Working of various parts of engine in valve timing

@puneetverma-cfL67U • Oct 15, 2024

Oct 15, 2024

1.2K

Can Somebody Please enlighten me up about working of various parts of engine in valve timing. I need to know about whole working of Camshaft, Rocker arm, push rods, tappets etc.

Thanks.

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Gurjap

@gurjap-blPmg9 • Jun 12, 2012

I'd refer you to Heywood's Internal Combustion Engines and Pulkrabek's Engineering Fundamentals of IC Engines.
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mechky

@mechky-jbqpJD • Jun 12, 2012

The camshaft is driven by crankshaft and is connected to it by set of gears or a chain. The camshaft rotates at half the engine speed. This is achieved by having number of teeth on camshaft gear or sprocket to be double than that of crankshaft gear or sprocket.
When the camshaft rotates, the cam projection lifts the tappet which then operates the push-rod. The push-rod causes one end of the rocker arm to rotate about a rocker shaft. The other end of rocker arm pushes down the valve stem, due to which, the valve is opened. As this happens the valve spring gets compressed. As the camshaft rotates further, the tappet moves down and the valve is now closed by expansion of valve spring.
A tappet clearance is provided between the rocker arm and the bottom of the valve stem. The clearance can be adjusted by means of an adjusting screw. A valve clearance is also provided between the rocker arm and the valve stem which allows for the expansion of valves when engine is hot.
Valve spring retainer is used to keep the valve spring properly pressed with the valve stem. Valve guide is fitted in the cylinder head which allows the valve to move up and down and also acts as a seal to prevent the gases from passing from the valve port to the valve chamber of the engine block.

I have explained one type of valve mechanism above. There is another type - OHC (Overhead Camshaft) in which push-rods are not present and rocker arms may or may not be present.
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PuneetVerma

@puneetverma-cfL67U • Jun 12, 2012

Thanks mechky... Actually I have to study IC Engines Deeply in 6th semester (I'm entering 5th in July).

I was searching for this information for a long time. In My Industrial Training too, no Engineer at Engine R&D could explain this well.

Now I have gained up to some extent..

Thanks 😀

P.S. : Can you please share the source of above ??

How many times cam shaft rotates w.r.t to crankshaft in TWO STROKE ENGINES ??
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white_hat

@white-hat-RTFca6 • Jun 12, 2012

For one rotation of crankshaft the camshaft rotates twice.
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mechky

@mechky-jbqpJD • Jun 12, 2012

pverma
Thanks mechky... Actually I have to study IC Engines Deeply in 6th semester (I'm entering 5th in July).

I was searching for this information for a long time. In My Industrial Training too, no Engineer at Engine R&D could explain this well.

Now I have gained up to some extent..

Thanks 😀

P.S. : Can you please share the source of above ??

How many times cam shaft rotates w.r.t to crankshaft in TWO STROKE ENGINES ??
There is no particular source for this explanation. You can refer to Automotive mechanics by William Crouse if you wish to know more about the constructional details and working of various parts of engines.

In case of 'Two Stroke Engines' we don't have valves and ports are present that allow intake and exhaust. Ports operate automatically due to pressure difference in the cylinder. So, there is no need for camshafts in case of two stroke engines.
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