Brushed Motor School
Many of us have been cursed with the bane of brushed motors in our heli's.
Some get 30 flights. Others get 70. My first motor is on at least that.
Today, I got 20 flights out of a motor, and wanted answers.
One of the brushes had folded in half and broken, and when I got
to looking at it, I noticed they are held in place by plastic guides.
The plastic melted, and let the brush move out of place.
I also noticed that the soldering looked different on my 70+ flight motor.
Then it hit me. The reason there is a PCB on the end, is for a brush
heatsink. Notice how on the "good" motor, there are "blobs" of solder
on the leads. This is actually a good thing. It is transferring heat from
the brushes to the PCB, wire, capacitors... the whole end of the motor.
Looking at it now, it has more than enough solder, but that is only because I
touched it up.
Before touching it up, one side had a blob, the other independent joints.
The brush with the blob has less wear than the brush with clean independent
joints. Imagine that.
Look on the one that failed (the one with one black wire) and notice how most
of the brush lead is exposed, with no solder on one side.
Also notice the PCB has separate lands for soldering the brush end,
and the wire. That shiny section of bare copper is there for a reason, the
wires are supposed to be soldered there. Copper is a wonderful heat conductor,
and pulls the heat from the brush joint to the motor lead.
They don't have to be soldered together in one blob, but it will
transfer more heat, and your brushes will last longer.
The brushes are usually the first thing to go on these motors, and the cooler
they run the better.
Next, when you get a new motor, break it in. Run it on 1 to 1.5 volts for
5 minutes at least to seat the brushes properly.
Worst case, just don't give it full power until you get a pack through it.
Last, when oiling these, only oil the pinion end, and use a TINY bit.
Use too much and your motor will be junk. Most are probably better
off leaving them alone, as the bushings have lubricant built it.
If the bushing is worn enough to make the motor "howl", you need to
replace it, but oiling might get you a few more flights.
I'm angry with myself that I didn't notice the poor soldering on the
new motor, and it is a $6.00 mistake that now you won't have to duplicate.
My pack just finished charging, so time to go
Last edited by Steve_; Dec 09, 2012 at 01:33 PM.
I know there are cheaper places, but my last order was at my door
in 3 days. I figured the 2 bucks was worth it
The old motor I installed is still going... ran 6 packs through already.
My 9116 is back in tune... so my posts per day should decrease
Last edited by Steve_; Dec 09, 2012 at 03:20 PM.
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