Tuesday, March 11, 2014

Motion and Machines:

Motions in Machine - Generally speaking:

In the last five posts the content was confined to linkages. There are few more points, about linkages, which will need further attention, we will come back and revisit linkages after some time.
Moving on to examine some of the basic principles of physics, which must be touched upon, before we go on to start designing machines or the components which make machines. 
In the 'linkages section' the movement was assumed to be in the parallel planes, thus keeping things simple. But in practice the motion, the forces, the acceleration etc take place in the three dimensional space.
Assuming that you must be conversant with basics of Physics, such as displacement, speed, velocity, acceleration, relative motions etc.
It would be prudent to focus our attention to topics e.g. transmission of motion, line of transmission, connectors (between between drivers and the driven), types of contacts etc. We start off with the concept of transmission of motion.

Transmission of motion & force:

Machines are meant to transmit motion and force both, then only they will be able to do useful work. Moreover, all the machines are designed to provide definite motion along with the transmission of definite forces to give us an output which can be termed as useful work.  
It is necessary to understand that the manner in which the motion and the force are transmitted from one member to another have a lots in common, as such in order the minimise confusion there is a need to draw a boundary line between the two and consider them separately. Motion and force may be transmitted as follows:

1) Using an intermediate rigid connectors, for example - links, rollers etc. Graphically these are shown in the diagrams below;



2) Using an intermediate flexible connectors such as pulleys & belts, springs, hydraulically or pneumatically, some diagrams are posted below; 




3) By direct contact such as gear teeth, cams, friction-connectors, see the sketch below;




4) Using magnetic force i.e. magnetic field etc. such as electric motors etc. Hydraulic and pneumatic are also considered as indirect type of connector. 

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