what do 300, 370, 400, 450 sizes mean?

[Samick]

i've seen this notation for awhile now, and have even been asked what size motors i'm using in regard to this metric.. So what do these numbers refer to and what is this metric called?

 

[Montiey]

I think its an equivalent to gas or nitro power, or just a sizing system that has nothing to do with anything useful.

 

[AirTrafficJO]

I believe it is how they sized brushed motors. So i guess that would be the brushless equivilent.

 

[mesolost]

From what I've come across this is in regards to their nitro/gas engine cc equivalent. I could be off though but I'm fairly confidant it's not the brushed/brushless equivalency number. Those numbers are also used as a size reference for the entire aircraft in regards to helicopters, MR too I believe. If I'm wrong I know someone will come along and correct me and I'll read it and pass on the correct info from then on. =p

 

[Epitaph]

On multirotors and helicopters it usually means the size class of the frame.

On small electric brushless motors it is referring to the size equivalent in brushed Permax motors. In this case you might also hear "a size .41 motor" or "size .25 motor" and things like that... this is making equivalence with nitro motors of those sizes

On large motors (very large) it would refer to the equivalence in cc... but take into account that the size of plane used for a 450 gasser would be pretty big!!

 

[Kelsoe]

there is absolutely no way that number is sized for a fuel motor displacement neither in inches and cc's

 

[Kelsoe]

sense I opened my mouth I figured I could do the research....seems to be an OLD motor classification system that I first ran across in RC and slot cars literally decades ago..the useage I knew was something like Mabuchi 540 is the size found in 10th and 12 scale RC cars and IRRC, Mabuchi 380 was the slot car "can" size...

 

[Kelsoe]

ok I didn;t remember the numbers right for the slot car...but that's what the number is it's an old classification system from brushed motors that described the "can" size and the power output in a "standard" configuration...

 

[Kelsoe]

I haven't found any direct listing or explanation saying that...if a motor has a 3 digit number...that's what is it is.... it's a Mabuchi reference number..

Mabuchi reseach developed the permanent magnetic techonolgy and went on to founded the small electric DC motor industry and still pretty much owns it....just wiki Mabuchi ...then wiki Mabuchi and a few different motor size numbers like 540 and 380 and 260 and see what you think...

 

[Kelsoe]

this is probably the most convincing thing I have found yet

http://www.mabuchi-motor.co.jp/en_US/product/p_0306.html

 

[PeterGregory]

Interesting note on Mabuchi.
The numbering system probably has departed from any connection with dimensional characteristics of the motor itself, but lingers on from days gone by.
On another thread I was just comparing ratings for, say, different offerings of the Turnigy Park250's. In one can size you can get 3 different motors.
They differ on KV, power, current, and other characteristics.
So, even within the same can size from a manufacturer, things differ quite a bit - by 100's of watts, sometimes.

Conclusion - just a rough number to possibly start comparing motors.
Correction, both are only rated for 2S --> I even just noticed the e-Flite Park250 is apparently rated only up to 2S LIPO's, whereas the Turnigy knockoffs are rated for 3S.
In practice, I suspect e-Flite's can handle that, too.