en-academic.com
Open in
urlscan Pro
2a01:4f9:c01e:78::1
Public Scan
Submitted URL: http://en.academic.ru/dic.nsf/enwiki/334115
Effective URL: https://en-academic.com/dic.nsf/enwiki/334115
Submission: On May 13 via api from US — Scanned from FI
Effective URL: https://en-academic.com/dic.nsf/enwiki/334115
Submission: On May 13 via api from US — Scanned from FI
Form analysis 1 forms found in the DOM
Name: formSearch — GET /searchall.php
<form action="/searchall.php" method="get" name="formSearch">
<table>
<tbody>
<tr>
<td id="td-search">
<input type="text" name="SWord" id="search-query" required="" value="" title="Enter text to search in dictionaries and encyclopedias" placeholder="Enter text to search in dictionaries and encyclopedias" autocomplete="off">
<div class="translate-lang">
<select name="from" id="translateFrom">
<option value="xx">Все языки</option>
<option value="ru">Русский</option>
<option value="en" selected="">Английский</option>
<option value="es">Испанский</option>
<option disabled="">────────</option>
<option value="ak">Akan</option>
<option value="sq">Albanian</option>
<option value="gw">Alsatian</option>
<option value="al">Altaic</option>
<option value="ar">Arabic</option>
<option value="an">Aragonese</option>
<option value="hy">Armenian</option>
<option value="rp">Aromanian</option>
<option value="at">Asturian</option>
<option value="ay">Aymara</option>
<option value="az">Azerbaijani</option>
<option value="bb">Bagobo</option>
<option value="ba">Bashkir</option>
<option value="eu">Basque</option>
<option value="be">Belarusian</option>
<option value="bg">Bulgarian</option>
<option value="bu">Buryat</option>
<option value="ca">Catalan</option>
<option value="ce">Chechen</option>
<option value="ck">Cherokee</option>
<option value="cn">Cheyenne</option>
<option value="zh">Chinese</option>
<option value="cv">Chuvash</option>
<option value="ke">Circassian</option>
<option value="cr">Cree</option>
<option value="ct">Crimean Tatar language</option>
<option value="hr">Croatian</option>
<option value="cs">Czech</option>
<option value="da">Danish</option>
<option value="dl">Dolgan</option>
<option value="nl">Dutch</option>
<option value="mv">Erzya</option>
<option value="eo">Esperanto</option>
<option value="et">Estonian</option>
<option value="ev">Evenki</option>
<option value="fo">Faroese</option>
<option value="fi">Finnish</option>
<option value="fr">French</option>
<option value="ka">Georgian</option>
<option value="de">German</option>
<option value="el">Greek</option>
<option value="gn">Guaraní</option>
<option value="ht">Haitian</option>
<option value="he">Hebrew</option>
<option value="hi">Hindi</option>
<option value="hs">Hornjoserbska</option>
<option value="hu">Hungarian</option>
<option value="is">Icelandic</option>
<option value="uu">Idioma urrumano</option>
<option value="id">Indonesian</option>
<option value="in">Ingush</option>
<option value="ik">Inupiaq</option>
<option value="ga">Irish</option>
<option value="it">Italian</option>
<option value="ja">Japanese</option>
<option value="kb">Kabyle</option>
<option value="kc">Karachay</option>
<option value="kk">Kazakh</option>
<option value="km">Khmer</option>
<option value="go">Klingon</option>
<option value="kv">Komi</option>
<option value="mm">Komi</option>
<option value="ko">Korean</option>
<option value="kp">Kumyk</option>
<option value="ku">Kurdish</option>
<option value="ky">Kyrgyz</option>
<option value="ld">Ladino</option>
<option value="la">Latin</option>
<option value="lv">Latvian</option>
<option value="ln">Lingala</option>
<option value="lt">Lithuanian</option>
<option value="jb">Lojban</option>
<option value="lb">Luxembourgish</option>
<option value="mk">Macedonian</option>
<option value="ms">Malay</option>
<option value="ma">Manchu</option>
<option value="mi">Māori</option>
<option value="mj">Mari</option>
<option value="mu">Maya</option>
<option value="mf">Moksha</option>
<option value="mn">Mongolian</option>
<option value="mc">Mycenaean</option>
<option value="nu">Nahuatl</option>
<option value="og">Nogai</option>
<option value="se">Northern Sami</option>
<option value="no">Norwegian</option>
<option value="cu">Old Church Slavonic</option>
<option value="pr">Old Russian</option>
<option value="oa">Orok</option>
<option value="os">Ossetian</option>
<option value="ot">Ottoman Turkish</option>
<option value="pi">Pāli</option>
<option value="pa">Panjabi</option>
<option value="pm">Papiamento</option>
<option value="fa">Persian</option>
<option value="pl">Polish</option>
<option value="pt">Portuguese</option>
<option value="qu">Quechua</option>
<option value="qy">Quenya</option>
<option value="ro">Romanian, Moldavian</option>
<option value="sa">Sanskrit</option>
<option value="gd">Scottish Gaelic</option>
<option value="sr">Serbian</option>
<option value="cj">Shor</option>
<option value="sz">Silesian</option>
<option value="sk">Slovak</option>
<option value="sl">Slovene</option>
<option value="sx">Sumerian</option>
<option value="sw">Swahili</option>
<option value="sv">Swedish</option>
<option value="tl">Tagalog</option>
<option value="tg">Tajik</option>
<option value="tt">Tatar</option>
<option value="th">Thai</option>
<option value="bo">Tibetan Standard</option>
<option value="tf">Tofalar</option>
<option value="tr">Turkish</option>
<option value="tk">Turkmen</option>
<option value="tv">Tuvan</option>
<option value="tw">Twi</option>
<option value="ud">Udmurt</option>
<option value="ug">Uighur</option>
<option value="uk">Ukrainian</option>
<option value="ur">Urdu</option>
<option value="uz">Uzbek</option>
<option value="vp">Veps</option>
<option value="vi">Vietnamese</option>
<option value="wr">Waray</option>
<option value="cy">Welsh</option>
<option value="sh">Yakut</option>
<option value="yi">Yiddish</option>
<option value="yo">Yoruba</option>
<option value="ya">Yupik</option>
</select>
</div>
<div id="translate-arrow"><a> </a></div>
<div class="translate-lang">
<select name="to" id="translateOf">
<option value="xx" selected="">Все языки</option>
<option value="ru">Русский</option>
<option value="en">Английский</option>
<option value="es">Испанский</option>
<option disabled="">────────</option>
<option value="af">Afrikaans</option>
<option value="sq">Albanian</option>
<option value="ar">Arabic</option>
<option value="hy">Armenian</option>
<option value="az">Azerbaijani</option>
<option value="eu">Basque</option>
<option value="bg">Bulgarian</option>
<option value="ca">Catalan</option>
<option value="ch">Chamorro</option>
<option value="ck">Cherokee</option>
<option value="zh">Chinese</option>
<option value="cv">Chuvash</option>
<option value="hr">Croatian</option>
<option value="cs">Czech</option>
<option value="da">Danish</option>
<option value="nl">Dutch</option>
<option value="mv">Erzya</option>
<option value="et">Estonian</option>
<option value="fo">Faroese</option>
<option value="fi">Finnish</option>
<option value="fr">French</option>
<option value="ka">Georgian</option>
<option value="de">German</option>
<option value="el">Greek</option>
<option value="ht">Haitian</option>
<option value="he">Hebrew</option>
<option value="hi">Hindi</option>
<option value="hu">Hungarian</option>
<option value="is">Icelandic</option>
<option value="id">Indonesian</option>
<option value="ga">Irish</option>
<option value="it">Italian</option>
<option value="ja">Japanese</option>
<option value="kk">Kazakh</option>
<option value="go">Klingon</option>
<option value="ko">Korean</option>
<option value="ku">Kurdish</option>
<option value="la">Latin</option>
<option value="lv">Latvian</option>
<option value="lt">Lithuanian</option>
<option value="mk">Macedonian</option>
<option value="ms">Malay</option>
<option value="mt">Maltese</option>
<option value="mi">Māori</option>
<option value="mj">Mari</option>
<option value="mf">Moksha</option>
