New G27 motor run/break in... for vintage racing

[Marky]

I'm reading conflicting reports about whether the new motors require the old break in/run in methods or not?

Do they or don't they? And why?

Eg diffrent brush types or ?

Bonus points if you can tell me what the successful vintage racers do!

Cheers

[GoMachV]

Brushless motors don't have brushes to break in. I have no idea what a G27 is though. If it's brushless, you are good to go.

[juicedcoupe]

It is a sealed endbell motor, similar to a Mabuchi or Johnson (may actually be one of them).

[RogueIV]

yeah the closed endbell brushed motors still require break in to get the best performance. Nothing has changed there.

[RogueIV]

Personally I do something close to this https://www.youtube.com/watch?v=ekRkDZfD9sw

[Dangeruss]

Personally I do something close to this https://www.youtube.com/watch?v=ekRkDZfD9sw

Excellent video!... though... where do I get the wuhter he used? Is that only available on the East Coast? Like how I have to special order all my al-u-mini-um from England?

[RogueIV]

Excellent video!... though... where do I get the wuhter he used? Is that only available on the East Coast? Like how I have to special order all my al-u-mini-um from England?

hahahaha

[TRX-1-3]

I remember breaking in motors using similar methods bitd. Saw in Pit Tips, RCCA....I remember thinking, "but won't the water nuke the whole process?" Hooked up to the ProTech 702, lowering the motor into the Mason jar full of water......thought I was gonna die from electrocution. But it worked.

[R6cowboy]

Regarding the water break-in method video posted above. Near the end of the video he states, before the break-in process the motor drew 2.4 amps running at 3.0 volts.
Then after the break-in the motor drew 3.6 amps at 3.0 volts. Isn't this backwards for motor efficiency? Meaning at a specific voltage, the more amps a motor draws, the more effort it is taking for the motor to spin (in other words, the motor is working harder to spin at the same voltage)...?

[Marky]

(in other words, the motor is working harder to spin at the same voltage)...?

I thought with the same voltage on your battery (the fixed value when driving your car as it only has the volts it has) it draws more amps cos it's doing more spinning?

I did mine for much less time than the vid then cleaned/dried it by dunking in IPA.

Hopefully it works better than it would if I just put it in the buggy (swb mardave meteor)

[RC10th]

I think the idea of the water bath is to prevent arching between comm segments and flush away any carbon deposits.

[RogueIV]

I think the idea of the water bath is to prevent arching between comm segments and flush away any carbon deposits.

It speeds up the break in process a lot as well.

Most closed can motors feature brushes that are extremely hard and not at all conformed to the surface of the com and out of the box is often running on very skinny portions of the brush. Most of the motors have the face of the brush cut in the shape of a "u" but it's not the direction you'd think it'd be in like open endbells motors. Instead they're rotated 90 degrees result in the tiny tips being in contact with the comm, this is to aid in the break in of the brushes over normal use but on it's own it could take several race days to break in a motor.

You can see this is the this Mini JRX2 motor but it's the same for the bigger motors too. (these are just easier to open without destroying) Note the wear pattern on the comm, tiny little stripes are where this motor was making contact out of the box. This limits the current the motor can actually draw, meaning less magnetic power and in turn less torque to get up to speed. Also more heat at the tips of the brushes since there' almost no contact area.

Now look at the wear pattern on the well broken in motor.

The brushes are making full contact with the comm now allowing it to draw way more current and in turn more torque.

Unbroken in brushes are basically the same as running power cables that are far too thin for the current draw.

[R6cowboy]

I thought with the same voltage on your battery (the fixed value when driving your car as it only has the volts it has) it draws more amps cos it's doing more spinning?

I get what you're saying, but honestly don't know how that could be the case. I do know increased load causes more amps drawn at a fixed voltage. Take for instance, a motor with brass bushings, let's say at 7.2 volts. Now swap out the brass bushings with good bearings. The motor will now draw less amps at the same 7.2 volts, while possibly increasing rpm. Because of decreased friction/drag.
Another example: a motor with a large heavy pinion gear attached to the shaft will draw more amps than the same motor with a small lighter pinion gear. Because it take more effort to rotate a larger/heavier object. Therefore the motor demands more current at the same fixed voltage.

[R6cowboy]

The brushes are making full contact with the comm now allowing it to draw way more current and in turn more torque.

Unbroken in brushes are basically the same as running power cables that are far too thin for the current draw.

Thanks for the explanation, makes perfect sense. Now I feel dumb because this seems like it should've been obvious.

[SPA240WS]

Think your're both right. Measured some silvercans time ago and eta % was max with "new" (just broken in) brushes, max power was rising with increasing contact area - but decreased with full contact. My thought was it's the (perhaps) already burned commutator. So gave it a skim and measured again: eta and power raised marginal, but never to the point of a new ( just broken in) one.
My break in method: 30min 4 Volt.