Machine Design

Looking Back

10 YEARS AGO — June 18, 1998

New treatment hardens chain drives: A new thermochemical process developed by Sedis, a French company, increases the hardness of industrial drive chains and makes them more wear resistant. The process boosts surface hardness from about 800 to 1,900 Vickers and is similar to chrome hardening: Atomic chromium combines with the steel to form a surface integral with that of the pin. This prevents flaking, a risk with electrolytic chrome plating. The high temperature diffusion process (around 1,832°F) produces uniformly thick surfaces which adhere closely to the substrate. The surface itself is a complex chromized coating primarily of extremely hard chrome carbide.

30 YEARS AGO — June 22, 1978
Additives silences squeal and stops fade in asbestos-free brake pads: Lubolid, by Dow Corning Corp., is a new friction-control additive that reduces squeal, fade, chatter, and cold-start sensitivity in disc brakes. With the elimination of asbestos and an increase in the use of highperformance disc brakes, frictionmaterial manufacturers needed a replacement. Dow Researchers found that the physical properties of friction materials could be modified selectively by blending various solids in specific concentrations. Further development led to the Lubolid additive, an inorganic gray powder, stable to at least 500°C for disc-brake pads.

50 YEARS AGO — June 26, 1958
Oil or gas
, or a combination of both, can be used as fuel in this pressurized- furnace steam generator. The unit, from Babcock & Wilcox Co., is designed for power, process, or heating loads requiring steam capacities to 400,000 lb/hr. An integral combustion air duct on top of the unit conserves space. At left center is the drainable superheater, which permits water draining after a boiler shutdown. Burners at extreme right are centralized for easy observation and adjustment.

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