The next thing to make is twelve tubes of white drafting paper to fit in holes of the core. If the armature is slotted, troughs should be made instead of tubes. These should be 3 in. long and with the tubes I would suggest the circumference of the tube be a little greater than that of the tube. The builder will find this of much benefit when he winds the armature, as it will prevent the sharp edges of the iron cutting the insulation as the wire is slipped through. The paper tubes should be well shellacked on the outside and then slipped into place, slitting the ends which project and turning them back against the core. The ends of the core should then be well shellacked and the cloth washers slipped into place, smoothing them down.

The fiber washers should be shellacked on one side and slipped on to be held in place by wire or string threaded through the holes. These fiber pieces will also hold the cloth and paper in place. This work completed, the armature should be set aside to dry. If put beneath the stove or in a very slow oven the drying will be hastened considerably.

While the armature is drying the field spools can be wound. Each pole will require 490 turns of No. 20 single cotton covered magnet wire. This can be wound directly on the pole piece or, what is better, wound on a frame and slipped on the pole completed. The form can be made as follows: Cut a piece of wood just the shape and size of the pole pieces. Its length should be that of the over all lengths of the field spool, which is 1 1/4 in. Wrap two layers of medium drawing paper around the form, shellacking both layers together. Do not shellac the paper to the form. Then cut the fiber ends for the field. These are made from 1-16 in. stock. The one to go next to the frame will be quite narrow, only 1/2 in. wide. Slip those onto the form and screw some pieces of wood on the ends to hold the fiber while winding.

Next put two more layers of paper around the form, using paper wider than the inside space, letting it come up on the fiber. Shellac the paper into place and against the fiber. Drill a hole through the large fiber and close to the bottom, and draw the end of the wire from inside out about 8 in. Now center the form in the lathe and wind. The first seven layers, or until the top of the small fiber end is reached, are wound the full length. After that drop one turn per coil at the small end until the requisite turn6 are on. Between every six or seven coils I would suggest putting on a layer of paper. This will help to keep the wire even. Give the coil a good coat of shellac and take it off the form, setting it aside to dry. It might be a good idea to see that plenty of shellac gets between the wire and fiber ends and then set the coil up in clamps so that the ends will stick firmly to the wire. Care should be taken that the second coil is wound in the right direction. It should be so wound that the winding in both coils turn in the same direction when in place.

Another good way to make the field spool is to use one turn of sheet tin in place of the first layers of paper. The tin should project out each side of the form and the extra part be bent over so as to hold the fiber ends in place when the coil is taken off the form. The size of wire and turns given require a field current of 1.5 amperes. If the builder is careful it is possible to to get approximately 730 turns of No. 22 wire on the spools, making the inside fiber piece 1 in. wide. This winding would require only 1 ampere of current and is, therefore, more desirable, giving a machine of higher efficiency. The field coils of No. 22 wire are recommended.

A 150 Watt Dynamo Part 2 50

Brush Holder Andig Rigging 150 Watt Dynamo

While the field coils are drying the armature may be wound. the wire to be used is No. 16 single cotton covered, and wind 18 wires in each slot. Before winding wrap the enlarged part of the shaft at the pulley end with cloth or tape for about 3/8 in., and put a fiber tube of 3/8 inside diameter and 1/4 in. long on the shaft against the core at the commutator end. These insulate the wire from the shaft, and the fiber tube also serves as a stop for the commutator to bear against. In winding do not exceed the limits of this insulation.

To begin winding, wrap the end of the wire two or three turns around the shaft and go through a slot coming back through the fifth slot to the right, look, ing at the core from the commutator end. In winding always have this end towards you. Wind on the 18 turns, taking care to have the wires as straight and even as possible and have them lay as tight as possible against the end of the core, remembering the limits set on the shaft for the wire. The wire from the last turn should be twisted into a loop about 2 in. long for material with which to connect to the commutator, and then carried over to the fifth slot beyond. With this slot as number one wind the second coil between this and the fifth slot away. Repeat this operation until all slots are full, when the last turn from the last coil will come in sequence to the loose end of the beginning. Twist these together and there will be six twisted loops sticking out for the armature. Numbering the slots to the right, looking at the commutator end, the coils will come as follows: Coil 1, slots 1-6; coil 2, 11-4; coil 3,9 2; coilj 4, 7-12; coil 5, 5-10, and coil 8,3-8.

After the wire is all on give the coils a good coat of shellac, especially at the ends and again dry the armature in a slow oven or under the stove. Do not place in too hot an oven as insulation would be likely tocharr. In using the single cotton covered wire great care should be taken not to scratch or break the insulation. If the builder could afford it double silk covered magnet wire would be much better. After winding each coil it should be tested with a lamp resistance on 110 volts to see that there is no ground between the coil and the iron core.