Assembling a BLDC motor [serious]

How I assemble a BLDC motor.

Starting with a stator, a rotor, three bearings, a circlip, a circlip tool, some spacers, oil, three M4x8 bolts and a wrench for them, a hammer, an 8mm shoulder bolt, a dry washcloth, a motor pulley, a motor mount plate, maybe a tiny piece of griptape/sandpaper, and maybe a skateboard wheel bearing spacer:

First, I start with the stator

bolt it to a mount plate

grab a shoulder bolt or something else

I lightly hammer one bearing in with the head of the shoulder bolt

Then I put two drops of oil on the bearing

Then I lightly hammer in the second bearing and put a drop of oil on it

Get the rotor

Make sure the bearing slides all the way down the shaft without strong resistance. Sand the shaft a tiny bit if needed. then remove the bearing from the rotor

Put a cloth folded in half on the stator like so —

:exclamation: Make sure when the axle pokes out the back side that it’s not going to poke into your hand

:exclamation: Make sure you keep your fingers clear, the rotor will come down hard, fast, and sudden

Gently push the rotor on until it POPS down onto the cloth. The cloth prevents a crash-landing.

Pull the rotor up slightly while removing the cloth, and remove it from the mount plate.

Now, see this hole?

I fill it up with oil almost to the top. Do not fill it all the way up to the bearing seat. 60% full is ideal.

Slide the third bearing onto the shaft

Use a pulley or something else to gently tap the bearing in with a hammer.

Now it should appear as such:

Obtain a circlip and some spacers of various thicknesses

Use the spacers and the circlip to snug the rotor onto the stator

Put a drop of oil on the top of the bearing.

Now, do a hand test on the motor.

Enjoy :slightly_smiling_face:

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Could you recommend a place to buy replacement bearings and possibly list what bearings are used in different motors?

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All the esk8 motors I have worked on used:

two 688ZZ bearings, 8mm⌀ x 16mm⌀ x 5mm
one 698ZZ bearing, 8mm⌀ x 19mm⌀ x 6mm

The last ones I obtained from here:

However, not all motors are the same.

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Love it. Something I’ve wondered about for a while now.

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If you live in Sunny Southern California and you use your board solely as a toy instead of as a transportation tool, you can probably safely skip all the steps involving oil.

The oil is to help extend bearing longevity with wet operation.

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What bearing oil do you use ?

Why not use RS (rubber sealed) bearings and avoid the oil mess?

Also no issue with the board dripping oil?

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Haven’t tried it. If you try it, let us know :slight_smile:

Not that I’m aware of. I’m not cleaning the streets with a toothbrush, either :rofl:

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I’ve used them since forever, no issues and they seem to keep going

But not all RS bearings are made the same, for example, in my “new” TB bearings, they do ship with them, but they are fairly noisy, must have between 500 and 1000 km on them, if i were to guess I’d say they are either using bearings with a not so good seal or using the low friction variant that doesn’t seal so well

As soon as I have time they will be swapped to SKF ones that will probably outlast the motor

My issue with the oil would be dripping inside and making a mess while the board is not being used

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Do you have a link to the good bearings?

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The oil is optional.

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Great write up Brian

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Bookmaked 10billgordon

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Any from the 1st class industrial brands such as SKF, NSK, Nacchi, Schaeffler and NTN

For SKF the suffix should be 2RS1, 2RS2, 2RSH, don’t get the 2RSL or 2RST, these are the low friction ones that don’t seal as good

Also, since you are a fan of waterproofing, you could try to find them with the W prefix for stainless construction

For example, a wheel bearing with the proper seal and made of stainless would be W 608-2RS1

And also I would recommend buying for a reputable source since there is ton of fakes out there

https://www.skf.com/us/products/rolling-bearings/ball-bearings/deep-groove-ball-bearings/productid-W%20608-2RS1

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Where did you get those spacers/circlip? I am currenly looking to aquire some.

The circlip is from amazon, the 8mm copper washer is from amazon, the bronze spacer was on this motor or another one, the steel washer is a skateboard speed ring.

https://smile.amazon.com/gp/product/B013G215SO/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

https://smile.amazon.com/gp/product/B01LZBCJHE/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

https://smile.amazon.com/gp/product/B07S4BL118/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

Those thin bronze washers are the most useful for this, but I don’t have a handy source for them. Don’t lose them when you remove them from motors.

You need to adjust the height to match so it holds the can as tight as possible so you don’t get clunking noises while in operation.

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Thanks a lot, any tips on how to select the right circlip dimension? I guess it depends on the motor?

All of these parts are for 8mm shafts.

Motors with a 10mm shaft may be all different sized washers, bearings, and circlips.

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