The Perfect Machine (36 page)

Porter answered the questions with sketches of an elevator that would ride up the edge of the shutter opening in the dome and an extending platform that would reach almost to the observer’s cell. The observer would only have to step across ten inches from the platform to the prime focus cell.

For the Cassegrain focus behind the primary mirror, Porter came up with an equally ingenious observation platform. Because the end of the tube would rise and fall as the orientation of the telescope slewed in declination, Porter proposed a pivoting observation platform with a central portion on retracting cables. Electric motors would lower the center of the platform to the floor for observers or equipment. The pivoting platform would rotate so that the platform was always level with the floor, no matter what the orientation of the telescope. A few astronomers on the advisory committee raised questions about ascending to the telescope in what looked like a large children’s swing, but the simplicity of the mechanism, without ladders to move and get in the way, was immediately appealing.

The details fell into place. Still, the biggest decisions—the design of the mounting that would hold and point the mirror, how and where to build it, and the final choice of a site for the telescope—remained open. Deciding those issues before they had a mirror was tempting the gods.

Corning’s advertising motto was Corning Means Research in Glass. At the beginning of 1933, unbeknownst to the Observatory Council in Pasadena, the Corning engineers were going to have to make good on that slogan.

It had been McCauley’s decision that they keep the disastrous test results on the sixty-inch disk from the Observatory Council. The initial thirty-inch test disk, which had been annealed only a short time, had passed the tests of the opticians in Pasadena. It was only the larger disks that suffered the increased water solubility of the glass, because of their long annealing. McCauley’s plan was to use the period when they were
building the large annealing oven and molds for the next steps to develop a new glass.

Harrison Hood, who had the nickname Sage of Glasslore at Corning, got the assignment of coming up with a new glass formulation. He had previously developed glasses that would survive long annealing, but none with the desirable low expansion of the 702-EJ glass McCauley had used for the trial disks.

Hood’s initial formulations, tried in a small day tank in C factory, might have met the specifications, but they were so difficult to melt and work that the glassmakers rejected them. Each trial meant dismantling, emptying, and rebuilding the tank, and days or weeks to assemble the materials and get the melt up to the proper temperature, well over 1000°C for these borosilicate Pyrex glasses, before the glass could be ladled into test molds. Hood’s next try used the same amount of silica as laboratory Pyrex, with more boric acid and less alkali. The mixture proved workable, and the glassmakers were able to pour a block, approximately thirty inches square and thirteen inches high. The block was covered with Sil-o-Cel insulating powder and allowed to cool slowly in an effort to duplicate the effects of long annealing.

The block survived the test unbroken and emerged with less opalescence than the same treatment would have produced in 702-EJ glass. Hood made a few more adjustments to his formula, ran it through another series of tests, and named the new formulation 715-CF Pyrex. On extensive testing the new glass held up, after the long cooling period, with no problem of water solubility. The formulation required higher working temperatures, in excess of 1500°C, but it also had a temperature coefficient 25 percent lower than the previous formulation and did not devitrify at the higher temperatures.

Arthur Day was already scheduled to meet with George Hale, so he was entrusted with the “good” news that Corning had developed a new formulation with reduced temperature coefficient that would make even better mirror disks. He mentioned not a word about the water solubility problems that had condemned the sixty-inch disk, and no one in Pasadena knew how close Corning had come to failure. Hale cheerfully welcomed the news about the new glass formulation and answered that there was no need to recast the sixty-inch disk because the latest design of the telescope would use smaller secondary mirrors that could be cast later. Sometimes a hiatus in communications can do wonders for a relationship.

McCauley’s crews continued their work on the molds and annealing ovens and tried a test disk with the new formulation. The higher temperature in the melting tank required for the new Pyrex reduced devitrification on the surface of the glass in the ladles, so they no longer had to skim the ladles before pouring. At the same time McCauley discovered that the ¾-inch-thick ladles were heating excessively
in the period between filling with glass and pouring into the mold. The high temperatures scaled iron oxide off the ladle rims, which in turn introduced traces of discoloration into the tank when the ladles were dipped in for another load of glass.

