Page:Popular Science Monthly Volume 91.djvu/627

 Making a Practical Vacuum Cleaner

I. — Details in the construction of the universal motor By L. E. Swindell

��THE machine described is not a difficult piece of apparatus to construct, and it will do the work equally as well as a standard make. However, building it yourself will not reduce the cost to any appreciable degree. The only thing gained will be the satisfaction of saying "I made it myself." The essential parts are a high, speed electric motor to drive the centrif- ugal fan, and a suitable case with a shoe or nozzle to collect the dust from the floor and discharge it into a cloth bag which retains the dust and releases the air.

The following materials are necessary in the construction of the vacuum cleaner.

Materials for the Motor

90 pieces transformer iron 0.015 in - thick, 3^

in. sq. 90 pieces transformer iron 0.015 ln - thick, 2 in. sq.

1 shaft, cold rolled steel Y% in. diameter and

7% in. long

2 bolts x /i in. diameter and 4 in. long, threaded

1 % in. on each end 2 hardwood blocks 3^ by 3^ by 1 in.

1 piece iron h /% by 7 by Ys in.

2 iron washers 1 Yz in. diameter, %-'m. hole 2 8-32 brass screws 1 in. long

2 pieces brass tubing Y\ by Y\ by % in. (inside

measure) 4 fiber washers % in. square, J^-in. hole, 1/16 in.

thick 1 commutator, 22 segments Yl lb. No. 26 gage enameled magnet wire % lb. No. 29 gage enameled magnet wire.

Materials for the Shoe

Enough sheet iron 1-16 in. thick 15 soft iron rivets }/$ by % in.

6 8-32 brass screws Y in. long

I cylinder of brass 1Y3 in. long by Y% in. diameter J^-in. hole

1 piece of fiber 1 in. thick 2 by 2 in. square

2 pieces iron % by Y% by 14 in.

1 hardwood handle 3Y2 ft. long, iYs in. diameter

If you can secure a fan motor of suitable size you will save yourself considerable time and labor. For the benefit of those who cannot obtain a motor, or who wish to build their own, the necessary directions will be given for the construction. If a motor cannot be procured some machine work on a lathe and drill-press must be done.

��The Motor

The motor is of the alternating current series type, wound for use on no- volt circuits. It may also be used on direct current. The field for use on direct current could be of solid iron, but for alternating current it must be laminated because of eddy-currents and excessive heating.

The dimensions of the field magnet are given in Fig. 1. A stack of transformer iron 2>)/2 m - square and \Yi in. thick should be clamped between two hardwood blocks by means of the two 4-in. bolts as shown in Fig. 2. Now proceed to turn the mass of iron and wooden blocks to a diameter of 3/<£in. Use a high speed and a very sharp tool, cutting toward the lathe chuck. The center should be turned out to a diameter of 1 9/16 in. The wooden blocks should now be removed and the pole pieces machined. This is the most difficult for the amateur to do. If the directions are followed and a little patience used, a neat job will result. If a row of holes are drilled between the pole pieces just inside the 2 J/2 m - diameter, the remaining ma- terial can be easily removed with a sharp cold chisel and finished with a round file, The laminae can now be taken apart and each varnished with black insulating var- nish. When dry, reassemble the laminae and proceed to wind the field.

Each pole is surrounded by a coil of 200 turns of No. 26-gage enameled magnet wire thoroughly insulated from the iron by empire cloth. The wire should be wound on by hand so that it will occupy as little space as possible. The field poles should be thoroughly insulated by means of strips of empire cloth wound tightly around them and then varnished. The leads should be brought out and the coils connected in series; i.e., the end of one coil should be connected with the beginning of the other. The two free ends should be brought out and protected from injury, and the finished field set aside while the armature is built.

The armature is of the usual drum type, with eleven drilled slots to receive the windings. The shaft is of cold rolled steel,

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