The shaft ends are made to a butt each other a single key is fitted directly in the keyways of both the shafts. One-half of the muff is fixed from below and the other half is placed from above.
Both the halves are held together by means of mild steel studs or bolts and nuts. The number of bolts may be two, four or six. The advantage of this coupling is that the position of the shafts need not be changed for assembling or disassembling of the couplings.
Flange coupling A flange coupling usually applies to a coupling having two separate cast iron flanges. Each flange is mounted on the shaft end and keyed to it.
The faces are turned up at right angle to the axis of the shaft Flange coupling are 1. Unprotected type flange coupling 2. Protected type flange coupling 3. Marine type flange coupling. Conclusion: Coupling designed according to the above considerations will be more suitable, but the modifications according to our needs can also be made for more better results.
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The flange coupling is adopted to heavy loads and hence it is used on large shaft- ing. The flange couplings are of the following three types : 1. In an unprotected type flange coupling, as shown in Fig. Generally, three, four or six bolts are used. The keys are staggered at right angle along the circumference of the shafts in order Flange Couplings. The usual proportions for an unprotected type cast iron flange couplings, as shown in Fig.
Protected type flange coupling. In a protected type flange coupling, as shown in Fig. Protective type flange coupling. The thickness of the protective circumferential flange tp is taken as 0. The other proportions of the coupling are same as for unprotected type flange coupling.
Marine type flange coupling. In a marine type flange coupling, the flanges are forged integral with the shafts as shown in Fig. The flanges are held together by means of tapered headless bolts, numbering from four to twelve depending upon the diameter of shaft. The number of bolts may be choosen from the following table.
Number of bolts for marine type flange coupling. The flange coupling is designed as discussed below : 1. Therefore from the above relation, the induced shearing stress in the hub may be checked. The length of hub L is taken as 1. Design for key The key is designed with usual proportions and then checked for shearing and crushing stresses. The length of key is taken equal to the length of hub.
Design for flange The flange at the junction of the hub is under shear while transmitting the torque. Therefore from the above relation, the induced shearing stress in the flange may be checked. Design for bolts The bolts are subjected to shear stress due to the torque transmitted. The number of bolts n depends upon the diameter of shaft and the pitch circle diameter of bolts D1 is taken as 3 d.
Now the diameter of bolt may be checked in crushing. Design a cast iron protective type flange coupling to transmit 15 kW at r. The service factor may be assumed as 1.
Design for hub First of all, let us find the diameter of the shaft d. Let us now check the induced shear stress for the hub material which is cast iron. Considering the hub as a hollow shaft. We know that the maximum torque transmitted Tmax. Design for key Since the crushing stress for the key material is twice its shear stress i.
From Table The length of key l is taken equal to the length of hub. Let us now check the induced stresses in the key by considering it in shearing and crushing. Design for flange The thickness of flange tf is taken as 0. Let us now check the induced shearing stress in the flange by considering the flange at the junction of the hub in shear.
Design and draw a protective type of cast iron flange coupling for a steel shaft transmitting 15 kW at r. The working stress in the bolts should not exceed 30 MPa. Assume that the same material is used for shaft and key and that the crushing stress is twice the value of its shear stress.
The shear stress for cast iron is 14 MPa. Design for hub First of all, let us find the diameter of shaft d. Let us now check the induced shear stress for the hub material which is cast iron, by considering it as a hollow shaft.
Design for key Since the crushing stress for the key material is twice its shear stress, therefore a square key may be used. Design for flange The thickness of the flange tf is taken as 0. Let us now check the induced shear stress in the flange, by considering the flange at the junction of the hub in shear. Design and draw a cast iron flange coupling for a mild steel shaft transmitting 90 kW at r.
The allowable shear stress in the coupling bolts is 30 MPa. Let us now design the cast iron flange coupling of the protective type as discussed below : 1. Let us now check the induced shear stress in the hub by considering it as a hollow shaft. The shear stress for the hub material which is cast iron is usually 14 MPa.
The length of key l is taken equal to the length of hub L. Assuming that the shaft and key are of the same material. Let us now check the induced shear stress in key. Let us now check the induced shear stress in the cast iron flange by considering the flange at the junction of the hub under shear.
