From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
From Wellworthy Limited detailing the importance, manufacturing challenges, and development of the piston ring.
| Identifier | ExFiles\Box 16\1\ Scan140 | |
| Date | 15th September 1922 guessed | |
| WELLWORTHY LIMITED THE PISTON RING is one of the vitally important members of the internal combustion engine, or of any other mechanism in which a gas-tight piston is used. Consider its function: it is the means by which the gases are retained during compression and explosion, and upon its efficiency depends the power of the engine. Cast iron is an essential to its manufacture, because no other metal possesses the same characteristics or suitability in general. Much money and time has been spent in research work to determine the best grade of iron for the job, and to-day the knowledge on this head obtained by the Specialist is that the material can be controlled within such narrow limits as to remove any danger of failure through faulty and defective castings, and, further, the system of inspection in works organised like those of WELLWORTHY obviates the possibility of a ring with a blowhole or segregation of any kind passing the view. Given the right material and the most perfect system of inspection, there arises the difficult matter of producing a ring which must, in the first place, be something larger in diameter than the cylinder in which it is to work, in order that there should be sufficient metal to fill the circle of the cylinder wall, after a piece of the circumference of the ring has been removed, to provide for the gap in the ring. Here is the problem. The ring being diametrically larger than the cylinder, when closed on the piston is not cylindrical, and depends upon the spring of the ring to accommodate itself to a fit. What happens is a bearing here and there on the cylinder wall, with the result that lapping in becomes a necessity in order to make the larger radii conform to the smaller. This begets certain troubles—firstly, the abrasive used for the purpose is deleterious and sets up unnecessary wear of the engine parts with which it comes in contact, and, secondly, the rubbing down of the high points results in the widening of the gap and consequent loss of efficiency, added to which is the waste of mechanic's time in the performance of this unmechanical duty. The problem of obtaining a cylindrical ring has baffled the students of the subject for many years, as the problem is perfectly well known to engineers, and many devices have been made to overcome the difficulty. Some of the ingenious schemes produced in the United States of America, such as inserted pieces, attain the desired end in part, but do not fill all the essential conditions, and, further, the two-piece ring adds materially to the cost, and to complications, whilst in no case does this construction meet the crux of the question—viz., to provide a ring which possesses a truly cylindrical fit within the cylinder walls and which exerts an absolutely UNIVERSAL RADIALLY DIRECT PRESSURE. The WELLWORTHY Piston Ring is the result of some years of practical study of the question. This Company was selected by the British Air Board to make large quantities of piston rings for aviation engines, and exemplifies the efficacy of original thinking. Piston rings were required which would fit perfectly ; of equal radial pressure and of a given free gap, the ring should take a parallel bearing, and abrasive in the fitting should be anathema. This was the starting point, but no ring had yet been manufactured which answered to this demand. Messrs. Gray and Howlett were the men in whose hands the problem lay as far as WELLWORTHY were concerned, and bit by bit they worked it out. Firstly, they improved the existing and well-known | ||