Criteria S.I. Engine (Petrol or Spark Ignition Engine) C.I. Engine (Diesel or Compression Ignition Engine) Working Cycle Works on Otto Cycle or Constant Volume Cycle. Works on Diesel Cycle. Mixture During Suction Stroke Takes a mixture of air and petrol during the suction stroke. Takes only air during the suction stroke. Fuel Used Uses petrol as fuel. Uses diesel as fuel. Compression Ratio Has a compression ratio that varies from 6 to 10. Has a compression ratio that varies from 16 to 20. Engine Weight and Cost S.I. engines are lighter and cheaper. C.I. engines are heavier and costlier. Initial Cost Initial cost is lower compared to C.I. engines. Initial cost is high due to high compression ratio. Starting Starting is easy. Starting is difficult, especially in cold conditions. ...
| Criterion | Machine (M/C) | Structure |
|---|---|---|
| Energy Transformation | It transforms energy | It does not transform energy |
| Relative Motion | Relative motion between its parts | No relative motion between its parts |
| Function of Links | In this link, motion and power are transmitted | In this link, it carries loads having straining actions |
Examples:
- Machine (M/C) Examples:
- Lathe
- Shaper
- Structure Examples:
- Roof
- Trusses
Q-8.what is constrained motion
And :- The motion which is take place in a definite direction.
It has 3 types
1. Completely Constrained Motion:- Motion occurs in a definite direction regardless of applied force.
Example:- Motion of a piston in a cylinder.
2. Incompletely Constrained Motion:- Motion occurs in more than one direction.
Example:- Motion of a pair taking place in various directions.
3.Partially or Successfully Constrained Motion:-Motion is not completed by itself but by some other means.
Example:-The shaft in a footstep bearing may rotate or move upward.
•Kinematic Pairs:- A kinematic pair is formed when there is contact between two links of a mechanism, allowing relative motion between the two links. Examples include a cylinder, piston, connecting rod, and crank.
•Classification of Kinematic Pairs
Kinematic pairs can be classified into three categories based on the type of contact between the elements.
(A) Type of Contact Between the Elements
1. Lower Pair:- A kinematic pair that has surface contact between its links while transmitting motion.
Example:- Shaft revolving in a bearing.
2.Higher Pair :- A kinematic pair that has point or line contact between its links while transmitting motion.
Examples:- Belts, ropes, chain drives, and
cams.
(B) Type of Closure Between Elements:-
1. Open Pair:- When two links of a kinematic pair are not held together mechanically but remain in contact with each other under the action of force.
Example:- Cam follower.
2. Closed Pair:- When two links of a kinematic pair are held together mechanically in such a way that only the required type of relative motion occurs.
Examples:-Screw pair, spherical pair, etc.
(C) Type of Relative Motion of the Elements
1. Sliding Pair:- When two links of a kinematic pair are connected in such a way that one link glides relative to another.
Example:- Piston reciprocating in the cylinder of an internal combustion engine.
2. Turning Pair:- When two links of a kinematic pair are connected in such a way that one link can only turn about a fixed axis of another link.
Example:- Shaft revolving in a bearing.
3. Rolling Pair:- When two links of a kinematic pair are connected in such a way that one link rolls on another link.
Example:- Belt and pulley.
4. Screw Pair:-When two links of a kinematic pair are connected in such a way that one link turns about another link by means of threads.
Example:- Assembly of a nut and bolt.
5.Spherical Pair:- When two links of a kinematic pair are connected in such a way that one link, in the form of a sphere, turns about another fixed link.
Examples:- Ball and socket joint, pen stand.