In today’s throw away world it
seems no one wants to fix things any more. That is probably because most of the
things built today are designed as throw away items. This is not the case with
Cycle Electric Inc. generators. These generators where used on Harley
Davidson’s from 1958 to 1984. They are designed to be rebuilt and Cycle
Electric Inc. still makes all the parts for them. If you are willing to get
your hands dirty here are some tips on repairing them.
I believe it is important to understand how things are
supposed to work before you can figure out why they don’t work. I will start of
with a little theory of operation. These generators are an A type exited field
two brush DC generator. On an excited field generator the magnetic force of the
field is produced by an electro magnet. This makes it possible to control the
generator out put by controlling the amount of current flowing through the
field coils. A type exited field generators draw the field current from the
armature. B type excited field generators get their field current from a
battery.
The field circuit consists of two coils of wire wound around
iron poll shoes. The poll shoes are mounted opposed each other on the inside of
the generator housing. One end of the coils connects to the A terminal and the
other end connects to the F terminal on the generator. The armature is mounted
on bearings and held between the poll shoes. When the generator is first built
it needs to be polarized. This is done by flowing current through the field
coils. This current makes a magnetic field and magnetizes the poll shoes. One
shoe will have its north poll facing the armature; the other poll shoes south
poll will face the armature. The polarity of the poll shoes will determine the
polarity of the out put voltage at the A terminal. When polarizing it is
important the make the A terminal more positive than the F terminal. Flowing
current the other direction will make the A terminal have a negative voltage.
When the generator starts to spine, the residual magnetism
from the poll shoes will induce a voltage into the armature windings. Two
carbon brushes are used to make an electrical connection between the commutater
on the armature and the brush plate. One brush is positive and the other is
negative. The positive brush is connected to the A terminal with a wire. The
negative brush is grounded to the brush plate. When the armature voltage gets
high enough to turn on the regulator, the regulator turns on and ground the F
terminal. This will allow current from the A terminal to flow through the field
coil to ground. At this point the generator is full fielded and producing full
power. A properly working regulator monitors both voltage and current. If
either voltage or current go high the regulator shuts down the field. When the
field shuts down generator output drops off. Voltage and current go low so the
regulator turns back on. This cycle repeats it self several times a second to
maintain proper voltage or limit current.
On less you have a generator test stand it is easiest to
test the generator while it is mounted on the motor. See testing two brush
generators. Once you determine that your generator doesn’t work, remove it from
the motor. Find a suitable stand with that will support the generator with the
armature shaft sticking down. Remove the chrome end cover if installed. Remove
the brush strap if installed. Remove the two ¼- 24 lock nuts from the generator
tie bolts. Use a soft mallet to tap the commutater end bell loose and remove
it. Use a 3/8” nut driver or wrench to remove the nut that holds the positive
lead wire to the brush plate. Remove the brush plate. If you need to inspect
the armature hold the generator housing in your hand and lightly tap the
commutater end of the armature shaft with a soft mallet to separate the end
plat from the housing. Do not hit too hard or you will damage the ball
bearing.
Excluding physical damage to the housing, end bells and
bearings there are three main components to test when looking for a problem.
The brush plate, field coils and Armature.
Inspect the brush plate assembly. Check the condition of the
brushes and brush springs. You can tell a lot about the generator by looking at
the brushes. When the brushes are new they do not start out with perfect contact
on the commutater. After a couple thousand miles the brushes seat in and should
have full contact. This leaves a shinny finish on the contact aria. The brushes
should move freely in the brush holders and have a shiny contact surface. A
dull satin finish is an indication the brush has been arcing. A brush that is
sticking, a collapsed brush spring or a commutater problem can cause arcing.
Sometimes a brush will stick when the generator gets worm and the out put will
drop-off. When the generator cools down the brush loosens up allowing contact
to the commutater and the generator will put out again. This will cause
intermittent output. A sticky brush may
also ware at an angle. Check for swollen or warped insulators between the brush
holder and plate. Replace if necessary.
Use an ohmmeter or continuity tester to test for continuity
between the brush holders and brush plate. The positive brush holder should be
insulated and has no continuity to the brush plate. The negative brush holder
should have continuity to the brush plate.
One end of the field coils connects to the A terminal and
the other end connects to the F terminal. The easiest way to test the field
coils is with an ohmmeter. Check the resistance of the field coils. Use an
ohmmeter on the Rx1 scale. Probe between the A and F terminals 6-volt field
coils should read between 2.5 and 3.5 ohms. 12-volt coils should read between 5
and 6 ohms. With the brush plate removed, probe between the A terminal and the
case of the generator. This should show no continuity. If you get the correct
readings the field coils and insulators are good. If not you will have to
disassemble the terminals and check the insulators and field coils separately.
A field coil that has no continuity has a broken wire or a bad connection. This
almost always happens at one of the terminals or where the two coils are
spliced together. This can usually be fixed. Low resistance indicates
winding-to-winding shorts. A sorted coil will need to be replaced.
The easiest way to get the poll she screws out is to drill
them out. Start with a center punch in the middle of the screw slot. Then use a
drill a little larger then 3/8. Drill slowly until the head of thee screw pops
of.
The best way to test an armature
is with a growler. The growler is a tool that is designed to magnetically
excite the armature. Once excited the armature can be tested for
winding-to-winding output, shorts and opens. If you do not have access to a
growler the only way to test the armature is to install it in a working
generator and test for proper out put. You can start by removing the armature
and giving it a visceral inspection. The steel lamination stack should be
shiny. A little rust wont hurt any thing. If it is discolored from heat, this
is an indication of a problem. The windings should be more of a Caramel copper
varnish color. Black or burnt winding in another indication the armature has
been over heated. Inspect the bars on the commutator for sines of uneven ware.
Shorted winding can cause arcing. This will cause excessive ware on one or two
of the bars on the commutator. Inspect the bearing surface on the commutator
end of the shaft. The needle-bearing ride on this surface so it needs to be in
good shape. An armature that shows any
of these problems should be replaced. Reassemble the generator and test for
proper out put. If the field coils and brush plate check out good, and you do
not get the proper out put try a new armature.
Of coerce if you don’t want to get
your hands dirty or just want a the reliability of a new generator with a two
year guaranty we make new ones every day.
Let the road you choose to ride
bring you happiness.
Karl Fahringer
Cycle Electric Inc
www.cycleelectricinc.com