Stroke engine: Working Principles, DIY Builds, and Common Uses

The efficiency and reliability of many modern machines, including those used in agriculture and transportation, rely on the workhorse of stroke engines. They perpetually power industries by converting fuel to mechanical power using piston movements. 

In this guide, we’ll unlock what the stroke engine is, and its types including the 2-stroke engine and the 4-stroke engine. We’ll also explore working principles, the extensive uses of stroke engines, and share with you the step-step tutorial for building stroke engine models at home via DIY engine model kit. So, brace yourself as we reveal the mysteries of these mighty engines!

1) Understanding the basics of Stroke Engines

 

• What Is a Stroke Engine?  

A stroke engine falls under the category of an internal combustion engine that extracts power through the vertical motion of a piston within a confined cylinder. The movement of the piston occurs in increments or steps, referred to as strokes, and each step aids in completing one full power cycle. 

These stroke engines create mechanical energy to power vehicles, tools, and various machinery. 

• Types of Stroke Engines: 2 stroke engine vs 4 stroke engine   

Stroke engines are divided into two categories based on the number of piston movements, or strokes, required for a power cycle. Each stroke commences with an intake, compression, power, and exhaust phase. Moreover, some specialized designs like rotary and 6-stroke engines, although uncommon, are still used in niche fields. So, let's get started!

i) 2-Stroke Engine 

A two-stroke engine performs a complete power cycle in two piston strokes—the up and down motions of a piston towards the crankshaft and a 360 degree rotation of the crankshaft. Each turn of the crankshaft produces power. For compact, high speed machines, this rapid cycle provides ample power for the size of the engine.

You will commonly find two-stroke engines in motorcycles, outboard motors, chainsaws, and small gardening equipment because they are lightweight and easy to use.

Pros	Lower weight and small in size. High power per unit weight, as power is gained during each revolution. The basic structure makes it easy to repair and reassemble in field settings.
Cons	Ineffective fuel combustion. Shortened equipment life due to intense and rapid use of fuel combustion. Tools or vehicles that incorporate this design are more abrasive and produce more noise.

ii) 4-Stroke Engine 

A four-stroke engine incorporates two more piston strokes, totaling four: two upward and two downward, for one complete power cycle. This can be accomplished over 720 degrees of crankshaft rotation; power is produced once in every two revolutions. 

Unlike the 2-stroke engine, it maintains a slower performance cycle, however, this results in a cleaner and more fuel efficient operation.This kind of engine powers a considerable number of vehicles, from cars and lawnmowers to generators and larger motorbikes. Its steady cycle improves fuel efficiency and extends the engine’s life.

Pros	Enhanced fuel combustion efficiency. Reduces hazardous emissions (green). Balanced operation increases the longevity of the engine. Lower noise levels and smoother operation.
Cons	Increased weight and more complicated design. Extra moving components like valves and camshafts. Higher maintenance costs and increased time to service the engine.

• Other Variants

The 2-stroke and 4-stroke engines are the traditional standards, but some have tried to implement different concepts to improve performance. A good example is the 6-stroke engine, which adds two extra strokes for recovering heat or “breathing”—which in turn reduces the amount of fuel needed and lowers emissions. Even though it is uncommon, there are tests being conducted on it for use in clean technologies.

Another example is the rotary (or Wankel) engine, which substitutes the pistons for a spinning triangular rotor. This engine provides greater reduced motion and minimized componentry. However, these engines tend to be used on race cars and other vehicles such as older Mazdas, so sealing problems and poor fuel economy stagnated wider adoption.

 

2) Working Principles of Stroke Engines

 

Stroke engines serve as the power source of devices, ranging from automobiles to lawn mowers. However, understanding the mechanics involved in their fuel-to-motion conversion processes is necessary weather you are an enthusiast, or student.

     Main Components of a Stroke Engine  

Before we explore how stroke engines operate, we should first outline the key components relevant to the operation.  

• Cylinder: A hollow metal tube where a piston is placed that moves vertically.  

• Piston: A solid metallic piece rotating within the cylinder to compress and subsequently expel the mixture of fuel and air.  

• Crankshaft: It’s a metal device with offset arms and counterweights which converts the linear motion into rotational motion to drive the wheels.

• Spark Plug: It’s also a metal device that starts the combustion in petrol engines by igniting the fuel-air mixture.  

