Chevron (pronounced shev-ruhn (U) or shev-run (non-U))
(1) In heraldry, an ordinary
in the form of an inverted V-shaped charge on a shield, one of the most ancient
of the English ordinaries.
(2) An insignia consisting
of stripes meeting at an angle, worn on the sleeve by non-commissioned officers
(NCO) in the military, police officers etc, as a mark of rank (variously upwards
or downwards), length or service or for other purposes (usually always
upwards). In casual use, the use to the
display the NCO ranks are referred to as “stripes”.
(3) In interior decorating, an
ornamental form in a zigzag pattern used often on moldings and also called a dancette;
the design most historically most associated with romanesque architecture in
France, England and Sicily.
(4) In the manufacture of fabrics,
as chevron weave, the application of the shape (the herringbone a subset of
this use).
(5) In road-traffic
management (1) a pattern of horizontal black and white V-shapes on a road sign
indicating a sharp bend (usually in the plural) or (2) one of the V-shaped
markings on the surface of roads used to indicate minimum distances between
vehicles (use varies between jurisdictions).
(6) In design, any V-shaped
pattern or device.
(7) In language, an informal
term for the guillemet, either of the punctuation marks “«” or “»”, used in
several languages to indicate passages of speech (the equivalent convention in the
English language the same placement of inverted commas (“_”).
(8) In language, as “inverted
chevron”, an informal term for a háček, a diacritical mark resembling an inverted
circumflex.
(9) In publishing, an angle bracket
used both as a typographic and scientific symbol.
(10) In architecture, a rafter
(a specialized type of strut or beam) of this shape, usually load-bearing and supporting
a structure such as a roof and sometimes exposed, doubling as a decorative
device.
(11) In aerospace, components
fashioned in a saw-tooth patterns used internally (and externally (briefly) on
exhaust nacelles as a noise-suppression mechanism) in jet engines.
(12) In anatomy, a bone of
this shape.
(13) In entomology, the moth
Eulithis testata.
(14) In geology, (1) a fold of
this shape in layers of rock and (2), a sediment deposit in this shape across
the surface.
(15) In pediatric medicine, as
chevron nail, a rare transient fingernail ridge pattern seen only in children.
(16) In mathematics, as chevron
plot, a technique of data representation.
(17) In computing, the
informal term for the angle bracket when used in HTML (also sometimes called
the “wicket” reflecting the English origins of HTML in the Conseil européen pour la recherche nucléaire (CERN; the European
Organization for Nuclear Research)).
(18) In folk arts & crafts,
as chevron bead, glass beads in this shape.
(19) A style of moustache in
this shape.
(21) In music, a wavy line
indicating a trill
(22) In the optical devices
associated with ballistics, a symbol used in reticles in firearm scopes.
1300–1350: From the Middle
English cheveroun, from the Old
French chevron (rafter; chevron), from
chévre (a goat), from the Vulgar
Latin capriōnem & capriōn- (stem of capriō), ultimately from the Latin caper (goat). The
alternative spelling was cheveron which
in commercial use is still used, presumably as means to achieve product
differentiation. Chevron is a noun &
verb, noun, chevroned & chevrony (also as chevronny) are adjectives, chevroning
& chevroned are verbs and chevronwise is an adverb; the noun plural is
chevrons.
The
technical class into which architects classify decorative (as opposed to
structural) chevrons is “inflected ornament” or, in the slang the “zig-zag” (or
zigzag) and they were widely used in romanesque architecture in France, England
and Sicily. In this decorative mode, it’s
though at least one inspiration for their use was the metal casings frequently
seen in early wood columns. The meaning
of the word in French is said to be based on structural engineering, the
reference the rafters of a shallow roof, the idea based on there being some resemblance
to the rather angular hind legs of a goat, the Vulgar Latin capriōnem & capriōn being from the Classical Latin caper (goat). This actually had echoes in the Latin capreolus (props, stays, short pieces of
timber joined at angles for support) which translated literally as “wild goat;
chamoix”. However, some historians of
architecture doubt the story about the hind legs, suggesting the image was more
likely the horns of a butting goat and there’s some support for this in that
the first use of the word in English was in heraldry when chevrons began appearing
on shields, the horns of a charging beast presumably more appealing to the
military mind than the beast’s back legs.
1938 Citroën 11B Traction Avant Coupé (sometime referred to as the Faux Cabriolet) with the company’s distinctive double chevron emblem in the radiator grill.