Design a rigid flange coupling to transmit a torque of N-m between two co- axial shafts. The shaft is made of alloy steel, flanges out of cast iron and bolts out of steel.
Four bolts are used to couple the flanges. The shafts are keyed to the flange hub. The stresses developed in the various members may be checked if thumb rules are used for fixing the dimensions.
Let us now check the induced shear stress in the flange by considering the flange at the junction of the hub in shear. The bolts are subjected to shear stress due to the torque transmitted. Two 35 mm shafts are connected by a flanged coupling.
The flanges are fitted with 6 bolts on mm bolt circle. The shafts transmit a torque of N-m at r. For the safe stresses mentioned below, calculate 1. Key dimensions From Table The shaft and the flange of a marine engine are to be designed for flange coupling, in which the flange is forged on the end of the shaft.
The taper on the bolt may be taken from 1 in 20 to 1 in Let us now check the induced shear stress in the flange by considering the flange at the junction of the shaft in shear. Diameter of flange The diameter of flange D2 is taken as 2. In the case of a direct coupled drive from a prime mover to an electric generator, we should have four bearings at a comparatively close distance.
In such a case and in many others, as in a direct electric drive from an electric motor to a machine tool, a flexible coupling is used so as to permit an axial misalignemnt of the shaft without undue absorption of the power which the shaft are transmitting.
Following are the different types of flexible couplings : 1. Bushed pin flexible coupling, 2. Oldham's coupling, and 3. Universal coupling.
We shall now discuss these types of couplings, in detail, in the following articles. Bushed-pin flexible coupling. A bushed-pin flexible coupling, as shown in Fig. The coupling bolts are known as pins. The rubber or leather bushes are used over the pins. The two halves of the coupling are dissimilar in construction. A clearance of 5 mm is left between the face of the two halves of the coupling.
There is no rigid connection between them and the drive takes place through the medium of the compressible rubber or leather bushes. In designing the bushed-pin flexible coupling, the proportions of the rigid type flange coupling are modified. The main modification is to reduce the bearing pressure on the rubber or leather bushes and it should not exceed 0.
In order to keep the low bearing pressure, the pitch circle diameter and the pin size is increased. The threaded length of the pin should be as small as possible so that the direct shear stress can be taken by the unthreaded neck. The bush portion of the pin acts as a cantilever beam of length l. Note: After designing the pins and rubber bush, the hub, key and flange may be designed in the similar way as discussed for flange coupling.
Design a bushed-pin type of flexible coupling to connect a pump shaft to a motor shaft transmitting 32 kW at r. The overall torque is 20 percent more than mean torque. The material properties are as follows : a The allowable shear and crushing stress for shaft and key material is 40 MPa and 80 MPa respectively.
Draw neat sketch of the coupling. Design for pins and rubber bush First of all, let us find the diameter of the shaft d. Power is transmitted from driving shaft to flange on driving shaft through key, from flange on driving shaft to the flange on driven shaft through bolts and then to the driven shaft through key again. Projection is provided on one of the flanges and a corresponding recess is provided in the other for proper alignment.
Flange coupling is of two types — unprotected and protected. These are shown in Figure If in case failure of bolts occurs during the operation, the bolts may hit the operator in case of unprotected flange coupling.
To avoid this, protective circumferential flanges are provided in the protected type flange coupling. Flange of a protected type flange coupling has three distinct regions — inner hub, flanges and protective circumferential flanges. Following standard proportions are used in the design of flange coupling:. Hub is designed considering it as a hollow shaft, with inner diameter equal to diameter of shafts and outer diameter double of that.
It is checked for torsional shear stress. In this case two separate keys are used for the two shafts. Key is designed as discussed earlier. In this case, length of key, length of the hub. The flange is subjected to shear at the junction of the hub as it transmits torque through the bolts.
Area resisting shear. If T is the torque to be transmitted, tangential force,. Due to transmission of torque, force acts perpendicular to the bolt axes and the bolts are subjected to shear and crushing stresses. Let n be the total number of bolts.
Force acting on each bolt,.
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