CLASSIFICATION OF ENGINES AS PER SPEED

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1. Slow Speed Engines: 100 to 150 r.p.m.

2. Medium Speed Engines: 300 to 1000 r.p.m.

3. High Speed Engines: More than 1000 r.p.m.

The following table compares the various aspects of Slow Speed, Medium Speed and High Speed Engines:

	Slow Speed.	Medium Speed.	High Speed.
1. 2.	No Gearing.   Four or Two Stroke acceptable.	Gearing Necessary. Four Stroke better.	Gearing Necessary. Four Stroke only.
	Slow Speed.	Medium Speed.	High Speed.
3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.	Poor quality fuel acceptable. Crankcase can be separated from combustion zone. Less noise and vibration. Less fatigue failure. Fewer stresses due to heavier scantling. Heavy and Large Size. More head-room required.            Heavy Lifting Gear required for heavy parts. Engine r.p.m. is       limited by propeller efficiency. Can have long strokes. Large bore cylinders. Heavy & large pistons. Round section connecting rod. Failures less and easier to manage.	Better Fuel required. Diesel oil/Gas oil. Trunk Piston type.     More noise. More. More.   Compact. Less.    Light parts easy to handle. Engine r.p.m. limited by piston speed. Small strokes. Small bore. Light and small piston. ‘I’ section connecting rod.  More and difficult to manage.	Distillate Fuel only. Trunk Piston Type. Most vibration and noise.                Most. Most. Extremely Compact. Least. Lighter parts can be handled manually. Engine r.p.m. limited by piston speed. Smallest stroke. Smallest. Lightest & smallest piston. ‘I’ section connecting rod. Most and very difficult to manage.