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Technical Paper


A practical method of nickel-plating is outlined and the various processes are described by which the Packard Motor Car Co. has been successful in producing a durable coating of nickel on automobile parts in general, and the radiator shells, the rim plates and the tire-carrier plates, in particular. These are the parts of greatest exposure, and for plating them a new system of moving-cathode tanks was installed. The three problems to which special attention was devoted were rusting, pitting and peeling. No effort was made to secure a coating of any designated depth but reliance was placed solely on the results indicated by a 24-hr. salt-spray test, which was considered to be the equivalent of 2 years' exposure to the usual weather conditions. Peeling was overcome by thoroughly cleaning the parts before plating. New equipment was purchased and laid out in accordance with the system decided upon, namely, copper-plating, buffing and nickel-plating.
Technical Paper


PROBLEMS of suspension spring design that have been of major interest in recent years, such as spring life and reliability, hardness and settling, fatigue, shot peening, and presetting, are presented here. Various types of springs are discussed by Mr. Schilling, who concludes that no one type is superior in all respects, hence commercial applications of different types have remained competitive. He feels that this picture will not change in the future, that is, no one type will be used exclusively. Considering the great superiority of some types in economy of material, however, he expects that the less economical springs will gradually be replaced unless their weight can be substantially reduced.
Technical Paper

Temperature Gradients and Heat Stresses in Brake Drums

The main purpose of this paper is to show that the phenomena classed under the generic thermal failure are not due to excessive temperature alone, but to a combination of high stresses and high temperature; other factors of importance are brake design, geometry, physical properties of brake lining, and those of the drum. Concerning stresses, it will be shown that temperature gradients alone can cause them to reach well into the plastic state, even in a comparatively cool drum. Such heat stresses are known to give rise to crazing of the track, but in addition it is explained here that they are also responsible for heavy scoring, heat checks, or outright fracture. A detailed analysis indicates why and how certain purely mechanical design aspects lower stresses and heat concentrations, thereby mitigating or even preventing the onset of thermal failure.
Technical Paper

Effect of Temperature on Endurance Limit and Relaxation of Spring Materials

ENDURANCE limits and load losses at various temperatures from -75 F to 650 F for several spring materials are reported in this paper. The materials tested were in the form of helical springs, both shot peened and unpeened. Some general observations made by the authors include: 1. Shot-peened springs had higher endurance limits and greater relaxation than unpeened springs at -75 F and 75 F. 2. As test temperatures rose above atmospheric, endurance limit of all unpeened springs tended to hold steady or increase somewhat, while that of shot-peened springs tended to decrease. 3. Except for high-speed steel and stainless steel, chrome-silicon steel showed lowest load loss in both static and dynamic tests in the temperature range from atmospheric to 450 F. 4. Both unpeened and shot-peened high-speed-steel springs showed high endurance limits at all test temperatures. 5. Endurance limits at -75 F were similar to those at atmospheric temperature, but the amount of set was less, on the average.
Technical Paper

Effect of Shot-Peening Variables and Residual Stresses on the Fatigue Life of Leaf-Spring Specimens

RESULTS of an investigation into the effect of shot-peening variables and the resulting residual stresses on fatigue life are reported in this paper. Leaf springs were the simple specimens heat-treated, cold worked, and tested in this study. Some of the conclusions reached are: 1. There is a minimum shot velocity for each shot size to obtain best fatigue life, and this value is much lower than that normally used. 2. Exposure time for this type of shot-peened specimen beyond some minimum value is wasteful and costly. 3. Shot size has little influence on fatigue life for these specimens. 4. Shot peening specimens while under tensile strain greatly increases fatigue life at 200,000 psi nominal stress over that of nonpeened or strain-free-peened specimens. 5. Shot peening these specimens gave residual compressive stresses 50% of yield strength, and these stresses can be increased to more than 50% by strain peening. 6.
Technical Paper


