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1929 Lister D   1931 Lister DK   1945 Lister A

How it works...  (for the novice)

On this page you will hopefully be able to understand how my 1929 Lister D works.
These engines are very simple and ideal for the novice to learn on.  Everything is readily accessible, with removable plates and covers for easy inspection of components.

Click on a picture to enlarge (back to return).

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1.  The four stroke petrol cycle.
The four strokes are... Induction, Compression, Power, Exhaust.

Induction... The piston is at the top of the cylinder.  The inlet valve opens and the piston moves down drawing in the petrol/air mixture.
Compression... The inlet valve closes and the piston moves up the cylinder again, compressing the petrol/air mixture as it does so.
Power... A spark is produced at the spark plug which ignites the compressed mixture, sending the piston down the cylinder again.
Exhaust...

The exhaust valve opens and the piston rises in the cylinder again, forcing the waste gases out through the exhaust.

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The separated engine block and head.

This is the engine block.

ListerD-DecokedBlock.jpg (52248 bytes)  

Here the piston is at the top of it's stroke inside the cylinder.
Note the head gasket in place ready for the head to be fitted.

    

This is the engine head 
(upside down, to show the cylinder top).

ListerD-DecokedHead.jpg (49222 bytes)  

This picture shows the cylinder top with the inlet and exhaust valves in place.
The hole in the side near the valves is threaded to take the spark plug.

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2.  The Carburettor.  
A supply of petrol and air needs to be available for each induction, compression and power stroke.  This is where the carburettor comes in.

There are two inlets to this device; a fuel pipe and an air intake.  The fuel pipe comes directly from the petrol tank on this engine.
More modern engines have a float chamber, which ensures a constant level of fuel even if the level in the tank is low.
The air intake is simply a spring loaded disc covering an opening at the end of the carburettor.

The fuel pipe is connected to a needle valve at the bottom of the mixture screw.
The air is simply drawn in past this valve and into the cylinder.

The piston moving down the cylinder on the induction stroke causes a suction in the carburettor, which draws the petrol and air into the cylinder, mixing it on the way.
The amount of petrol is controlled by the mixture screw, and the amount of air is controlled by adjusting the spring tension on the inlet.

The overall amount of fuel/air mixture that is allowed to enter the cylinder with each induction stroke is regulated by the butterfly valve.
This is a disc within the carburettor body near the engine.  In it's horizontal position the carburettor tube is unrestricted,
allowing the maximum amount of mixture into the cylinder, and hence the maximum engine speed.
In it's vertical position the tube is blocked, allowing no mixture to pass, and hence the engine will stop.
The normal running position is somewhere in between.  This is controlled by the governor.

This is the Carburettor.

ListerD-Carburettor.jpg (64881 bytes)

This picture shows the copper petrol pipe connected to the bottom of the needle valve.  The mixture adjusting screw (wheel) can be seen on the top of the carburettor.
The brass plate with the three screws is the air inlet.  On the top is the adjuster for the spring tension.
This picture also shows the horizontal shaft near the engine which controls the 'butterfly valve' (see next section).

     

This is the needle valve.

ListerD-Carburettor Needle Valve.jpg (86778 bytes)

This is the needle valve unscrewed from the carburettor body.
Note the long taper to give good control over the amount of fuel allowed into the cylinder.  Also note the pitting, but it still works remarkably well.

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3.  The Governor.
This takes the place of the accelerator on a car, and controls the engine speed automatically.

The governor is directly connected to the engine.
It consists of 'bob weights' that are thrown outwards as the mechanism spins inside the governor body.
As the weights move out as engine speed increases a shaft is pushed further out of the front.
This in turn is connected to the linkage to the butterfly valve in the carburettor.
This means that the faster the engine runs, the further out the bob weights are thrown,
the more the linkage is moved and the butterfly valve is moved more towards the closed position,
reducing the amount of mixture allowed into the engine.  As engine speed reduces the opposite happens.
In reality a 'regulating' point is quickly reached and the engine maintains a steady speed.

The Governor, with the front plate removed to show the inside.

ListerD-GovernorInside.jpg (77605 bytes)

The bob weights can be seen with the retaining springs attached.

 

The removed front plate of the governor.

ListerD-GovernorPin.jpg (103361 bytes)

This pin moves in and out as the weights move.
As the speed increases the pin is pushed further through the plate.

  

The picture on the main 1929 Lister D page clearly shows how this is all linked up.

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4. The Magneto.  

Unlike a modern car these engines do not have a battery.  The high voltage for the spark plug is generated by the magneto.
This basically consists of a coil and a magnet which is rotated within a body.  The magneto is connected to the engine by a shaft and a linkage.
Later engines use a chain to drive the magneto.  As the engine spins so do the magnets within the magneto which generate a high voltage within the copper windings.
The timing of this high voltage to the spark plug is critical and is controlled by the 'points' under the inspection plate and the position of the shaft..  The actual spark occurs
just before the piston reaches the top of it's stroke.  This gives the maximum power and efficiency.  The setting for this engine is 15 degrees before top dead centre (15deg BTDC).
If the spark occurred at the top of the stroke, the piston would already be partway down the cylinder before the mixture actually exploded and gave off it's power.

 

The Magneto, with the points access cover removed.

ListerD-MagnetoPoints.jpg (76326 bytes)

This picture shows the adjustable points within the magneto. Note the felt pad which contains a small amount of oil to lubricate the shaft.
Too much oil and it will get onto the points, shorting them out and stopping the engine.

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5.  The Valves.

The engine contains two valves, an inlet and an exhaust.  Their use has already been explained, but how do they operate?

The bottom of the piston is connected to a rod (the connecting rod, or 'con rod').  The other end of this rod is connected to the rotating crank shaft.
This is the way in which the up and down movement of the piston is converted into rotary motion.
Connected to the crank shaft via a gear is the 'cam shaft'.  This shaft has two oval sections on it; one for the inlet valve and one for the exhaust valve.
The base of a vertical 'push rod' sits on this oval and the top sits against a 'rocker'.
As the push rod moves up on the oval, the rocker actually rocks and the other end pushes on the valve stem to move it away from it's seat.
When the push rod drops the opposite happens, closing the valve.  The valves are held shut by strong springs.

 

The Crankshaft and gears, as seen when
the side inspection plate is removed.

ListerD-Crankshaft.jpg (75231 bytes)

This picture shows the crankshaft and gears to the camshaft.  The horizontal centre line of the shaft is in line with the small gearwheel.
To the top of the picture is the big end (the bottom of the con rod).  The 'webs' that appear to be hanging down are weighted to balance
the crankshaft.  Fitted to the lower part of the big end is the oil dipper.  This engine is not lubricated under pressure like a modern car engine.

 

On the end of the crankshaft is the flywheel.  This is where the power of the engine is taken off and used, via drive belts.

 

This view clearly shows the valve rockers,
as seen with the top plate removed.

ListerD-InsideRockerBox.jpg (88201 bytes)

On the left you can see the springs that keep the valves firmly against their seats when closed.
To the right are the tops of the push rods.  Note the adjusting screws and lock nuts to set the
gap between the left hand face of the rocker and the top of the valve stem (in this engine they
are both set to 31thousandths of an inch).

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Thank you for reading this.

I hope you have found it interesting and informative.
I have tried to keep the explanations as simple as possible.  In reality there is a little more to each component and it's set up.

After reading this section you should be able to look at a part on similar engines and know what it is and what it does.

If you think this section could be improved or made clearer please email me - there is no point in creating this if people can't understand it!

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