Essay: VALVE TIMING OPTIMIZATION AND REDESIGN OF CAM FOR COMPRESSED AIR ENGINE

In “VALVE TIMING OPTIMIZATION AND REDESIGN OF CAM FOR COMPRESSED AIR ENGINE”. We will try to optimize the timing of inlet and exhaust valve. We will also work on the modified design of CAM-FOLLOWER for compressed air engine (C.A.E) where the engine will run on highly pressurized (Compressed) air. Now a days cost of fuel is major problem for everyone. Moreover pollution occurs by various gasoline fuels is also other major problem to globe. So this whole project will helpful as alternative fuel to the gasoline and diesel which is ENVIRONMENT FRIENDLY as well as ECONOMIC.
LIST OF FIGURES
Figure No. Figure Description Page No.
1.2.1 First Compressed Air Engine 15
2.1 Diagram of two-stroke pneumatic engine
2.1.1 CAM Nomenclature
2.1.2 Valve
2.1.3 Piston Nomenclature
2.1.4 Crank Shaft
2.1.5 Connecting Rod
2.3.1 Plate Cam
2.3.2 Cylindrical Cam
2.3.3 Faced Cam
3.1 Components of Pneumatic system
3.2 Valve timing
3.3 Pressure Angle
3.4.1 Four Stroke Engine Valve Timing Diagram
3.4.2 Compressed Air Engine Valve Timing Diagram
4.1.1 Design Of Cam-Follower
LIST OF TABLES
Table No. Description of table Page no.
2.1 Pressures & RPM speed
2.2 Pneumatic pump optimum angles
2.3
 
LIST OF NOMENCLATURE
NOMENCLATURE DESCRIPTION
R Radius of Circular Arc
d1 Diameter of Base Circle
d2 Diameter of Nose
r1 Radius of Base Circle
r2 Radius of Nose
l Length Of Stroke
2α Total Angle of Action of Cam
Φ Angle of the Cam of the Circular Arc
α Semi Angle of Action of Cam
N Speed
D Dwell
θ1 Outer Stroke
θ2 Return Stroke
U Velocity
W Accelaration
INDEX
Contents Page no.
Declaration 1
Certificate 2
Acknowledgement 3
Abstract 4
List of figures 5
List of tables 6
List of Abbreviations 7
Table of Contents 8
1 :- INTRODUCTION 12
1.1 Overview 13
1.2 Brief History 14
2 :- LITERATURE REVIEW 16
2.1 Compressed Air Engine Components
2.1.1 CAM Nomenclature
2.1.2 Valve
2.1.3 Piston and Cylinder
2.1.4 Crank shaft
2.1.5 Connecting Rod
2.2 Types of Valves
2.2.1 Poppet Valve
2.2.2 Piston Valve
2.2.3 Pinch Valve
2.3 Types of CAM
2.3.1 Plate CAM
2.3.2 Cylindrical CAM
2.3.3 Face CAM
2.4 Types of Follower
2.4.1 Roller Follower
2.4.2 Knife-Edge Follower
2.4.3 Flat-Face Follower
2.4.4 Spherical Follower
3 :- WORKING AND IMPLEMENTATIONS
3.1 Operation Of Pneumatic System
3.2 Valve Timing
3.3 Pressure Angle
3.4 Compression of Valve Timing Diagrams
3.5 Advantages And Disadvantages of its
3.6 Plan Work
4 :- CALCULATIONS
4.1 Design of CAM-Mechanism
4.2 CAM Material Selection
4.3 Future Plan of work
5 :- CONCLUSIONS
6 :- FUTURE SCOPE
REFERENCES
CANVAS
1. INTRODUCTION
1.1 Overview
In the present study, emphasis was given to conversion of a two stroke single cylinder SI engine into a compressed air engine with minimum possible modification of the existing design. The design is based on a rather simple working principle.
The compressed air is the source of energy that is stored in a high pressure cylinder. Basically this cylinder is re-filled by the compressor. But in the present case, the compressed air is supplied directly from a compressor at a pressure of 10-12 bar.