<option value="mn">Mongolian</option>
<option value="no">Norwegian</option>
<option value="cu">Old Church Slavonic</option>
<option value="pr">Old Russian</option>
<option value="pi">Pāli</option>
<option value="pm">Papiamento</option>
<option value="fa">Persian</option>
<option value="pl">Polish</option>
<option value="pt">Portuguese</option>
<option value="qy">Quenya</option>
<option value="ro">Romanian, Moldavian</option>
<option value="sr">Serbian</option>
<option value="sk">Slovak</option>
<option value="sl">Slovene</option>
<option value="sw">Swahili</option>
<option value="sv">Swedish</option>
<option value="tl">Tagalog</option>
<option value="ta">Tamil</option>
<option value="tt">Tatar</option>
<option value="th">Thai</option>
<option value="tr">Turkish</option>
<option value="ud">Udmurt</option>
<option value="ug">Uighur</option>
<option value="uk">Ukrainian</option>
<option value="ur">Urdu</option>
<option value="vi">Vietnamese</option>
<option value="yo">Yoruba</option>
</select>
</div>
<input type="hidden" name="did" id="did-field" value="enwiki">
<input type="hidden" id="search-type" name="stype" value="">
</td>
<td>
<button id="search-button">Search!</button>
</td>
</tr>
</tbody>
</table>
</form>Text Content
en-academic.com
* EN
* RU
* DE
* ES
* FR
* Remember this site
* Embed dictionaries into your website
ACADEMIC DICTIONARIES AND ENCYCLOPEDIAS
Все
языкиРусскийАнглийскийИспанский────────AkanAlbanianAlsatianAltaicArabicAragoneseArmenianAromanianAsturianAymaraAzerbaijaniBagoboBashkirBasqueBelarusianBulgarianBuryatCatalanChechenCherokeeCheyenneChineseChuvashCircassianCreeCrimean
Tatar
languageCroatianCzechDanishDolganDutchErzyaEsperantoEstonianEvenkiFaroeseFinnishFrenchGeorgianGermanGreekGuaraníHaitianHebrewHindiHornjoserbskaHungarianIcelandicIdioma
urrumanoIndonesianIngushInupiaqIrishItalianJapaneseKabyleKarachayKazakhKhmerKlingonKomiKomiKoreanKumykKurdishKyrgyzLadinoLatinLatvianLingalaLithuanianLojbanLuxembourgishMacedonianMalayManchuMāoriMariMayaMokshaMongolianMycenaeanNahuatlNogaiNorthern
SamiNorwegianOld Church SlavonicOld RussianOrokOssetianOttoman
TurkishPāliPanjabiPapiamentoPersianPolishPortugueseQuechuaQuenyaRomanian,
MoldavianSanskritScottish
GaelicSerbianShorSilesianSlovakSloveneSumerianSwahiliSwedishTagalogTajikTatarThaiTibetan
StandardTofalarTurkishTurkmenTuvanTwiUdmurtUighurUkrainianUrduUzbekVepsVietnameseWarayWelshYakutYiddishYorubaYupik
Все
языкиРусскийАнглийскийИспанский────────AfrikaansAlbanianArabicArmenianAzerbaijaniBasqueBulgarianCatalanChamorroCherokeeChineseChuvashCroatianCzechDanishDutchErzyaEstonianFaroeseFinnishFrenchGeorgianGermanGreekHaitianHebrewHindiHungarianIcelandicIndonesianIrishItalianJapaneseKazakhKlingonKoreanKurdishLatinLatvianLithuanianMacedonianMalayMalteseMāoriMariMokshaMongolianNorwegianOld
Church SlavonicOld RussianPāliPapiamentoPersianPolishPortugueseQuenyaRomanian,
MoldavianSerbianSlovakSloveneSwahiliSwedishTagalogTamilTatarThaiTurkishUdmurtUighurUkrainianUrduVietnameseYoruba
Search!
* Wikipedia
* Interpretations
WIKIPEDIA
MANUAL TRANSMISSION
*
*
*
*
*
*
*
*
Manual transmission
Transmission types Manual
* Sequential manual
* Non-synchronous
* Preselector
Automatic
* Manumatic
Semi-automatic
* Electrohydraulic
* Dual clutch
* Saxomat
Continuously variable Bicycle gearing
* Derailleur gears
* Hub gears
v · d · e
A floor-mounted gear shift lever in a modern passenger car with a manual
transmission
A manual transmission, also known as a manual gearbox or standard transmission
(informally, a manual; standard, straight shift; stick (shift), (US); or
straight drive) is a type of transmission used in motor vehicle applications. It
generally uses a driver-operated clutch, typically operated by a foot pedal
(automobile) or hand lever (motorcycle), for regulating torque transfer from the
internal combustion engine to the transmission, and a gear stick, either
operated by foot (as on a motorcycle) or by hand (as in an automobile).
A conventional manual transmission is frequently the base equipment in a car;
other options include automated transmissions such as an automatic transmission
(often a manumatic), a semi-automatic transmission, or a continuously variable
transmission (CVT).
CONTENTS
* 1 Overview
* 2 Unsynchronized transmission
* 3 Synchronized transmission
* 4 Internals
* 4.1 Shafts
* 4.2 Dog clutch
* 4.3 Synchromesh
* 4.4 Reverse
* 4.5 Design variations
* 4.5.1 Gear variety
* 4.5.2 External overdrive
* 4.5.3 Shaft and gear configuration
* 5 Clutch
* 6 Gear shift types
* 6.1 Floor-mounted shifter
* 6.1.1 "Four on the floor"
* 6.2 Column-mounted shifter
* 6.3 Console-mounted shifter
* 6.4 Sequential manual
* 6.5 Semi-manual
* 7 Benefits
* 7.1 Fuel economy
* 7.2 Longevity and cost
* 7.3 Performance and control
* 7.4 Engine braking
* 8 Drawbacks
* 8.1 Complexity and learning curve
* 8.2 Shifting speed
* 8.3 Ease of use
* 8.4 Stopping on hills
* 9 Applications and popularity
* 10 Truck transmissions
* 11 Maintenance
* 12 See also
* 13 References
OVERVIEW
Manual transmissions often feature a driver-operated clutch and a movable gear
stick. Most automobile manual transmissions allow the driver to select any
forward gear ratio ("gear") at any time, but some, such as those commonly
mounted on motorcycles and some types of racing cars, only allow the driver to
select the next-higher or next-lower gear. This type of transmission is
sometimes called a sequential manual transmission. Sequential transmissions are
commonly used in auto racing for their ability to make quick shifts.[citation
needed]
Manual transmissions are characterized by gear ratios that are selectable by
locking selected gear pairs to the output shaft inside the transmission.
Conversely, most automatic transmissions feature epicyclic (planetary) gearing
controlled by brake bands and/or clutch packs to select gear ratio. Automatic
transmissions that allow the driver to manually select the current gear are
called Manumatics. A manual-style transmission operated by computer is often
called an automated transmission rather than an automatic.
Contemporary automobile manual transmissions typically use four to six forward
gears and one reverse gear, although automobile manual transmissions have been
built with as few as two and as many as eight gears. Transmission for heavy
trucks and other heavy equipment usually have at least 9 gears so the
transmission can offer both a wide range of gears and close gear ratios to keep
the engine running in the power band. Some heavy vehicle transmissions have
dozens of gears, but many are duplicates, introduced as an accident of combining
gear sets, or introduced to simplify shifting. Some manuals are referred to by
the number of forward gears they offer (e.g., 5-speed) as a way of
distinguishing between automatic or other available manual transmissions.
Similarly, a 5-speed automatic transmission is referred to as a "5-speed
automatic."
UNSYNCHRONIZED TRANSMISSION
Main article: Non-synchronous transmission
The earliest form of a manual transmission is thought to have been invented by
Louis-René Panhard and Emile Levassor in the late 19th century. This type of
transmission offered multiple gear ratios and, in most cases, reverse. The gears
were typically engaged by sliding them on their shafts (hence the phrase
shifting gears), which required a lot of careful timing and throttle
manipulation when shifting, so that the gears would be spinning at roughly the
same speed when engaged; otherwise, the teeth would refuse to mesh. These
transmissions are called sliding mesh transmissions or sometimes crash boxes,
because of the difficulty in changing gears and the loud grinding sound that
often accompanied. Newer manual transmissions on cars have all gears mesh at all
times and are referred to as constant-mesh transmissions, with "synchro-mesh"
being a further refinement of the constant mesh principle.
