Isolastic

Isolastic (pronounced ahy-soh las-tik)

An engine-mounting system developed for the Norton Commando motorcycle.

1967: The construct was iso- + e(lastic).  The prefix iso- is from the Ancient Greek, a combining form of ἴσος (ísos) (equal).

Elastic (also as elastik) was from the mid seventeenth century French (coined as part of the technical language of chemistry to describe gases “having the property of recovering its former volume after compression”), from the New Latin elasticus (expanding spontaneously), the construct being the Ancient Greek elast(ós) (a late variant of elatós (ductile, beaten (of metal)) and derivative of elaúnein & elân (beat out, forge, render from metal)) + -icus (-ic-).  The Greek elastos (ductile, flexible) & elaunein are of uncertain origin but some speculate the source was the primitive Indo-European base ele- (to go).  Elastic (and elastik) came to be applied to solids after the 1660s in the sense of "possessing the nature to return to the form from which it is stretched or bent after the applied force is removed".  Figurative use to describe things as diverse as the principles of politicians or statistical properties emerged by 1859 and the most widely used modern form, the noun meaning "piece of elastic material" (originally a cord or string woven with rubber) dates from 1847 as an invention of American English.  The noun elasticity (the property of being elastic) dates from the 1660s, either from the French élasticité or else as the ad-hoc construction from elastic + -ity.  The adjective inelastic began in 1748 as part of the jargon of physical science and engineering meaning “not restored to original shape after responding to strain" and was simply the technical antonym of elastic while the figurative sense of "rigid, unyielding" dates from 1867 but general use didn’t endure as the word became associated with fields such as economics.

In scientific use, the prefix iso- was used to indicate “equal (as in isometric, isobar, isocyanic acid et al); having equal measurements”.  As a word and abbreviation, iso had its quirks even before it became popular oral shorthand to refer to the various states of isolation imposed during the early months of the COVID-19 pandemic.  The use to describe the specifications of standards (eg ISO 9001 et al) defined by the Organisation internationale de normalisation (International Organization for Standardization) leads many to believe ISO is an acronym or initializm.  However, the organization notes that when founded, it was given approved the short form “ISO”, a nod to the Ancient Greek ἴσος (ísos) (equal), the implication being the equalization (ie standardization) of rules and terminology across jurisdictions.  Despite that, there appears to be no documentary evidence to support the pedigree of the name and most folk who give the matter a moment’s thought probably assume it means “International Standards Organization”.

In film and television production, an “iso” is an isolated camera (a camera used to isolate a subject, usually for instant replay, a use dating from 1967 in sports broadcasting).  In executive salary packaging, tax minimization etc, an ISO incentive stock option) is a right extended to an employee to buy shares of company stock at a discounted price (the realized profit on which are taxed usually at a concessional rate).  In a number of sports, iso is used as a clipping of isolation to refer to tactical plays and in category theory it’s a clipping of isomorphism (morph a back-formation from morpheme, from the Ancient Greek μορφή (morphḗ) (form, shape).  In optics, isochromatic (iso- +‎ chromatic) refers to "possessing the same colour or wavelength; of or corresponding to constant colour".  Chromatic was from either the French chromatique (chromatic) or directly from its etymon the Latin chrōmaticus, from Ancient Greek χρωματικός (khrōmatikós) (relating to colour; one of the three types of tetrachord in Greek music), from χρῶμα (khrôma), (colour; pigment; chromatic scale in music; music), ultimately from the primitive Indo-European ger- (to grind; to rub; to stroke; to remove), presumably in the sense in which pigments were found.

1966 Iso Grifo Spyder (left), 1971 Iso Fidia (centre) & 1973 Iso Grifo 7 Litre (penthouse).

Iso Autoveicoli SpA (subsequently several times re-named) was an automobile and motorcycle maker in Italy, active between 1939-1974, their most fondly remembered cars from the 1960s & 1970s being sold under the Iso brand.  The Iso name was derived from the company’s pre-war origin in Genoa as a manufacturer of refrigeration units when it was called Isothermos, the construct being iso + thermos, from the Ancient Greek θερμός (thermós) (warm), the implied sense being "something which maintains the correct temperature".  In 2022, the corporate name is IsoRivolta and it continues to operate as a low-volume manufacturer.

