American Machinist Gear Book; Simplified Tables and Formulas for Designing, and Practical Points in Cutting All Commercial Types of Gears

📓 This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 Excerpt: ...a pitch angle. The number of cases cited is too few for certainty in drawing general conclusions, but the testimony is unmistakable in its confirmation of the theory of the influence of the angle of the thread. It will be seen that every case having an angle above 12 30' was successful, and every case below 9 unsuccessful, the overlapping of the successful and unsuccessful worms in the intervening region being what is to be expected in the border region between good and bad practice. This band of uncertain results is in fact narrowei than we would have any right to expect from a collection of data from miscellaneous sources, and could the inquiry be widened in scope the width of this band would doubtless be increased. As throwing light on these cases, it should be remembered that case 16 is known to have been madi successful only by careful attention to the material used, the first worms made having been failures, and that 3, which is near 16 and was a failure, had an excessive speed, while 11, at a lower angle and a success, had a very moderate speed. At a higher speed 11 would probably have failed, and at a lower speed 3 would probably have been a success. It is believed that Chart ii points out clearly the nature of the worm problem and the conditions of success in its solution. EFFICIENCY AND TEMPERATURE The unavoidable sliding action between the threads of the worm and the teeth of the gear represents lost energy which must be measured by the amount of friction heat generated. The elevation in the temperature of the lubricating oil about a worm drive should then approximate the efficiency of the construction. The relationship between the efficiency of a journal bearing and its rise in temperature is similar and is generally recognized as a reliable ind...