Let's Draw Insulator Shapes
by Jack H. Tod

Reprinted from "INSULATORS - Crown Jewels of the Wire", September 1972, page 7

Some collectors have occasion to make drawings of insulators to record their specimens, report new finds to the magazine, or just for the heck of it. The drawings in the porcelain Universal Style Chart and the glass Consolidated Design charts are accurately made with very elaborate profiling machines and photo-mechanical setups, but there are several methods collectors can use to make pretty fair drawings. The one below is the easiest and yet gives very good results. It requires only a pencil, ruler, drafting triangle and carbon paper. Although not necessary, it also helps to have large calipers and a small light-box.

Assuming the light 7 1/2' above the floor, the error in drawing size (too large) ranges from 1.12% for a 2" insulator up to 3.45% for a 6" one. You can eliminate almost all error by determining the half-widths for the centerline by measuring the specimen with calipers and by adjusting the base upwards to actual insulator measurement. The errors can be reduced to absolute zero by using the sun as a light source, but setup is a bothersome thing. Insulator and the paper must be kept in the plane normal to rays of the sun.

PROCEDURE. Unscrew all but one bulb from the ceiling fixture and place insulator on paper directly underneath it on a smooth floor. Prop up insulator level and make the shadow outline as shown in Figure 1. Then go to your desk. 

Determine centerline points A and B as shown, or for greater accuracy measure insulator at those points and set marks in half the diameters from the right hand profile. 

Fold paper on centerline, markings outside. Place on top of carbon paper (carbon facing up) with insulator profile upwards. Trace profile, and carbon duplicates this on under side as in Figure 3. Now unfold and add horizontal lines as in Figure 4. Measure pin hole depth C, threads collar height D and skirt width E. Add these marks to your drawing.


Now, as in Figure 5, complete internal surface through points D and E. Cut out the threads template provided here and place this behind your drawing, with the centerlines matched up and with threads top brought to point C. Trace threads. A light-box helps for this, or put a lamp under your glass coffee table. If don't have, hold up to window. 

Complete the drawing by adding cross-hatching as shown in Figure 6. For methods to easily duplicate the insulator marking as shown here, tune in next month - same magazine'.

The drawings here are 80% size per magazine reduction, but the threads template is actual size here (1" threads).

For use in magazine, do not use blue or green pencil or ink which will not come out on photo. Use black pencil or ink. Make work lines in light blue pencil if you want, as these won't show up in the photo. If it takes you more than 5 minutes to make your drawing, you're doing something wrong! 

If your insulator has petticoats or other internal details, you can add theme by measuring them as shown here. Place a straight edge across the bottom and make pertinent measurements as shown in Figure 7. Your shadow drawing should already look like Figure 8, and you can add in theme measured points. As in Figure 9, connect up these points and you're done. Similarly, you can also add details which don't show in the shadow-crown details, undercut side skirts, etc.