The obvious solution was heavier ladles. Corning had little experience with ladles, and queries indicated that even the big window-glass-makers had never used ladles thicker than ¾ inch. When even the window-glassmakers shifted to machines for plate glass, ladle technology had stopped. Fortunately, the purchasing office queries led to Bethlehem Steel in Buffalo, which still had the dies they had once used to press ladles for the window-glass industry. The depression had left their mill slack, and they were willing to bring out the old dies and press one-inch-thick ladles—all within fifteen days.

By early April 1933, McCauley was ready to cast a 120-inch disk. The masons and electricians built a new annealing oven, large enough for the two-hundred-inch disk. McCauley’s conservative calculations came up with 516 for the number of oversize GE heating elements needed to maintain the temperature of the oven. To avoid the possibility of shorts, the heating elements were mounted in rows on the sides and bottom of the oven cover, with heavy-enough wiring and masonry to survive an annealing period, at high temperature, of up to one year. The thirty-five-volt circuitry reduced the insulation problems, but the increased current required large-diameter wiring from the panels of reactors and theater-dimming controls. Ten thermocouples were spaced around the upper, lower, and wall surfaces to continuously monitor the internal temperature. The controls were set up so an operator could control the internal temperature to within 1 degree in the range between 400° and 550°C.

The cores for the new mold were secured with cold-rolled steel rods to avoid an accident like the floating core that had marred the 60-inch disk. Just in case, McCauley had the masons prepare a spare set of cores. If the mold failed during the pour, they could quickly build a new mold for another try.

Corning masons converted one of the large melting tanks in A Factory to what the glass industry called a “day tank” for the 715-CF glass. Normally melting tanks had a bridge wall that separated freshly introduced materials in the back of the tank from the ready glass in the front. With the bridge wall removed, the tank could melt a single large batch of glass. Millwrights installed overhead tracks to support the heavy ladles, leading from three openings in the tank to three openings in the igloo over the mold, each 120 degrees apart around the mold. McCauley designed the tracks so the “tank and casting oven operated like the moon, with the same surfaces facing away from the workmen.” In the heat and panic of filling a mold, he didn’t want workmen confused by having to spin around and change directions while they were guiding ladles filled with 750 pounds of molten glass at 1500°C.
McCauley also had three special wheelbarrows fabricated for the ladle heels, with two wheels in front, to make it easier to avoid sideways tipping when the workmen were moving around the tank in the heat and confusion of a long pour.

At the end of April the tank was lit, and the filling began with 715-CF batch. Wheelbarrow after wheelbarrow went up the ramps to the loading shovel at the opening. Thirty tons of glass requires an enormous supply of sand, borax, soda, and lime. The level of molten glass inside the tank rose four inches per day. After a few days a workman discovered a break in the tank lining. McCauley ordered the tank cooled and rebuilt. There weren’t enough of the special low-contamination refractory bricks on hand, so the masons cannibalized bricks from the floor of the tank to fix the walls and built a new floor from common bottom bricks like those used in the normal production tanks, with a four-inch layer of clay tamped over it. No one was sure a tamped bottom would work for a melting tank, but the alternative was to wait months for the Pot and Clay Department to prepare a batch of new bricks. After the months lost searching for a new glass formula,
delay
wasn’t a welcome word.

Within the world of astronomy, observatory directors followed every move of the group at Caltech, hoping they could piggyback on the research efforts to obtain disks and technology for their own planned telescopes. Dr. O. A. Gage, head of the Aircraft and Instruments Division at Corning, took advantage of the talk to solicit more orders for telescope blanks for Corning. Telescopes would always be a small portion of Corning’s business, but once a portion of the facilities had been set aside for the bulky casting and annealing ovens, a large melting tank had been dedicated to the special glass for the telescopes, and personnel—not only the ladlers but electricians, millwrights, carpenters, masons, tinsmiths, and glassmakers—had been assigned temporarily from other work to the telescope project. Aside from the juggling of the annealing ovens, more orders just meant an economy of scale for the operation.

