How Does a Chainsaw Work?

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Trees take years to grow yet the chainsaw brings them down violently in seconds. What is the mechanism behind the working of the chainsaw?

A chainsaw has two main parts. It has a saw blade that is wrapped around the guide bar and built on a chain. It has a small petrol /gasoline engine or electric motor that is motorized by a battery pack or cord. The chain resembles the chain of bicycle.

How it works:

  1. Put fuel in the gas tank of the chainsaw (for those that use fuel). The fuel contains chemicals that will be converted into energy. A typical tank holds 1.1 pints of petrol or gas.
  2. The fuel passes through the carburetor, and it mixes well with the air.
  3. The mixture of air and fuel passes into the cylinder. The cylinder resembles the one found in the car engine. However, this cylinder is a simple two-stroke action engine unlike the four-stroke required in cars.
  4. In the cylinder, the spark plug ignites the air plus fuel mixture. It burns releasing energy while pushing the piston backward and forward.
  5. The piston inside the engine of the chainsaw has a diameter of 1.75 inches (45mm) and a travelling distance of 33mm. The crank and connecting rod converts the back and forth piston movement to revolving motion.
  6. The power of the centrifugal clutch is taken over by the drive shaft
  7. The engine will be running the entire time. However, the chain should not be spinning not unless you are cutting wood. A spinning chain when not in use wastes energy and it is dangerous.
  8. The problem is solved by the clutch. The centrifugal clutch enjoins the engine and the chain whenever the engine speed is fast. This happens when the operator pulls the throttle. Also, the clutch stops the chain from running whenever the speed of the engine is low, or the saw is idling.
  9. The power travels to the sprocket from the clutch.The sprocket holds the chain in place.
  10. The guide offers room for the chain to spin. The guide bar is made of a long steel plate. In the process, it spits out wood dust in its motion.

How a chainsaw engine works

A chainsaw has a two-stroke engine. Some of the benefits include:

  • It does not have a valve. It simplifies construction and lowers its weight
  • The engines fire once in every revolution giving it a significant power boost.
  • It can work in any orientation which an important aspect for the chainsaw.


  • The engine does not last for long. It lacks a dedicated lubrication system resulting in engine wear at a faster rate.
  • The two oil stroke is costly. It uses a lot of fuel
  • The engine does not consume fuel efficiently
  • It produces a lot of pollution from the oil combustion. Chainsaws with badly worn engines tend to emit clouds of oily smoke.

Two cycle basics

A cycle or a stroke refers to a single trip that the piston makes up or down in a cylinder. It takes two strokes to make the crankshaft rotate once. The power strokes determine the rotations that will be made.

Power stroke happens when the piston makes a movement after being pushed by the combustion engine. It gives the engine its power. This means a two-cycle engine gains power after every two cycles.

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