares pretty close to the Align 430L as far as efficency and max wattage. It's Xheli's basic 450 motor.   

[kloner]

That's an excellent point. What knowing the max amps to a guy that actually puts a meter on it when they set it up is it lets them run x amount of recommended volts and there target to load the motor with pitch or prop should keep the meter in the max amperage range. That is for people like me that don't understand how to calculate one thing on a calculator set one up and use a watts up type meter

Watts is a stat tell me how much power were talking about. Go to any conversion site and type in watts to horsepower (electric) and it gives you some basic numbers to talk about in layman car guy terms

The big question is what are you trying to do and how much power do you need versus how long of flight times do you want. I bought a 2221-10 just to put on a metal version exi 450 but it has that d2830 and honestly, i like that little motor, lets me fly what feels like forever and does everything i ask like a big boy. There are several motors on the market, but when you start throwing around kv numbers like 5250kv, that is the wrong way to go for a 450, now if you looking at a 250, your in the ballpark.

Lighter in weight - a good thing> doesn't matter in a heli except batteries to power it can get ya off cg
more efficient - up to 98%> only means longer flight times but sacrifices power, usually
and draw less amps.>See #2

More watts equals more pressure placed on the mainframe equals if it ain't right and it has lots of power, it'll rip itself appart, worse case scenario. I've been trying and haven't seen it yet running 4200 watts, but i haven't flown 300 flights with it yet either

[Thx1326]

Check out this motor and let me know what you think.  Since I have my 450 apart - I figure do the upgrades now so I don't have to take it apart again.  My fingers are too big to handling all these little screws and parts.

e B a y item #220543501341

The web site is: http://www.aeolianmotor.com/

Note the bottom of the casing has the mounts beveled and curved to act as fan blades for cooling without adding extra weight with a bigger case.  Seems pretty well built.

At $21.00 - it can't be too big of a mistake if it's a dud.


Specification:
Rotational Speed  5200 (kv) RPM/V 
Continuous Current  15A 
Max. Current  20A 
Input Voltage  6 - 14.8V 
Max. Efficiency  98%
No Load Current  1.2A
Internal Resistance  99m(Omega)
Motor Weight (Motor only) 49g
Motor Dimensions (Diameter x Length)  28mm x 25mm
Input Battery Types  NiCd/ Nimh/ Li-po Battery
Recommend Model  Airplane/Helicopter


Thanks

[dditch66]

I don't think that's a good 450 heli motor.
Kv is way higher than what most people run.
3000-4200 is about the useful range on 3S.
Most people run 3500-4000.
With 5200Kv, you will have to run a really small pinion.
15A of continuous current is barely enough to keep a hover.
I think my 450 hovers around 12A so 15A max continous tells me it will BOG serously.

This is NO upgrade if you already have an Alpha 400 motor which is a pretty decent basic 450 motor. 
If you want more gusto, you can start by putting a 25C or 30C lipo in it.

[kloner]

even there 450 motor isn't much of an upgrade. You want scorpion , raiden, or the like to feel an upgrade in power. Get the d2380 if you want an imporovement in power and keeping flight times where there at. My 450 scorpion on 2200 mah flies for 4:00-4:30.

[dditch66]

Thx, what kind of batteries are you using and what are you looking to accomplish with an upgrade?

[Thx1326]

I'm using 25c 2200mahr Lipos.  I'm not really looking to accomplish anything special - just thought while I had it apart, I'd pop in a faster motor if it made sense should I ever try to attempt 3d.  Thanks for the input... it seems most of these motors seem defy the normal specs of electrical theory and motor concepts for some reason.

I don't fully grasp why a lower KV motor would be better just because it draws more amps at any given RPM - seems counter-productive to efficiency.  If a motor will maitain its RPM spec with less amps, and if you gear it down a bit with a 10 or 11 tooth pinion - you should be able to maintain power at your desired revolution at a lower percentage of its max RPM spec - thus drawing less amps at the same RPM and power.  All in all, it should be a more efficient system in this case with room to grow should you want more headspeed.

