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The 90 Miles of Wire in Your Home
October 1961 Popular Science

October 1961 Popular Science

October 1961 Popular Science Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Popular Science, published 1872-2021. All copyrights hereby acknowledged.

90 miles of wire in an average home is a lot of wire. That includes not just the wire used for supplying 120 VAC receptacle and light lines within the walls and ceiling, but also the wire in motors, relays, and transformers in appliances and various subsystems (HVAC, attic fans, shop tools, etc.). When this article appeared in Popular Science magazine in 1961, the average size of an American home was around 1,300 square feet. In 2024, it is around 2,600 square feet*. That's a doubling in size with fewer people per household (mine is smaller than the 1960 standard). The typical house now has more AC wiring in it due to electrical code changes requiring ceiling lights in all rooms, more receptacles, more feeder circuits, etc. Adding a ground wire increases the copper in a length of Romex by 33% to 50%. Most kitchens have more appliances on the counter, and the proliferation of cordless tools has added significantly to the number of motors. Most houses did not have air conditioning in 1961, so add a compressor motor into the average. If there was 90 miles of wire in the average home in 1961, you can probably apply a multiplication factor of at least three or four. * I don't use the U.S. Census numbers because they report the current size of houses built in 1960, which includes additions to the original house.

The 90 Miles of Wire in Your Home

Twelve-Ton breakdown machine (above) turns out a mile of heavy wire each minute. It holds four coils of copper rod, welded end to end. Zigzagged through 13 ever-smaller dies, the rod is reduced at the finish line to 18·gauge wire.

Taper at Entering End of each die (above, left) is so slight no metal is scuffed off.

Tough dies in tandem speed modern wire drawing

1. Modern Wire-Drawing Rig has a series of progressively smaller dies to reduce copper rod to wire.

2. End of Rod is point-shaped. This forced into the largest die with a pair of pliers.

3. Power Capstan, at right, draws about 20 feet of rod through first die. Smaller dies then take over.

4. Resembling Beads, widely spaced, dies are clamped in the rig. Draw blocks do the tugging.

By Henry B. Comstock

Robot rigs stretch metal like taffy to make - The 90 Miles of Wire in Your Home

Strung, bent, coiled and crisscrossed, there's enough wire in the average six-room house to reach from New York City to Philadelphia. The reasons add up.

It takes a quarter of a mile to make your doorbell chimes go "bing-bong." There's over half a mile in the box springs and mattress coils of a twin-bed set, and a mile in a 36-by-80-inch screen door. Statistically, you own 37 small electric motors. Their collective field and armature windings total 35 miles. Even a yard of lamp cord contains 240 feet of strands, hair-thin to make it flexible.

To meet demands for wires like these, a single machine in a modern mill may whip out 10,000 feet of wire a minute. Watching the shiny stuff streak from the rig, it's easy to forget that the basic routine hasn't changed since the 14th century.

It was then that an unknown German genius dis-covered the trick of pointing a metal rod and yanking it through progressively smaller holes in a hard-wood block, with tongs. Until then, all wire had been formed by spiraling and hammering thin sheets. With the drawing method, anyone could make it better and faster.

Wire−Making Starts in a Rod−Rolling Mill

The Job: To turn 265-pound copper bars into 90-foot-lon coils of 5/16-inch rod.

Preparation: Heat the bars cherry-red in a furnace to make them soft and workable.

The Method: Elongate the metal by squeezing it alternately oval and square in section.

Forming Procedure: Slam the metal bars between rolls with crescent- and V-grooves.

Thank Rudolph

Soon another German added a fillip that turned the craft into today's major industry. Rudolph of Nuremburg loaded the shaft of a water wheel with cams. As the big oak axle turned, the cams rocked a line of bell cranks. Attached to these, heavy tongs called "dragons" alternately snapped at wire projecting through dies, and advanced it with short tugs. Rudolph's mechanized shop could fill orders for a ton of wire a week.

Last year, American plants spooled three-quarters of a million tons of copper wire alone. Fortunately this most-used metal is the easiest to draw.

It's an Electronic Show

For a curtain raiser, go to Linden, N.J., where the Hatfield division of Continental Copper and Steel Industries has just opened the world's most fully automated rod mill. There, a single engineer sits in an elevated control center, the "pulpit," and holds the reins on an acre of machinery, with only two cranemen to help him.

Into one end of the $3 million plant go 265-pound copper slabs called "wire bars." This is no ordinary metal. Because a single pound may eventually be stretched into nearly 20 miles of 44-gauge wire, it must be pure.