When the piston is at TDC (Top dead center) then the inlet cam allows the inlet follower rod to open the inlet port and let the compressed air enter into the air chamber. In this situation the exhaust port is closed by the respective follower controlled by the exhaust cam.
The high pressure air introduced to the chamber passes through the inlet passage and creates a downward thrust on the piston and the piston starts moving downwards. After pushing the piston downwards the air is then reflected towards the other passage of the chamber and meanwhile the exhaust cam opens the exhaust port to leave the air by the use of a follower rod. The inlet cam has to close the inlet port with the help of the inlet follower before the piston reaches the BDC (Bottom dead center).
The first evidence about compressed air used in vehicle found in 17th century, which is used by Dennis Papin (royal society London 1687). While in 1872 the Mekarski air engine was used for street transport consisting single stage engine. However first urban transport locomotive was introduce by Hoadley & Knight in 1898 & was based on principle that longer the air is kept in engine the more heat it absorbs and greater its range. As a result they introduce two stage engine.
The most remarkable work was done by Charles B.Hodges who remembered as father of compressed air concept applied in cars not only invent car driven by compressed air engine but also got commercial success in it. After twelve year of research and development Guy Negre has developed an engine that could become one of the greatest technological advanced of this century. He is of French origin and Engineer by profession. Guy Negre is the head of research and development at Moteur Development International (MDI) cars. Where Zero Emission Vehicle (ZEV) prototype has been in production since 1994.
The environmental pollution in the metropolitan cities is increasing rapidly mostly because of the increased number of fossil fuel powered vehicles. The main objective of this paper is to design a high power to weight ratio compressed air engine which doesn’t require start up power. It can be said as a green environmental protection vehicle with near zero pollution in the metropolitan cities. Many alternative options are now being studied throughout the world .This can be reduce and controlled by using compressed air engine to produce energy, which runs on air which is abundantly available in atmosphere.. One of the alternative solutions can be a compressed air driven vehicle
1.2 Brief History
The first compressed air vehicle was established in France by a Polish engineer Louis Mekarski in 1870.It was patented in 1872 and 1873 and was tested in Paris in 1876. The working principle of Mekarski’s engine was the use of energy stored in compressed air to increase gas enthalpy of hot water when it is passed through hot water. Another application of the compressed air to drive vehicles comes from Uruguay in 1984, where Armando Regusci has been involved in constructing these machines. He constructed a four-wheeler with pneumatic engine which travelled 100 km on a single tank in 1992.
The Air Car was developed by Luxembourg-based MDI Group founder and former Formula One engineer Guy Negre is which works on compressed air engine (CAE). He developed compressed air- 4- cylinders engine run on air and gasoline in 1998 which he claims to be zero pollution cars. It uses compressed air to push its pistons when running at speeds under 35 mph and at higher speeds of 96 mph, the compressed air was heated by a fuel (bio fuel, gasoline, or diesel),due to which the air expanded before entering the engine. A fuel efficiency of about 100 mpg was observed.
Light weight vehicles are the next advancement in the development of automobiles. Reducing the weight of the vehicle has many advantages as it increases the overall efficiency of the vehicle, helps in improving maneuverability, requires less energy to stop and run the vehicle. The latest researches are going on around
the world in order to come up with innovative ideas. But global warming is also one of the problems which is affecting the man. The temperature of the earth is increasing drastically and this in turn is causing climatic changes.
The fossil fuels are widely used as a source of energy in various different fields
like power plants, internal & external combustion engines, as heat source in manufacturing industries, etc. But its stock is very limited and due to this tremendous use, fossil fuels are diminishing at faster rate. So, in this world of energy crisis, it is necessary to develop alternative technologies to use renewable energy sources, so that fossil fuels can be conserved.
One of the major source of the pollution is the smoke coming out from the automobiles. So an alternative way of producing the running the vehicle must be made so that we can prevent further damage to the earth. The alternative sources of energy available are solar, electric, atmospheric air etc. Air acts like a blanket for the earth. It is the mixture of gasses, which makes it neutral and non-polluting. It has the property to get compressed to a very high pressure and retain it for a long period of time. It is cheap and can be found abundantly in the atmosphere. So it can be used as an alternative fuel for the automobiles. Much research is going on in this field and scientist are trying to improve the effectiveness of this technology. It is experimentally found that the efficiency of the vehicle ranges from 72-95%. So this can be considered as one of the preferable choices to run the vehicle.