In both types, a particular gear combination can only be engaged when the two
parts to engage (either gears or clutches) are at the same speed. To shift to a
higher gear, the transmission is put in neutral and the engine allowed to slow
down until the transmission parts for the next gear are at a proper speed to
engage. The vehicle also slows while in neutral and that slows other
transmission parts, so the time in neutral depends on the grade, wind, and other
such factors. To shift to a lower gear, the transmission is put in neutral and
the throttle is used to speed up the engine and thus the relevant transmission
parts, to match speeds for engaging the next lower gear. For both upshifts and
downshifts, the clutch is released (engaged) while in neutral. Some drivers use
the clutch only for starting from a stop, and shifts are done without the
clutch. Other drivers will depress (disengage) the clutch, shift to neutral,
then engage the clutch momentarily to force transmission parts to match the
engine speed, then depress the clutch again to shift to the next gear, a process
called double clutching. Double clutching is easier to get smooth, as speeds
that are close but not quite matched need to speed up or slow down only
transmission parts, whereas with the clutch engaged to the engine, mismatched
speeds are fighting the rotational inertia and power of the engine.
Even though automobile and light truck transmissions are now almost universally
synchronised, transmissions for heavy trucks and machinery, motorcycles, and for
dedicated racing are usually not. Non-synchronized transmission designs are used
for several reasons. The friction material, such as brass, in synchronizers is
more prone to wear and breakage than gears, which are forged steel, and the
simplicity of the mechanism improves reliability and reduces cost. In addition,
the process of shifting a synchromesh transmission is slower than that of
shifting a non-synchromesh transmission. For racing of production-based
transmissions, sometimes half the teeth (or dogs) on the synchros are removed to
speed the shifting process, at the expense of greater wear.
Heavy duty trucks often use unsynchronized transmissions, though military trucks
usually have synchronized transmissions, allowing untrained personnel to operate
them in emergencies. In the United States, traffic safety rules refer to
non-synchronous transmissions in classes of larger commercial motor vehicles. In
Europe, heavy duty trucks use synchronized gearboxes as standard.
Similarly, most modern motorcycles use unsynchronized transmissions: their low
gear inertias and higher strengths mean that forcing the gears to alter speed is
not damaging, and the pedal operated selector on modern motorcycles is not
conducive to having the long shift time of a synchronized gearbox. Because of
this, it is necessary to synchronize gear speeds by blipping the throttle when
shifting into a lower gear on a motorcycle.
SYNCHRONIZED TRANSMISSION
Top and side view of a typical manual transmission, in this case a Ford
Toploader, used in cars with external floor shifters.
Most modern manual-transmission vehicles are fitted with a synchronized gear
box. Transmission gears are always in mesh and rotating, but gears on one shaft
can freely rotate or be locked to the shaft. The locking mechanism for a gear
consists of a collar (or dog collar) on the shaft which is able to slide
sideways so that teeth (or dogs) on its inner surface bridge two circular rings
with teeth on their outer circumference: one attached to the gear, one to the
shaft. When the rings are bridged by the collar, that particular gear is
rotationally locked to the shaft and determines the output speed of the
transmission. The gearshift lever manipulates the collars using a set of
linkages, so arranged so that one collar may be permitted to lock only one gear
at any one time; when "shifting gears", the locking collar from one gear is
disengaged before that of another is engaged. One collar often serves for two
gears; sliding in one direction selects one transmission speed, in the other
direction selects another.
In a synchromesh gearbox, to correctly match the speed of the gear to that of
the shaft as the gear is engaged the collar initially applies a force to a
cone-shaped brass clutch attached to the gear, which brings the speeds to match
prior to the collar locking into place. The collar is prevented from bridging
the locking rings when the speeds are mismatched by synchro rings (also called
blocker rings or baulk rings, the latter being spelled balk in the U.S.). The
synchro ring rotates slightly due to the frictional torque from the cone clutch.
In this position, the dog clutch is prevented from engaging. The brass clutch
ring gradually causes parts to spin at the same speed. When they do spin the
same speed, there is no more torque from the cone clutch and the dog clutch is
allowed to fall in to engagement. In a modern gearbox, the action of all of
these components is so smooth and fast it is hardly noticed.
The modern cone system was developed by Porsche and introduced in the 1952
Porsche 356; cone synchronisers were called Porsche-type for many years after
this. In the early 1950s, only the second-third shift was synchromesh in most
cars, requiring only a single synchro and a simple linkage; drivers' manuals in
cars suggested that if the driver needed to shift from second to first, it was
best to come to a complete stop then shift into first and start up again. With
continuing sophistication of mechanical development, fully synchromesh
transmissions with three speeds, then four, and then five, became universal by
the 1980s. Many modern manual transmission cars, especially sports cars, now
offer six speeds.
Reverse gear is usually not synchromesh, as there is only one reverse gear in
the normal automotive transmission and changing gears into reverse while moving
is not required. Among the cars that have synchromesh in reverse are the
1995-2000 Ford Contour and Mercury Mystique, '00-'05 Chevrolet Cavalier,
Mercedes 190 2.3-16, the V6 equipped Alfa Romeo GTV/Spider (916),[1] certain
Chrysler, Jeep, and GM products which use the New Venture NV3500 and NV3550
units, the European Ford Sierra and Granada/Scorpio equipped with the MT75
gearbox, the Volvo 850, and almost all Lamborghinis and BMWs.
INTERNALS
SHAFTS
Like other transmissions, a manual transmission has several shafts with various
gears and other components attached to them. Typically, a rear-wheel-drive
transmission has three shafts: an input shaft, a countershaft and an output
shaft. The countershaft is sometimes called a layshaft.
In a rear-wheel-drive transmission, the input and output shaft lie along the
same line, and may in fact be combined into a single shaft within the
transmission. This single shaft is called a mainshaft. The input and output ends
of this combined shaft rotate independently, at different speeds, which is
possible because one piece slides into a hollow bore in the other piece, where
it is supported by a bearing. Sometimes the term mainshaft refers to just the
input shaft or just the output shaft, rather than the entire assembly.
In many transmissions the input and output components of the mainshaft can be
locked together to create a 1:1 gear ratio, causing the power flow to bypass the
countershaft. The mainshaft then behaves like a single, solid shaft: a situation
referred to as direct drive.
Even in transmissions that do not feature direct drive, it's an advantage for
the input and output to lie along the same line, because this reduces the amount
of torsion that the transmission case has to bear.
Under one possible design, the transmission's input shaft has just one pinion
gear, which drives the countershaft. Along the countershaft are mounted gears of
various sizes, which rotate when the input shaft rotates. These gears correspond
to the forward speeds and reverse. Each of the forward gears on the countershaft
is permanently meshed with a corresponding gear on the output shaft. However,
these driven gears are not rigidly attached to the output shaft: although the
shaft runs through them, they spin independently of it, which is made possible
by bearings in their hubs. Reverse is typically implemented differently, see the
section on Reverse.
Most front-wheel-drive transmissions for transverse engine mounting are designed
differently. For one thing, they have an integral final drive and differential.
For another, they usually have only two shafts; input and countershaft,
sometimes called input and output. The input shaft runs the whole length of the
gearbox, and there is no separate input pinion. At the end of the second
(counter/output) shaft is a pinion gear that mates with the ring gear on the
differential.
Front-wheel and rear-wheel-drive transmissions operate similarly. When the
transmission is put in neutral and the clutch is disengaged, the input shaft,
clutch disk and countershaft can continue to rotate under their own inertia. In
this state, the engine, the input shaft and clutch, and the output shaft all
rotate independently.
DOG CLUTCH
Dog clutches. The gear-like teeth ("dogs", right-side images) engage and
disengage with each other.
Among many different types of clutches, a dog clutch provides non-slip coupling
of two rotating members. It is not at all suited to intentional slipping, in
contrast with the foot-operated friction clutch of a manual-transmission car.
The gear selector does not engage or disengage the actual gear teeth which are
permanently meshed. Rather, the action of the gear selector is to lock one of
the freely spinning gears to the shaft that runs through its hub. The shaft then
spins together with that gear. The output shaft's speed relative to the
countershaft is determined by the ratio of the two gears: the one permanently
attached to the countershaft, and that gear's mate which is now locked to the
output shaft.