THIS paper deals with cavitation pitting where vacuum bubbles exist. Experiments are described which attempt to correct this condition where plating of liners varied in composition and thickness. It was concluded that a nickel-chrome plating has very good resistance to cavitation-pitting attack. Investigation of cylinder-wall vibration was made to find out about the cause of cavitation. Minimum liner wall vibration results with use of a 2-piece heavy wall liner and a piston with 20% less clearance. Endurance tests prove that on these pitting has been eliminated.
Technical Paper


DATA presented in this paper indicate the bearing corrosion problem to be fairly straightforward in that: 1. Corrosion of copper-lead bearings specifically can be reduced by improving the fineness of the microstructure; 2. All bearings appear to be aided greatly by reduction of operating temperatures; and 3. Treating the corrodible bearings by special processes, such as indium plating, greatly increases their corrosion resistance. However, anomalies are cited which indicate that bearing and oil combinations do not behave in relatively the same manner in all engines. Different types of corrosion may occur in different engines or bearings, or a mechanical or assembly defect, rather than a corrosive oil, may be responsible for bearing failure. The appearance of a bearing frequently fails to indicate the reason for its failure, and more thorough investigation must be made. In his conclusion the author emphasizes that the field of bearing corrosion still has large unexplored areas.
Technical Paper

The Development of “Proferall” Cast Camshafts

DEVELOPMENT of cast camshafts at the Campbell, Wyant & Cannon Foundry Co., starting in 1924, proceeded slowly until a material was developed that met all requirements from metallurgical, engineering, and manufacturing standpoints. “Proferall,” the name given this material, means processed-ferrous-alloyed iron made by the duplexed-electric-furnace process. Camshafts of this material have a Brinell hardness of 262-293, as cast. A series of tests, equivalent to runs of 46,560 miles, showed that both chemical analysis and hardness affect camshaft-gear wear. Comparative wear tests on bearings showed more than three times as much wear on steel camshafts as cast ones. Other tests showed the cast shafts expanded less than those of steel. After describing foundry processes the paper concludes by summing up the advantages of cast camshafts, such as the smaller cost of patterns as compared with forging dies and the elimination of heat-treating, copper plating, carburizing, and hardening.
Technical Paper

STAINLESS STEELS - Hot and Otherwise

AIRCRAFT exhaust systems must be designed to withstand service conditions that include severe vibrations, high temperatures from the hot exhaust gases passing along the inside of the pipes at relatively high velocities, while the outside of the pipe system may be subjected to rain and sea atmosphere. These extreme conditions of operation led to difficulties in the application of stainless steel to the exhaust system. Failures caused by intergranular corrosion from carbide precipitation need no longer be feared when properly stabilized 18-8 stainless steel is used. Stainless steel can be stabilized with either titanium or columbium, the cheaper and more easily worked titanium-type steel being satisfactory for most installations, although there are applications where the columbium type must be used because of its higher yield and tensile strengths. This improved stainless, however has not solved the problem of corrosion at high temperatures in the presence of zinc.
Technical Paper


The quality of plated steel may be tested by exposing the article to the action of a salt spray and noting the appearance at intervals. A numerical method of rating the appearance is presented, and the rust resistance of steel plated with nickel and copper is shown to be dependent on the thickness of the plating. The effect on the salt-spray resistance of some common variables in nickel-plating, such as boric acid, ferrous sulphate, current density and defective steel, is disclosed and charted. The need of close technical control of the plating process is indicated, and some of the advantages of controlled electroplating at high current-densities are set forth.
Technical Paper

Aluminum Die-Cast Cylinder Blocks in Outboard Motors

THIS PAPER describes 20 years experience in developing and using die-cast aluminum cylinder blocks in outboard motors. Several different types of cylinder blocks, ranging in size from 1½ to 50 hp, are described, with an outline of the design procedure of the 50-hp V-4 block. Production details included are: die construction method and casting data, process for impregnating, machining and air testing, use of dry liners, and plated and sprayed coatings.