I agree that 5200 is insane headspeed and was never contemplating using it - through gearing and throttle curve setting, I was going to step this back to just slightly higher than the stock Alpha.

Looks like I will be keeping the Alpha till she goes.

Thanks for the input.

[chris.7935]

Kloner and ditch are right that motor is not powerful enough for a 450. 15amp draw?

The real key to look at on a motor is the WATTS.
This will tell you a no bullshiit rating of how powerful it is.

The problem with your theory is they do not have the torque available to gear it down anymore..
I am unsure the watts on that motor you list, but I assume it is for a 3 cell battery so 12 X 15 = only 180watts.
The align 430l (stock motor on the new trex450's is a 300 watt motor.)
the scorpion-6 V2 (what I want for my 450) is a 525watt motor.

That 180watt motor is woefully underpowered for a 450.

[dditch66]

3D, what's 3D I try to say. 3D is not a manuver (Sarcasm on the overuse of the term 3D, sorry)

My blueray 450 came with Alpha 400 and 13T pinion. That will ZIP up the helicopter.
I only ran I think +/-9 or 10 degrees of pitch and got it to do all kinds of flips and such.
Loops, rolls, stall turns, backflips etc are all within the range of the Alpha 400 on a 13T and a 25C battery.
Quick punchy manuvers like a tic toc is where it can bog down.
Yank any flybar weights, CF blades and a 3000RPM headspeed and even with the alpha, it becomes rather agile.

I will say that power does help you get out of trouble though. But if you have too much pitch and power, it will make you fly like your heli is unstable (yo yo) till you get used to it.

[Thx1326]

As ususal... thanks for the advise.

I still must admit that I am still not grasping the total power thing.  Just because a motor produces more watts does not necessarily make it more powerful or more efficient.  If a motor through gearing can maintain a torque and rpm rating - then if it consumes less amps, it will still have a lower wattage rating.  If a motor is more efficient and draws less amps, it will obviously have a lower watt rating - does that alway translate into lesser power for the task.  It certainly means less amp draw and longer run times.

So from what all of your are saying, that two motors - given the same end RPM production (through gearing), the one that consumes the most amps at that given RPM is the more powerful - even though it is the least efficient?

Thanks again for the tutorial.

[kloner]

Watts is everything when it comes to electricity and measuring it's energy. You buy a vacuum, they tell you it is a 10 amp (1000 watt) vacuum, bigger the number, more power it has. You buy a light bulb, it is measured in watts, and the higher the watts, the brighter it gets.

My big helicopter is 4200 watts, that tells me how much power it has. The rpm it is going to turn or the kv, lets me know that it'll spin a certain speed wide open which is where you'd like to keep the motor spinning. Anytime you throttle back, you are not using it to it's potential. Your 450 wants a 3500kv motor unless your whiling to step up voltage, that is the only reason to not run 3500 kv

Hopefully i didn't make it worse.

[Thx1326]

Kloner...

Not at all... I'm always willing to learn.  And by the way, your Chinese Tail Kit in on its way.

[chris.7935]

As ususal... thanks for the advise.

I still must admit that I am still not grasping the total power thing.  Just because a motor produces more watts does not necessarily make it more powerful or more efficient.  If a motor through gearing can maintain a torque and rpm rating - then if it consumes less amps, it will still have a lower wattage rating.  If a motor is more efficient and draws less amps, it will obviously have a lower watt rating - does that alway translate into lesser power for the task.  It certainly means less amp draw and longer run times.

So from what all of your are saying, that two motors - given the same end RPM production (through gearing), the one that consumes the most amps at that given RPM is the more powerful - even though it is the least efficient?

Thanks again for the tutorial.

"If a motor through gearing can maintain a torque and rpm rating - then if it consumes less amps, it will still have a lower wattage rating."

Thats the catch is that it can't. It dows not have enough torque. For that motor in question in your first post I would guess You would have to run a 5-6t to get enough torque to keep the blades from bogging down when pitch is applied.
Then you head speed is way to slow. Watts = power in electric motors. Gearing can only do so mcuh.