Locking the output shaft with a gear is achieved by means of a dog clutch
selector. The dog clutch is a sliding selector mechanism which is splined to the
output shaft, meaning that its hub has teeth that fit into slots (splines) on
the shaft, forcing that shaft to rotate with it. However, the splines allow the
selector to move back and forth on the shaft, which happens when it is pushed by
a selector fork that is linked to the gear lever. The fork does not rotate, so
it is attached to a collar bearing on the selector. The selector is typically
symmetric: it slides between two gears and has a synchromesh and teeth on each
side in order to lock either gear to the shaft.
SYNCHROMESH
Synchronizer rings
If the teeth, the so-called dog teeth, make contact with the gear, but the two
parts are spinning at different speeds, the teeth will fail to engage and a loud
grinding sound will be heard as they clatter together. For this reason, a modern
dog clutch in an automobile has a synchronizer mechanism or synchromesh, which
consists of a cone clutch and blocking ring. Before the teeth can engage, the
cone clutch engages first which brings the selector and gear to the same speed
using friction. Moreover, until synchronization occurs, the teeth are prevented
from making contact, because further motion of the selector is prevented by a
blocker (or baulk) ring. When synchronization occurs, friction on the blocker
ring is relieved and it twists slightly, bringing into alignment certain grooves
and notches that allow further passage of the selector which brings the teeth
together. Of course, the exact design of the synchronizer varies from
manufacturer to manufacturer.
The synchronizer[2] has to overcome the momentum of the entire input shaft and
clutch disk when it is changing shaft rpm to match the new gear ratio. It can be
abused by exposure to the momentum and power of the engine itself, which is what
happens when attempts are made to select a gear without fully disengaging the
clutch. This causes extra wear on the rings and sleeves, reducing their service
life. When an experimenting driver tries to "match the revs" on a synchronized
transmission and force it into gear without using the clutch, the synchronizer
will make up for any discrepancy in RPM. The success in engaging the gear
without clutching can deceive the driver into thinking that the RPM of the
layshaft and transmission were actually exactly matched. Nevertheless,
approximate rev. matching with clutching can decrease the general change between
layshaft and transmission and decrease synchro wear.
REVERSE
The previous discussion normally applies only to the forward gears. The
implementation of the reverse gear is usually different, implemented in the
following way to reduce the cost of the transmission. Reverse is also a pair of
gears: one gear on the countershaft and one on the output shaft. However,
whereas all the forward gears are always meshed together, there is a gap between
the reverse gears. Moreover, they are both attached to their shafts: neither one
rotates freely about the shaft. What happens when reverse is selected is that a
small gear, called an idler gear or reverse idler, is slid between them. The
idler has teeth which mesh with both gears, and thus it couples these gears
together and reverses the direction of rotation without changing the gear ratio.
In other words, when reverse gear is selected, it is in fact actual gear teeth
that are being meshed, with no aid from a synchronization mechanism. For this
reason, the output shaft must not be rotating when reverse is selected: the car
must be stopped. In order that reverse can be selected without grinding even if
the input shaft is spinning inertially, there may be a mechanism to stop the
input shaft from spinning. The driver brings the vehicle to a stop, and selects
reverse. As that selection is made, some mechanism in the transmission stops the
input shaft. Both gears are stopped and the idler can be inserted between them.
There is a clear description of such a mechanism in the Honda Civic 1996-1998
Service Manual, which refers to it as a "noise reduction system":
> Whenever the clutch pedal is depressed to shift into reverse, the mainshaft
> continues to rotate because of its inertia. The resulting speed difference
> between mainshaft and reverse idler gear produces gear noise [grinding]. The
> reverse gear noise reduction system employs a cam plate which was added to the
> reverse shift holder. When shifting into reverse, the 5th/reverse shift piece,
> connected to the shift lever, rotates the cam plate. This causes the 5th
> synchro set to stop the rotating mainshaft.
> —(13-4)
A reverse gear implemented this way makes a loud whining sound, which is not
normally heard in the forward gears. The teeth on the forward gears of most
consumer automobiles are helically cut. When helical gears rotate, there is
constant contact between gears, which results in quiet operation. In spite of
all forward gears being always meshed, they do not make a sound that can be
easily heard above the engine noise. By contrast, most reverse gears are spur
gears, meaning that they have straight teeth, in order to allow for the sliding
engagement of the idler, which is difficult with helical gears. The teeth of
spur gears clatter together when the gears spin, generating a characteristic
whine.
It is clear that the spur gear design of reverse gear represents some
compromises (less robust, unsynchronized engagement and loud noise) which are
acceptable due to the relatively small amount of driving that takes place in
reverse. The gearbox of the classic SAAB 900 is a notable example of a gearbox
with a helical reverse gear engaged in the same unsynchronized manner as the
spur gears described above. Its strange design allows reverse to share cogs with
first gear, and is exceptionally quiet, but results in difficult engagement and
unreliable operation. However, many modern transmissions now include a reverse
gear synchronizer and helical gearing.
DESIGN VARIATIONS
GEAR VARIETY
Older cars were generally equipped with 3 or 4-speed transmissions for high
performance models and 5-speeds for the most sophisticated of automobiles; in
the 1970s, 5-speed transmissions began to appear in low priced mass market
automobiles and even compact pickup trucks, pioneered by Toyota (who advertised
the fact by giving each model the suffix SR5 as it acquired the fifth speed).
6-speed transmissions started to emerge in high performance vehicles in the
early 1990s. In three or four speed transmissions, in most cases, the topmost
gear is direct (i.e. a 1:1 ratio). For five-speed or higher transmissions, the
highest gear is usually an overdrive gear, with a ratio of less than 1:1.
Today, mass market automotive manual transmissions are nearly all 6-speeds with
5-speed transmissions available in smaller vehicles and entry-level
models.[citation needed] Recently Porsche announced the next-generation 911 will
be available with a 7-speed manual transmission, the first of its kind for a
normal automobile[3][4] with the first six gear ratios the same as the 6-speed
gearbox and the 7th gear being of a higher ratio.
Initially the Tesla Roadster was intended to have a purpose built two-speed
manual transmission[5] but this gearbox proved to be problematic and was later
replaced with a fixed-ratio transmission.
EXTERNAL OVERDRIVE
On earlier models with three or four forward speeds, the lack of an overdrive
ratio for relaxed and fuel-efficient highway cruising was often filled by
incorporating a separate overdrive unit in the rear housing of the transmission.
This unit was separately actuated by a knob or button, often incorporated into
the gearshift knob. However, in the 20th century USA, Borg-Warner overdrives
were quite common.[6][7](scroll down to "Overdrive in North America") These were
engaged simply by temporarily lifting the driver's foot from the gas pedal (if
the car was traveling above 28 mph). To leave overdrive, the driver would simply
"floor" the gas pedal briefly. The overdrive knob disabled overdrive for unusual
situations; it was rarely disabled.
SHAFT AND GEAR CONFIGURATION
On a conventional rear-drive transmission, there are three basic shafts; the
input, the output, and the countershaft. The input and output together are
called the mainshaft, since they are joined inside the transmission so they
appear to be a single shaft, although they rotate totally independently of each
other. The input length of this shaft is much shorter than the output shaft.
Parallel to the mainshaft is the countershaft. There are a number of gears fixed
along the countershaft, and matching gears along the output shaft, although
these are not fixed, and rotate independently of the output shaft. There are
sliding dog collars, or dog clutches, between the gears on the output shaft, and
to engage a gear to the shaft, the collar slides into the space between the
shaft and the inside space of the gear, thus rotating the shaft as well. One
collar is usually mounted between two gears, and slides both ways to engage one
or the other gears, so on a four speed there would be two collars. A front-drive
transmission is basically the same, but may be simplified. There often are two
shafts, the input and the output, but depending on the direction of rotation of
the engine, three may be required. Rather than the input shaft driving the
countershaft with a pinion gear, the input shaft takes over the countershaft's
job, and the output shaft runs parallel to it. The gears are positioned and
engaged just as they are on the countershaft and output shaft of a rear-drive.
This merely eliminates one major component, the pinion gear. Part of the reason
that the input and output are in-line on a rear drive unit is to relieve
torsional stress on the transmission and mountings, but this isn't an issue in a
front-drive as the gearbox is integrated into the transaxle.
The basic process is not universal. The fixed and free gears can be mounted on
either the input or output shaft, or both.
