We now come to the preparation of the rubber, which is an important detail. Get a wooden block 1¼ inches by ½ inch and 1 inch shorter than the cylinder. Smoothe off all the corners, and glue on one long edge, a piece of thin leather (chamois will do); fold over the flat side, and then glue it again at the other long edge; double it back loosely, and glue again in original place. This should make a sort of bag on one side of the block, which should now be stuffed with dry wool or hemp, and the two ends fastened down. A piece of black silk, about 5 inches by 9 inches, must be attached to the bottom edge.
Front View, Showing Rubber Seen Through Cylinder; Conductor Removed. A A Supports; R Rubber; B Brace Board; C C Adjusting Screws; F Rubber Stand.
End View. H Handle; D Conductor; E Glass Support. Rubber, Silk Flap and Support. A HOME-MADE ELECTRICAL MACHINE.
Now place the cylinder on its bearings, and press the rubber against the middle of one side, which will show what length to make the rubber stand. The thickness may be ¼ inch, and the breadth 2 inches; one end being screwed to the rubber block at the back, and the other resting on the base-board, but attached to the brace piece by two bolts with adjustable nuts. These you can get at an ironmonger’s—thumb nuts are preferable, as they can be tightened up without pliers.
As this board will be on a slope, the cushion block must be bevelled off with a chisel, so that it may rest “squarely” against the glass. The adjusting screws will enable the pressure on the glass to be regulated. Be careful to see that the silk flap (attached to the bottom edge of the rubber) comes between the leather and the cylinder, and then folds over the cylinder to about the middle of the opposite side.
We next come to the “prime conductor,” which is a piece of rounded wood, 2 inches in diameter and 1 inch less than the length of the cylinder. The end corners must be made round with a knife and sandpaper, so the whole surface may be quite smooth. Then lay on evenly with paste, a sheet of tinfoil, notching it so that it may fold nicely over the spherical ends, and take out any ridges by rubbing with the knife handle.