Fig 1.2.1: First Compressed Air Engine
The principle of Mekarski’s engine was the use of energy stored in compressed air, passed through a tank of hot water to increase gas enthalpy. Replenishment took place at purpose-built compressor points at tram stops.
 
2. LITERATURE REVIEW
The basic principle of compressed air engine is slightly different from the engines which runs on gasoline fuel. In petrol engines, petrol burns itself & produces in the gases which are used to move the piston[1] cylinder arrangement same principle is used in CAE but instead of using petrol only compressed air is used to displacement piston. In CAE compressed air tank is the energy storage medium similar to a fuel tank is gasoline operated vehicles. Compressed air tank is used to supply necessary amount of air to the engine which is required foe engine operation to run the vehicle efficiency the energy. Density of fuel used will be high but in fact compressed air is having less energy density as compressed to conventional fuels &rechargeable batteries. But it is possible to increase energy density of air by with greater storage tank pressure. Various gas lows explain how
compressed air behaves. Boyles low state that if volume of air halves during compression then pressure is doubled. Also, Charles low state that volume of gas changes in direct proportion to temperature.
1. Stage First-
Compressed air provided by compressor having capacity to produced compressed air up to 10 bar .Air is injected at TDC by injector at the cylinder head. The injected air immediately acquires passage above the piston at that time inlet valve remain open and exhaust valve get closed.
2. Second Stage-
In second stage exhaust valve get opens and inlet valve get closed. So it causes expelling the air to the atmosphere through outlet and piston will move from Bottom Dead Center to Top Dead Center.
Original Engine Specifications
For this experiment we use four stroke single cylinder petrol engine made by Hero-Honda Private Limited. It having robust construction and also light weight.
1. Company Name-Hero Honda Private Limited
2. Engine type-Single Cylinder Four Stroke Petrol Engine
3. Power-9.65Hp(7.0Kw) @8000RPM
4. Gearbox-Four Speed
5. Final Drive-Chain
The significant part of experimentation was concentrated on one aspect, Running the engine at different pressures and observing different speed in RPM. The engine was successfully tested at majorly two pressures at 4 bar and 3 bar respectively without load. The pressure required to start the engine is 4 bar while engine will be shut off below pressure 1.5 bar.
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Sr. No. Pressure in Bar Speed in RPM
1. 4-3 bar 1650(Average)
2. 3-2 bar 1600(Average)
Table No.2.1: Pressures & RPM speed
From above table it is clear that engine will gives about 4000RPM at pressure of 10 bar without load.
The engine is filled only by the air at high pressure when the [3] piston is at TDC. The pneumatic engine can be simply done by modification of the design of the classic two-stroke engine. The engine does not require the inlet port delivering the air to the crankcase. The crankcase has a vent which causes only small compression of the air. However, the crankshaft is made traditionally with rolling bearing. The lubrication takes place at lower temperatures of the charge and elements.The oiling of the bearings and the cylinder surface is ensured by a small oil pump or by oil drop valve in a close cycle. The schematic idea of the pneumatic two-stroke engine is shown in below figure.The engine has any transfer ports, because delivering of the air is not from the crankcase. Only one exhaust port is used for the gas exchange in the cylinder. The engine has an injector or pneumatic valve controlled by the electronic unit. The bottle of certain volume contains the air at highpressure. The pressure of stored air in the bottle or tank (about 300 bar) is reduced by pressure
regulator to smaller injection pressure about 20-30 bar. The pressure is controlled by the sensor and the air is delivered by the pipe of small diameter (about 5-8 mm) to the valve.[2] The air volumetric flow rate through the valve is rather high in comparison to the liquid fuel injection. The use of the electromagnetic stem valve requires high voltage and high electric power. For that case the electromagnetic pneumatic valve used in industry is better solution. The air flow control should enable the high pressure in the cylinder ATDC and on the other hand the opening of the pneumatic valve lasts very short (about 40-60 deg CA) and for this reason the natural frequency of the moving elements in the valve should be high.