The distribution of the shifters is also a matter of design; it need not be the
case that all of the free-rotating gears with selectors are on one shaft, and
the permanently splined gears on the other. For instance a five speed
transmission might have the first-to-second selectors on the countershaft, but
the third-to-fourth selector and the fifth selector on the mainshaft, which is
the configuration in the 1998 Honda Civic. This means that when the car is
stopped and idling in neutral with the clutch engaged and the input shaft
spinning, the third, fourth and fifth gear pairs do not rotate.
In some transmission designs (Volvo 850 and V/S70 series, for example) there are
actually two countershafts, both driving an output pinion meshing with the
front-wheel-drive transaxle's ring gear. This allows the transmission designer
to make the transmission narrower, since each countershaft need only be half as
long as a traditional countershaft with four gears and two shifters.
CLUTCH
Main article: Clutch
In all vehicles using a transmission (virtually all modern vehicles), a coupling
device is used to separate the engine and transmission when necessary. This is
because an internal-combustion engine has to continue to run when it's in use;
it essentially can't be stopped when the wheels stop, although a few modern cars
with automatic transmissions shut off the engine at a stoplight. The clutch
accomplishes this in manual transmissions. Without it, the engine and tires
would at all times be inextricably linked, and any time the vehicle stopped the
engine would stall. Without the clutch, changing gears would be very difficult,
even with the vehicle moving already: deselecting a gear while the transmission
is under load requires considerable force (and risks significant damage). As
well, selecting a gear requires the revolution speed of the engine to be held at
a very precise value which depends on the vehicle speed and desired gear – the
speeds inside the transmission have to match. In a car the clutch is usually
operated by a pedal; on a motorcycle, a lever on the left handlebar serves the
purpose.
* When the clutch pedal is fully depressed, the clutch is fully disengaged, and
no torque is transferred from the engine to the transmission (and by
extension to the drive wheels). In this uncoupled state it is possible to
select gears or to stop the car without stopping the engine.
* When the clutch pedal is fully released, the clutch is fully engaged and all
of the engine's torque is transferred. In this coupled state, the clutch does
not slip, but rather acts as rigid coupling to transmit power to gearbox.
* Between these extremes of engagement and disengagement the clutch slips to
varying degrees. When slipping it still transmits torque despite the
difference in speeds between the engine crankshaft and the transmission
input. Because this torque is transmitted by means of friction rather than
direct mechanical contact, considerable power is wasted as heat (which is
dissipated by the clutch). Properly applied, slip allows the vehicle to be
started from a standstill, and when it is already moving, allows the engine
rotation to gradually adjust to a newly selected gear ratio.
* Learning to use the clutch efficiently requires the development of muscle
memory and a level of coordination.
* A rider of a highly tuned motocross or off-road motorcycle may "hit" or "fan"
the clutch when exiting corners to assist the engine in revving to the point
where it delivers the most power.
The clutch is typically disengaged by a thrust bearing that makes contact with
pressure petals on the clutch ring plate and pushes them inward to release the
clutch pad friction. Normally the bearing remains retracted away from the petals
and does not spin. However, the bearing can be "burned out" and damaged by using
the clutch pedal as a foot rest, which causes the bearing to spin continuously
from touching the clutch plates.
GEAR SHIFT TYPES
FLOOR-MOUNTED SHIFTER
Main article: Gear stick
A gear stick
In most vehicles with manual transmission, gears are selected by manipulating a
lever called a gear stick, shift stick, gearshift, gear lever, gear selector, or
shifter connected to the transmission via linkage or cables and mounted on the
floor, dashboard, or steering column. Moving the lever forward, backward, left,
and right into specific positions selects particular gears.
A sample layout of a four-speed transmission is shown below. N marks neutral,
the position wherein no gears are engaged and the engine is decoupled from the
vehicle's drive wheels. The entire horizontal line is a neutral position, though
the shifter is usually spring-loaded so it will return to the centre of the N
position if not moved to another gear. The R marks reverse, the gear position
used for moving the vehicle rearward.
This layout is called the shift pattern. Because of the shift quadrants, the
basic arrangement is often called an H-pattern. The shift pattern is usually
molded or printed on or near the gear knob. While the layout for gears one
through four is nearly universal, the location of reverse is not. Depending on
the particular transmission design, reverse may be located at the upper left
extent of the shift pattern, at the lower left, at the lower right, or at the
upper right. There is often a mechanism that allows selection of reverse only
from the neutral position, or a reverse lockout that must be released by
depressing the spring-loaded gear knob or lifting a spring-loaded collar on the
shift stick, to reduce the likelihood of the driver inadvertently selecting
reverse.
"FOUR ON THE FLOOR"
Four-speed transmissions with floor-mounted shifters were sometimes referred to
as "four on the floor" during the period when the steering column was the more
common shifter location. The latter, often being the standard non-performance
transmission, usually had only three forward speeds and was referred to as
"three on the tree."
Most front-engined, rear-wheel drive cars have a transmission that sits between
the driver and the front passenger seat. Floor-mounted shifters are often
connected directly to the transmission. Front-wheel drive and rear-engined cars
often require a mechanical linkage to connect the shifter to the transmission.
COLUMN-MOUNTED SHIFTER
Column mounted gear shift lever in a Saab 96
Some cars have a gear lever mounted on the steering column of the car. A 3-speed
column shifter, which came to be popularly known as a "Three on the Tree", began
appearing in America in the late 1930s and became common during the 1940s and
'50s. If a U.S. vehicle was equipped with overdrive, it was very likely to be a
Borg-Warner type, operated by briefly backing off the gas when above 28 mph to
enable, and momentarily flooring the gas pedal to return to normal gear. The
control simply disables overdrive for such situations as parking on a hill or
preventing unwanted shifting into overdrive.[8](Scroll down to "Overdrive In
North America".)
Later,[vague] European and Japanese models began to have 4-speed column shifters
with this shift pattern:
The column-mounted manual shifter disappeared in North America by the mid 1980s,
last appearing in the 1987 Chevrolet pickup truck. Outside North America, the
column mounted shifter remained in production. All Toyota Crown and Nissan
Cedric taxis in Hong Kong had the 4-speed column shift until 1999 when automatic
transmissions were first offered. Since the late 1980s or early 1990s,[vague] a
5-speed column shifter has been offered in some vans sold in Asia and Europe,
such as Toyota Hiace and Mitsubishi L400.
Column shifters are mechanically similar to floor shifters, although shifting
occurs in a vertical plane instead of a horizontal one. Because the shifter is
further away from the transmission, and the movements at the shifter and at the
transmission are in different planes, column shifters require more complicated
linkage than floor shifters. Advantages of a column shifter are the ability to
switch between the two most commonly used gears—second and third—without letting
go of the steering wheel, and the lack of interference with passenger seating
space in vehicles equipped with a bench seat.
CONSOLE-MOUNTED SHIFTER
Newer small cars and MPVs, like the Suzuki MR Wagon, the Fiat Multipla, the
Toyota Matrix, the Pontiac Vibe, the Chrysler RT platform cars and the Honda
Civic Si EP3 may feature a manual or automatic transmission gear shifter located
on the vehicle's instrument panel. Console-mounted shifters are similar to
floor-mounted gear shifters in that most of the ones used in modern cars operate
on a horizontal plane and can be mounted to the vehicle's transmission in much
the same way a floor-mounted shifter can. However, because of the location of
the gear shifter in comparison to the locations of the column shifter and the
floor shifter, as well as the positioning of the shifter to the rest of the
controls on the panel often require that the gearshift be mounted in a space
that does not feature a lot of controls integral to the vehicle's operation or
frequently used controls, such as those for the car stereo or car air
conditioning, to help prevent accidental activation or driver confusion,
especially in right-hand drive cars.
More and more small cars and vans from manufacturers such as Suzuki, Honda, and
Volkswagen are featuring console shifters in that they free up space on the
floor for other car features such as storage compartments without requiring that
the gear shift be mounted on the steering column. Also, the basic location of
the gear shift in comparison to the column shifter makes console shifters easier
to operate than column shifters.
SEQUENTIAL MANUAL
Main article: Sequential manual transmission
Some transmissions do not allow the driver to arbitrarily select any gear.
Instead, the driver may only ever select the next-lowest or next-highest gear
ratio. Sequential transmissions often incorporate a synchro-less dog-clutch
engagement mechanism (instead of the synchromesh dog clutch common on H-pattern
automotive transmissions), in which case the clutch is only necessary when
selecting first or reverse gear from neutral, and most gear changes can be
performed without the clutch. However, sequential shifting and synchro-less
engagement are not inherently linked, though they often occur together due to
the environment(s) in which these transmissions are used, such as racing cars
and motorcycles.
