digplanet beta 1: Athena
Share digplanet:

Agriculture

Applied sciences

Arts

Belief

Business

Chronology

Culture

Education

Environment

Geography

Health

History

Humanities

Language

Law

Life

Mathematics

Nature

People

Politics

Science

Society

Technology

For the lathe tool, see lathe center. For the author of the "Top Dead Center" column, see Kevin Cameron (journalist).

In a reciprocating engine, the dead centre is the position of a piston in which it is farthest from, or nearest to, the crankshaft. The former is known as top dead centre (TDC) while the latter is known as bottom dead centre (BDC).

More generally, the dead centre is any position of a crank where the applied force is straight along its axis, meaning no turning force can be applied. Many sorts of machines are crank driven, including unicycles, bicycles, tricycles, various types of machine presses, gasoline engines, diesel engines, steam locomotives, and other steam engines. Crank-driven machines rely on the energy stored in a flywheel to overcome the dead centre, or are designed, in the case of multi-cylinder engines, so that dead centres can never exist on all cranks at the same time. A steam locomotive is an example of the latter, the connecting rods being arranged such that the dead centre for each cylinder occurs out of phase with the other one (or two) cylinders.

## Bicycles

Bicycle cranks have dead centres at approximately 12 o'clock and 6 o'clock where simple pushing down of the pedal will not turn the chainwheel, but the rider's leg is able to apply tangential force at the pedal to overcome it. Fixed-gear bicycles (without a freehub) use the momentum of the bicycle and rider to keep the chainwheel turning even if the rider makes no attempt to pedal in a circular motion.

## Reciprocating engine

In a reciprocating engine, top dead centre of piston #1 is the datum point from which ignition system measurements are made and the firing order is determined. For example, ignition timing is normally specified as degrees before top dead centre (BTDC) although a very few small and fast-burning engines require a spark just after top dead centre (ATDC), such as the Nissan MA engine with hemispherical combustions, or hydrogen engines.

Top dead centre for cylinder one is often marked on the crankshaft pulley, the flywheel or dynamic balancer or both, with adjacent timing marks showing the recommended ignition timing settings as decided during engine development. These timing marks can be used to set the ignition timing either statically by hand or dynamically using a timing light, by rotating the distributor in its seat.

In a multi-cylinder engine, pistons may reach top dead centre simultaneously or at different times depending on the engine configuration. For example:

• In the V-twin configuration, the two pistons reach TDC at different times, equal to the angular displacement between the cylinders.
• In the flat twin configuration, two opposing pistons reach TDC simultaneously, which is also called 0° displacement - but one piston will be at TDC of the compression stroke, the other on TDC of the exhaust stroke.
• In the straight-4 configuration, the two end pistons (pistons 1 and 4) reach TDC simultaneously, as do the two centre pistons (pistons 2 and 3), but these two pairs reach TDC with an angular displacement of 180°. Similar patterns are found in almost all straight engines with even numbers of cylinders, with the two end pistons and two middle pistons moving together (not necessarily 180° out of phase however) and the intermediate pistons moving in pairs in mirror-image around the centre of the engine.
• In the flatplane V8 and many larger V engines, the piston motion within each bank is similar to that of a straight engine, however in the crossplane V8 and all V10 engines the motion is far more complex.

The concept of top dead centre is also extended to pistonless rotary engines, and means the point in the cycle in which the volume of a combustion chamber is smallest. This typically occurs several times per rotor revolution; In the Wankel engine for example it occurs three times for every one revolution of the rotor.[citation needed]

Finding the volume of the cylinder using TDC and BDC and multiplying it by the number of cylinders will give the engine displacement.

## Steam engine

As steam engines are commonly horizontal, the relevant terms are front dead centre and back dead centre rather than "top" and "bottom".[citation needed]

If a single-cylinder steam engine stops in either of the dead centre positions it must be moved off the dead centre before it will restart. In small engines this is done by turning the flywheel by hand. In large engines the flywheel is moved with a lever or "turning bar". Both operations must be done with care to avoid the operator becoming entangled in the machinery. Even larger engines might require the use of a barring engine.

Steam locomotives normally have two cylinders with the cranks set at right angles so one piston will always be off the dead centre and no starting assistance is required.[citation needed]

## Other machines

This term is also used in the realm of production equipment. A mechanical punch press employs a crankshaft similar to that found in an engine. In the punch press the crankshaft drives a ram which when it is farthest away from the platen of the press is considered to be in the position of top dead centre.[citation needed]

