MECHANICALFUNDA for Mechanical Engineers

Introduction :
A capstan and turret lathe is a production lathe. It is used to manufacture any number of identical pieces in the minimum time.
These lathes were first developed in the United States of America by Pratt and Whitney in 1960.

Types of the machine :
There are two main types of horizontal lathe of this family are :

The capstan or Ram type lathe
The turret or Saddle type lathe

The capstan or Ram type lathe :

The ram-type lathe carries the hexagonal turret on a ram or a short slide.

The ram slides longitudinally on a saddle and clamp-on lathe bed ways.

This type of machine is lighter in construction and it is suitable for machining bar of smaller diameter. The tools are mounted on the square turret and six faces of the hexagonal turret.

Ram moves from left to right the feeding movement is obtained.

The turret or Saddle type lathe :

The hexagonal turret-mounted directly on a saddle and the whole unit moves back and forth on the bed ways to apply feed.
This type of turret lathe is heavier in construction and is particularly used for larger diameter bar work and chucking.work.

Principle parts of Capstan and Turret lathe :

Bed :
The bed is long box-like casting provided with accurate guide ways upon which are mounted the carriage and turret saddle.
The bed is designed to ensure strength, rigidity and permanency under heavy duty services.

Head stock :
The head stock is a large casting located at the left hand of the bed.
Different types of head stock maybe use that are listed below :

Step cone pulley driven head stock
The direct electric motor is driven head stock
All geared head stock
Perspective head stock

Cross-slide & Saddle :

In small capstan and turret lathe hand-operated cross-slide and saddle are used which are clamped on the lathe bed at the required position.

The larger capstan lathes are usually used two designs of the carriage like :

Conventional type carriage
Side hung type carriage

The turret saddle and auxiliary slide :

The turret saddle bridges the gap between two-bed ways and the top face is accurately machined to provide a bearing surface for the auxiliary slide.

The hexagonal turret is mounted on the auxiliary slide.

Capstan and turret lathe mechanism :

The carriage, cross-slide and turret slide may be fed into the work by hand or power.

The various mechanism for machining.

Turret indexing mechanism
Bar-feeding mechanism

Capstan and turret lathe operation :

In this lathe operations are similar to that of the centre lathe machine.

The usual operations performed in this lathe are :

Straight turning
Shoulder turning
Taper turning
Chamfering
Thread cutting
Facing
Knurling
Forming
Drilling
Reaming
Boring
Counter boring
Tapping
Undercutting
Parting off

Cutting speed, feed and depth of cut are similar to the simple lathe machine.

Full form of PDI in automobile

What is the full form of PDI?

Answer :

Pre Delivery Inspection

What does PDI mean?

It is the inspection only to make sure that the vehicle is 100% perfect condition and make a finishing touch before the customer takes delivery.

In the inspection finishing touch such as following.

Feeling the car up with gas
Washer fluid
Engine oil
Installing the radio and license plate brackets
Bolt checking
Check for damage

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Difference between capstan turret and engine lathe

A capstan and turret lathes are the development of an engine lathe. The capstan lathe was first developed in the United States of America by Pratt and Whitney in 1860. These types of lathe are the development of an engine lathe so they possess certain basic difference as their construction, operation and use. Let us have a deep insight into the comparison and difference between them.

Difference :

The headstock of a turret lathe is similar to that of an engine lathe in construction but it has a wider range of speeds.
Engine lathe required motor of 3 h.p. to drive its spindle and other parts whereas capstan and turret lathe requires high power as 15 h.p. for a high rate of production.
The tailstock of and engine lathe is replaced by a turret in turret lathe thus it resembles a big six-sided nut with can carry six tools for rotating jobs on the other side engine lathe holds one tool of limited size.
Turret lathe it acts like production machines while engine lathe is used for various types of odd jobs within limits.
In a turret lathe, combination cuts can be taken while in centre lathe this type of arrangement is quite uncommon.
The labour cost required to operate a capstan and turret lathe is less than that required in centre lathe.
Capstan and turret lathe are not usually fitted with lead screws for cutting threads similar to an engine lathe.
In capstan and turret lathe one time setting of job then you must not change the tools while in engine lathe you can change tools as per your requirement.
Turret movement can be controlled automatically. engine lathe tool movement can control manually.
In capstan and turret lathe number of speeds is more in engine lathe number of speeds is less.
Capstan and turret lathe is suitable for mass production while engine lathe is not suitable for that.
Capstan and turret lathe tool is centred automatically while an engine lathe tool is centred manually after changing the tool.

Summary :

An engine lathe is a versatile machine capable of machining any types of jobs with different sizes and shapes. The machine is not suitable for production unit because time is taken to set different tools on the tool post of lathe after each and every operation.

On the other hand capstan and turret lathe is a mass-production machine. They are unsuitable where only one or a few jobs are to be machined. The high initial setting time compared to an engine lathe.

Factors affecting charge efficiency

There is a various factor affecting charge efficiency. let we check it out below :

The compression ratio.
The amount of heat picked up during passage of the charge through the intake manifold.
The valve timing of the engine.
The resistance offered to air-fuel charge during its passage through induction manifold.