Fig 2.1: two-stroke pneumatic engine
For each mode, the optimum opening timing for charging valve has been determined with a constant closure at TDC. In the specific case of the 2-stroke mode, Inlet Valve Closure and Opening timings were optimized too. The criterion used was to maximize the air sent to the air tank, without worrying about Indicated Work. Indeed, during pneumatic pump mode, energy can be considered without any cost, as there is more energy available than can be stored during each braking phase. Table 1 shows the optimized timings, expressed in crank angle, and Figure 10 displays the effect of the opening timing in the specific case of 4-stroke pneumatic pump mode. (Reference angle is for end exhaust/start inlet TDC.)
4-stroke 4-stroke exhaust-off
2-stroke full variable
Inlet open -10° 710° 35°
Inlet close 190° 190° 190°
Charging open 310° 310° 310°
Charging close 360° 360° 360°
Exhaust open 530° x x
Exhaust close 10° x x
Table No.2.1: Pneumatic pump optimum angles
Table 2 displays the indicated work, the pumped air mass sent to the air tank, and the Specific Pump Consumption (SPC) defined [7] by Equation for each simulated mode. It can be seen that the lower the SPC is; the best the conversion from mechanical energy to pneumatic potential energy. 
2.1 Pneumatic Components
2.1.1 CAM Nomenclature
Fig 2.1.1: CAM Nomenclature
Trace point: A theoretical point on the follower, corresponding to the point of a fictitious knife-edge follower. It is used to generate the pitch curve. In the case of a roller follower, the trace point is at the center of the roller.
Pitch curve: The path generated by the trace point at the follower is rotated about a stationary cam.
Working curve: The working surface of a cam in contact with the follower. For the knife-edge follower of the plate cam, the pitch curve and the working curves coincide. In a close or grooved cam there is an inner profile and an outer working curve.
Pitch circle: A circle from the cam center through the pitch point. The pitch circle radius is used to calculate a cam of minimum size for a given pressure angle.
Prime circle (reference circle): The smallest circle from the cam center through the pitch curve.
Base circle: The smallest circle from the cam center through the cam profile curve.
Stroke or throw: The greatest distance or angle through which the follower moves or rotates.
Follower displacement: The position of the follower from a specific zero or rest position (usually its the position when the follower contacts with the base circle of the cam) in relation to time or the rotary angle of the cam.
 
2.1.2 VALVE
In four stroke the “Poppet Valve” performed the opening of the cylinder to inlet or exhaust manifold at the correct moment. Generally the face of valve is ground at 45 degree but in some cases it is ground at 30 degree also. It is not important to have a same angle of face in inlet and exhaust valve of same engines. To make it in right order, the valve may be reground after some use. There is some margin provided to avoid sharp edges. The groove, retain the valve spring which aids in keeping the valve pressed against the seat when closed and thus seal the combustion space tightly. In close position, the valve face, fits the accurately matched ground seat in the cylinder block. Generally replaceable ring inserts are used for exhaust valve seat. The inlet valves are made from plain nickel, nickel chrome or chrome molybdenum. Whereas exhaust valves are made from nickel chrome, silicon chrome steel, high speed steel, stainless steel, high nickel chrome, tungsten steel and cobalt chrome steel. A poppet valve (also called mushroom valve is a valve typically used to control the timing and quantity of gas flow into an engine. It consists of a hole, usually round or oval, and a tapered plug,
Fig 2.1.2: VALVE
The poppet valve is fundamentally different from slide and oscillating valves; instead of sliding or rocking over a seat to uncover a port, the poppet valve lifts from the seat with a movement perpendicular to the port. The main advantage of the poppet valve is that it has no movement on the seat, thus requiring no lubrication. Poppet valves are used in most piston engines to open and close the intake and exhaust ports in the cylinder head. The valve is usually a flat disk of metal with a long rod known as the valve stem attached to one side. The stem is used to push down on the valve and open it, with a spring generally used to return it to the closed position when the stem is not being depressed. At high revolutions per minute (RPM), the inertia of the spring makes it too slow to return the valve to its seat between cycles, leading to ‘valve float’. In this situation desmodromic valves are used which, being closed by a positive mechanical action instead of by a spring, are able to cycle at the high speeds required in, for instance, motorcycle and auto racing engines
2.1.3 PISTON AND CYLINDER
A piston is a component of reciprocating engines among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. The piston of an air compressed air is acted upon by the pressure of the expanding compressed air in the space at the top of the cylinder. This force then acts downwards through the connecting rod and onto the crankshaft. The connecting rod is attached to the piston by a swiveling gudgeon pin. This pin is mounted within the piston: unlike the steam engine, there is no piston rod or crosshead. The pin itself is of hardened steel and is fixed in the piston, but free to move in the connecting rod. A few designs use a ‘fully floating’ design that is loose in both components. All pins must be prevented from moving sideways and the ends of the pin digging into the cylinder wall.