• Valves (Intake and Exhaust): Regulates the air-fuel admission and the exhaust gas release.  

• Connecting Rod: Transfers motion between the piston and the crankshaft whereby the piston and the crankshaft are joined through this piece.  

    Step-by-Step Working Procedure

The work done by stroke engines consists in repeating a cycle of four phases which are performed continuously. Each of the phases is governed by physics principles like Boyle’s Law, concerning the relationship between pressure and volume, as well as Newton’s Third Law of Motion, which defines action and reaction. These laws are important to understand the functioning of the engine.

 

Step 1) Intake Stroke: 

During the intake stroke, the piston moves downwards. Well! The piston's downward movement increases the volume of gas inside the cylinder thereby creating a low-pressure zone inside it ( Boyl’s law ). 

Thus, the intake valve opens at the same time and this pressure difference ( higher outside atmospheric pressure and low cylinder pressure) pulls the air-fuel mixture from outside into the cylinder. This is because gases naturally move from regions of higher pressure to lower pressure. 

 

Step 2) Compression Stroke:

Now, once the cylinder gets filled with air-fuel mixture the intake valve closes. As a result the piston moves in an upward direction, thus decreasing the volume inside the cylinder and thereby increasing pressure. 

Owing to increased pressure the air-fuel mixture in the cylinder is compressed, also resulting in a temperature increase (following Boyle's Law, and Gay-Lussac's Law which states pressure in a closed system increases with temperature). Here, the point to be noted is that fuel under higher pressure is easier to ignite with a spark.

Step 3) Power Stroke:  

Here, the piston is still in upward direction compressing the air-fuel mixture. It was ignited by the spark plug. Thus, this ignition rapidly increases the temperature over 2,000°C inside the cylinder causing the gases to expand. According to Newton's III Law, the expansion of gases will exert force on the piston, then there will be equal and opposite force on the crankshaft converting the fuel chemical energy to mechanical energy (motion).  

Step 4) Exhaust Stroke:  

Lastly, as the piston continues to move upwards, the pressure inside the cylinder gets increases as discussed earlier. Thus, the exhaust valve opens causing the spent gases to be pushed out of the cylinder. You might be curious that why is this important? Well! Fresh air and fuel should come into the cylinder to start the next cycle which is only possible by the removal of spent gases. 

Do remember! For a 4-stroke engine, the entire process occurs in 2 full crankshaft revolutions (720°). In comparison, a 2-stroke completes this process in 1 revolution (360°) more frequent power delivery but lesser efficiency.

3) Common Uses of Stroke Engines

 

Stroke engines are used in many machines that need energy and power. So, let's have a closer look at different sectors utilizing the power of stroke engines!

i) Transportation  

In the transportation industry, stroke engines are majorly found in motorcycles and scooters, particularly 4-stroke engines. These have long been the preferred type to use in vehicles as fuels are burnt completely, as a result, you will cover more distance per litre of fuel and also reduce the emissions of pollutants. Thus, making it an environmentally friendly choice.

Similarly, in situations where the vehicle needs to be lightweight like with outboard motors on boats or go-karts, 2-stroke engines dominate in popularity because of their small size and lightweight nature.

ii) Lawn and Garden Equipment

Moreover, lawn and garden equipment like lawn mowers, yard trimmers, and even chainsaws are also powered by 2-stroke engines. This is because beyond their lightweight and compactness, it is easy to maintain these engines and they provide ample power for tree trimming or grass cutting. Thus, their simplicity along with a favorable ratio of weight to power makes them handy for portable garden tools that require easier maneuverability.  

iii) Agricultural and Industrial Machinery  

Similarly, industrial and agricultural machinery also benefit from stroke engines. Small generators along with water pumps and tillers make use of 4-stroke engines and thus are powered by them. These engines are well known for their reliability and durability over long periods of use. 

They deliver steady power for tasks that are hard to perform over long durations. As with most industrial applications, when every second counts, the ability of the 4-stroke engine to operate seamlessly for long hours with minimal upkeep is invaluable.

iv) Applications of Hobby and RC Vehicles 

Finally, in the sphere of leisure activities, remote control cars, boats, and airplanes have incorporated 2-stroke engines which serve these models well. The engines need to be lightweight and provide a high power to weight ratio, especially for the enthusiast looking to shave weight while still enabling the vehicle to attain high speeds.