## References

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Dead_centre — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
 1000000 videos foundNext >
 Left 4 Dead 2 Realism: Dead Centre - The Hotel Including All 8 SurvivorsAll 8 Survivors sourcemod plugin link(Probably no longer works): https://forums.alliedmods.net/showthread.php?t=181946&highlight=l4d2+survivors. SacredEyeExclusive - Dead CentreYouTube: https://www.youtube.com/user/SacredEyeExclusive Misc Playlist: https://www.youtube.com/playlist?list=PL8EB44EF2D50F9E7F Image Albums:- http://thepri... Left 4 Dead 2: Glitches And Shortcuts 1 (Dead Centre and Dark Carnival)After watching this over I have seen that I should have put in video text about the glitches.... turn on annotations. Top Dead Centre Finder Tool Top Dead Centre - Tu RideThe brand new video release by Top Dead Centre...Tu Ride. TOP DEAD CENTRE - "ON A TRAIN""On a Train" by Top Dead Centre from the album "Far From Nowhere" 2008 Album available on itunes via The official Top Dead Centre website... www.tdcband.com. Blot Mine - Dead CentreIncantations swarming the east Beasts Gather for the feast Maledictions from the west Blood flows at my behest North, the direction in which a flow of the so... MVI 0254 making a dead centre with drawbar for the Taig lathevideo is in two parts, my camera keeps timing out, I used a Taig blank collet to make this, the material is all stainless 304 except the hand knob and collet... Dead Centre of Ireland is ... confusing (1971)A bit of a tongue-in-cheek hunt for the exact dead centre of Ireland, first broadcast by RTE in 1971 and carried out by reporters Frank Hall and George Devlin. Dead Centre by Andy McNab - the brand new Nick Stone thrillerSomalia -- a lawless, violent land, ignored by the West, ripped apart by civil war and famine, fought over by drug-fuelled, gun-crazy clan fighters. They wan...
 1000000 videos foundNext >
 189 news items
 American Association Stars Strut Their Skills CJOB Mon, 28 Jul 2014 21:18:45 -0700 Gac did delight the fans as well hitting four monster shots including one of the top of the lights in left field, one of the score board in dead centre and another across Waterfront Drive in to the trees. In the throwing competition Nick Van Stratten ... Ottawa Citizen Tim Clark wins Canadian Open Eyewitness News Mon, 28 Jul 2014 02:11:15 -0700 JOHANNESBURG - South African Tim Clark clinched his second PGA Tour title when he sank a six-foot par putt to beat American Jim Furyk by one stroke at the Canadian Open on Sunday. Clark knocked his clutch putt in dead centre to edge Furyk in a battle ... TheChronicleHerald.ca Q&A with Jim Kerr: 1971 Plymouth Duster oil pressure gauge problems; can't ... TheChronicleHerald.ca Mon, 28 Jul 2014 10:48:45 -0700 These engines have the top of the block machined at angle so the combustion chamber is formed in the 'wedge' shape of the block when the piston is at top dead centre. Your 340 engine doesn't have an angle machined block and the combustion chamber is ... Oman Daily Observer Clark edges Furyk to win Canadian Open Oman Daily Observer Mon, 28 Jul 2014 11:33:45 -0700 MONTREAL — South African Tim Clark clinched his second PGA Tour title when he sank a six-foot par putt to beat American Jim Furyk by one stroke at the Canadian Open on Sunday. Clark knocked his clutch putt in dead centre to edge Furyk in a battle ... Irish Times Puppets, booze and swine flu: Irish fringe activities in Edinburgh Irish Times Sun, 27 Jul 2014 17:00:12 -0700 Dead Centre's Lippy, which won this year's Irish Times Irish Theatre Award for best production, is represented by artistic director Bush Moukarzel, and will be heading to Edinburgh's Traverse theatre. The voice of reason is provided, not infrequently ... Cambridge News Commonwealth Games: Rifle has a lot to shoot about in Jenny Corish's final Cambridge News Sun, 27 Jul 2014 23:00:00 -0700 Imagine having to find your range, remain stock still and keep hitting the bullseye where every tiny little fraction away from the dead centre is a decimal point that could prove crucial in overall terms while having a baying crowd whooping away in the ... Vogue Australia Vogue Japan does a 90s supermodel cover Vogue Australia Sun, 27 Jul 2014 20:11:15 -0700 The 15 models (one for each year) are styled in what could be described as normcore futurism with the navy turtlenecks, dead-centre hair parts, bowl-cut crops, minimal make-up and primary-coloured coats. As good as the cover is, we're still hankering ... World Matchplay Darts 2014: Phil Taylor nine-darter hailed by Rod Harrington SkySports Thu, 24 Jul 2014 06:46:10 -0700 The darts weren't landing in the corner of the bed, they were dead centre. As soon as the first treble of the last 144 went in, our chalker Gary Wood was willing to bet £100 that the nine-darter was going in. He could tell that Taylor wasn't going to ...
 Limit to books that you can completely read online Include partial books (book previews) .gsc-branding { display:block; }

Oops, we seem to be having trouble contacting Twitter

# Talk About Dead centre

You can talk about Dead centre with people all over the world in our discussions.

#### Support Wikipedia

A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia. Please add your support for Wikipedia!
 Copyright © 2009-2014 Digparty. All rights reserved.