25-02-2018, 05:53 PM
Armature fault location. First go around all the commutator segments with a ground down thin hacksaw blade, possibly dislodging any short circuits, bits of solder and carbon dust. In the past GROWLERS were used to locate armature faults, these are a thing of the past as are magneto re-magnetisers. Larger garages had growlers to test dynamo armatures, now all modern cars have alternators. For those who have access to a milling machine it is possible to make a growler. A growler is part of a transformer, which has had its secondary winding removed. A vee is machined away in which to lay an armature, the armature forms the secondary of the transformer. When the armature is in position and power is switch on to the transformer primary, and a feeler gauge or thin hacksaw blade is held very slightly above the armature a buzzing sound is made as the armature is rotated. If there is a short circuit a large current will flow and the blade will be pulled sharply down onto the armature laminations. Specialist motor bike and classic car restoration people have growlers, if however a growler isn’t available, below is a test you can do. This test is often much better, (its known as drop test), you need a 12 volt battery and a 24 watt bulb, connected one side of the battery to one side of the bulb. Using an elastic band wrapped around the commutator attach one end of the battery and one lead from the bulb, both about 120˚ apart. Using a centre zero milli ammeter fitted with two probes, move around the commutator one segment at a time, (mark where you have tested with a felt tip pen). If the armature is sound, all indications will be the same. If you get an abnormally high indication you have a faulty connection, which might be fixed. If all you have is a milli ammeter then you need to switch the probes around as you go. An AVO is ideal but you do have to switch leads, I think better than a digital type, but not everyone has both types Don’t forget armatures can also have earth faults, which are difficult to locate. Again using an elastic band connect one lead to the commutator and the other to the shaft, hopefully you’ll get an infinity reading or very close. Arcoy were very well made tools so I would hunt around hoping to locate a re- winder who has the expertise to wind the armature and importantly balance it afterward. I thought you may like to read the above, its worked for me in the past.Ted
