Noob - The second # in a motor spec?

[srfnmnk]

I don't get what the, after the slash, spec is about. Could you help?

Example -

2208/17 - I get the stator size in the 2208, but what's the "/17" about?

Thanks

http://www.altitudehobbies.com/suppo-motors/brushless-motor-370-28-26-1100kv-suppo-2208-17

 

[Fygar]

Its the number of turns of copper around each stator. It determines the kV of the motor for a given stator size.

a Suppo 2208-17 is 1100 kV the same motor set up with 14 instead of 17 turns is a 2208-14 and is 1450kV.

The size of the stator does matter. a 2208-12 is 1800 kV and a 2810-12 is 1000kV even though both have 12 turns.

 

[srfnmnk]

Ok, stators, equal, the higher the kv the higher the wattage??

What's the formula to figure out the kv based on that last number? how does a 2208-12 = 1800 kv?

Thanks for your help!

 

[Craftydan]

Depends on the OEM, but the frequent meaning is "number of turns" -- the number of loops around each arm in the armiture.

For some OEM's, that's a gospel number -- you see a "-7", it has 7 loops. For others, it's just a model code, but usually follows the trend -- you see a "-7" it might be 12 turns, but the "-9" will be more than 12, and a "-5" will be less.

While the motor size itself can give a hint that motor A *might* be more powerful than motor B, and the number of turns can hint at relitive speed, take care in comparing numbers between motor OEMs -- the sizes aren't *ALWAYS* stator size, but they usually are, and the "-" isn't *ALWAYS* the number of turns, but it hints at relitive kV, and *NOBODY* specs the strenght of their magnets. comparing prop/thrust data (if you can find it) or measured kV/max current/power generally give you a better feel of how two motors compare to each other.

 

[Fygar]

Crafty is right. I didn't mean to make it sound like there were hard and fast equations you could plug numbers into to get wattage and other comparisons. Sorry.

Its even harder than that because in addition to the power of the magnets you also have the gauge and quality of the copper in the motor. If you take a big 40xx motor and wrap it with the thin gauge copper they they use in a 15xx or a 17xx you might get close to the same kV but you lose the wattage because you can't pump enough amps through the thin wire.

Best bet is to surf the forum and see what others are using and happy with for a similar craft size.

 

[srfnmnk]

That's interesting. Thank you both for helping me on this. Happy 4th!