KV Motors

[XH558]

As someone who freely admits to not understanding electrickery I invariably build and fly stuff copying what others have done and installed .....

But I would like to understand one thing .... I';ve been looking at motors to replace some old GWS things I have on my current quad ... and the KVs seem to range from 600 up to over 1500 ... and ... correct me if I';m wrong ... but the more KVs the cheaper the motor seems to be on the HK site 

I know it stands for KiloVolts before you go off at a tangent explaining that  but what bearing does the KV level have on the quad ....

For batteries I have available 4 x Turnigy 3s 2200mah - 1 x 3s 3300 and 1 x 3s 4400 ... if that makes a difference .. a KK2 board and I am open to changing the escs - maybe 4 of these
http://www.ebay.co.uk/itm/330841043120?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649   already SimonK flashed 

So what KV and why 

PS - no need for FPV [yet] and no acrobatics ... just stooging about 

[XH558]

Anybody   

[Vidal]

I don';t know much at all about motors but the higher the kv. (More times it turns in a minute) the fast the prop will spin. But you have to use a smaller prop. So you get less power. I think it';s something like that. Look on giant shark website. They have a big write up on what it all means. Although I';ve read it twice and still don';t have a clue. Lol.

[Gaza07]

Im not sure higher kv motors are cheaper than lower ones 

Copied from another thread

The Kv rating tells you the speed of the prop at a given voltage if I read it right that is, Im sure its much more complex but its 1000rpm per volt so a motor with 1200kv at 11.1v would spin at 1332rpm
worked out 1200 x 11.1 = 13320 a 750kv motor at 11.1v would give 8325rpm which is 750 x 11.1 = 8325,
So you can see the lower kv motors are much more suited to a larger prop up to 12" on the 750kv,
where the 1000kv motor is more suited to a smaller prop and runs much faster, I prefer my motors around the 900 to 1000kv and run with 10" props I think that combo suits a wide range of multi rotors before having to change thing to much 

[XH558]

Thanks for that Gaz...

Now I failed my maths ';O'; Level twice - and never passed it - but I believe there may be a flaw in your workings out ...

surely if 750 x 11.1 = 8325     then     1200 x 11.1 = 13320 ... not 1332 

I just made a quick excel spreadsheet with formulas to work it out for me because I don';t trust my own maths and taking out the decimals gives the answers above ....

Which makes sense - the lower the KV number the slower the rotation 

Is that right - in essence 

[Gaza07]

You are correct I had written it down incorrectly  :embarrassed the funny thing is, it was taken from an old thread where no one else noticed   

[XH558]

There you go ... maths crap .... observation AOK... 

[KK1W]

There';s a number of electric flight motor calculators available, some are in the $40 (US) range. Here';s a link to one that is freeware (donations accepted) and offers calculations for multirotors too.

http://www.ecalc.ch/xcoptercalc_e.htm?ecalc

You still should have some kind of watt meter to verify what the calculators predict. The ';Watts-up'; type of meter can tell you a lot about your power system and let you ballpark your lipo needs as well.

In regular R/C aircraft the larger planes tend to go with low KV motors, large props and higher cell counts to get the correct RPM. Higher cell count lets you lower the current but keep your power (watts) in the required range for good performance. The advantage of the motor calculators is they help you find the most efficient range of props for a given motor. That turns into longer flight times, always a good thing.

Hope this helps

[XH558]

Thanks for that ....I had happened upon that very page myself whilst attempting to discover the mystery that is KVs .. 

I took one look at it and almost fainted  Talk about over complicated ....in fact over everything 

I don';t really want to know THAT badly  ::) ::)

So .....I';ve ordered 4 of these on a whim based on ';about 1000kv'; and they';re cheap .....
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=28675

and 4 of these http://www.ebay.co.uk/itm/330841043120?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 SimonK already on board 

The way I look at it they';ll work ....or they won';t ... how';s that for a calculator 

[pheasant_plucker]

kv in this case is different to Kv. It stands for 1000rpm per volt (kilo per volt)

Gerry

[XH558]

kv in this case is different to Kv. It stands for 1000rpm per volt (kilo per volt)

Gerry

Aha ... 1st time I';ve heard that ... makes sense 

[guest325]

Thanks for that ....I had happened upon that very page myself whilst attempting to discover the mystery that is KVs .. 

I took one look at it and almost fainted  Talk about over complicated ....in fact over everything 

I don';t really want to know THAT badly  ::) ::)

So .....I';ve ordered 4 of these on a whim based on ';about 1000kv'; and they';re cheap .....
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=28675

and 4 of these http://www.ebay.co.uk/itm/330841043120?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 SimonK already on board 

The way I look at it they';ll work ....or they won';t ... how';s that for a calculator 

I would have gone for the 30A esc';s myself - with budget priced esc';s it pays to have a bit of headroom, if you want good stuff have a look at Puffin models, the Jetti stuff is the mutts but it';s expensive.
I';ve got rctimer 2212 1000 kv motors (the blue ones) on mine running 8x4.5 props.
with 30A rctimer esc';s.

[XH558]

I would have gone for the 30A esc';s myself - with budget priced esc';s it pays to have a bit of headroom, if you want good stuff have a look at Puffin models, the Jetti stuff is the mutts but it';s expensive.
I';ve got rctimer 2212 1000 kv motors (the blue ones) on mine running 8x4.5 props.
with 30A rctimer esc';s.

I agree - I went for the 30A .... but Eyeflying on Ebay only had 1 available and I wanted 4 
So the 20s will do for now 
I can see the actual RCTimer site is cheaper still ...but then it';s the wait for the stuff to arrive 

For my purposes I';m sure it';ll be fine