• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Why spend more money for one motor than another? Aren't they all the same?

FlyingMonkey

Stuck in Sunny FL
Staff member
Admin
#1
One would think. I love being cheap, but sometimes being cheap can be expensive.

I got in a rush, and bought some budget motors that I knew would ship to me fast.

It caused a crash of my quad yesterday. No matter what I have tried, I can't seem to eliminate the high end vibrations from my motors. I did the zip tie trick, added tape, balanced and rebalanced my props, and for some reason they just won't stop vibrating at higher RPMs.

Then I took it apart to try to balance it another way, and this is what I found....

1317_10201017791180758_1280745079_n.jpg

There's a giant puddle of epoxy inside the bell. There's a few globs in other places, but this one's the worst.

It will make balancing my motor almost impossible. I can only assume that all four are the same way.

I'll spend the extra couple dollars per motor, to make sure I get one that's got a little better quality control from now on.
 

Cyberdactyl

Misfit Multirotor Monkey
#3
I believe that's intentional.

That's used for a quick and dirty balancing method at the factory.

It may be 13 year old Chinese girl doing the balancing was thinking about the 16 year old boy flirting with her in the next seat over on the assembly line.
 

FlyingMonkey

Stuck in Sunny FL
Staff member
Admin
#5
Yeah, I tried to scrape it out, it isn't budging.

They'll be fine motors for foamies, but the vibration is too much for a multi rotor. Messes with the board too much.
 

FlyingMonkey

Stuck in Sunny FL
Staff member
Admin
#6
I've purchased fancy pants motors to find they are rebranded cheapies. Quite often in fact.

Yeah, but what they are, are the ones that passed quality control. The "seconds" go out with the generic brand sticker on them.


Aiidan, what plane is that in your avatar?
 

colorex

Rotor Riot!
Mentor
#8
I'm going to bite the bullet and get the often recommended SunnySky X2212 980kv motors instead of the usual DT750's - for the quad I'll use for FPV and Aerial Photography and Video.
 

willsonman

Builder Extraordinare
Mentor
#9
There are some differences in the more expensive motors that are hard to tell to the naked eye.

Some motors include ceramic bearings which are smoother and last longer. They also cost more. smoother bearings will give less resistance and allow for better efficiency and give your stronger power and longer run times. Go to boca bearings and check them out. If you have a bad bearing replace it with ceramic and I'm willing to bet it will run better than new.

Magnet quality. The high-energy magnets that are in our outrunners are actually formulated. Its all the same basic stuff but hirger ratios of this and that can determine the strength and symmetry of the magnetic field. Bad symmetry means the magnetic forces are not concentrated toward the stator and you get bad efficiency. Different metals (rare earth parts) are costly and you can get by with less but the cost is evident.

Copper. Copper winding on your stator can be good quality or messy. This too will effect your symmetry of field. Also, the quality of the copper can degrade performance. Too much oxygen in the copper and you can get higher resistance which will make more heat. Remember... copper oxidizes with oxygen... its called tarnish. Most wires for this application come from a factory pre-treated with an insulative layer. Some better than others. Some insulate heat better... some just electricity. Some are better at insulating against oxidization. And it can come in varying thicknesses. The thickness of the insulation will increase your gap between the coils and decrease efficiency because of... you guessed it... field asymmetry.

So, the more high-dollar motors DO in fact have value but for the average person I think the cheapies are just fine.
 

Tritium

Amateur Extra Class K5TWM
#12
If I pay much more than $20 for a motor it will be from an USA source with a guarantee. Hobby shops selling motors for $50 to $150 and 5 to 9 at a time (tricopter to octocopter + spares) WILL STAND behind it if they want my business.

Thurmond
 

xuzme720

Dedicated foam bender
Mentor
#13
If I pay much more than $20 for a motor it will be from an USA source with a guarantee. Hobby shops selling motors for $50 to $150 and 5 to 9 at a time (tricopter to octocopter + spares) WILL STAND behind it if they want my business.

Thurmond
I'll second that! Of course it will be awhile before I'll be ready to risk $30+ motors on my multi's. I still tend to bend...