Internal Combustion Engines and vibration

Today I've done some reading about the conversion of mechanical effort, from a translation setting - linear applied force, and linear movement - to a rotational one : torque and spinning motion.

What I had in mind is a piston, with a connecting rod and a crank that drives a wheel around an axis. The typical mechanism you see in a steam engine.

Then, while exploring the subject, I've realised that car engines are built mainly on the same principle, although they have -nowadays - not one, but 4, 6 or 8 pistons. As I had suspected, a single piston does a very imperfect conversion of mechanical power. Some of the translational effort is lost in the process, through friction or - even worse - vibration. I found out that the supression of the vibration movements that come from piston motion in an automobile engine is quite an engineering topic. It is called engine balancing or - as refering to what it is meant to achieve instead of the process itself - engine smoothness.
Better balancing of the engine means energetic efficiency - thus lower fuel consumption, - less mechanical stress on the crankshaft and pistons - therefore a car engine that lives longer - and, last but not least, less noise and vibration for the driver to endure. The gains become all the more important when the engine is designed to run at high rev.

The balancing of an engine is mainly an issue for the engine designer - who decides how many pistons, and their relative configuration - V, W, straight or boxer - as well as complementary balancing mechanisms, such as flywheels and balance shafts. But it is also a puzzle for the mechanic who tunes the engine: the balance is initially calculated for an engine with all its original parts. If some parts are replaced or simply become loosened through use, then a retuning becomes crucial.

Your usual car cruises between 2 000 and 6 000 rpm, but Formula 1 racing monsters can handle up to 20 000 rpm. When the rev doubles the centrifugal / centripetal efforts on the rotating parts quadruple ! Needless to say that F1 cars use the most accurate balancing techniques. And in spite of that end up in a museum (at best) after only a few races - well, engine wear-off is not the only one responsible for their demise. It would be actually interesting to know what can still be used from a racing car when it is deemed to be no longer fit for competition.

Back to engine smoothing ! The subject is vast; I'll come back to it later, perhaps with some math in support, to give a feeling of the challenges involved.

Definition of an interface

The blog is dedicated to displaying my personal areas of interest in science and technology, under a particular type of classification, based on interfaces between scientific domains, technology fields ar merely physical world aspects.

An academic definition of the word "interface" can be found here. What I focus on in the meaning of word interface are the "boundary surface" aspect as well as the "communication or interaction" aspects.

Let's have some examples of "interfaces" I'd like to explore in this blog.

• science / technology - those two domains have a common aspect, which is the manifestation of human knowledge and intellect. However, just like two phases of chemical a substance, there are very different laws governing each of them. Science and scientists are driven by the knowledge, understanding and explanantion of the (physical, social, economic ...) world in which we live, while technology and 'techies' are bent upon acting and modeling the world to their needs, views or ambitions. But here comes into play the 'communication' and 'cooperation' meaning of interface : for science to become ever more knowledgeable, complex measurement and observation tools need to be built (like the electron microscope or the LHC); these require a great deal of technology effort. Also, science needs to rely on complex social structures and organization to provide an environment for the most talented scientists to fulfill their goals. On the other hand, complex technical realizations are upon rigourous fundamental-science studies and theories. And the social hierarchy and structures ( companies, NGOs, governments, teams ) benefit from the development of social sciences.

So, basically what characterizes an "interface" is

1. two domains of equivalent importance that share some common aspect
   
2. very distinct laws that govern the cores of the two domains
3. a vague, changing, ambiguous frontier between the domains
4. a continuous give-and-take exchange, communication between them

Other examples:

• social sciences / exact sciences

• formal sciences / natural sciences

• technical language / commercial language

• technical innovation / commercial innovation

Within the technology branch:

• rotational motion / translational motion

• air / water (or gas / liquid)

• software / hardware

• digital / analog

• mechanical / electrical

Within sciences :

• biology / chemistry
  

• chemistry / physics