Sequential transmissions are generally controlled by a forward-backward lever,
foot pedal, or set of paddles mounted behind the steering wheel. In some cases,
these are connected mechanically to the transmission. In many modern examples,
these controls are attached to sensors which instruct a transmission computer to
perform a shift—many of these systems can be switched into an automatic mode,
where the computer controls the timing of shifts, much like an automatic
transmission.
Motorcycles typically employ sequential transmissions, although the shift
pattern is modified slightly for safety reasons. In a motorcycle the gears are
usually shifted with the left foot pedal, the layout being this:
The gear shift lever on a 2003 Suzuki SV650S motorcycle.
6 - 5 - 4 - 3 - 2 N 1
The pedal goes one step–both up and down–from the center, before it reaches its
limit and has to be allowed to move back to the center position. Thus, changing
multiple gears in one direction is accomplished by repeatedly pumping the pedal,
either up or down. Although neutral is listed as being between first and second
gears for this type of transmission, it "feels" more like first and second gear
are just "further away" from each other than any other two sequential gears.
Because this can lead to difficulty in finding neutral for inexperienced riders
most motorcycles have a neutral indicator light on the instrument panel to help
find neutral. The reason neutral does not actually have its own spot in the
sequence is to make it quicker to shift from first to second when moving.
Neutral can be accidentally shifted into, though most high end, newer model
motorcycles have means of avoiding this.[citation needed] The reason for having
neutral between the first and second gears instead of at the bottom is that when
stopped, the rider can just click down repeatedly and know that they will end up
in first and not neutral. This allows a rider to quickly move his bike from a
standstill in an emergency situation. This may also help on a steep hill on
which high torque is required. It could be disadvantageous or even dangerous to
attempt to be in first without realizing it, then try for a lower gear, only to
get neutral.
On motorcycles used on race tracks, the shifting pattern is often reversed, that
is, the rider clicks down to upshift. This usage pattern increases the ground
clearance by placing the riders foot above the shift lever when the rider is
most likely to need it, namely when leaning over and exiting a tight turn.
The shift pattern for most underbone motorcycles with an automatic centrifugal
clutch is also modified for two key reasons - to enable the less-experienced
riders to shift the gears without problems of "finding" neutral, and also due to
the greater force needed to "lift" the gearshift lever (because the gearshift
pedal of an underbone motorcycle also operates the clutch). The gearshift lever
of an underbone motorcycle has two ends. The rider clicks down the front end
with the left toe all the way to the top gear and clicks down the rear end with
the heel all the way down to neutral. Some underbone models such as the Honda
Wave have a "rotary" shift pattern, which means that the rider can shift
directly to neutral from the top gear, but for safety reasons this is only
possible when the motorcycle is stationary. Some models also have gear position
indicators for all gear positions at the instrument panel.
SEMI-MANUAL
Some new transmissions (Alfa Romeo's Selespeed gearbox and BMW's Sequential
Manual Gearbox (SMG) for example) are conventional manual transmissions with a
computerized control mechanism. These transmissions feature independently
selectable gears but do not have a clutch pedal. Instead, the transmission
computer controls a servo which disengages the clutch when necessary.
These transmissions vary from sequential transmissions in that they still allow
nonsequential shifts: BMWs SMG system, for example, can shift from 6th gear
directly to 4th gear.
In the case of the early second generation Saab 900, a 'Sensonic' option was
available where gears were shifted with a conventional shifter, but the clutch
is controlled by a computer.
BENEFITS
FUEL ECONOMY
The manual transmission couples the engine to the transmission with a rigid
clutch instead of the torque converter on an automatic transmission or the
v-belt of a continuously variable transmission,[9] which slip by nature. Manual
transmissions also lack the parasitic power consumption of the automatic
transmission's hydraulic pump. Because of this, manual transmissions generally
offer better fuel economy than automatic or continuously variable transmissions;
however the disparity has been somewhat offset with the introduction of locking
torque converters on automatic transmissions.[10] Increased fuel economy with a
properly operated manual transmission vehicle versus an equivalent automatic
transmission vehicle can range from 5% to about 15% depending on driving
conditions and style of driving.[11] The lack of control over downshifting under
load in an automatic transmission, coupled with a typical vehicle engine's
greater efficiency under higher load, can enable additional fuel gains from a
manual transmission by allowing the operator to keep the engine performing under
a more efficient load/RPM combination. Also, manual transmissions do not require
active cooling and because they are, mechanically, much simpler than automatic
transmissions, they generally weigh less than comparable automatics, which can
improve economy in stop-and-go traffic.[10]
LONGEVITY AND COST
Because manual transmissions are mechanically simpler and have fewer moving
parts than automatic transmissions, they require less maintenance and are easier
to repair.[citation needed] This is one of the many reasons manual transmissions
are still offered today, and why the demand for them still has a place in the
market. The price of a new car with a manual transmission will often be lower
than the same car with an automatic transmission.[citation needed]
PERFORMANCE AND CONTROL
Manual transmissions generally offer a wider selection of gear ratios. Many
vehicles offer a 5-speed or 6-speed manual, whereas the automatic option would
typically be a 4-speed. This is generally due to the increased space available
inside a manual transmission compared with an automatic, since the latter
requires extra components for self-shifting, such as torque converters and
pumps. However, automatic transmissions are now adding more speeds as the
technology matures. ZF currently makes 7- and 8-speed automatic transmissions.
The increased number gears allows for better use of the engine's power band,
allowing increased fuel economy, by staying in the most fuel-efficient part of
the power band, or higher performance, by staying closer to the engine's peak
power.
Because the driver has more direct control over the car with a manual than with
an automatic, an experienced, knowledgeable driver who knows the correct
procedure for executing a driving maneuver, and wants the vehicle to realize his
or her intentions exactly and instantly, can perform actions difficult or
impossible with automatic transmissions. When starting forward, for example, the
driver can control how much torque goes to the tires, which is useful on
slippery surfaces such as ice, snow or mud. This can be done with clutch
finesse, or by starting in second gear instead of first. However, some automatic
transmissions, particularly those with tiptronic gear selectors, can be placed
in second gear for starting on slippery surfaces. An engine coupled with a
manual transmission can often be started by the method of push starting. This is
particularly useful if the starter is inoperable or defunct, or the battery has
drained below operable voltage. Similarly, a vehicle with a manual transmission
and no clutch/starter interlock switch can be moved, if necessary, by cranking
the starter while in gear. This is useful when the vehicle will not start but
must be immediately moved, e.g. off the road in the event of a breakdown, if the
vehicle has stalled on a railway crossing, or in extreme off-roading cases such
as an engine that has stalled in deep water.
ENGINE BRAKING
In contrast to most manual gearboxes, most automatic transmissions have a
free-wheel-clutch. This means that the engine does not slow down the car when
the driver steps off the throttle, also known as engine or compression braking.
This leads to more usage of the brakes in cars with automatic transmissions,
which can potentially overheat them in hilly or mountainous areas, causing
reduced braking ability and the potential for complete failure. However, the
automatic gearboxes in commodity Nissans and Hondas disable the free wheel
operation completely if the driver has selected a gear position other than "D" -
either "1", "2", or "D with overdrive off". This works by blocking the
free-wheel sprag using a multi-disk clutch called the "overrun clutch".
Similarly, many trucks have a "tow mode" that allows engine braking.
DRAWBACKS
COMPLEXITY AND LEARNING CURVE
There is a significant learning curve with a manual transmission, and the
smoothness and correct timing of gear shifts are wholly dependent on the
driver's experience and skill. Because the driver must develop a feel for
properly engaging the clutch, especially when starting forward on a steep road
or when parking on an incline, an inexperienced driver can easily stall the
engine, or cause the car to jerk and bounce abruptly, which is not only
uncomfortable, but could potentially be dangerous in an area with little room
for error. Additionally, if an inexperienced driver selects the wrong gear by
mistake, they can do damage to the engine and/or transmission. Selecting too
high a gear can "lug" the motor, lowering the lifespan over time, while
selecting too low a gear for the speed of the car can over-rev the engine,
causing severe damage very quickly.
Attempting to select reverse while the vehicle is moving forward causes severe
gear wear (except in transmissions with synchromesh on the reverse gear).
