TECHNOLOGY
Aluminum Hopper Car Has New Design Aeronca's articulated aluminum hopper car uses design advantages to increase payload A new approach to rail car engineering may open the door to cheaper transportation of chemicals in bulk. As major car builders turn out ever larger freight cars, a newcomer to the field has taken the opposite tack. Aeronca's articulated hopper car, just released for unit-train testing on the Southern Railway System (C&EN, Aug. 16, page 37), uses the design advantages of a short unit to increase payload. A builder of airframe and spacecraft components, Aeronca began with a computer analysis of rail car dynamics. The design program, undertaken jointly with Southern Railway, produced a four-wheel aluminum unit just half the length of an ordinary hopper car. What rolled out of Aeronca's Middletown, Ohio, shops was a fourunit car, permanently connected, that can haul more than 5 lb. of payload per pound of car—40% more payload than carried by a conventional alumi-
num hopper rail car built for unit-train service. Heavier loading per car often means lower freight rates to a shipper. This has brought increasingly larger cars into use, especially for low-density cargoes such as plastic resins and soda ash. To protect their tracks, however, railroads set a limit on the gross weight of a car. A car builder, to gain payload, must make an equal cut in the car's dead weight. Lighter. An aluminum body is one way out. American Car & Foundry's Center Flow tank-hopper car, for example, is more than one quarter lighter in aluminum than it is in steel, picking up more than 8 tons capacity per car. Against this advantage is the higher cost of aluminum fabrication— 50 to 60% more expensive than steel for Center Flow and similar tankhoppers. The balance favors aluminum in a growing number of cases. Aluminum
freight cars ordered through June are taking more than 22 million lb. of the light metal, according to Reynolds Metals Co. This is twice the quantity used in all of 1964. Almost all of these cars are covered hoppers. Aluminum Co. of America, which furnished design and fabrication assistance in Aeronca's project, sees a continuing annual growth rate of 10% in the rail car market for aluminum. Most of the aluminum hoppers being assembled are general-purpose cars and closely follow the equivalent design for steel cars. When aluminum is used in cars built for chemical traffic—expensive designs even when built in steel—the cost often dampens a shipper's enthusiasm. ACF, which has put together 8000 Center Flow tank-hoppers since 1961, has delivered fewer than 400 in aluminum. Union Tank Car's Pressure Flow tankhopper, available since 1963, has yet to be built in aluminum. Sharp cuts in dead weight, as in Aeronca's approach to car design, could work in aluminum's favor in the specialty car market. Car Length. The high payload-todead weight ratio of Aeronca's prototype is a direct result of car length. The hopper unit's dimensions were established by a computer study as the most stable configuration for rail travel. The object was to avoid railjoint resonance: swaying and pitch-
ARTICULATED. This articulated aluminum hopper car was built for testing on Southern Railway. The car, fabricated from specially formed aluminum plate and extrusions supplied by Alcoa, can carry a 260-ton load
46
C&EN
AUG.
2 3, 196 5
ing induced in a car as its wheels repeatedly strike the staggered rail joints along the tracks. Such motion can cause derailment. The computer's solution was a 26-ft.-long unit—about half the length of a conventional 100ton hopper car. For such a short unit, the undercarriage could be radically redesigned. This part of a rail car—the underframe, trucks, and suspension system—is usually all steel, even when the car body is aluminum. The main structural member around which a conventional car is built, called the center sill, is a heavy steel channel running the car's length along its bottom. An aluminum center sill would be too subject to bending for use on a freight car of the usual length. But for its shorter unit, Aeronca is able to use a tubular aluminum sill of rectangular cross section. Weight Pared. More weight was pared from the design by simplifying the trucks. The 26-ft. unit can readily negotiate curves with wheels that are bolted directly to the car frame. A single axle at each end is adequate. The usual dual-axle truck assembly, connected to the car frame at a swivel joint, is eliminated. Because of its high loaded-to-empty weight ratio ( 7 : 1 , compared to 4.5:1 for most aluminum open hoppers) the Aeronca unit has a dual-rate suspension system—a set of springs for each condition. In all, the articulated design cuts the steel required to about 24 tons for the 40-ton, four-unit prototype, compared to some 38 tons of steel in a pair of conventional aluminum unit-train hoppers. Usable volume is about the same in both cases. The prototype is designed for unittrain service only. For ordinary service, the car would have to be fitted with draft gear to take the shocks of switching and classification. This would add from 1 to l 1 / 2 tons to each unit. Plans should be at the negotiating stage in about a month for a covered version of the articulated car. The roof can be very light—perhaps less than 500 lb.—since it won't be a loadbearing structure. Working with a major chemical firm, Aeronca also is looking at a pressure-unloading hopper design. Although this car won't follow the articulated-car approach, the company doesn't rule out a combination of these features in future designs.