To make it that way, electrolytic refineries sandwich castings of conventionally smelted copper between thin sheets of highly refined copper. When the bundle is lowered into the electrolyte and direct current turned on, all the pure copper in the castings floats over and clings to the pure-copper sheets. These are melted down and recast in pans to form the wire bars.

Metal Dispatched Like Trains

In Continental's new rod plant, craneman No.1 spots the 52-inch bars on a conveyer that pops one into a huge, gas-fired furnace every 27 seconds. There, "walking beams" hump up from below, inching the bars gently along. This prevents distortion as the copper soaks up 1,650 degrees of heat.

Each time a bar enters the furnace, another flashes out, glowing cherry-red and looking like an old-time interurban car. Almost at once, the bar slams between the five sets of rolls of a roughing mill. Squeezed, and then snatched up and reversed before it leaves, the "car" becomes a "train."

Now thin enough to lace around horse-shoe curves, it gets a last six squeezes in finishing mills. At the end it's automatically coiled and set on one of the arms of a turnstile.

All this time, the pulpit engineer has watched the bar's progress like a railroad dispatcher. Every control has been preset, but he can override it instantly in an emergency.

In the final act, craneman No. 2 snatches the coils from the turnstile and trundles them to a succession of tanks where they're first pickled in dilute sulfuric acid to rid them of scale, and then dunked in neutralizers and rinses to remove the acid.

Fourteenth-Century Wire was made by the same drawing process used today. Curiously, Rudolph's mechanized mill of 1350 was far ahead of England's most productive 16th-century shop. In the latter, operators sat in slings, snatching at the metal with crank-connected tongs. Hard pressed for wire during the American Revolution, colonists resorted to still more primitive machines. These can be seen at far right.

The Final Stretch

A few miles away, in Union, N.J., Continental gives the rods the one-way stretch that turns them into wire.

If soft metals such as copper or aluminum are being drawn, the technique is "wet." The machines - covered for safety reasons - coat the wire and dies with soapy lubricants and coolant so that friction heat won't melt the metal. But steel and other tough alloys are drawn into wire "dry."

At the first stage, copper-rod coils are reduced to heavy wire-usually 18 gauge. Big "breakdown" machines take four coils, welded end to end, and zigzag them through 13 dies of constantly decreasing size.

One thing troubles you. How do you thread a 5/16-inch rod through dies with holes shrinking to 0.04-inch? You get the answer when a coil runs out and an operator flips back a cover as wide as the door of a two-car garage. Quickly he removes the dies from their holders and lines them up in order. Then he points the end of the next bundle and, with a power winch and pliers, tugs one die after another onto a starting length, like wide-spaced beads. He threads this section around the drawing blocks, replaces the dies in their holders, and fastens the end of the copper to the barrel of a 30-inch receiving reel.

Fully loaded reels are placed on what looks like a giant cook-stove burner. The wire, stress-hardened during drawing, must now be re-softened with heat.

You can go on to smaller machines that reduce 18-gauge wire to gossamer. In the process there are several gimmicks that would have pleased old Rudolph immensely.

One of the slickest has just been developed by the Syncro Machine Co. of Perth Amboy, N.J., an outfit whose name is synonymous with advanced wire-making equipment. Syncro's new rig gobbles up the output of a light wire-drawing machine, first charging it with just enough current to set up a warming resistance. Then, while the wire races through a non-oxidizing steam bath, more juice is poured in to bring the wire to the right temperature for softening.

Continuous Production

More and more, wire-drawing and processing machines are being lined up in tandem, for continuous automated production. In a Western Electric plant in Omaha, Nebr., the wire that goes into your dial phone is passed through consoles that draw and tin it, apply plastic insulation colored for coding, and then sheathe bundles in tightly woven fabric.

Still, the only tools that make it possible for you to have 90 miles of wire in your home are the drawing dies. About as big around and three times as thick as a wrist watch, these are disks of steel in which are bedded either tungsten carbide or diamond cores. The holes in the cores are tapered part way through, then straight-walled, and, at the outgoing end, expanded slightly.

The angle of the taper is important. If it's much more than 15 degrees, stresses are far higher at the surface of the wire than at the core, causing what's called cup-and-plug fractures. On the other hand, too small a taper produces intense friction heat.

Rugged as they are, modern dies get out of gauge after about eight hours of continuous use. The holes are then ground to the next-larger gauge size. This can be done as many as 10 or 12 times before they're through. That's fortunate, because a tungsten carbide die for heavy-wire drawing costs from $10 to $15, and a fine-wire diamond die, from $45 to $100.



Posted May 23, 2024

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