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Thread OP
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Question
What do the numbers on the motor mean???
Guys, I need your help!
I know very little about motor sizes. What do the numbers on the motors mean? For example, I understand E-flite motor numbers because they list them like glow powered engines i.e.: Power 46 is a two-stroke 46 glow motor right? But what about a electric motor with the number 2820 1800kv? What does the 2820 mean? I've been told they are for length and diameter but that doesn't check out for me. Is there info on motor sizing anywhere on this thread that is easy to understand? It would be nice to see a sticky on this. Thanks for any help on this! |
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Yes, numbers like 2820 refer to length and diameter, but they can be of the ouside of the casing, or of the stator inside, depending on manufacturer. These numbers don't give you the power, or the electrical spec, of the motor. For these you need to look at maximum volts, maximum (or most-efficient) amps, and watts (= volts x amps if they don't give a number).
1800kv simply means that the motor will try to turn at 1800rpm for every volt you give it, so about 22,000rpm with a fully-charged 3S LiPo battery. There's a thread about motor selection here https://www.rcgroups.com/forums/showthread.php?t=739069 which might be useful |
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Quote:
The two things that matter are weight and Kv - the size and shape of the rotor or stator or case that are used to get there are only really relevant when you're trying to physically fit something. Weight largely determines the ability of the motor to dissipate the waste heat generated in operation, and it turns out that average outrunner motors can handle input power up to around 3-4W/gram motor weight without getting too hot. If know how much the model will weigh and how you want it to fly, you can figure out the input power, and thus motor weight range from the watts/lb guidelines - have a look thru the stickies in the beginners forum or visit the Ampeer website. Selecting Kv is trickier - refer to the motor that is recommended for the model as a good starting point. Or, putting the two together try using WebOCalc - you don't need details on the arcane electrical characterisatics of the motor - just the basics. Also, if you scroll to the bottom of this thread, I suspect there may be a list of similar threads - this question comes up frequently Nup, not on this thread |
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Last edited by scirocco; Jan 14, 2013 at 03:53 AM.
Reason: checked the similar threads
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The reason some motor manufactures produce motors labeled as glow equivalents is because they design them to perform Prop/RPM as if it really is a glow engine. Some of the concept is that their ARF's will have similar performance weather glow or electric. That style of motor building completely ignores all the good reasons to power props with electric motors. BUT it sells motors to the low info folks.
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