4) DIY builds of the Stroke engine

Now, you might be wondering that whether it is possible to built stroke engine model at home. Well! Whether you are an enthusiast or a student, we understand your curiosity level, that’s why we at engineDIY have come up with a DIY engine model kit containing all the tools and equipment needed to design a working stroke engine model at home. 

All you need to do is to read the instructions given inside the kit and you can start assembling it. Well! For your further assistance; we are going to share with you a step-by-step tutorial. By following this guideline you will definitely face no problems while building and would spark your creativity!

 Parts Included in a Standard DIY 4-Stroke Engine Kit

• Engine Block

• Crankshaft

• Pistons with Piston Rings

• Connecting Rods

• Cylinder Head

• Camshaft

• Valves

• Rocker Arms & Pushrods

• Valve Springs & Retainers

• Carburetor or Throttle Body

• Spark Plug

• Flywheel

• Oil Pan

• Gaskets & Seals

• Instruction Manual 

      Step-by-Step Assembly Tutorial

Step 1) First of all, you need to unpack your DIY kit and inside you will see an instruction manual which proves very beneficial throughout the process. So, you need to match each part with the manual to ensure all pieces are there and nothing is missing.

Step 2) Well! We strat with crankshaft assembly and the components required for its assembly will be in a separate box labelled as crankshaft components. So, you need to follow the manual instructions and also add a little piston into it. Don't forget to grease the moving parts for smoother running. 

Step 3) Next, you need to put the engine block and assemble both its lower and upper ends if they are separated and insert the crankshaft.

Step 4) Now, it's time to assemble cylinder head components including valve buckets. rockers, intake ( 45 degrees cut ) and exhaust valve ( 33 degrees cut ) and also the camshaft. So, firstly put 2 valve buckets at the top cylinder head having two holes as shown in picture below!

Then take a miniature camshaft and insert cam gear. Do remember that mark goe up and lobe goes down.

Step 5) Now, put this camshaft assembly right into the cylinder head and the gasket should be placed as well. The head bolts should be tightened diagonally to the head.

Step 6) The marks of the crankshaft and camshaft should align. The insertion of timing gears or chain/belt should be done to both of them as well. The remaining pieces like rocker arms and pushrods should be fitted into the valve train. Rocker arms should be set for valve lash. The listed gaskets should be used in order to bolt the intake and exhaust manifolds on. 

Step 7) The intake side should have the carburetor mounted directly to it. Afterwards installation of fuel lines should follow. The ignition coil and wires should be connected to the spark plug after its installation.

Step 8) The display base should have the engine secured to it and the flywheel mounted. Finally, an optional cooling fan can be added if desired.

Step 9) Lastly, add oil if needed. Hand-crank the crankshaft. If the setup is powered, connect the starter, fuel and test-run the system.

5) Conclusive Notes

 

From all the above discussion, we have concluded that whether you are a hobbyist or an emerging engineer, building an engine from a DIY kit can certainly be a thrilling and gratifying undertaking. Using basic knowledge, and the right tools you can learn how your transportation sector works and drive cars, motorcycles, etc. 

So, are you eager to embark on this journey? Visit EngineDIY now, and check out our extensive collection of DIY engine kits suitable for every engine-building enthusiast. So, do not just read—construct and fuel your enthusiasm now!

6) FAQs related to the stroke engine

 

i) What is the difference between a 2-stroke and a 4-stroke engine?  

A 2-stroke engine offers higher power-to-weight efficiency, but completes a power cycle in two strokes of the piston. On the other hand, a 4-stroke engine is better for fuel economy and produces less emissions, completing the cycle in four strokes.  

ii) Can I build a stroke engine myself?  

Absolutely yes, you can build a stroker engine by yourself at home using a DIY kit. This kit contains all the necessary components and tools enabling you to build a stroke engine. However, you’ll need extensive knowledge of a motor’s mechanics and how it is assembled to be functional and secure.  

iii) What are common applications for 2-stroke engines?  

If we talk about 2-stroke engine, then keep in mind that are mostly used in motorcycles, scooters, outboard motors, and go-karts. I must say that they are designed for small, lightweight vehicles.

iv) How do stroke engines work?  

Stroke engines work through a sequence of piston movements like intake, compression, power, and exhaust, thus converting fuel into mechanical energy. In case of 4-stroke engines these movements occur over 4 cycles, however, 2-stroke engines do it in one revolution.

 

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