Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Top Dead Centre shopping experience:
1. Compare - without doubt the biggest advantage that the Top Dead Centre offers shoppers today is the ability to compare thousands of Top Dead Centre at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Top Dead Centre? Wrong! If the Top Dead Centre is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Top Dead Centre then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Top Dead Centre? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Top Dead Centre and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Top Dead Centre wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Top Dead Centre then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Top Dead Centre site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Top Dead Centre, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Top Dead Centre, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
Top dead centre (
TDC) in a piston engine, is the position of a
piston in which it is farthest from the
crankshaft. The position closest to the crankshaft is known as
bottom dead centre (
BDC).
Internal combustion engine
Top dead centre is the datum point from which engine timing measurements are made. For example, ignition system 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 combustion chambers, or Hydrogen vehicle.
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 boxer twin configuration, two opposing pistons reach TDC simultaneously, which is also called 0° displacement.
- 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 engine 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 engine 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.
Steam engine
As
steam engines are commonly
Horizontal plane, the relevant terms are
front dead centre and
back dead centre rather than "top" and "bottom".
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 re-start. 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.
Steam locomotives normally have two Cylinder (steam locomotive) with the
Crank (mechanism) set at right angles so one
piston will always be off the dead centre and no starting assistance is required.
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 center.
Top dead centre (
TDC) in a
piston engine, is the position of a
piston in which it is farthest from the
crankshaft. The position closest to the crankshaft is known as
bottom dead centre (
BDC).
Internal combustion engine
Top dead centre is the
datum point from which engine timing measurements are made. For example, ignition system 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 combustion chambers, or Hydrogen vehicle.
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 boxer twin configuration, two opposing pistons reach TDC simultaneously, which is also called 0° displacement.
- 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 engine 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 engine 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.
Steam engine
As
steam engines are commonly Horizontal plane, the relevant terms are
front dead centre and
back dead centre rather than "top" and "bottom".
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 re-start. 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.
Steam locomotives normally have two
Cylinder (steam locomotive) with the
Crank (mechanism) set at right angles so one piston will always be off the dead centre and no starting assistance is required.
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 center.
MySpace.com - Top Dead Center - PLACERVILLE/SACRAMENTO - Metal / Rock ...
MySpace music profile for Top Dead Center with tour dates, songs, videos, pictures, blogs, band information, downloads and more
Dead centre - Wikipedia, the free encyclopedia
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 ...
LaserTools | Top Dead Centre Indicator - Italian (3493)
LaserTools, Top Dead Centre Indicator - Italian, essential tool for measuring the cylinder position at top dead centre on multi valve engines
top dead center - Wiktionary
edit] English [edit] Noun. Top dead center (automotive) A position in the four-stroke combustion process wherein the piston is at the topmost point in its stroke.
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