Oven Cleaners Become More Sophisticated To Meet Demands of a Growing Market Chemistry, which has helped solve a variety of difficult cleaning problems, is bringing a fresh approach to one of the toughest of them all—oven cleaning. Currently, the most widely used cleaners are spread-on, sodium hydroxide formulations which are messy to apply and must be handled with care. Coming to the housewife's aid, however, are new products which are easier to apply and safer to use. Now available, too, are products to protect ovens from soils and make them easier to clean. Earlier this month, for instance, Dow Chemical introduced a new sodium-hydroxide based, aerosol oven cleaner which is applied to a preheated oven. The new cleaner works on both fat and carbon deposits and yet is safe enough to use in the home, according to Dow. Already on the market is a cleaner which works in much the same way as Dow's new product. Called Jif Foam, it also relies on heat, which triggers its action, according to developer Winfield Brooks Co. Several firms are offering products to spray on freshly cleaned ovens to help keep them clean longer. Basic component of these products, which are packaged as aerosols, is a silicone release agent. Biggest seller at present is Oven-Gard, made by Drackett Co. Market Growing. All this activity is generating a rapidly growing market for oven-care products. Retail sales of such products this year will probably reach $22 million, more than double 1964 sales, according to Dow. By 1970, the market could approach $50 million. Ovens are plagued by many types of soils. These include fats (partially or completely resinified), carbon, proteinaceous materials, and carbohydrates. Deposits of combined soil will vary in quantity and tenacity on the different surfaces of an oven and broiler. Fats are generally deposited from broiling or roasting and the carbon deposits result primarily from spillage. These two are the most difficult deposits to remove. Until recently housewives didn't have much to choose from in the way of oven cleaners. Most of the established products are based on sodium
hydroxide in a cornstarch paste carrier. Fairly effective but hard to use, they work by simply hydrolyzing the fat. However, because of their high caustic content—usually 7 to 8% by weight—they can be hazardous. Aerosols. Many of the newer oven cleaners are aerosols, which are more easily applied and more convenient. They have a lower concentration of sodium hydroxide or other alkaline compounds such as sodium silicate or potassium hydroxide. They usually contain a nonionic or ionic detergent. Solvents include water, poly ethers, and methylene chloride. For instance, Dow's first oven cleaner, introduced early last year, contained sodium silicate, an alkanolamine, methylene chloride, and ammonia. Although these products are usually safer to use, the majority of them aren't as effective as the higher-caustic-content cleaners. However, Dow feels that its new, reformulated oven cleaner is as effective. This reformulated cleaner contains sodium hydroxide, ammonia, and water plus other ingredients. Concentration of the sodium hydroxide, however, is only 3 ° . A key factor in its effective use is preheating the oven. The recommended procedure is to heat the oven to 200°F., turn it off, and spray on the cleaner. The cleaner is allowed to work five to 10 minutes and is then wiped off. Another advantage of the new cleaner is the fact that it works two ways to remove deposits. Besides eroding away deposits, it gets underneath and lifts them off. Playing a significant role in this two-way action is ammonia. But Dow won't define exactly the ammonia's function. Hot Oven. Similar to Dow's new cleaner is Jif Foam, an aerosol packaged and marketed by Shelco Sales Co. under a license from developer Winfield Brooks Co. Introduced in 1963, Jif Foam also depends on a hot oven for effective action. The product contains sodium hydroxide and glycols (which have some solvent properties). Other components are detergent and water. Winfield Brooks will say only that Jif Foam works by a "catalytic action" triggered at 140°F. The heat speeds its action, particularly on carbon deposits, the company explains. AUG.
2 3, 1 9 6 5
C&EN
47
