Test: Design of Friction Drives - 2 - Mechanical Engineering MCQ

What is the efficiency of a self-locking power screw?  

Which one of the following is the value of helix angle for maximum efficiency of a square threaded screw? [ø = tan^-1μ ]   

Consider the following statements in respect of flexible couplings:

1. The flanges of flexible coupling are usually made of grey cast iron FG200.                

2. In the analysis of flexible coupling, it is assumed that the power is transmitted by the shear resistance of the pins.

3. Rubber bushes with brass lining are provided to absorb misalignment between the two shafts.

Which of the statements given above are correct?  

Which one of the following is not a friction clutch? 

Which one of the following pairs of parameters and effects is not correctly matched?    

Assertion (A): In case of friction clutches, uniform wear theory should be considered for power transmission calculation rather than the uniform pressure theory.

Reason (R): The uniform pressure theory gives a higher friction torque than the uniform wear theory. 

In a flat collar pivot bearing, the moment due to friction is proportional to (r₁ and r₂ are the outer and inner radii respectively)  

In a multiple disc clutch if n₁ and n₂ are the number of discs on the driving and driven shafts, respectively, the number of pairs of contact surfaces will be 

Which one of the following is the correct expression for the torque transmitted by a conical clutch of outer radius R, Inner radius r and semicone angle α assuming uniform pressure? (Where W = total axial load and μ = coefficient of friction)  

Consider the following statements regarding a centrifugal clutch: It need not be unloaded before engagement.            

1. It enables the prime mover to start up under no-load conditions.

2. It picks up the load gradually with the increase in speed

3. It will not slip to the point of destruction

4. It is very useful when the power unit has a low starting torque

Which of these are the advantages of centrifugal clutch?  

The creep in a belt drive is due to the  

In flat belt drive, if the slip between the driver and the belt is 1%, that between belt and follower is 3% and driver and follower pulley diameters are equal, then the velocity ratio of the drive will be   

The length of the belt in the case of a cross-belt drive is given in terms of centre distance between pulleys (C), diameters of the pulleys D and d as  

Assertion (A ): In a short centre open-belt drive, an idler pulley is used to maintain the belt tension and to increase the angle of contact on the smaller pulley.   

Reason (R): An idler pulley is free to rotate on its axis and is put on the slack side of the belt. 

In the case of a vertical belt pulley drive with T_c as centrifugal tension and T_o as the initial tension, the belt would tend to hang clear of the tower pulley when    

In a flat belt drive the belt can be subjected to a maximum tension T and centrifugal tension T_{c .}What is the condition for transmission of maximum power?   

Which one of the following statements with regard to belt drives is NOT correct? 

Assertion ( A): For similar materials having the same maximum permissible tension V-belt transmits more power than flat belt with same velocity ratio and centre distance.                      

Reason (R): As tw o sides of V-belt are in contact with side faces of pulley groove, larger contact area gives greater effective frictional force.  

Consider the following:

 V-belts are specified by their          

1. Nominal inside length in mm  

2. Nominal pitch length  

3. Belt cross section symbol  

4. weight/unit length of the belt  

Which of the above are correct? 

Which one of the following drives is used for a constant velocity ratio, positive drive with large centre distance between the driver and driven shafts? 

Sources of power loss in a chain drive are given below:         

1. Friction between chain and sprocket teeth.  

2. Overcoming the chain stiffness.  

3. Overcoming the friction in shaft bearing.  

4. Frictional resistance to the motion of the chain in air or lubricant.  

The correct sequence of descending order of power loss due to these sources is  

In a 6 × 20 wire rope, No.6 indicates the 

Given that W = weight of load handled, W_r = weight of rope and f = acceleration, the additional load in ropes of a hoist during starting is given by 

Power screws are used to produce uniform, slow and powerful motion such as required in presses, jacks and other machinery. 'V' threads are usually not used for this application due to low efficiency. This is because:   

The following parameters are to be calculated while designing screw jack.

1. Core diameter of screw  

2. Torque required to rotate the screw  

3. Principal stresses  

4. Height of the nut          

The correct sequence of the calculation of these parameters is 

The diameter of tommy bar for a screw jack is designed for  

The load cup of a screw jack is made separate from the head of the spindle to