over the course of human existence the most significant catalyst for growth has been our ability to draw energy from our world taming fire gave birth to the modern human and drawing power from the wind allowed early explorers to travel the world but today we're going to explore the history and science behind one of humanity's greatest inventions the steam engine the evolution of the steam engine completely revolutionized their society it opened new avenues for trade and cost mass migrations of rural populations into the newly industrialized cities what I found most fascinating was their lessons is evolution taught us about science and engineering this is one of the first practical steam engines and it was used to pump water the engine was incredibly inefficient this machine was not going to start any Industrial Revolution but had found a niche in coal mining where its fuel was cheap and readily available to investigate why this engine was so inefficient let's first talk about how it works the engine takes energy stored in coal and converts it to heat that heat is used to form steam which expands into a piston cylinder causing the pressure to increase and forcing the piston to rise against atmospheric pressure no mechanical work occurs on the stroke because this chain can only transmit force in tension the power stroke occurs when cold water is sprayed into the cylinder this lower is the temperature causing the pressure to drop atmospheric pressure now pushes the piston back down we want to be able to quantify how much work is being done per cycle of this engine to do that we plot the pressure and volume inside the piston cylinder for one cycle like this the area inside is the work done but this is the idealized PV diagram in practice there is a lot more energy being wasted we lose a big chunk here because the steam is prevented from expanding to its full volume a lot of energy is lost to the environment too this is clearly visible with thermal imaging the effect is made worse by cooling the entire cylinder with cold water so an immediate improvement is to make a separate condenser here the steam can be cooled without cooling the entire cylinder there are a lot more inefficiencies involved that reduce the total work done many of them are unavoidable but we can improve the situation by upgrading the piston cylinder the manufacturing techniques needed to bore accurate and strong piston cylinders were not available in the early days of the steam engine that changed when John Wilkinson invented this machine this boring machine allowed for precise machining of solid iron cylinders which reduced steam leakage and made the piston cylinder stronger thus allowing the max pressure to rise we are starting to see a steam engine capable of sparking an industrial revolution but this reciprocating motion isn't much used for most applications especially with this flexible chain connecting them what we need is rotational motion which requires a different setup to convert this linear motion to rotational motion we need a crankshaft and connecting rod we have turned this piston cylinder on its side so atmospheric pressure can no longer force the piston back down so we need to use steam on the return stroke this requires a control valve to control when the steam enters and leaves each side of the cylinder the valve is controlled by a cam the steam engine is now working on both strokes of the engine improving its efficiency and power the piston engines like this do not produce constant torque they'll pulsate and speed and torque during a single cycle like this this can cause vibrations and jerky movement we can reduce this with the use of a flywheel which stores rotational energy with inertia and evens the torque out it's essentially a mechanical battery David Robert demonstrates this beautifully with the v8 solenoid engine of his own creation here you can see the engine will continue to rotate without additional power but the engine comes to a dead stop without a flywheel attached the development of steam engines thought us a lot about thermal and mechanical efficiencies and you may think that steam engines have become obsolete but nearly all of our large power stations still use steam technology to convert heat energy whether that be from coal nuclear or solar to mechanical energy the technology is simply evolved into an even more efficient form with steam turbines thanks for watching I have one last device I want to include in the development of steam engines which is one of the most iconic inventions of the Industrial Revolution the centrifugal governor I'm already hearing the angry screams in the comments section about me using the word centrifugal so I'm going to talk about this device in a completely separate video to discuss the differences between centripetal and centrifugal force if you'd like to see that don't forget to subscribe if you'd like to see more content or support real engineering the links from my 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