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Author Topic: Bearings found in Electric motors  (Read 1168 times)

Offline ericrule

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Bearings found in Electric motors
« on: April 06, 2014, 04:11:29 PM »
For the past 8 years I have been examining many brands of the electric motors we use in Control Line and speaking with the engineering departments of many of the companies who produce them. After gathering a whole lot of data I have concluded that there are three main areas that differentiate these motors.
1) Bearings
2) Stator cores
3) Magnets

Of these areas the one that causes most of us problems is the bearings. If a motor is manufactured with low quality bearings this almost guarantees that you will have to replace the bearings after little more that 1 year of running. It will also reduce the efficiency of the motor which means you have more heat build up. This means you have to use a higher amp ESC (more cost plus weight).

I have attached a picture of the three main types of bearings found in our electric motors. A glance at these bearings will show the vast difference in the quality.

With bearings as with almost anything in life higher quality means a higher cost. One way of checking the quality of the bearings in a motor is to ask what replacement bearings cost. An example of this is found in one of the popular brands that many people use. Replacement factory bearings cost around $5.00. The better quality bearing from Bocca cost around $14.00 while the top quality bearings will run you almost $39.00. Before you purchase a motor ask yourself how long you can reasonably expect a $5.00 bearing to run efficiently.

Eric Rule

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Offline Tim Wescott

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Re: Bearings found in Electric motors
« Reply #1 on: April 06, 2014, 04:15:14 PM »
Nice graphic.  It does tempt me to buy a cheap motor, keep an eye on the bearing, and replace it with a good one when the time comes.

But then I'd find out that the accuracy of the machining of the shaft and the pocket in the bell where the bearing goes have a bearing (as it were) on the ease of changing things, and/or the ultimate longevity of even a good bearing.

Sigh.  Everything good costs money.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline 55chevr

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Re: Bearings found in Electric motors
« Reply #2 on: April 06, 2014, 04:46:05 PM »
Depending on what type of flying you are doing. You can buy an "inexpensive" motor for less than $25.  Use it for a season and then throw it away. This winter I caught a sale on Cobra motors for $20 each.
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Joe Daly

Offline Bob Hudak

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Re: Bearings found in Electric motors
« Reply #3 on: April 06, 2014, 07:11:10 PM »
I had a set in an Emax 2826 that started growling in less than a month. Ordered a set (2) of ceramic bearings from Boca Bearing for about $23 I believe it was. 2 seasons and still rolling.
Bob
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Offline William DeMauro

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Re: Bearings found in Electric motors
« Reply #4 on: April 06, 2014, 07:13:28 PM »
Eric,
Good stuff and very true. These are the same conclusions, I've come up with after playing with many cheap and expensive or so called higher end motors. I've also changed bearing in both cheap motors and "better" motors. I've learned a few things. My Scorpion stock bearings were lasting me 120-150 flights and cost me $5.00 to replace in my 3 bearing motor. In my 2 bearing Scorpion they were lasting 50-75 flights and cost me about $3 to replace. I could tell they were failing because I log every flight and I easily saw my mah consumption rise before I could even tell in a run that my bearings were failing. As soon as I saw that I would change them right out and my numbers would drop right back to normal. I am currently flying ceramic bearings in my 2 bearing Scorpion's It's going to be interesting to see how they hold up and if they were worth the extra cost. Now lets look at this from a practical point of view. For the average sport flyer who is using a 20-50 dollar motor, they can get 75-100 flights out of those cheap bearing(maybe even more). If they want they can throw the $20 motor out like Joe says or they put another set of $5 or under bearings in and go fly another 100 flights. Now here is my argument for the cheapo bearing. For arguments sake, lets say a glow plug cost $5 these days. Lets even say that plug will last 100 flights. We don't throw our glow engine out when that plug fails. We replace that plug. So like that glow plug replace that cheap bearing with another cheap bearing and go fly 100 more times. I have also found that bearing oil from boca or scorpion is cheap and if you oil those bearings before you install them the motors run quieter and smoother and I'm sure that even the cheapo bearings last a little longer.
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Offline ericrule

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Re: Bearings found in Electric motors
« Reply #5 on: April 07, 2014, 06:24:06 PM »
The points above that everyone has made are all true.

I certainly agree with the comment that I can buy a motor for $20, run it for a year or until the bearings go bad and throw it away. If this was the case for most of us the only question I have is why do so many people buy the $75-130 motors that have the low cost bearings in them? All you have to do is to take a look at the "list your set up" section of this forum to see what I mean. I know from personal experience that most of us buy the same equipment that the top competitors do. Heck, if it works for them it should work for me too! If I am not aware that there are differences in the quality of the stuff inside a motor that could reduce the effectivness of the motor how do I make an educated decision to purchase or not?

We all learned about bearings with glow powered motors. All we had to do to make our Super Tigres run smoother was to replace the factory installed bearings with good ones from Bocca. The only problem was that so many of us either did not know how to do this or simply did not want to mess with the process. In addition we had no way of checking the bearings before we purchased the engine. This is not the case with electric motors. If we look closely we can actually see the bearings in almost all of the electric motors.

The reason I posted the pictures of the three different bearings was that if we take the time to check on the bearings we can see maybe we will decide to look at something that has better bearings in it before we plunk down $75-130 for an electric motor. Maybe if we actually know something we can make a better purchasing decision. I know that in Wlliam's case that's what he has done. He does not just follow along with what "everyone else does". He makes rational decisions based upon knowledge. To my way of thinking that is what I want to do. Think about it for yourself and decide what is best for you.
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