EXPERIMENT No. 1


                                                     EXPERIMENT No. 1
9.0 Observations:
In witworth quick return mechanism slotted bar is pivoted in between and it oscillates on that pivoted point. Where as in crank and slotted lever quick return mechanism slotted bar is pivoted at the lower end and it oscillates around that pivoted point.
10.0     Questions for confirmation of learning:
1. Hand pump to fetch water from underground
2. Four links are required to form a constrained kinematic chain.
3. Motion in a definite direction is called as constrained motion. Slider and slotted bar, Crank and slider  have constrained motion in crank and slotted bar mechanism.
4. Four links and four pairs are present in single slider crank chain.
5. Angle β made by the forward c stroke is greater than angle α described by the return stroke.
12.0     1.     Three and One
            2.      perpendicular    
As it is necessary to give more time for the cutting stroke because of the smooth material removal  operation at less mean speed; it is relevant to faster idle or return stroke. As no material removal during return stroke is taking place. It also saves time by faster return stroke.
Questions:
1.    It is the method of obtaining different mechanisms by fixing different links in a kinematic chain.
2.    a) Pendulum pump or bull engine,  b) Oscillating cylinder engine, c) Rotary I. C. engine, d) Crank and slotted lever Q. R. M. e) Witworth quick return mechanism
3.    In witworth quick return mechanism slotted bar is pivoted in between and it oscillates on that pivoted point.Where as in crank and slotted lever quick return mechanism slotted bar is pivoted at the lower end and it oscillates around that pivoted point.
4.    It is used in shaping and slotting machines. Faster return or idle stroke requirement is fulfilled by quick return mechanism.
5.    During return stroke the ram moves at a faster speed because of the special  
arrangement in the mechanism. The angle by which crank rotates about ‘O’ is β i.e. angle COA as shown in figure. As there is no metal cutting or metal removal process during return stroke the load on the ram is negligible.
6.    In shaper quick return mechanism the stroke length of ram is changed by  varying the radius of the crank. In order to adjust the position of the ram, the ram fixing screw is loosened. the ram is moved to the required position and the screw is tightened again. 
7.    During cutting stroke it is necessary that a tool should cut or remove material from a work piece. While doing this the mean speed of the ram should be less to do the smooth cutting or material removing process. It is also required that tool or ram should move maximum distance so as to take a larger cutting and in one stroke the material removal should be more. To achieve this and to give movement to the ram and tool larger cutting angle    is necessary. In idle stroke the material removal does not take place so it is not necessary to spend much time by providing larger angle β for the idle stroke.
8.    For changing the length of the cutting stroke of ram of the machine we have to  
adjust the radius of crank and ram position should be changed.
9.    Slotted bar (lever) and slider are the two links between which there is a sliding  pair.
10.  Lower pairs have surface contact between them when relative motion takes place. sliding pairs, turning pairs, screw pairs are the lower pairs. Crank with slider –turning pair. Slider with slotted bar or slotted lever – sliding pair. Crank with fixed link- turning pair. Slotted bar with fixed link- turning pair.
11.  Higher pairs have line or point contact between them when relative motion takes place. As bearings etc. which have line or point contact are not forming important part of the mechanism which will transform or transmit motion.  
12. Elliptical Trammel – Links 1 and Link 3 ( slider a and b) slides in a groove of 
      slotted plate. Link 1 and link 4 – sliding pair1, Link 3 and Link 4 – sliding pair 
      2.Link 1 and Link 2- Turning pair 1, Link 2 and Link 3 –Turning pair 2.

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