Once he found out that Caltech was abandoning all work at GE, Harlow Shapley canceled his order for two 60-inch disks from GE and ordered them from Corning. The David Dunlap Observatory at Toronto asked for a 76-inch disk, which would ultimately become a 74-inch telescope blank, and the McDonald Observatory of the University of Texas ordered an 82-inch disk. Heber Curtis, Shapley’s old adversary in the great debate, who had left Lick Observatory for the University of Michigan,
^*
ordered a large disk of undetermined size.
Each order for a primary mirror was accompanied by orders for one or two auxiliary disks.

In all it was enough work to keep the tanks and glassmakers busy for over a year. And since the available annealing tanks and casting igloos were limited to casting one large mirror at a time, and the 120- and two-hundred-inch disks for the Observatory Council would keep those busy—between casting and annealing time—for at least the next two years, McCauley had another set of molding and annealing equipment built south of the existing set, but close enough to the big 3A tank to use the same batches of glass. The new kiln was big enough for an 84-inch mirror. The smaller molds and kiln required less elaborate equipment for raising and moving than the big molds and kiln for the 120- and 200-inch mirrors.

By the third week of June the 3A tank was filled and the glass mixture had set (the glassmakers would say it had been allowed to “plain”) for nine days until the glass was deemed ready. It was a Wednesday when the Pyrex was ready to pour. McCauley decided to use the 76-inch mirror for Toronto as a trial for the molding procedure, and to postpone the 120-inch disk for the Observatory Council until Saturday morning, when the regular blowing room personnel would not be in the factory to distract the ladlers and other crew.

The pour of the 76-inch disk went without a hitch, and it was consigned to the smaller annealing oven. The melting tank was topped up with enough batch mixture to replace the
2½
inches of glass that had been used from the tank. The crew to pour the 120-inch disk—the largest piece of glass ever poured—would be the same crew that had poured the 76-inch, augmented by the additional personnel needed for an operation that would keep three ladling positions busy. Two additional men operated switches on the overhead tracks that supported the heavy ladles. Two more men worked the additional ladles, and four men ran two more wheelbarrows to carry the ladle skins back to the tank. Because the journey from the tank to the mold was longer, three men with backpack spray tanks carried ring-shaped nozzles they could hold over the lips of the ladles while they sprayed water to keep the lip of the ladle cool. After each ladle was dumped, the sprayers would retreat to a recharge station to get their backpacks refilled with water and compressed air. From the first simple pours with one man handling a ladle, the operation had become a precisely choreographed ballet with a company of dozens of men.

On Wednesday evening, June 21, McCauley ordered the burners of the casting oven igloo lit in preparation to cast the disk the next Saturday, only to discover that the expansion of the metal anchor bolts that had been added to hold down the cores had dislocated the tops of the cores. The masons came in for repairs and finished on Saturday morning at 5:00 A.M., just as the pouring crew assembled. Except for a furnace
staff to attend the fire under the tank, the factory was empty when McCauley gave the order to begin.

With no audience to distract the crew, the procedure went smoothly. Everyone worked according to the script. The area around a fired glass tank—with the roar of the furnace, the clanging of the metal doors, the rumbling of ladle carrier tracks on the overhead rails, and the rattle of the metal barrow wheels against the steel floor—was far too noisy for verbal cues from a stage manager. And the sheer level of activity—along with the danger of moving ladles, each filled with 750 pounds of molten glass, heavy equipment, and barrows of glass slag—was far too dangerous for visual cues.

As each ladle of Pyrex emerged from the tank, the switchers had to route it to the correct port on the mold. A sprayer stood ready, avoiding the two men on the ladle arm and the heat of the full ladle of molten Pyrex as he held the ring of his sprayer centered around the ladle’s lip. The threesome walked under the track together, the ladle handlers maneuvering the ladle with its load of molten glass as the carrier rolled along the tracks to the opening over the mold. The sprayer pulled back just before the ladlers lifted the cup of the ladle into the opening in the igloo over the mold. When the molten glass was tipped into the mold, half would remain in the ladle, cooled enough by the journey to stick to the steel boilerplate walls of the ladle. As the ladle came back out of the mold, men were ready to empty the ladle skin into a waiting wheelbarrow, which was wheeled to the rear of the tank to be returned to the cauldron of molten glass.