|
For much of human history, harnessing power have been the main goal in most of its engineering endeavors. However there's another story to that, that of transmitting and controlling that power. There's no point to have something if you can't use it or control it.
This article is an overview of that history... |
"The history of the development of mechanics is quite indispensable to a full comprehension of the science in its present condition. It also affords a simple and instructive example or the processes by which natural science generally is developed." - Ernst Mach, "The Science of Mechanics"
So you’ve reached that age where driving a car becomes some sort of high-stakes social litmus test. Hopefully you’re also interested in how the thing works rather than just how it can get you a date with some girl. Ah, the follies of youth… so let’s get started.
Contrary to popular belief, mechanical power transmission (i.e. engineered means to transmit mechanical power from one place to another) goes way before the Industrial Revolution. As a matter of fact, it’s history is as old as our ability to harness power in the first place. And at the beginning was the waterwheel.
Though they were independently invented in almost all part of the world, the Greco-Roman world provides the most well–documented development of the wheel-based technologies. Hellenic engineers were the first to document their use in irrigation and as a power source, and in these cases the issue of power transmission is not that big. Waterwheels tend to be where the work is needed, grain mills are located beside rivers, farms and aqueducts are just next door. Transmission is limited to changing the rotary motions of the wheel into reciprocating motions, or vice versa, depending on what the power will be used for.
Contrary to popular belief, mechanical power transmission (i.e. engineered means to transmit mechanical power from one place to another) goes way before the Industrial Revolution. As a matter of fact, it’s history is as old as our ability to harness power in the first place. And at the beginning was the waterwheel.
Though they were independently invented in almost all part of the world, the Greco-Roman world provides the most well–documented development of the wheel-based technologies. Hellenic engineers were the first to document their use in irrigation and as a power source, and in these cases the issue of power transmission is not that big. Waterwheels tend to be where the work is needed, grain mills are located beside rivers, farms and aqueducts are just next door. Transmission is limited to changing the rotary motions of the wheel into reciprocating motions, or vice versa, depending on what the power will be used for.
This doesn’t change much from then until the early modern times (16th to 18th century) when the proto-industrial society picks up, and much of the power is needed somewhere else (factories, mines, etc…). The engineers of the day have two choice, either divert a river to where power is needed, or find some way to transmit the work from an existing waterwheel to it. The first is rather costly, especially considering the limits of civil engineering in those times, so they settled for the latter.
A method born out of this necessity is the flatrod system or Stangenkunsten as the Germans called it, and was used mainly for pumping water from mines, but most extensively in the town of Marly beside the river Seine to pump water to feed France's king, Louis XIV’s fountains in Versailles. It’s an evolution of the crank and connecting rod on a major scale, where the reciprocal motion is transferred by the way of a network of adjoining pivoting rods attached as far as four kilometers away. A simple and elegant solution, but much of the power is wasted from friction and the weight of the system itself.
A method born out of this necessity is the flatrod system or Stangenkunsten as the Germans called it, and was used mainly for pumping water from mines, but most extensively in the town of Marly beside the river Seine to pump water to feed France's king, Louis XIV’s fountains in Versailles. It’s an evolution of the crank and connecting rod on a major scale, where the reciprocal motion is transferred by the way of a network of adjoining pivoting rods attached as far as four kilometers away. A simple and elegant solution, but much of the power is wasted from friction and the weight of the system itself.
A stangenkunsten
|
La Machine de Marly
|
With the advent of the industrial age, the steam engine became the standard source of power, and mechanical power transmission became limited to balance the use of torque and speed as further developments in physics allow for the application of classical mechanics into engineering. In this context torque is the force applied at a rotational axis, and it’s a tradeoff between this and its rotational speed. For example, when a car is climbing a steep hill it needs more torque to counter the forces of gravity, while on a level road having too much torque is a waste – unless it is needed to pull a great load (think fully-loaded container trucks).
Of course this is not only applied in transportation. During the Industrial Revolution, the application of mass production requires high torque to efficiently transmit power to all the machinery on a factory floor through a system of belts and pulleys on overhead line shafts. If a machine requires more speed, this is solved using gearboxes, and as a result power is not wasted where it’s not required. This is where things get interesting. The gearbox, that jumble of intermeshing cogs in your car, is probably one of the greatest creation in engineering history.
