View Full Version : what am I reading?

09-04-2005, 07:24 AM
Would someone tell me what the letters /numbers mean that describe an electric motor? Just starting out in E models and ordering things by their letters/numbers that the instructions suggest but I'm not understanding what I'm doing...some letters/numbers mean power? ....no. of windings?.... no. of volts?....also need same kind of info. for the new li-po batteries.....can you recommend a good book that will wise me up? Been in nitro engines all this time and never considered going electric but with the electric plane explosion, I find that I cannot ignore this phenom. and get with the crowd.

Mike Parsons
09-06-2005, 07:36 PM
Most manufacturers name their motors on the diameter, length and number of turns the motor has. So you have a Mega 16/15/3 for example equates to= 16mm rotor, 15mm length, and 3 turns (wire). An AXI 2820/10 can be broken down in the same manner= 28mm, 20mm and 10 turns. The turns really tell the tale as the lower the turns the hotter the wind. This essentially means that it will turn a smaller prop at higher rpm for the same voltage.
By themselves these number are usless to those trying to figure out which motor is right. However combined with a good motor calc program (www.motocalc.com or www.e-calc.com) as well as the KV, RM and Io ratings of the motor, one can get in the ballpark of a good setup and then fine tune it to real world results.
The next best way of getting the right set up the first time is to ask on these forums and follow what other members have already implemented that match what you are looking for price wise as well as performance.

There arent any books that I am aware of that will outshine what these forums can answer for you. If there are/were books out there, they would be outdated as soon as they went to print. Things move to rapidly in the electric technology realm and that is another point that makes these forums so invaluable. Real time answers as the shift in technology grows/changes.


Matt Kirsch
09-06-2005, 09:48 PM
Actually, Mike, the numbers are STILL meaningless. The only useful numbers for calc programs are Io, Kv, and RM. You could call the motor "Fred" instead of 2808/24, and have all the information you need to plug into the calc programs.

If you don't have a calc program, ALL the numbers are useless because the calculations are too complicated to perform on paper... That's why I recommend buying from motor manufacturers who produce application charts for their motors. You know how many Watts you need, and you know how much prop clearance you have... All you need to do is look it up on the application chart.

Mike Parsons
09-06-2005, 09:50 PM
Actually, Mike, the numbers are STILL meaningless.
Can't disagree with you there :)

Dr Kiwi
09-07-2005, 04:20 AM
That's why I recommend buying from motor manufacturers who produce application charts for their motors.

I agree with you Matt, when the application charts are well-founded in good science - but too many manufacturers generate overly optimistic charts, so, for their products, you are still in the dark as to what is going to happen in the real world.

Cheers, Phil

09-07-2005, 04:35 AM
TX Mike...Matt...Dr.Kiwi for answering my thread...I will of course monitor these threads faithfully if I want to learn about electric flying....TX again!!