Powerchair (Power Wheelchair) MOTOR BRUSHES!
users should never worry about Motor Brushes as they are probably going to
live longer than your Powerchair.
But not every
user or every powerchair is the same.
Powerchairs or Powerchair users, wear out these easily replaceable parts much faster than others. If you are
interested in looking after your best interests it would pay you (or someone
more technical) to read this page.
Detailed Full PowerChair Related ONLY Menu HERE
Obviously in a reasonably new Powerchair, there is no
point in checking or replacing the Motor's Brushes, unless you do actually have reason
or suspect a problem.
They will likely not be worn or
faulty or burned unless you are very very unlucky! And most likely your
chair will still be under warranty anyway.
If its not, and you have a fault. for e.g. if the Motor "stops" one one side
intermittently or for the first time. Or if the Chair
starts to pull left or right intermittently. Or if it's making a "Strange" new
completely different noise... THEN you need to check.
Motor brushes are made from Carbon (mostly, but a mixture of carbon
and other materials) and they are very soft.
You can scrape, file or sandpaper the brush
material away very easily. It just makes a pile of carbon dust, and if you try this
and then you need a new one! So don't! It also makes it trivial in
an emergency to fit the brush from a current powerchair into an old no longer
made one that parts are unavailable for. A little careful selection, and a file
and it can be done.
Brushes transfer the POWER (from your batteries
via the controller)
to the motors rotating internals. They do this by riding on a segmented copper thing called a
Commutator. Shown below.
This it the part that spins
inside your motor and that the Motor's brushes
(that we will be examining) run on. A spring provides some pressure. They are
free to move as they wear to maintain contact. They provide up to 120 amps of power in a modern
powerchair to this copper "ring".
Usually the faster / bigger Powerchair has 4 brushes on each
Commutator. Its called a 4 pole motor. Smaller powerchairs use 2 pole motors
which tend to eat brushes faster in my experience.
brushes above. One is shorter than the other due to wear/arcing and use. All four from this motor were the same,
and worn out...
The longer one is a NEW one shown as a comparison. You need a new one to compare the length.
These though are actually from two different "years" of the same motor.
The cleaner and longer one is the replacement. Also examine the "tip" for burning, and chips or bits missing
Obviously the shorter one is absolutely knackered here! I check and swap mine as
needed. Worn brushes eventually cause breakdown, and damage to the armature from
arcing as the spring pressure is then too low.
"run in or break in" they "wear" and conform to the curved shape of
the commutator. Actually they more "burn in" to begin with due to the
small contact area of the new "square" ended brush. So it pays to go steady and
avoid heavy loads like ramps and hills for a few days with a new powerchair. If
you have the patience!
When new they are generally just square ended
like the new one seen above. But once bedded in they have a "curve" that
the commutator (WAY above!) as you can see in this close up picture below. And
all the tiny grooves in its surface match too. The commutator also wears as it runs
as well but does so much slower. This brush below is perfect with no burning (arcing) or
any real wear or other damage or chips or pits. Pits and chips actually
happen due to arcing as these things have a very large current going through
them at times depending on chair and user!
Its just 5mm shorter than the brand new
one. If it was 8 to 10mm shorter it would go in the bin. It can only go into the motor one way due to the design of the brush
"holder" shown later. It fits into a rectangular slot, (below) It therefore sits
in "exactly" the same position (as it should) as it did before it was ever
removed. It cant really do any other. This one will go back in as its perfect.
motors it is possible to replace the brushes in "reversed" and although its not
that detrimental, it's still best to make a note of which one went where
and its orientation. Its because of those tiny grooves you can
see and the exact angle of the "worn in" end. If you get it wrong it will
soon "wear in" again regardless as its soft. You will not notice any
real difference. But that
"wearing in" takes a very small amount of material away and shortens the life a
little! Likely you wont care once you see how easy they are to swap and they are
pretty cheap too.
continue to wear / burn away slowly throughout the life of the powerchair.
Brushes are like brake pads for your car, they are considered as items that are
replaceable. That's why your powerchair manufacturer carries these as a spare
and why you can swap them in minutes in situ.
Although they are
generally good enough to last many thousands of hours with an average user on
with average programming. If
that's you and you have a quality branded powerchair with no odd noises then
don't bother checking them for about 3 to 4 years!
you have a some attitude, do Powerchair basketball, football, etc. And if you REALLY USE
and hammer your powerchair to the extent that a set of batteries will
last you about a year or less then check them yearly! And or you do
hills, ramps, off road, winter, and especially if your chair is
programmed to get the most possible out of it then it also pays to check
yearly! You see not everyone is the same. The ones in
my chairs are about half worn
after 12 months of the kind of daily abuse I give them... If this sounds like
you it would pay to remove the brushes (takes just minutes on many powerchairs)
and to examine them.
manufacturers see no problems with brushes since the average user sits about,
doesn't go off road, on beaches, or discharge a set of batteries almost
completely every single day. Normally they sit at a desk, or at a computer all
day, or in front of the fire. If they do "go out", they are not aggressive and do
it only a few times a week and don't go very far. If you
do USE yours, then you are outnumbered by about 1000
to 1 and considered an aberration! You are not part of their figures.
You do not need to
disassemble your motor!!!
was just an old dead abused 2 pole one that was going in a "robotic" vehicle.
When you remove
them to check condition BLOW ALL THE CARBON DUST OUT! You will get a cloud of horrid
I got several egg cups full out of
this old 2 pole motor!
That dust gets into bearings and the
motors windings as the whole internals are sat in a pool of it! There was
so much in this motor it sounded weird... Don't take
the end off like this! use an airline in the positions where the brushes were to
If the powerchair is correctly
designed (amazingly some are!) you will
be able to remove 2 or 4 caps from your motor casing to access the brushes in
just a couple on minutes in place.
Its really simple and if nothing else, it gives
you some peace of mind. Or shows you how fast they are actually wearing in your
The tag in the centre of the photo is where the motor wiring loom plugs on.
Some are different and have a cable emerging from the motor and a screw cap
rather than a sliding one. (see end of page)
Here that square plastic thing just slides out as below to reveal the brush...
There are 4 obviously on this motor. Some have 2.
Slide out like this (at least on this motor...)
Cap removed! That took 2.5 seconds and about 5 mins to find the camera
to start with...
Brush just lifts/pulls out. another 2.5 seconds!
Looks like new.
But not a waste of time since these motors were sold to a friend. (I don't want
to sell a set of motors to someone without knowing they are still good to go!
I also blew out all the dust, checked the bearings, the gearbox backlash and the
Cush drive/motor coupling while I had chance. And tested them on a
battery. (Reason? Unknown history!)
Needs the dust blowing out, the brushes wiping
on a cloth (they were coated in dust that made them not slide freely as they are
supposed to do. Then put all 8 back into both motors IN THE SAME
POSITIONS, AND THE SAME WAY AROUND as you took them out. Mark them with a CD
writing pen with an arrow and a number. Write the same number on the motor.
This is the same brush.
And the slide out cap. Its only fault was the carbon that was jamming it.
See the chamfer on the long edge facing you? You can see some of the carbon
along there that I have not yet removed. There is just a few mm missing from
this brush so I will put it back! That black carbon is on my bed! GF pleased.
Of course you must have a new
one to compare it too. Or at least a measurement! But if you go to the trouble
of taking them out it makes sense you have some spares just in case.
I check all my powerchairs
regularly. I log the brush length against the powerchairs "hours" to give me
some idea how long they will last this year! But I am an animal and put more
amps through these brushes than they were actually designed for.
An alternative brush cap.
Another alternative! Both these need a screwdriver, but have the same result!