Of course this is not only applied in transportation. During the Industrial Revolution, the application of mass production requires high torque to efficiently transmit power to all the machinery on a factory floor through a system of belts and pulleys on overhead line shafts. If a machine requires more speed, this is solved using gearboxes, and as a result power is not wasted where it’s not required. This is where things get interesting. The gearbox, that jumble of intermeshing cogs in your car, is probably one of the greatest creation in engineering history.
The very first gearboxes were not based on intermeshing gearwheels, this is of course found in the first car. In 1886, Karl Benz unveiled his Patent-Motorwagen Nummer 1, now regarded as the world’s first automobile. Powered by a simple two-stroke engine, not much is need to handle in terms of transmission, which is for just a single speed with power shifting between a loose (idle/neutral) and fixed driving disc (go) using drive belts, just like in the factories of the day.
Benz’s Motorwagen however have its drawbacks. Being a direct-drive mechanism – that is, a single driving gear directly connected to the wheels – doesn’t give it the full range of control over torque and speed. If you want to go faster you need to spend more fuel, which might strain the engine. Try ramming the accelerator of a manual car on 1st gear at 100km/h, you won’t get far.
In 1890, a couple of French engineers by the name of Louis Rene Panhard and Emile Levassor developed the first multiple gear transmission. These are engaged by sliding them on their shafts (thus we get the term “shifting” gears). This is difficult as to engage one gear to another you have to time it right, or else they would only grind against one another, resulting in costly damage. To avoid this, it’s better to disengage from the engine, change gears and then reengage the transmission, and this is done using the clutch mechanism.
Things seems to be working fine for a while, though as IFSA tradition demands, technology marches on. The manual transmission described previously is adequate though it was then improved. The original system requires that the gears themselves to be shifted around, this creates more problems due to the many moving parts involved.
But what if there’s no need for them to be shifted? What if the shaft alone that moves, and when required would engage the right gear as demanded by the driver? How about the gears and cogs system itself? Can they be replaced with something else that wouldn’t be affected by frictional damage, that wouldn’t require lubrication, and won’t overheat?
These are indeed questions that were pondered and will continue to be pondered on by engineers in the past and the future. And in the following engineering articles we will do the same as well.
Benz’s Motorwagen however have its drawbacks. Being a direct-drive mechanism – that is, a single driving gear directly connected to the wheels – doesn’t give it the full range of control over torque and speed. If you want to go faster you need to spend more fuel, which might strain the engine. Try ramming the accelerator of a manual car on 1st gear at 100km/h, you won’t get far.
In 1890, a couple of French engineers by the name of Louis Rene Panhard and Emile Levassor developed the first multiple gear transmission. These are engaged by sliding them on their shafts (thus we get the term “shifting” gears). This is difficult as to engage one gear to another you have to time it right, or else they would only grind against one another, resulting in costly damage. To avoid this, it’s better to disengage from the engine, change gears and then reengage the transmission, and this is done using the clutch mechanism.
Things seems to be working fine for a while, though as IFSA tradition demands, technology marches on. The manual transmission described previously is adequate though it was then improved. The original system requires that the gears themselves to be shifted around, this creates more problems due to the many moving parts involved.
But what if there’s no need for them to be shifted? What if the shaft alone that moves, and when required would engage the right gear as demanded by the driver? How about the gears and cogs system itself? Can they be replaced with something else that wouldn’t be affected by frictional damage, that wouldn’t require lubrication, and won’t overheat?
These are indeed questions that were pondered and will continue to be pondered on by engineers in the past and the future. And in the following engineering articles we will do the same as well.
Ponder this
If the gear is simply a never ending series of levers, what about the other five simple machines (wheel and axle, pulley, inclined plane, wedge and screw)? Are there any complex derivatives of them?
Considering the flatrod system, how would we solve their problems of inefficiency using the materials of the time? Consider as well the technological and material limits of the day.
Discuss
The transmission of power from one place to another is subject to counterforces such as friction, material elasticity and deform, vibrations, whether created internally or due to external factors. How do we overcome these problem? Propose designs, materials and approaches to solve this.
Further readings
The flatrod system, probably the first attempt to transmit power over long distances.
La Machine de Marly, built to feed water to the fountains of the Palace of Versailles, was considered an engineering marvel of its time.
Line shaft pulleys and belting, probably the most comprehensive information on line shafts in the internet.