Fig 2.1.3: PISTON
Gas sealing is achieved by the use of piston rings. These are a number of narrow iron rings, fitted loosely into grooves in the piston, just below the crown. The rings aresplit at a point in the rim, allowing them to press against the cylinder with a light spring pressure. Two types of ring are used: the upper rings have solid faces and provide gas sealing; lower rings have narrow edges and a U-shaped profile, to act as oil scrapers. There are many proprietary and detail design features associated with piston rings. A cylinder is the central working part of a reciprocating engine the space in which a piston travels. A cylinder’s displacement, or swept volume, can be calculated by multiplying its cross-sectional area (the square of half the bore by pi ) and again by the distance the piston travels within the cylinder (the stroke). The engine displacement can be calculated by multiplying the swept volume of one cylinder by the number of cylinders.
2.1.4 CRANK SHAFT
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating motion into rotary motion or vice versa. Crank shaft consists of the shaft parts which revolve in the main bearing, the crank pins to which the big ends of the connecting rod are connected, the crank webs or cheeks which connect the crank pins and the shaft parts.
Crank shafts can be divided into two types: 1. Crank shaft with a side crank or overhung crank. 2. Crank shaft with a centre crank. A crank shaft can be made with two side cranks on each end or with two or more centre cranks. A crank shaft with only one side crank is called a single throw crank shaft and the one with two side cranks or two centre cranks as a multi throw crank shaft.
.
Fig 2.1.4: CRANK SHAFT
The overhung crank shaft is used for medium size and large horizontal engines. Its main advantage is that only two bearings are needed, in either the single crank or two crank, crank shafts. Misalignment causes most crank shaft failures and this danger is less in shafts with two bearings than with three or more supports. Hence, the number of bearings is very important factor in design. To make the engine lighter and shorter, the number of bearings in automobiles should be reduced. For the proper functioning, the crank shaft should fulfill the following conditions: 1. Enough strength to withstand the forces to which it is subjected i.e. the bending and twisting moments. 2. Enough rigidity to keep the distortion a minimum. 3. Stiffness to minimize. And strength to resist, the stresses due to torsional vibrations of the shaft. 4. Sufficient mass properly distributed to see that it does not vibrate critically at the speeds at which it is operated. 5. Sufficient projected areas of crank pins and journals to keep down the bearing pressure to a value dependent on the lubrication available. 6. Minimum weight, especially in aero engines.
The crank shafts are made much heavier and stronger than necessary from the strength point of view so as to meet the requirements of rigidity and vibrations. Therefore, the weight cannot be reduced appreciably by using a material with a very high strength. The material to be selected will always depend upon the method of manufacture i.e. cast, forged, or built up. Built up crank shafts are sometimes used in aero engines where light weight is very important.
In industrial engines, 0.35 carbon steel of ultimate tensile strength 500 to 525 MPa and 0.45 carbon steel of ultimate tensile strength of about 627 to 780 MPa are commonly used. In transport engines, alloy steel e.g. manganese steel having ultimate strength of about 784 to 940 MPa is generally used. In aero engines, nickel chromium steel having ultimate tensile strength of about 940 to 1100 MPa is generally used.
