On 04/04/2012 01:31, Arfa Daily wrote:


"Ron" wrote in message
...
On 03/04/2012 01:36, Arfa Daily wrote:

I don't think that in 35 years of owning washing machines, I have ever
had one with anything other than a "universal" (as in field coils and
armature in series) brush-geared motor fitted for drum drive. Mostly the
pump motors are brushless induction motors, and certainly, all of the
tumble dryers that I have owned have had induction motor drive.

Bear in mind that in the UK, unlike in the U.S. , we went straight from
twin-tub machines, with a vertical actuator in a static tub, and a
vertical spin dryer, to front loading 'automatics'. Very considerable
oomph is needed to shift a horizontal rotating drum full of water and
washing, and even more to get it up to 1000 RPM and beyond, for spin
drying. I'm not sure that a compact induction motor would have the power
and revs range to be able to do that. Not so easy to control the
rotation direction either for the anti-tangle reversing washing action.
At least I have always assumed that was the reason that brush-geared
motors were used in these machines ??

Arfa

Hi Arfa

I spent over 20 years repairing domestic appliances. You are right
about the twintub/front loader thing. A couple of manufacturers made
top loaders, Hotpoint, which was a huge machine used a very
complicated gearbox and centrifugal clutch arrangement - when the
motor ran in one direction it agitated the washing, and circulated the
water, and in the other direction spun the drum and drained out. All
relatively trouble free.

Philips made a compact top loader with a low voltage DC motor (using
the heating element as a dropper resistor) and a silly bakelite
centrifugal clutch and variable cone drive. The drum was similar to a
front loader but mounted sideways with a hatch in the periphery.

Most if not all British front loaders used brushed motors, continental
machines generally used induction motors using capacitor control.
A couple of exceptions were Indesit and Zanussi which used brushed
motors in their high spin speed machines, I think about 800 rpm was
about the limit with an induction motor.

The few Brit machines which used induction motors - Hotpoint twintub
and top loader - used a 'relay' in series with the field coil to
momentarily energise the starting windings. If the relay stuck the
magic smoke was released!

I have no idea how many pairs of Hotpoint/Hoover/Servis/ motor brushes
I`ve changed, but it must be many many hundreds.

You can readily get service manuals for all Hotpoint machines btw.

Ron


Hi Ron. All interesting stuff. The brushes were taken out by my mate who
was here fixing my son's car whilst I was out. He took them off the
motor by leaning the machine over at 45 degrees, and taking them out
from underneath. Not so easy putting the new ones back in that way,
because they are about 1.5" inches long with new springs behind them.
Also, because the carriers are inclined at about 45 deg on the motor
frame, the new brushes have a similar 45 deg 'rake' machined on the end
of them so that they sit 'square' on the commutator. It was like trying
to force a jack-in-the-box into a bean can, and getting the screws back
in from that angle was nigh on impossible. Eventually, I just took the
motor out, as it was only two bolts. Then very easy to do out on the
bench. I turned the machine right over on its side to refit it. All
worked ok, so all back together now and back in service :-)

So where can you get Hotpoint service manuals ?

Arfa

I can't for the life of me remember where I used to get them from,
possibly Willow Vale or Electrue - which are now both assimilated into
Connect Services, but I think Hotpoint themselves will sell you one.
Whenever one of the local appliance engineers got a new manual, we would
make copies for the rest of us.

Ron