Fluorescent "Bombing"

Fluorescent lighting faces the biggest boom in its four-year existence (estimated sales for 1942: 40 million tubes). Recently the infant industry's 37-year-old James L. Cox, Hygrade Sylvania Corp. engineer, announced the demise of a technical "bug" that has been lurking in the luminescent tubes: the unpredictable "lumen slump" (blackened end-bands, dark streaks and splotches) that afflicts many lamps. Cox's bug killer: a technique for dosing each lamp with the exact amount of mercury needed for adequate ultraviolet radiation.

Common practice has been to deposit a small amount of mercury in each tube from a mechanical "eye-dropper," which was not very precise. Insufficient mercury, Cox explained, makes the light slump quickly; too much mercury produces blotches and discoloration. Hygrade's new process seals the mercury in long sections of thin nickel tubing, feeds the tubing into a precision machine which nips off "mercury bombs" of specified length, carries the "bombs" under a magnetic device which picks out of line and discards any capsule holding even 1/1,000 gram less than the amount required.

The mercury "bomb" is spot-welded to one cathode and is exploded by heat applied just before the fluorescent tube is sealed, thus releasing mercury vapor into the argon-filled lamp. Twofold result, claimed by Hygrade Sylvania: 1) stable performance of every tube; 2) savings of up to 50% of mercury previously wasted.

Tin Cans

Having lately been taught to consider cans as valuable metal, Americans, as they emptied their soup, beans and tomatoes from tin containers last week, wanted to know: What to do with empty cans?

Many had written to Washington ("hundreds of thousands of letters," said one WPB official) demanding to know why, if the Government needed tin to replenish dwindling stockpiles, it didn't come and get it. WPB's Bureau of Industrial Conservation admitted that the long-delayed nationwide campaign to salvage tin would soon get under way, could not say when, how, where the detinning would be done. The only positive, encouraging word came from harassed metalmen themselves: detinning of used cans is a perfectly feasible if not profitable operation.

Present tin cans are about 98.5% sheet steel, 1.5% tin. (A recent WPB order has reduced the tin content of future cans to 1.25%.) By washing and shredding the cans, then treating with caustic soda and other chemicals, it is possible to extract about 25 Ib. of tin oxide (readily smelted to a grade equivalent to Straits tin) per ton. The detinned sheet steel, once despised and used only for rough castings such as sash weights, is now in big demand by scrap-hungry steelmakers.

There are about 2,000,000 tons of tin cans discarded annually in the U.S., of which an estimated 700,000 tons might be collected, shipped and processed economically. Today, the toughest problem facing WPB planners is getting greater detinning plant capacity. Of the seven large plants now in operation, Metal & Thermit Corp. (East Chicago, Ind.; South San Francisco; Carteret, N.J.) and Vulcan Detinning Co. (Neville Island, Pa.; Sewaren, N.J.) do about 85% of the business. New plants are being built by the Defense Plant Corporation at Houston, Dallas, Kansas City.

Since March the New York City Salvage Committee has rounded up over 1,000 tons of cans, most of them cleaned, crushed, with tops and bottoms removed as per instructions-''fancy" scrap, in the industry's jargon. The experiment (still continuing) has moved so smoothly that there is high good feeling even between the municipal administration and the metalmen. "I've never been so impressed in my life as I have been by the New York City Sanitation Department," said Robert Mac-Millen, representing both M. & T. and Vulcan, last week. "It moves like clockwork."

Metalmen believed that other cities could do as well, but they said that the next move would have to come from Washington.

Seadrome Light-up

Last week a demanding customer, the U.S. Navy, was hauling away from Westinghouse plants certain huge, vertical-striped rubber doughnuts as fast as it could get them. This meant that at many a marine base big flying boats would soon be able to drop from the night skies to perfect landings on water "runways" as plainly marked with contact and boundary lights as the ground runways of any airport.

Lighting the waterways for night landings has defeated many an illumination engineer in the past ten years. Floodlighting is impracticable: reflection from floodlighted water confuses the pilot, gives him no clear perception of the surface. Floating flares, properly reserved for emergency landings, are dangerous when dropped over bases or busy harbors. Lines of marine-type buoys, heavy enough (about four tons) for stability, present a series of collision hazards. Lightweight floats, unstable even in smooth water, give the incoming pilot the disconcerting sensation of aiming his ship at a writhing snake.

Westinghouse and Firestone engineers got their idea from the bi airplane tire. As a floating platform it is buoyant, lightweight, offers small collision hazard. A full-swiveling gimbal, mounted in the rim, would keep the light post vertical while the tire followed the shifting contour of the water. Crude early models, demonstrated for Navy observers, produced results that "were astounding compared to previous methods," said Westinghouse Engineer Willis A. Pennow in Aviation. The latest model adheres to the basic conception, incorporates these refinements: > The gimbal is gone. The rubber float (no longer an airplane tire) is now self-stabilizing, shaped like a "diamond cross-section in revolution," according to Pennow, which gives resistance to sideslip on the slope of a wave, keeps the buoy upright in choppy water. > With carefully adjusted wall thickness, low-pressure inflation, the float offers less than 25 ft.-lb. impact, virtually eliminating collision hazard.

> The light unit (radio-controlled) includes: 1) a dry-type battery; 2) a small power unit to convert low-voltage D.C. current to high-voltage A.C.; 3) a fluorescent lamp with large light output, no shimmer or glare; 4) a Fresnel lens which directs light rays on to the channel.

During a year's service tests, under actual operating conditions, the contact and boundary lights proved visible at three to five miles in normally clear weather, compared favorably with land lights under limited visibility conditions, "remained as steady and solid as a row of contact lights on a concrete runway."

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