| There was once a shepherd-boy who kept his flock at a little distance from the village. Once he thought he would play a trick on the villagers and have some fun at their expense. So he ran toward the village crying out, with all his might,-- ... Read more of THE BOY WHO CRIED "WOLF!" at Children Stories.ca |  InformationalPrivacy |
Steel MakingThe Forging Of SteelSo much depends upon the forging of steel that this operation... Short Method Of Treatment In the new method, the packed pots are run into the case-har... Highly Stressed Parts The highly stressed parts on the Liberty engine consisted of ... Hardness Testing The word hardness is used to express various properties of me... The Pyrometer And Its Use In the heat treatment of steel, it has become absolutely nece... Carbon Steels For Different Tools All users of tool steels should carefully study the different... Correction By Zero Adjustment Many pyrometers are supplied with a zero adjuster, by means ... High Speed Steel For centuries the secret art of making tool steel was handed ... Annealing There is no mystery or secret about the proper annealing of d... Preventing Carburizing By Copper-plating Copper-plating has been found effective and must have a thick... Hints For Tool Steel Users Do not hesitate to ask for information from the maker as to t... Typical Oil-fired Furnaces Several types of standard oil-fired furnaces are shown herew... Pyrometers Armor plate makers sometimes use the copper ball or Siemens' ... Introduction Of Carbon The matter to which these notes are primarily directed is the... Open Hearth Process The open hearth furnace consists of a big brick room with a l... High-carbon Machinery Steel The carbon content of this steel is above 30 points and is ha... Fatigue Tests It has been known for fifty years that a beam or rod would fa... Uses Of The Various Tempers Of Carbon Tool Steel DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres... Vanadium Vanadium has a very marked effect upon alloy steels rich in c... Testing And Inspection Of Heat Treatment The hard parts of the gear must be so hard that a new mill f... |
Connecting RodsCategory: APPLICATION OF LIBERTY ENGINE MATERIALS TO THE AUTOMOTIVE INDUSTRY The material used for all connecting rods on the Liberty engine was selected at the option of the manufacturer from one of two standard S. A. E. steels, the composition of which are given in Table 13. TABLE 13.--COMPOSITION OF STEELS NOS. X-3,335 AND 6,135 Steel No. X-3,335 6,135 Carbon, minimum 0.300 0.300 Carbon, maximum 0.400 0.400 Manganese, minimum 0.450 0.500 Manganese, maximum 0.750 0.800 Phosphorus, maximum 0.040 0.040 Sulphur, maximum 0.045 0.045 Nickel, minimum 2.750 Nickel, maximum 3.250 Chromium, minimum 0.700 0.800 Chromium, maximum 0.950 1.100 Vanadium minimum 0.150 All connecting rods were heat-treated to show the following minimum physical properties; Elastic limit, 105,000 lb. per square inch: elongation in 2 in., 17.5; per cent, reduction of area 50.0; per cent., Brinell hardness, 241 to 277. The heat treatment used to secure these physical properties consisted in normalizing the forgings at a temperature of from 1,550 to 1,600 deg.F., followed by cooling in the furnace or in air. The forgings were then quenched in oil from a temperature of from 1,420 to 1,440 deg.F. for the No. X-3,335 steel, or from a temperature of from 1,500 to 1,525 deg.F. for No. 6,135 steel, followed by tempering at a temperature of from 1,075 to 1,150 deg.F. At the option of the manufacturer, the normalizing treatment could be substituted by quenching the forgings from a temperature of from 1,550 to 1,600 deg.F., in oil, and annealing for the best machineability at a temperature of from 1,300 to 1,350 deg.F. The double quench, however, did not prove satisfactory on No. X-3,335 steel, due to the fact that it was necessary to remove forgings from the quenching bath while still at a temperature of from 300 to 500 deg.F. to eliminate any possibility of cracking. In view of the fact that this practice is difficult to carry out in the average heat-treating plant, considerable trouble was experienced. The most important criterion in the production of aviation engine connecting rods is the elimination of burned or severely overheated forgings. Due to the particular design of the forked rod, considerable trouble was experienced in this respect because of the necessity of reheating the forgings before they are completely forged. As a means of elimination of burned forgings, test lugs were forged on the channel section as well as on the top end of fork. After the finish heat treatment, these test lugs were nicked and broken and the fracture of the steel carefully examined. This precaution made it possible to eliminate burned forgings as the test lugs were placed on sections which would be most likely to become burned. There is a great difference of opinion among engineers as to what physical properties an aviation engine connecting rod should have. Many of the most prominent engineers contend that a connecting rod should be as stiff as possible. To produce rods in this manner in any quantity, it is necessary for the final heat treatment to be made on the semi-machined rod. This practice would make it necessary for a larger percentage of the semi-machined rods to be cold-straightened after the finish heat treatment. The cold-straightening operation on a part having important functions to perform as a connecting rod is extremely dangerous. In view of the fact that a connecting rod functions as a strut, it is considered that this part should be only stiff enough to prevent any whipping action during the running of the engine. The greater the fatigue-resisting property that one can put into the rod after this stiffness is reached, the longer the life of the rod will be. This is the reason for the Brinell limits mentioned being specified. In connection with the connecting rod, emphasis must be laid on the importance of proper radii at all changes of section. The connecting rods for the first few Liberty engines were machined with sharp corners at the point where the connecting-rod bolt-head fits on assembly. On the first long endurance test of a Liberty engine equipped with rods of this type, failure resulted from fatigue starting at this point. It is interesting to note that every rod on the engine which did not completely fail at this point had started to crack. The adoption of a 1/32-in. radius at this point completely eliminated fatigue failures on Liberty rods. Next: Crankshaft Previous: Rate Of Cooling
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