However, most manual transmissions have a gate that locks out reverse directly
from 5th gear to help prevent this. In order to engage reverse from 5th, the
shift lever has to be moved to the center position between 2nd and 3rd, then
back over and into reverse. Similarly, many newer six-speed manual transmissions
have a collar under the shift knob which must be lifted to engage reverse to
also help prevent this.
SHIFTING SPEED
Some automatic transmissions can shift ratios faster than a manual gear change
can be accomplished, due to the time required for the average driver to push the
clutch pedal to the floor and move the gearstick from one position to another.
This is especially true in regards to dual clutch transmissions, which are
specialized computer-controlled manual transmissions. Even though some automatic
transmissions and semi-automatic transmissions can shift faster, many purists
still prefer a regular manual transmission.
EASE OF USE
Because manual transmissions require the operation of an extra pedal, and
keeping the car in the correct gear at all times, they require a bit more
concentration, especially in heavy traffic situations. The automatic
transmissions, on the other hand, simply require the driver to speed up or slow
down as needed, with the car doing the work of choosing the correct gear. Manual
transmissions also place a greater workload on the driver in heavy traffic
situations, when the driver must operate the clutch pedal quite often. Because
the clutch pedal can require a substantial amount of force, especially on large
trucks, and the long pedal travel compared to the brake or accelerator requires
moving the entire leg, not just the foot near the ankle, a manual transmission
can cause fatigue, and is more difficult for weak or injured people to drive.
Additionally, because automatic transmissions can be driven with only one foot,
people with one leg that is missing or impaired can still drive, unlike the
manual transmission that requires the use of two feet at once. Likewise, manual
transmissions require the driver to remove one hand periodically from the
steering wheel while the vehicle is in motion, which can be difficult or
impossible to do safely for people with a missing or impaired arm, and requires
increased coordination, even for those with full use of both hands.
STOPPING ON HILLS
The clutch experiences most of its wear in first gear because moving the car
from a standstill involves a great deal of friction at the clutch. When
accelerating from a standstill on an incline, this problem is made worse because
the amount of work needed to overcome the acceleration of gravity causes the
clutch to heat up considerably more. For this reason, stop-and-go driving and
hills tend to wear out clutches very quickly. Automatic transmissions are better
suited for these applications because they have a hydraulic torque converter
which is externally cooled, unlike a clutch. Torque converters also do not have
a friction material that rubs off over time like a clutch. Some automatics even
lock the output shaft so that the car cannot roll backwards when beginning to
accelerate up an incline. To reduce wear in these applications, some manual
transmissions will have a very low, "granny" gear which provides the leverage to
move the vehicle easily at very low speeds. This reduces wear at the clutch
because the transmission requires less input torque.
Many drivers use the parking brake to prevent the car from rolling backward when
starting to accelerate up a steep hill. This saves precious clutch life.
APPLICATIONS AND POPULARITY
Many types of automobiles are equipped with manual transmissions. Small economy
cars predominantly feature manual transmissions because they are cheap and
efficient, although many are optionally equipped with automatics. Economy cars
are also often powered by very small engines, and manual transmissions make more
efficient use of the power produced.
Sports cars are also often equipped with manual transmissions because they offer
more direct driver involvement and better performance. Off-road vehicles and
trucks often feature manual transmissions because they allow direct gear
selection and are often more rugged than their automatic counterparts.
Conversely, manual transmissions are no longer popular in many classes of cars
sold in North America, Australia and some parts of Asia, although they remain
dominant in Europe, Asia and developing countries. Nearly all cars are available
with an automatic transmission option, and family cars and large trucks sold in
the US are predominantly fitted with automatics, however in some cases if a
buyer wishes he/she can have the car fitted with a manual transmission at the
factory. In Europe most cars are sold with manual transmissions. Most luxury
cars are only available with an automatic transmission. In most cases where both
transmissions are available for a given car, automatics are an at cost option,
but in some cases the reverse is true. Some cars, such as rental cars and taxis,
are nearly universally equipped with automatic transmissions in countries such
as the US, but the opposite is true in Europe.[12] As of 2008, 75.2% of vehicles
made in Western Europe were equipped with manual transmission, versus 16.1% with
automatic and 8.7% with other.[13]
In some places (for example New Zealand (for the second-phase Restricted
licence, but not the final Full licence), Belgium, China, Estonia, Dominican
Republic, Finland, France, Germany, Ireland, Israel, Jordan, Netherlands,
Norway, Poland, Singapore, Slovenia, South Africa, South Korea, Spain, Sri
Lanka, Sweden, Turkey, U.A.E and the UK), when a driver takes the licensing road
test using an automatic transmission, the resulting license is restricted to the
use of automatic transmissions. This treatment of the manual transmission skill
seems to maintain the widespread use of the manual transmission. As many new
drivers worry that their restricted license will become an obstacle for them
where most cars have manual transmissions, they make the effort to learn with
manual transmissions and obtain full licenses. Some other countries (such as
India, Italy, Pakistan, Malaysia, Serbia, Brazil, Russia, Ukraine and Denmark)
go even further, whereby the license is granted only when a test is passed on a
manual transmission. In Denmark and Brazil drivers are allowed to take the test
on an automatic if they are handicapped, but with such a license they will not
be allowed to drive a car with a manual transmission.
TRUCK TRANSMISSIONS
Some trucks have transmissions that look and behave like ordinary car
transmissions - these transmissions are used on lighter trucks, typically have
up to 6 gears, and usually have synchromesh.
For trucks needing more gears, the standard "H" pattern can get very
complicated, so additional controls are used to select additional gears. The "H"
pattern is retained, then an additional control selects among alternatives. In
older trucks, the control is often a separate lever mounted on the floor or more
recently a pneumatic switch mounted on the "H" lever; in newer trucks the
control is often an electrical switch mounted on the "H" lever. Multi-control
transmissions are built in much higher power ratings, but rarely use
synchromesh.
There are several common alternatives for the shifting pattern. Usual types are:
* Range transmissions use an "H" pattern through a narrow range of gears, then
a "range" control shifts the "H" pattern between high and low ranges. For
example, an 8-speed range transmission has an H shift pattern with four
gears. The first through fourth gears are accessed when low range is
selected. To access the fifth through eighth gears, the range selector is
moved to high range, and the gear lever again shifted through the first
through fourth gear positions. In high range, the first gear position becomes
fifth, the second gear position becomes sixth, and so on.
* Splitter transmissions use an "H" pattern with a wide range of gears, and the
other selector splits each sequential gear position in two: First gear is in
first position/low split, second gear is in first position/high split, third
gear is in second position/low split, fourth gear is in second position/high
split, and so on.
* Range-Splitter transmissions combine range-splitting and gear-splitting. This
allows even more gear ratios. Both a range selector and a splitter selector
are provided.
Although there are many gear positions, shifting through gears usually follows a
regular pattern. For example, a series of upshifts might use "move to splitter
direct; move to splitter overdrive; move shift lever to No. 2 and move splitter
to underdrive; move splitter to direct; move splitter to overdrive; move shift
lever to No. 3 and move splitter to underdrive"; and so on. In older trucks
using floor-mounted levers, a bigger problem is common gear shifts require the
drivers to move their hands between shift levers in a single shift, and without
synchromesh, shifts must be carefully timed or the transmission will not engage.
For this reason, some splitter transmissions have an additional "under under"
range, so when the splitter is already in "under" it can be quickly downshifted
again, without the delay of a double shift.
Today's truck transmissions are most commonly "range-splitter". The most common
13 speed has a standard H pattern, and the pattern from left upper corner is as
follows: R, down to L, over and up to 1, down to 2, up and over to 3, down to 4.
The "butterfly" range lever in the center front of the knob is flipped up to
high range while in 4th, then shifted back to 1. The 1 through 4 positions of
the knob are repeated. Also, each can be split using the thumb-actuated
under-overdrive lever on the left side of the knob while in high range. The
"thumb" lever is not available in low range, except in 18 speeds; 1 through 4 in
low range can be split using the thumb lever and L can be split with the
"Butterfly" lever. L cannot be split using the thumb lever in either the 13 or
18 speed. The 9 speed transmission is basically a 13 speed without the
under-overdrive thumb lever.
