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| How
To Cut Your Electric RC Car Motor's Commutator |
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If
you want to be competitive in the stock or modified
class a comm lathe is a must have tool. The stock
class has changed drastically since the debut of
the first ROAR legal rebuildable stock motor. So
why is it necessary to have the commutator cut on
your electric motor every few races?
First of all, you need to ask yourself, do I need
to get my comm cut? As a general rule of thumb,
you should have it cut every 2-10 runs, depending
on your motor, brushes, and springs. If you are
using a hot modified motor with soft brushes and
hard springs, you should have it cut about every
2 runs. If you are using a stock motor, chances
are, it will only need to be done every 6-8 runs.
A black band or concave spots around the the comm
are signs that the comm needs to be cut. Here are
some examples of motor comm's, one on the left is
brand new and the one on the right needs a good
run through a lathe. |
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Here
are the tools you are going to need to cut a comm:
• Comm lathe with cutting bit and bit shims
and pulley band
• Small Philips screwdriver
• Red "Sharpie" marker
• Soldering iron
Remove the springs, brushes, and then unscrew the
two screws holding the endbell o the can. Remove the
endbell. Be careful not to loose any shims that may
be on the short shaft of the armature. Remove the
armature from the can. Remove any shims or washers
on the short shaft and place the armature on the lathe.
Add some bearing oil on the places where the shafts
will be in contact with the lathe.
Before you get ready to use the bit, remember that
you will need to shim the bit per your lathe's instructions.
Also, make sure you install the bit correctly. If
the slave motor is spinning the comm away form you,
the cutting edge of the bit should be down. If the
comm is spinning toward you, the cutting edge should
be up. Make sure you follow the directions that came
with your lathe for mounting the lathe motor. If the
lathe motor spins the wrong way, it will break the
bit.
You will need to have a power source to use your lathe.
Most people use a four cell battery pack. You can
also use a DC power supply. The next step is to mark
the comm with a red sharpie marker. This will help
you determine what part of the comm has been cut,
and what part hasn't. Turn on the lathe and slide
the marker along the comm to turn it red.
After the comm has been marked , SLOWLY move the bit
towards the comm by turning the depth wheel. Make
small passes to get close to the comm, when you see
the copper start to show, stop turning the depth wheel.
Slowly turn the cutting wheel and cut the comm. Stop
when you reach the end, and then turn the wheel in
the opposite direction to bring the bit to it's original
position. Be carefully not to go to close to the tabs
holding the wire.
Once you make your first pass, shut off the comm and
take a look. If there is still a black marks on the
comm.
Remark
the comm with the red marker and start the lathe again.
Adjust the depth wheel until the red disappears. Make
about 2 or 3 slow passes back and forth. This will
give you a mirror like finish on the comm.
When the arm shows no more signs of wear, remove the
armature from the lathe. Use the back of a xacto blade
to remove any burs or extra material in the comm slots.
You should also replace your brushes and oil all bearing/bushings.
Having your comm cut when it needs it will greatly
extend your motor's life and give you maximum performance. |
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