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Unformatted text preview: ME250 Design and Manufacturing I Winter 2011 Lecture HW #4 Name: ___________________________ UMID: _________________ Lab Section #: _______ Note: You must indicate name, UMID, and Lab Section # otherwise the homework will not be returned. 1. The figure shows a geared shaft with an overhanging pinion at C. We are interested in using a deep groove ball bearing for mounting at O and a cylindrical roller bearing for mounting at B. The shaft is to run at a speed of 550 rev/min. The solution of the statics problem gives the force of the bearing at O against the shaft as Ro = 582j +707k lb and the force of the bearing at B against the shaft as RB = 476j – 2430k lb, where j and k are unit vectors in y and z directions, respectively. Use the load‐application factor of 1.4 and L10 life of 40kh. Assume the bores of the bearings at O and B do not have to match. Use the spec sheets that were given in the lecture slides for ball bearings and roller bearings. [20pts] (a) Find the bearing required at O. [10pts] (b) Find the bearing required at B. [10pts] 2. A 1.25 X 1.25 [in] sleeve bearing supports a load of 810 lb and has a journal speed of 4000 rev/min. An SAE 30 oil used is assumed to have an average operating temperature of 200˚F. [20pts] (a) Using Fig. 12‐16 in the course‐pack, determine the radial clearance for minimum f and the radial clearance for maximum W. [15pts] (b) The difference between these two clearances is called the clearance range. Is the resulting clearance range attainable with regular turning, whose tolerances typically range between 1.2 × 10‐3 and 8.0 X 10‐3 [in]? [5pts] SAE 30 Oil oil
SAE 10 d = 1.25 in l= 1.25 in W = 700 lb W = 810 lb 3. A music wire helical compression spring, with ends squared and ground, has a wire diameter of 1.55 mm, an outside diameter of 13.50 mm, and a solid length of 16.10 mm. What is the upper bound value of the free length if the stress is never to be more than 90 percent of the shear yield strength? [20pts] 4. A 3/8 inch coarse‐thread SAE grade 5 bolt is tightened to a recommended preload. The stiffnesses of bolt and the members have already been calculated and are kb = 3.95 Mlbf/in and km = 12.84 Mlbf/in. The external load P is 4 kilopounds. [20 points] (a) What is the value of the recommended preload for this bolt? [5 pts] (b) What is the value of the joint constant, C? [5 pts] (c) Calculate the load factor against bolt yielding. [5 pts] (d) Calculate the load factor against joint separation. [5 pts] 5. Define the different components of the following thread notes (fastener callouts), and answer the questions given below. Write your answers on the lines below. [2 points each, 20 points total] 3/8 ‐ 16 UNC SAE 8 3/8 ___________________________________________ 16 ___________________________________________ UNC ___________________________________________ SAE 8 ___________________________________________ What is the pitch of this bolt? _________________________ If this bolt had the same nominal diameter but had a fine thread instead of a coarse thread, how many threads per inch would it have? _________________________ M8 X 1.25 M ___________________________________________ 8 ___________________________________________ 1.25 ___________________________________________ If this bolt is 30mm long, and is threaded along its full length, how many threads would it have?__________________ ...
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This note was uploaded on 09/12/2011 for the course MECHENG 250 taught by Professor Stevis during the Winter '09 term at University of Michigan.
- Winter '09