Failure of crank shaft may occur at the position of maximum bending; this may be at the centre of the crank or at either end. In such a condition the failure is due to bending and the pressure in the cylinder is maximal. Second, the crank may fail due to twisting, so the connecting rod needs to be checked for shear at the position of maximal twisting. The pressure at this position is the maximal pressure, but only a fraction of maximal pressure.
 
2.1.5 CONNECTING ROD
Connecting rod is a part of the engine which is used to transmit the push and pull from the piston pin to the crank pin. In many cases, its secondary function is to convey the lubricating oil from the bottom end to the top end i.e. from the crank pin to the piston pin and then for the splash of jet cooling of piston crown. The usual form of connecting rod used in engines has an eye at the small end for the piston pin bearing, a long shank, and a big end opening which is usually split to take the crankpin bearing shells. The connecting rods of internal combustion engine are mostly manufactured by drop forging. The connecting rod should have adequate strength and stiffness with minimum weight. The materials for connecting rod range from mild or medium carbon steel to alloy steels. In industrial engines, carbon steel with ultimate tensile strength ranging from 550 to 670 MPa is used. In transport engines, alloy steel having a strength of about 780 to 940 MPa is used e.g., manganese steel. In aero engines, nickel chrome steel having ultimate tensile strength of about 940 to 1350 MPa is most commonly used. For connecting rod of low speed horizontal engines, the material may be sometimes steel castings. For high speed engines, connecting rod may also be made up of duralumin and aluminum alloys
The usual shape of connecting rod is:
(1) Rectangular
(2) Circular
(3) Tubular
(4) I section
(5) H section
In low speed engines, the section is usually circular with flattened sides, or rectangular, the larger dimension being in the plane of rotation. In high speed engines, lightness of connecting rod is a major factor. Therefore tubular, I-section or H-section rods are used.
The length of the connecting rod depends upon the ratio of connecting rod length and stroke i.e. l/r ratio; on l/r ratio depends the angularity of the connecting rod with respect to the cylinder centre line. The shorter the length of the connecting rod l in respect to the crank radius r, the smaller the ratio l/r, and greater the angularity. This angularity also produces a side thrust of the piston against the liner. The side thrust and the resulting wear of the liner decreases with a decrease in the angularity. However, an increase of l/r ratio increases the overall height of the engine. Due to these factors, the common values of l/r ratio are 4 to 5.
Fig 2.1.5: CONNECTING ROD
The stresses in the connecting rod are set up by a combination of forces. The various forces acting on the connecting rod are:
1. The combined effect of gas pressure on the piston and the inertia of the reciprocating parts.
2. Friction of the piston rings and of the piston.
2.2 Types of Valve
2.2.1 Poppet Valve
The poppet valve is fundamentally different from slide and oscillating valves; instead of sliding or rocking over a seat to uncover a port, the poppet valve lifts from the seat with a movement perpendicular to the port. The main advantage of the poppet valve is that it has no movement on the seat, thus requiring no lubrication. The operating principle of poppet valves is described in the online article “How Poppet Valves Work”. In most cases it is beneficial to have a “balanced poppet” in a direct-acting valve. Less force is needed to move the poppet because all forces on the poppet are nullified by equal and opposite forces. The solenoid coil has to counteract only the spring force
.
2.2.2 Piston Valve
A piston valve is a device used to control the motion of a fluid along a tube or pipe by means of the linear motion of a piston within a chamber or cylinder.
Examples of piston valves are:
• The valves used in many brass instruments
• The valves used in pneumatic cannons
• The valves used in many stationary steam engines and steam locomotives
2.2.3 Pinch Valve
A pinch valve is a full bore or fully ported type of control valve which uses a pinching effect to obstruct fluid flow. There are a few types of pinch valves based upon application.
Pinch valves used for fluids usually employ a device that directly contacts process tubing. Forcing the tubing together will create a seal that is equivalent to the tubing’spermeability.
Major components of a pinch valve consist of body and a sleeve. The sleeve will contain the flow media and isolate it from the environment hence reducing contamination to the environment.  
