Mechanical Design of Machine Elements/Components Gandingan ( Coupling )

Gandingan Tujuan: Menyambung 2 aci hujung ke hujung. Sambungan boleh dilakukan dalam tiga keadaan kegunaan: paksi aci-aci adalah sepaksi(collinear) paksi aci-aci adalah bersilang(intersect) paksi aci-aci adalah selari(parallel) tetapi tidak sepaksi Menyambung aci mesin pemacu kepada aci mesin dipacu. Tiga keadaan penjajaran sambungan aci

Jenis-jenis Gandingan Gandingan Tegar (Rigid Couplings)~provide a connection between two perfectly aligned shafts. Frequently in use in industry ~ Steel, Copper, Paper, Petro-chemical, Food, Wastewater, Transportation and also for applications ~ Pumps; Compressors; Fans; Conveyors; anywhere motors, engines, and turbines are used cth: gandingan bebibir(flanged coupling), clamped coupling, tapered-sleeve coupling. Gandingan Mudah-Lentur (Flexible Coupling) cth: rubber element Flexible Coupling, Falk Flexible Coupling, roller chain Coupling, gear type Coupling, Oldham Coupling, Universal Joints (~ Hooke’s joint and Constant velocity Universal Joints ).

Jenis-jenis Gandingan

Rigid Coupling Flexible Coupling Locks the shaft together Alowing no relative motion between them No provision for misalignment between them Does not reduce shock or vibration across it from one shaft to the other suitable for low speeds, accurately aligned shafts Flexible Coupling Take care of a small amount of unintentional misalignment Allow radial, angular and axial misalignment Slight misalignment and vibration absorbed by coupling Provide for end float (axial movement of a shaft)

Flanged Rigid Coupling Keyed Coupling widely used coupling halves attached to shaft ends by keys used standard keys Compression coupling split double cone that does not move axially Design consideration for flanged coupling the torque capacity of the key or wedged friction connection with the shaft the strength of the relatively thin web portions that are drilled to accommodate the bolts the strength of the bolts. For this course only item 1 and 3 will be discuss. Db flange bolt key shaft

tall = 0.18Su or 0.3Syp (which is lower/small) Basic formula of shear stress analysis of bolts in coupling where To find the torque that can be transmited Where td =Ssy= 0.577Sy/N or td = tall tall = 0.18Su or 0.3Syp (which is lower/small) Nb= number of bolts Db= bolt circle diameter w = 2pn/60 rad/second P = Power, kW or hp n = rpm Ks= service factor for machinery To find the required bolts diameter

Ks = c1 + c2 Driving machines Driven machines Table of Service Factors for Machinery Ks = c1 + c2 Driving machines c1 Electric motors 0.5 turbomachinery 0.75 Reciprocating engines: 1.5 – 2.8 4-cylinder 6-cylinder 1 - 2 Driven machines c2 Machine tools 3 Rolling mills 1.6 -2 blowers 1.5 Textile machinery 1.6 – 2.2 Rotary pumps, compressors Rciprocating pumps, compressors 2.2 – 3.2 Paper mills 1.8 -3 Mixing machines Wood processing machines 2 - 3 Electric generators 1.1 – 1.3 hoists

Contoh: An electric motor is used to drive a blower at 600rpm Contoh: An electric motor is used to drive a blower at 600rpm. The shaft of the motor is connected to the shaft of the blower by flange coupling. Calculate the rated power of the flanged keyed coupling assembly as shown. Given that there are 6 bolts of diameter 15mm with allowable shear strength Sall 210MPa. The bolts circle diameter is Db = 150mm. Db Area in shear for one bolt is Allowable force for one bolt is Therefore the rated power is The torque that can be transmited by six bolts which are at a 75mm distance from the central axis is

A rigid flange coupling used 4 bolts A rigid flange coupling used 4 bolts. The bolts circle diameter is 125mm. If the bolt has an ultimate tensile strength of 550MPa and a yield point in tension of 345MPa, determine the bolts size if it is to transmit a torque of 2kN.m tall = 0.18Su = 0.18(550MPa) = 99MPa or tall = 0.3Syp= 0.3(345MPa) = 103.5MPa Use tall= 99MPa ; T = 2kN.m ; Nb= 4 Hence from Table 8-1, use M12 bolts.