Designed by French engineer André
Lefèbvre (1894-1964) and Italian industrial designer Flaminio Bertoni
(1903-1964), the Citroën Traction Avant was introduced in 1933 and was the machine
which more than any other legitimized both unitary construction (ie no separate
chassis) and the front-wheel-drive (FWD) configuration (Traction Avant
translates literally as “front traction”) in mass-produced cars. Although a great success and in production
until 1956 (with severe disruptions during wartime occupation 1940-1944), the costs
incurred in its development and the tooling needed for volume production meant
that by 1934 the company was compelled to declare bankruptcy, taken over by
Michelin, the most exposed creditor by virtue of having for some time supplied
tyres on the basis of “delayed payment”.
Although total Traction Avant production exceeded 760,000, there were
only 15 coupés, all from the pre-war years and of these, only four were built
in 1938.
1935 Citroën TA22 Traction Avant prototypes, cabriolet (left) and saloon (right). To mark the installation of a V8, an appropriate numeral adorned the double chevron. Unfortunately, because the chevrons weren’t inverted, the chance to make a “V8” statement was missed. Perhaps the French found such a thing vulgar.
Another genuine rarity among
the Traction Avants was the TA22, an intended top-of-the-range version equipped
with a 3.8 litre (232 cubic inch) V8 created by joining two of Citroën’s 1.9
litre (116 cubic inch) four-cylinder units in a common crankcase. Apparently 20 were built but the combination
of the financial turmoil of bankruptcy and Michelin’s subsequent rationalization
saw the project abandoned and although there are many stories about the fate of
the prototypes, eighty years on none have ever surfaced so it’s reasonable to
assume none survived (at least not with the unique power-train) although there
have been some privately built (partial) recreations, most using some variation
of the contemporary Ford Flathead V8 including the 2.2 litre (136 cubic inch) version
which was used in Europe or the later 2.4 litre (144 cubic inch) unit built by
Ford’s French operation (the tooling for which was sold to Simca which, in
small volumes, offered V8 cars between 1954-1961.
Daimler SP250 (1959-1964). Citroën’s double chevron remains their corporate emblem even though they no longer produce interesting or innovative machinery, their range in recent decades dreary and derivative. Many others however use chevrons and inverted chevrons from time to time, sometimes as part of emblems as Cadillac has done and sometimes as a decoration. Quite what the designers thought a chevron added to the Daimler SP250’s catfish-like face isn’t recorded but opinion seems to remain divided because some owners appear to have removed the embellishment. Daimler didn't take advantage of the chevron to add an "8" either, even though that the time their marvelous little hemi-head 2.5 litre (155 cubic inch) V8 was a unique selling point. They may have thought the splendid exhaust note was a sufficient advertisement.
Not all exhaust notes were as pleasing as those emitted by the Daimler V8s and for some years Boeing produced passenger airliners with
chevrons cut into the engine nacelles, a trick which reduced the blast noise by
up to 15 decibels on the ground and in the forward cabin, the engineers
referring to this as “fan-tone” adjustment.
Boeing defined and patented the technology as part of its second Quiet
Technology Demonstrator (QTD2) program in 2005 and it was adopted (regardless
of whether the installed engine was supplied by General Electric, Rolls-Royce, Pratt
& Whitney or CFM) for the 787 Dreamliner, 737 MAX aircraft and even the
747-8, the last generation of the old workhorse. One benefit of a lower fan-tone was that
Boeing was able to reduce the mass of sound deadening fitted to the fuselage by
some 600 lbs (272 kg), something which made a measurable difference to the rate
of fuel burn. The QTD2 programme was
conducted in conjunction with General Electric and the US National Aeronautics
and Space Administration (NASA), using a Boeing 777-300ER as a benchmark
device, a notable choice given it was already the quietest in its class.
Curiously,
given they were dealing with the same physics Airbus never used the chevrons on
the nacelles of their airplanes and according to them, Boeing’s patent had no
effect on their decision. Airbus say
they detected no advantages when testing the chevrons but there was a penalty
because fuel consumption increased.
Instead, Airbus developed what they call a “zero splice” acoustic inner
barrel to lower the fan-tone, the combination of new-generation insulation materials
and the zero-splice’s “high-bypass” technology achieving a similar outcome,
without the additional weight and fuel burn induced by the chevrons. Boeing too has recently announced development
of the chevrons would not continue and despite the early publicity shots of the
777X being built with the chevrons, the production versions have appeared without
them. That attracted some comment and
Boeing released a statement which indicated the change was part of normal
product development and that while the chevrons were at the time a way to
achieve noise reduction, ongoing research has found a method which achieves
that without the associated costs in drag, weight and thus fuel burn. The essence of the new system appears to be the
application of a honeycomb acoustic treatment in strategic areas of the exhaust
ducting, the drilling of thousands of holes in the composite skin to disperse
and capture noise in the core. It’s
noted however chevrons, for many reasons, remain an essential part of many
internal components in jet engines, as they’ve been since the early days of the
technology in the 1930s.