The suffix -ic was from the Middle English -ik, from the Old French -ique, from the Latin -icus, from the primitive Indo-European -kos & -ḱos, formed with the i-stem suffix -i- and the adjectival suffix -kos & -ḱos.  The form existed also in the Ancient Greek as -ικός (-ikós), in Sanskrit as -इक (-ika) and the Old Church Slavonic as -ъкъ (-ŭkŭ); a doublet of -y.  In European languages, adding -kos to noun stems carried the meaning "characteristic of, like, typical, pertaining to" while on adjectival stems it acted emphatically; in English it's always been used to form adjectives from nouns with the meaning “of or pertaining to”.  A precise technical use exists in physical chemistry where it's used to denote certain chemical compounds in which a specified chemical element has a higher oxidation number than in the equivalent compound whose name ends in the suffix -ous; (eg sulphuric acid (H₂SO₄) has more oxygen atoms per molecule than sulfurous acid (H₂SO₃).

Norton's isolastic engine mounting

Norton Featherbed frame.

Powerful as the engines were, much of the success in competition Norton’s motorcycles enjoyed in the 1950s were attributable to the “Featherbed” frame, introduced in 1950.  Designed with twin parallel rectangular loops, each formed from a single length of Reynolds steel tubing with crossed-over welded ends which met a securely braced headstock at the front and swinging arm mountings to the rear, the Featherbed frame was stiff, strong and surprisingly light and proved resistant to even sever road and transmission stresses.  It was state of the art but that state reflected the technology of the late 1940s and as the years went by, engine speeds, displacement and compression ratios increased so power and torque rose, imposing mechanical stresses and, most significantly, vibration levels became so pronounced that the big Norton twin-cylinder bikes were becoming less attractive to buyers; while all the power and torque was admired, for many it was rendered unusable by all the shaking which had to be endured at a wide range of engine speeds.

Norton Commando frame.

A new engine was the obvious solution but, despite years of success, by the early 1960s, the whole British motorcycle industry was under-capitalized and nothing emerged; Norton’s bankruptcy surprised few.  Re-structured in 1966 as Norton-Villiers Ltd, it was still obvious a new engine was needed to remain competitive and this was pursued but the engineers suggested a new frame might be a stop-gap solution while engine development proceeded.  Most attractive was that a new frame should cheap and fast to create.  Afforcing the engineering staff, even with a German nuclear physicist who had once worked for Rolls-Royce, work proceeded quickly even though the Featherbed’s box-frame approach was abandoned in favor of a single, large diameter top tube that ran from the top of the steering tube to the seat struts with a short, angled gusset (made from a tube of the same dimension) was incorporated to triangulate the steering/top tube connection.  Two smaller diameter tubes extended from the bottom of the steering tube, running underneath the engine-gearbox unit where, connected by the centre stand’s mounting tube, they curved upwards to meet the seat struts at the rear suspension top fixing brackets.  The frame was completed by a triangulation of the rear section, achieved by using two more tubes which ran from the rear engine-gearbox unit mounting bracket to midway along the large top tube.

As intended, the new frame was light and the torsional strength (the resistance to twisting) was even higher than the engineers’ theoretical calculations had projected.  The design imperatives had been surprisingly simple, a kind of “back to basics” approach which (1) ensured the relation between the front & rear wheels remained constant regardless of the roughness of the surface, and 2) the higher loadings were Imposed only on the straight tubes, the bent portions of the frame are stressed.  Most innovative was the isolastic mounting system for the engine-gearbox unit (which the factory initially dubbed “GlideRide”.  Although essentially an admission the vibrations inherent in big, twin-cylinder engines couldn’t (then) be fixed, they could substantially be isolated to the unit and not transmitted through the frame to the rider.  At the core of the problem was that as a crankshaft rotates, the engine’s centre of gravity describes a heart-shaped path around the crankshaft axis, the engine therefore tending to oscillate around that path.  What the isolastic system did was provide the engine with three suspension points: (1) at the front, (2) at the top-rear of the gearbox and (3) at the cylinder head.  The mountings were large because of the vibration they needed to absorb but with a torsional stiffness provided by a rigidity in the side mountings, the idea being that the engine must be free to move in the plane of the crankshaft but without twisting in the frame.

1972 Norton Commando 750 Combat.

When the Norton Commando was launched in 1967, the combination of frame and the isolastic engine-gearbox mounting system proved the inherent vibration problem associated with big twins, if not solved, had been artfully concealed.  The early implementations of both the isolastic plumbing and the frame did reveal some weaknesses but these problems quickly were solved and both enjoyed a decade long life, over 60,000 Commandos produced between 1976-1977.  However, the clever improvisation (driven by financial necessity) really just delayed the inevitable as the manufacturers from the Far East had proven their modern, four-cylinder concepts were a better direction for the high performance motorcycle.  In the ten years the Norton Commando was on sale, the Japanese improved their products while the British tinkered at the edges and by the time the last Commando was made, the superiority it once enjoyed in road-holding and handling had evaporated.  The British industry never recovered from the mistakes made during the 1960s and 1970s.