Lest you think Fig. 1 here is the remnant of some form of horrific engine blow-up, let me explain that what you are looking at is a ductile iron piston ring. Twisted and bent to all manner of shapes the resulting contortion demonstrates vividly how flexible the material can be.
Ductile iron comes from a class of materials referred to as SG (spheroidal graphite) irons. Similar in composition to the grey cast-irons used in older type piston ring technology, the carbon flakes in grey cast-iron have been converted into a round, nodular form, inhibiting the formation of micro-cracks and making the resultant iron considerably more ductile and very much less brittle. Read more…
I’ve always said that to be a good engineer takes many years of experience but to be a great one takes an appreciation of history as well. It’s a well-documented fact that very little is totally new in the world of automotive technology. For instance, four-valve chambers were first recorded in the Peugeot L3 of 1913, while the very first turbocharger came about in the mid-1920s - just two examples that readily spring to mind and were readily ‘re-invented’ later in the century. So when people talk about the latest in oil control ring 
For as long as I can remember, it has been considered best practice to position the ring gaps equidistant around the piston. The theory is that in doing so, gas leakage will be minimised so that it stays within the confines of the combustion chamber, expands and generates more shaft power. For some reason - and I no longer understand why - it just made common sense and was never really challenged. 
A phenomenon rarely heard of these days, is that of ring flutter. Manifesting itself in the form of unusual wear characteristics and possibly high exhaust gas blow-by, particularly at light load conditions, ring flutter if left unchecked, can even cause pre-ignition/detonation of the incoming fuel-air charge, eventually leading to piston failure. The solution however, is not always that obvious.
There have been many different types of piston ring developed over the years. Rectangular, taper face, barrel face, scraper, Napier, torsional twist, reversed torsional twist to name but a few. But one particular version that seems almost totally forgotten today, except for a few highly specialised applications is that of the Dykes ring. Peculiarly ‘L’-shaped in cross-section and named after it’s inventor not an embankment built to prevent flooding as might be at first thought, the Dykes ring was a regular feature on many a 
The UN summit meeting in Copenhagen, COP 15, has come and gone. A meeting whereby 192 or so countries met together to fudge some kind of global agreement to reduce greenhouse gas emissions yet again attracted that section of the environmental lobbyists who seem to be determined to press their cause via mayhem and violence. It is little wonder therefore that the authorities seeking to maintain law and order, and according to journalist types, threw a ‘ring of steel’ around the venue to safeguard those present. The connotation to all this is clearly one of strength and 
One of the most recent innovations in piston ring technology has been the invention of diamond-like-carbon coatings. The progressive move away from cast or ductile iron towards much stronger but less durable steel designs, made the development of suitable surface coatings a distinct priority.
I have to admit that at the moment, visits to our capital city are few and far between. The heart of business and finance maybe the place where many a motor sport deal is done, but the real action as far as I am concerned, is always in the workshop or on the track. But on those very occasional sojourns when needs must and when using the underground ‘tube’, I’m always reminded of one critical aspect of the piston ring. You see, at many of the stations when the train is just coming to a halt and doors open, the station announcer may call “mind the gap.” And lost in my own little world my mind immediately reverts 
If the top compression ring has the most difficult of tasks in the engine then, at the other end of the piston ring pack, the oil control ring doesn’t have it much easier. Travelling at an average speed approaching 4000 feet per second or so, the component has to strip away any excess oil from the cylinder bore on the downward stroke and ensure just sufficient passes to lubricate the upper rings. The excess oil is then forced through the ring and drains back to the crankcase via a series of slots or holes in the piston. 
Mention the subjects of durability and wear measurement in engine development and the image immediately conjured up is one of tests lasting hundreds of hours and lots of precise measurements, both before and after the test. When it comes to the piston ring we might want to check the ring gaps both free and as installed, measure the weight as accurately as we can, take a few harness measurements and visually examine the wearing surface. Apart from that there is little extra even the well-resourced development lab can do. Of course the rings may well be returned to the supplier for more 