2.3 Types of CAM
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice versa. It is often a part of a rotating wheel (e.g. an eccentric wheel) or shaft (e.g. a cylinder with an irregular shape) that strikes a leverat one or more points on its circular path. The cam can be a simple tooth, as is used to deliver pulses of power to a steam hammer, for example, or an eccentric disc or other shape that produces a smooth reciprocating (back and forth) motion in the follower, which is a lever making contact with the cam.
2.3.1 Plate CAM
The most commonly used cam is the plate cam (also disc cam or radial cam) which is cut out of a piece of flat metal or plate here, the follower moves in a plane perpendicular to the axis of rotation of the camshaft. Several key terms are relevant in such a construction of plate cams: base circle, prime circle (with radius equal to the sum of the follower radius and the base circle radius), pitch curve which is the radial curve traced out by applying the radial displacements away from the prime circle across all angles, and the lobe separation angle (LSA – the angle between two adjacent intake and exhaust cam lobes).
Fig 2.3.1: Plate CAM
The base circle is the smallest circle that can be drawn to the cam profile.
A once common, but now outdated, application of this type of cam was automatic machine tool programming cams. Each tool movement or operation was controlled directly by one or more cams. Instructions for producing programming cams and cam generation data for the most common makes of machine were included in engineering references well into the modern CNC era.[9]
2.3.2 Cylindrical CAM
A cylindrical cam or barrel cam is a cam in which the follower rides on the surface of a cylinder. In the most common type, the follower rides in a groove cut into the surface of a cylinder. These cams are principally used to convert rotational motion to linear motion parallel to the rotational axis of the cylinder. A cylinder may have several grooves cut into the surface and drive several followers. Cylindrical cams can provide motions that involve more than a single rotation of the cylinder and generally provide positive positioning, removing the need for a spring or other provision to keep the follower in contact with the control surface.
Fig 2.3.2: Cylindrical CAM
Applications include machine tool drives, such as reciprocating saws, and shift control barrels in sequential transmissions, such as on most modern motorcycles.A special case of this cam is constant lead, where the position of the follower is linear with rotation, as in a lead screw.
 
2.3.3 Face CAM
A face cam produces motion by using a follower riding on the face of a disk. The most common type has the follower ride in a slot so that the captive follower produces radial motion with positive positioning without the need for a spring or other mechanism to keep the follower in contact with the control surface. A face cam of this type generally has only one slot for a follower on each face. In some applications, a single element, such as a gear, a barrel cam, or other rotating element with a flat face, may do duty as a face cam in addition to other purposes.
Face cams may provide repetitive motion with a groove that forms a closed curve, or may provide function generation with a stopped groove. Cams used for function generation may have grooves that require several revolutions to cover the complete function, and in this case, the function generally needs to be invertible so that the groove does not self intersect, and the function output value must differ enough at corresponding rotations that there is sufficient material separating the adjacent groove segments. A common form is the constant lead cam, where displacement of the follower is linear with rotation, such as the scroll plate in a scroll chuck. Non-invertible functions, which require the groove to self-intersect, can be implemented using special follower designs.
Fig 2.3.3: Face CAM
2.4 Types of Follower
2.4.1 Roller Follower:
The Roller Follower is a compact and highly rigid bearing system. It contains needle bearings and is used as a guide roller for cam discs and linear motion. Since its outer ring rotates while keeping direct contact with the mating surface, this product is thick-walled and designed to bear an impact load.
Inside the outer ring, needle rollers and a precision cage are incorporated. This prevents the product from skewing and achieves a superb rotation performance. And, as a result, the product is capable of easily withstanding high-speed rotation. Roller Followers are divided into two types: separable type whose inner ring can be separated, and non-separable type whose inner ring cannot be separated. There are two types of the outer ring in shape: spherical and cylindrical. The spherical outer ring easily absorbs a distortion of the shaft center when the cam follower is installed and helps lighten a biased load.
The Roller Follower is used in a wide range of applications such as cam mechanisms of automatic machines, dedicated machines as well as carrier systems, conveyors, bookbinding machines, tool changers of machining centers, pallet changers, automatic coating machines, sliding forks of automatic warehouses.