Truck transmissions use many physical layouts. For example, the output of an
N-speed transmission may drive an M-speed secondary transmission, giving a total
of N*M gear combinations; for example a 4-speed main box and 3-speed splitter
gives 12 ratios. Transmissions may be in separate cases with a shaft in between;
in separate cases bolted together; or all in one case, using the same
lubricating oil. The second transmission is often called a "Brownie" or "Brownie
box" after a popular brand. With a third transmission, gears are multiplied yet
again, giving greater range or closer spacing. Some trucks thus have dozens of
gear positions, although most are duplicates. Sometimes a secondary transmission
is integrated with the differential in the rear axle, called a "two-speed rear
end." Two-speed differentials are always splitters. In newer transmissions,
there may be two countershafts, so each main shaft gear can be driven from one
or the other countershaft; this allows construction with short and robust
countershafts, while still allowing many gear combinations inside a single gear
case.
Heavy-duty transmissions are almost always non-synchromesh. One argument is
synchromesh adds weight that could be payload, is one more thing to fail, and
drivers spend thousands of hours driving so can take the time to learn to drive
efficiently with a non-synchromesh transmission. Heavy-duty trucks driven
frequently in city traffic, such as cement mixers, need to be shifted very often
and in stop-and-go traffic. Since few heavy-duty transmissions have synchromesh,
automatic transmissions are commonly used instead, despite their increased
weight, cost, and loss of efficiency.
Heavy trucks are usually powered with diesel engines. Diesel truck engines from
the 1970s and earlier tend to have a narrow power band, so need many
close-spaced gears. Starting with the 1968 Maxidyne, diesel truck engines have
increasingly used turbochargers and electronic controls that widen the power
band, allowing fewer and fewer gear ratios. A transmission with fewer ratios is
lighter and may be more efficient due to fewer transmissions in series. Fewer
shifts also makes the truck more drivable. As of 2005, fleet operators often use
9,10,13 or 18-speed transmissions, but automated manual and semi-automatic
transmissions are becoming more common on heavy vehicles, as they can improve
efficiency and drivability, reduce the barrier to entry for new drivers, and may
improve safety by allowing the driver to concentrate on road conditions.
MAINTENANCE
Because clutches use changes in friction to modulate the transfer of torque
between engine and transmission, they are subject to wear in everyday use. A
very good clutch, when used by an expert driver, can last hundreds of thousands
of kilometres (or miles). Weak clutches, abrupt downshifting, inexperienced
drivers, and aggressive driving can lead to more frequent repair or replacement.
Manual transmissions are lubricated with gear oil or engine oil in some cars,
which must be changed periodically in some cars, although not as frequently as
the automatic transmission fluid in a vehicle so equipped. (Some manufacturers
specify that changing the gear oil is never necessary except after transmission
work or to rectify a leak.)
Gear oil has a characteristic aroma due to the addition of sulfur-bearing
anti-wear compounds. These compounds are used to reduce the high sliding
friction by the helical gear cut of the teeth (this cut eliminates the
characteristic whine of straight cut spur gears). On motorcycles with "wet"
clutches (clutch is bathed in engine oil), there is usually nothing separating
the lower part of the engine from the transmission, so the same oil lubricates
both the engine and transmission. The original Mini placed the gearbox in the
oil sump below the engine, thus using the same oil for both.
* Reverse
* Neutral
* First gear
* Second gear
* Third gear
* Fourth gear
SEE ALSO
* Transmission (mechanics)
* Non-synchronous transmission
* Toploader Transmission
* Borg-Warner T-56
* Automatic transmission
* Preselector gearbox
* Freewheel
* Gear ratio
REFERENCES
1. ^ "Buyers Guide Alfa Romeo Spider & GTV 916". Alfisti.net.
http://www.alfisti.net/311.2.html?&L=1. Retrieved 2010-10-16.
2. ^ "Synchronizers; graphic illustration of how they work".
http://www.howstuffworks.com/transmission3.htm. Retrieved 2007-07-18.
3. ^ "Porsche 911: The latest intel including renderings!". Germancarblog.com.
2011-07-04.
http://www.germancarblog.com/2011/07/porsche-911-the-latest-intel-including-renderings/.
Retrieved 2011-09-01.
4. ^ "2012 Porsche 911 will feature a 7-speed manual transmission".
Worldcarfans.com.
http://www.worldcarfans.com/111060133807/2012-porsche-911-will-feature-a-7-speed-manual-gearbox.
Retrieved 2011-09-01.
5. ^ "2007 Tesla roadster". Supercars.net. 2006-07-19.
http://www.supercars.net/cars/3528.html. Retrieved 2011-09-01.
6. ^ http://www.fordification.com/tech/overdrive.htm
7. ^ http://en.wikipedia.org/wiki/Overdrive_(mechanics)
8. ^ http://en.wikipedia.org/wiki/Overdrive_(mechanics)
9. ^ An Investigation into The Loss Mechanisms associated with a Pushing Metal
V-Belt Continuously Variable Transmission, Sam Akehurst, 2001, PhD Thesis,
University of Bath.
10. ^ a b "U.S. Department of Energy vehicle fuel economy website".
Fueleconomy.gov. http://www.fueleconomy.gov. Retrieved 2010-10-16.
11. ^ An Overview of Current Automatic, Manual and Continuously Variable
Transmission Efficiencies and Their Projected Future Improvements, Kluger
and Long, SAE 1999-01-1259
12. ^ "Rick Steve's Europe: Driving in Europe". Ricksteves.com.
http://www.ricksteves.com/plan/tips/carrental_2005.htm. Retrieved
2010-10-16.
13. ^ "Why Dual Clutch Technology Will Be Big Business". Dctfacts.com.
http://www.dctfacts.com/archive/2008/why-dual-clutch-technology-big-business.aspx.
Retrieved 2010-02-07.
Categories:
* Automotive transmission technologies
* Automobile transmissions
Wikimedia Foundation. 2010.
Игры ⚽ Поможем решить контрольную работу
* List of Formula One Grands Prix
* Hosts file
LOOK AT OTHER DICTIONARIES:
* Manual transmission driving technique — wikibooks:transwiki:Manual
transmission driving technique This page is a soft redirect. Retrieved from
http://en.wikipedia.org/wiki/Manual transmission driving technique
Categories: Wikipedia soft redirects … Wikipedia
* manual transmission — noun Mechanical transmission which shifts gears by the
action of the drivers hand on the gearstick or gear lever, rather than
automatically; a manual gearbox. Syn: stickshift, standard transmission Ant …
Wiktionary
* manual transmission — an automotive transmission in which the driver shifts
gears manually. Also called manual. [1965 70] * * * … Universalium
* manual transmission — an automotive transmission in which the driver shifts
gears manually. Also called manual. [1965 70] … Useful english dictionary
* manual transmission — A transmission system in which gears are selected by
the driver by means of a hand operated gearshift and a foot operated clutch.
In a motorcycle the clutch is hand operated and the gearshift is foot
operated. Contrasts with an automatic… … Dictionary of automotive terms
* manual transmission — (in a car) gear system that must be operated by hand
(as opposed to an automatic transmission) … English contemporary dictionary
* Sequential manual transmission — A sequential manual transmission (or
sequential manual gearbox) is a type of manual transmission used on
motorcycles and high performance cars or auto racing, where gears are
selected in order, and direct access to specific gears is not… … Wikipedia
* Multimode manual transmission — (MMT or M/M, also Multimode Transmission)[1]
is a type of sequential manual transmission offered by Toyota. It uses a
traditional manual gearbox with an electronically controlled clutch.
Multimode Manual Transmission is available in the Aygo,… … Wikipedia
* Electrohydraulic manual transmission — or clutchless manual gear system is a
manual transmission system that works similar to a manual transmission but
operates the clutch automatically. To change gears, the driver selects the
desired gear, and the system automatically operates the… … Wikipedia
* F25 manual transmission — The F25 manual transmission was fitted to many
vehicles in the European General Motors production line up including the Opel
Calibra. It was a 5 speed transmission with the following configuration: *
Clutch Diameter 9.0 inches # gear ratio 3.38:1 … Wikipedia
18+
© Academic, 2000-2023
* Contact us: Technical Support, Advertising
Dictionaries export, created on PHP,
Joomla,
Drupal,
WordPress, MODx.
* Mark and share
*
* Search through all dictionaries
* Translate…
* Search Internet
SHARE THE ARTICLE AND EXCERPTS
*
*
*
*
*
*
*
*
DIRECT LINK
https://en-academic.com/dic.nsf/enwiki/334115 Do a right-click on the link above
and select “Copy Link”