digplanet beta 1: Athena
Share digplanet:


Applied sciences






















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.


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[edit]

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[edit]

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[edit]

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]


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 Survivors

All 8 Survivors sourcemod plugin link(Probably no longer works): https://forums.alliedmods.net/showthread.php?t=181946&highlight=l4d2+survivors.

SacredEyeExclusive - Dead Centre

YouTube: 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.


"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.

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.

Top Dead Centre - Tu Ride

The brand new video release by Top Dead Centre...Tu Ride.

Top Dead Centre Finder Tool

Blot Mine - Dead Centre

Incantations 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...

Dead Centre by Andy McNab - the brand new Nick Stone thriller

Somalia -- 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...

Repairing Lawnmowers For Profit Part 32 (Finding Top Dead Centre)

http://repairinglawnmowersforprofit.com Find out more about repairing lawnmowers for profit. This video shows you how to find top dead centre on the compress...

1000000 videos foundNext > 

244 news items

The Guardian

The Guardian
Thu, 07 Aug 2014 03:05:26 -0700

"Nothing will come of nothing," said King Lear. Too true. And yet something does come of nothing in this piece of edgy contemporary theatre created by Dublin's Dead Centre and directed by Ben Kidd, best known for his Headlong production of Spring ...
Mon, 01 Sep 2014 06:07:30 -0700

This decision placed us dead-centre in the flawlessly orchestrated pub-crawl. We moved through four of the most prestigious venues in close proximity and had an exquisite dish, with a perfectly paired drink, at each. We were making friends as the night ...
Sun, 31 Aug 2014 23:56:15 -0700

A real target is represented by a series of concentric circles, and there is only one objective: to hit dead centre. In marketing, if you aim both your offer and your communications at the bullseye of the real person you need to sell to, you will ...

Times of India

Times of India
Sun, 17 Aug 2014 15:50:01 -0700

LUCKNOW/NEW DELHI: Flood fury continued unabated in Uttar Pradesh claiming 28 lives and displacing over 60,000 people in nine districts bordering Nepal till Sunday evening. As Rapti, Saryu and Ghaghra rivers continue to flow above the danger mark, ...

Herald Scotland

Herald Scotland
Sun, 10 Aug 2014 19:09:03 -0700

Lippy is Dead Centre's third show. Their first, Souvenir, had as sources Marcel Proust's Remembrance of Things Past as well as material from Walter Benjamin, Theodor Adorno, TS Eliot, Shakespeare and Orson Welles. The company's follow-up, (S)quark!

The Eyeopener

The Eyeopener
Fri, 29 Aug 2014 12:30:00 -0700

Since we sit in the dead centre of Toronto, Ryerson also takes on the role of city-builder. Enter Ryerson President Sheldon Levy and his glorious “Master Plan.” Though his presidency is coming to an end after this year, Levy is credited with building ...

Toronto Star

Toronto Star
Wed, 27 Aug 2014 19:15:35 -0700

When Jose Bautista crushed a first-inning home run off the concrete facing in dead centre field, the blast gave the Jays their first lead in 32 innings. The last time they led had been the walkoff against the Rays on Aug. 23. What makes that statistic ...
Morning Star Online
Fri, 29 Aug 2014 04:26:15 -0700

This brilliant Dead Centre production, directed by Ben Moukarzel, tells that story in an extraordinary and groundbreaking way. It starts with a hilarious "post-show" interview with an actor who can lip-read who tells he how he was involved in the ...

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!