2.4.2 Knife-Edge Follower
When contacting end of the follower has a sharp knife edge, it is called a knife edge follower. This cam follower mechanism is rarely used because of excessive wear due to small area of contact. In this follower a considerable thrust exists between the follower and guide.
The follower moves in a plane perpendicular to the axis of rotation of the camshaft. A translating or a swing arm follower must be constrained to maintain contact with the cam profile.
 
2.4.3 Flat-Face Follower
When contacting end of the follower is perfectly flat faced, it is called a flat faced follower. The thrust at the bearing exerted is less as compared to other followers. The only side thrust is due to friction between the contact surfaces of the follower and the cam. The thrust can be further reduced by properly offsetting the follower from the axis of rotation of cam so that when the cam rotates, the follower also rotates about its axis. These are commonly used in automobiles.
2.4.4 Spherical Follower
When contacting end of the follower is of spherical shape, it is called a spherical faced follower. In flat faced follower’s high surface stress are produced. To minimize these stresses the follower is machined to spherical shape.
The roller follower operates in a groove cut on the periphery of a cylinder. The follower may translate or oscillate. If the cylindrical surface is replaced by a conical one, a conical cam results. 
3. WORKING AND IMPLEMENTATION
3.1 Operation of Pneumatic System
Pneumatic systems are designed to move loads by controlling pressurized air in distribution lines and pistons with mechanical or electronic valves. Air under pressure possesses energy which can be released to do useful work. Examples of pneumatic systems: dentist’s drill, pneumatic road drill, automated production systems.
Pneumatics is a section of technology that deals with the study and application of pressurized gas to produce mechanical motion. Pneumatic systems used extensively in industry are commonly powered by compressed air or compressed inert gases. A centrally located and electrically powered compressor powers cylinders, air motors, and other pneumatic devices. A pneumatic system controlled through manual or automatic solenoid valves is selected when it provides a lower cost, more flexible, or safer alternative to a electric motors and actuators. Pneumatics also has applications in dentistry, construction, mining, and other areas.
Fig 3.1: Pneumatic System
Compressor is the power source of a pneumatic system. It is usually driven by a motor or an internal combustion engine. The compressed air is first stored in a strong metal tank called reservoir. Before entering the cylinders and valves, the compressed air has to pass through the air treatment devices, including air filter to remove dust and moisture, pressure regulator to adjust pressure, and lubricator to spray lubrication oil.
3.2 Valve Timing
The timing gear is connected by chain, gears or a belt to the crankshaft at one end and the camshaft on the other. The timing gear is marked with tiny increments all around its perimeter.
The marks correspond to degrees of timing from the straight-up timing position of the camshaft and crankshaft In order to set an engine’s timing gear to the correct inclination, the mechanic must confer with the engine manufacturer as well as the camshaft manufacturer. The purpose of timing an engine with the timing gear is to ensure that the valves are opening and closing at the correct time to best fill the cylinder with an air/fuel mixture as well as to release all of the spent fumes from the exhaust cycle of the cylinder. A mere few degrees off on the timing gear can be the difference in an engine that performs perfectly and an engine that will not run correctly. A poor running engine will make less power and use more fuel than a properly-timed engine.
While the timing gear rotates a full 180 degrees, the timing marks are concerned with just a few degrees before and after top dead center of the piston’s rotation. Top dead center is when the piston is at its absolute highest point of travel within the cylinder or at the top of the stroke at the dead center of when the crankshaft is neither traveling up nor down in the cylinder. The timing gear is used to measure the amount of rotation in degrees in relation.
Fig 3.2: Valve Timing
3.3 Pressure angle
The angle at any point between the normal to the pitch curve and the instantaneous direction of the follower motion. This angle is important in cam design because it represents the steepness of the cam profile.
Fig 3.3: Pressure angle
3.4 Compression of Valve Timing Diagrams
Suction stroke: Fuel and air mixture introduced into the intake manifold. Inlet valve remains open and Exhaust valve closed as per Valve timing diagram. The piston moves from T.D.C to B.D.C.
Compression: The charge is compressed in the compressed stroke by moving th