Question

Piston, piston rod and cross-head of a steam engine constitute
1. one link
2. two link
3. three link
4. Do not constitute any link

Answer 1

Correct Answer - Option 1 : one link

Explanation:

Link:

• A link or an element may consist of a number of parts connected in such a way that they form one unit and have no relative motion with each other.
• Piston, piston-rod and cross-head of a steam engine constitute one unit and will be taken as one link or element.
• Similarly, the crank pin, crank webs, crank shaft, flywheel etc. constitute another unit and will be taken as one link.
• On the other hand, cross head, connecting rod, crank and frame of steam engine are different links.
• The link may be rigid such as crank, connecting rod etc. of a steam engine or may be flexible such as belts or may be fluid such as fluid used in hydraulic presses, hydraulic brakes and hydraulic jacks.
• Types of Links:
  • ​Rigid link: A rigid link is one which does not undergo any deformation while transmitting motion. In actual practice, no link is perfectly rigid, but as deformation of connecting rod, crank etc. is negligible, so these can be considered as rigid.
  • Flexible link: A flexible link is that which, while transmitting motion, is partly deformed in such a manner that transmission of motion is not affected. Such a link transmits motion in one direction only (push or pull). e.g., belts, ropes spring, chains etc.
  • Fluid link: It is formed by having fluid in receptacle and motion is transmitted through the fluid by pressure or compression. e.g., hydraulic jack, hydraulic brakes etc.