what's the quietest motor?

[Lunch-time flyer]

What's the quietest type of electric motor? I thought they were all the same until I bought my first outrunner and found it fantastically quiet - are all outrunners quiet? Are there other quiet motors??

 

[sparks59]

Hard to say without knowing which you bought. But all the ones I have are reasonably quiet when fitted with a balanced prop.

sparks

[Jonathan Lewzey]

well all my conventional ones are quiet, but got an 'outrunner in a can' in my funjet, which, erm, isn't

 

i tend to find cheaper motors with lower quality bearings make more noise due to the bearings, but you can easily put up with it. nothing like an ic engine

[Romeo Whisky]

In my experience inrunners are usually even quieter and smoother running than outrunners.

[Simon Chaddock]

Some out runners are noisier than others.

It appears to depend on the number of poles and the configuration of the windings.

The E-max type seem to be pretty quiet whereas the Blue Wonders make quite a whine.

This video demonstrates this (the prop is noisier only at full power) and what happens when it exactly matches the resonant frequency of the airframe!

 

When you switch off the motor you can hear it run down even at 500'!

Edited By Simon Chaddock on 11/09/2010 21:13:17

[sparks59]

I like the resonant 'howling' sound actually. Probably not the best for the longevity of your airframe though.

sparks 

[buster prop]

Some cheap motor are indeed noisy. I have a Towerpro 2408-21 bell motor that made an awful howl at anything over half throttle. It was very 'coggy' when turned by hand so I don't know whether this has anything to do with it. I suspect that it did. I alaways take care to balance props or an electric plane can sound as if it has a small i/c engine!

[Erfolg]

Quietness assessment can be a comparative process and without instruments pretty subjective.

 

If comparing an electric motor to an IC engine, I have never heard an electric motor that comes anywhere near the IC motor. Electric motors are intrinsically quite.

 

I now have approaching 20 brushless motors, none have caused me to consider the comparative noise, not even for a second. To my ears same level, with a differing sound.

 

If yo are asking is it possible to make an brushless motor noisy, yes of course. The commonest way is to use high revs, that is small diameter propeller, fix it as a pusher, close to the trailing edge, this will make lots of propeller noise due to the highest revs. Yes, this approach seems to make noise. There will be others. Purposely making a noisy set up seems irresponsible to me as an objective.

[Lunch-time flyer]

Well I'm amazed by the responses, I can understand the possibilities of making a noisy set-up, and cheap motors, but what I've got used to as quiet compared to an IC engine has been completely re-written by the outrunner that's far from small and powering my Spitfire at the moment, it just purrs through the sky and can hardly be heard, which called into question the other 8-odd motors I've had before, and the reason for the initial post.

 

I jut thought it was an outrunner thing!

 

[Boots]

My experience with brushless motors is

1. cheap motors are made to a price, so noisey bearings and badly fitted magnets, but I have had good and bad, its a lucky dip but having said this it is nothing a little TLC cant fix,repacking bearings with molybdenum grease is good, so i guess they are all good ones.

Because of the enormous price difference I would choose himodel or emax over say axi or turnigy everytime

2. a low kv motor  swinging a large prop will always tend to be quieter and prop noise will be less too, EDF being probably the opposite end of the scale which seem able to produce more noise than a 4stroke ic.

 

lack of noise is not the only plus to electric. I live in Cyprus, hot dry and dusty, I cant even imagine cleaning the plane after an ic flight, was bad enough in the uk

[Bert]

The quietest motors I've come across are the Nippy Black range. I have one in my Formosa.

 

Bert

[Romeo Whisky]

There is another significant factor at work here.  Different MODELS vary considerably in how much noise they make, even with the same motor.  It is down to resonance of the model itself. 

 

I call my Seagull EP Decathlaon "The Flying Cello", because it's got a big wide body with tight Oracover film over a very light frame and that and the big cowling are so resonant that it is the noisiest model I've got.  

 

Yet a similar motor in my Ealapor Foam Fun Cub is amazingly quiet.  Foam will absorb vibration, which is actually what noise is (air vibration). 

 

Your model looks as though it is foam, but it also looks as though the motor is a tight fit, so there in minimal air inside the fuelage to be vibrated by the motor.

[Steve Hargreaves - Moderator]

Usually the most noise is made by the prop...especially small high speed ones. Flying wing types arranged in a pusher cofig can be particularly noisy as the prop is in the disturbed air coming off the TE Of the wing

[Vecchio Austriaco]

Hacker motors are extreemly quiet - A30 12L  with a balanced 12x6 APC and you here more wind noise of the plane than anything else. (combination used on MEX Yak 54 1100mm)

People were asking me if the battery is empty until I showed endless vertical climb (not endless - my eyesight doesn't allow this)

Main reason may be stable mechanical design (5mm shaft) and good bearings.