Question

P6-17

a steel hub with an inside diameter of 1.5 in., an outside diameter of 3.75 in., and a length of 3.0 in. The impeller is pressed onto a steel shaft. What is the ultimate pressure required for assem- bly? (c) Give the expression for allowance for given pressure P6-16 Use Machinery's Handbook to answer the following questions about shrink fits. (a) Plot and interpret a curve showing P6-18 A 35 in. diameter ring gear of steel is to allowance as a function of the center diameter of a locomotive driving wheel tires. be shrunk onto a 30 in. diameter rim of cast iron. Calculate (a) the allowance corresponding to an allowable true tan- gential stress of 4000 psi, and (b) the temperature to which the ring should be heated above room temperature for clearance at assembly. (b) Give and interpret the formulas for calculating allowance and tem- peratures for proper assembly P6-17 An impeller for a centrifugal blower has

Answer 1

The force/pressure (in tons) required to assemble (press fit) cylindrical part depends upon the following:

1. Clearance / allowance between mating parts

2. Surface area of mating part

3. Pressure factor

Solutiom The force required to ascamble ( press fit) cylindvical parts depends upon the allowance between the lndrica parts for the fit, area of the positioned and fited surfaces, the pressure i-ncreasimą in proportion to the listance that the shaft feature is forced 1n The approximate ultimate pres sure m tons can be determined by the follouing formula s or clearance eqn. Cリ A. F) where ptmate pressure required (im tons AArea of surface in contact between the shaft and hole feature a- Total allowance on actual material İnterfen between tha shaft and hola feature (in inches 0%( pin diameter-bore diameter F Pre ssure fachor Assumption:-D『a meter 아 the hub (feature which force is applied to) is twice of the diamete of pin which is pressed into the bore, here pin can be considered as steel shaft .

Givem data: Inside diameter ‘f hub/bore diameterニ1,5·nch outer diameter of hub leu^th of Hhe hub Needs to be determined - As the assumption appnxỉ mate dian eter of- steel shaft ok pin diameter 3.7S 2. Diameter of hub (outer) 2_ d 1.975 inch Nex calculation ' → Total allowance (a) shaft diameter-bore diameter a=i.875-1.5 0.375 inch (Approx ) Tota l surface are a of Contact (A)ラ A 2T (bore diameteree shaf x lengh fhub 27て. ( 1.5 t l·875 2 오 31. 81 ỉnch~ (Approx → Pressure factor (F) : Thas is taken fvom the avai able data tablk wat the. Shaft diameter/ pin diameter

Shaft Pin DiameterPressure Shaft/Pin DiameterPressure (Inches) 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 Factor (F) 500 395 325 275 240 212 189 170 155 145 131 122 115 108 100 96 91 (Inches) 5.25 5.50 5.75 6.00 6.25 6.50 6.75 7.00 7.25 7.50 7.75 8.00 8.50 9.00 9.50 10.00 10.50 Factor (F) 86 82 78 75 72 69 64 61 59 57 52 48.8 46.0 43.5 41.3

From the toble for 1.75 İnch (Short diawetoY)ラ F-275 and for 2.oo ch He. ce b7 Using interpolation : at d-. 1.875 F=257.5 Hence use force factor F= 257.5 Fin! putting all the req us red data in e9n4) bA.a.F = 31.81 x 0.37 5 x 957.5 2. = i5 35.83 (Tons) p 1536 (tons) Approx Answer