Internal combustion engine efficiency

We expressing engine performance in terms of power, it is also essential to express in terms of efficiency.
Various efficiency are listed below :

Air-standard efficiency
Brake thermal efficiency
Indicated thermal efficiency
Mechanical efficiency
Relative efficiency
Volumetric efficiency
Scavenging efficiency
Charge efficiency
Combustion efficiency

we can discuss various engine efficiency one by one.

Air-standard Efficiency :

The air-standard efficiency is also known as thermodynamic efficiency. It is mainly a function of compression ratio and other parameters.

Brake thermal Efficiency :

The brake thermal efficiency is based on brake power of the engine. These efficiency give an idea of the output generated by the engine with respect to heat supplied in form of fuel.

Indicated thermal Efficiency :

The indicated thermal efficiency is based on indicated power of the engine.
In modern engine an it is almost 28% obtained with gas and gasoline spark-ignition engines having a moderate compression ratio.

Mechanical Efficiency :

Mechanical efficiency takes into account the mechanical losses in an engine.
There is various mechanical losses in the engine :
Friction losses as in case of pistons, bearing, gears, valve mechanisms etc.
Power is absorbed by engine such as fuel pump, lubricating oil pump, water circulating pump, radiator and distributor etc.
Ventilating action of the flywheel.
Charging in cylinder with fresh charge and discharging the exhaust gases during the exhaust stroke.
In general, mechanical efficiency of engines varies from 65 to 85%.

Relative Efficiency :

The relative efficiency is the ratio of actual efficiency obtained from an engine to the theoretical efficiency of the engine cycle.

Relative efficiency = Actual brake thermal efficiency / Air-standard efficiency

Volumetric Efficiency :

Volumetric efficiency is defined as the ratio of the actual mass of air drawn into the engine during a given period of time to the theoretical mass which should have been drawn in during that same period of time.

n_v = ṁ_act / ṁ_th

Scavenging Efficiency :

In case of two-stroke engines scavenging efficiency is defined as the ratio of the amount of air or gas-air mixture, which remains in the cylinder, at the actual beginning of the compression to the product of the total volume and air density of the inlet.

Charge Efficiency :

The charge efficiency shows how well the piston displacement of a four-stroke engine is utilized. Various factor affecting the charge efficiency.

Combustion Efficiency :

Combustion efficiency is the ratio of heat liberated to the theoretical heat in the fuel.
For a well adjusted engine it is varies form 92% to 97%.

Advantages and disadvantages of two stroke engine

A two-stroke cycle engine is a type of internal combustion engine that completes a single crankshaft revolution power cycle with two-piston strokes. This engine provided some advantages and disadvantages comparing with a four-stroke engine. Let us have a deep insight into the pros and cons of the two-stroke engine in this article.

Advantages of two-stroke engine :

Simpler in design because don't have valve only port.
Power developed is twice as compared to same dimensions four-stroke engine with the same operating speed.
The work required to overcome the friction of the exhaust and suction strokes is saved.
Burnt gases do not remain in the clearance space because of scavenging.
Two-stroke engines can work in any position since oil flow is not a concern with any valves to worry about.
It occupies lesser space.
Lighter in weight because the lighter flywheel is used.
Easy to maintain.
Less cost.
It produces Uniform torque.
Power to weight ratio is high.

Disadvantages of two-stroke engine :

A high-speed two-stroke engine is less efficient.
When the inlet valve of the engine is opened for the intake of the air-fuel mixture, the exhaust valve is also open so the part of the fuel is wasted this increase fuel consumption and reduce overall efficiency.
Effective compression is less in case of a two-stroke engine.
These engines are liable to cause heavier combustion of lubricating oil.
With heavy loads, it gets heated due to excessive heat produced.
Thermal efficiency is also less.
It causes pollution and smoky.

Types of two-stroke engine

A two-stroke engine is which it completes its cycle of operation in one complete revolution of the crankshaft in other word in two stroke of the piston.

Two-stroke engine are basically two types and its depend on the scavenging method.

Types of two-stroke engine are listed below :

Crankcase Scavenged Engine
Separately Scavenged Engine

The details of above two types of engine are describe below :

Crankcase scavenged engine :

It is one of the simplest types of two-stroke engine. In this engine the charge is compressed in the crankcase during the expansion stroke.

There are three ports in this engine :

Intake port at the crankcase
Transfer port
Exhaust port

Through the transfer port compressed charge passes into the engine cylinder and flushing the products of combustion is called scavenging.

Separately scavenged engine :

It is same engine as crankcase engine but in this engine uses external device like a blower to scavenge the products of combustion is called externally or separately scavenged engine.

Components of CRDI

CRDI is a modern fuel system and advanced technology used in an automobile. Let us know about the composition of that are listed below :

Pressure supply pump :

The electric fuel pump comprises:

Electric Moter
Roller-Cell Pump
Non-Return Valve
Rail-pressure sensor (RDS)
Injector

High-pressure pump :

The pump plunger moves downward
The inlet valve open
The fuel is drawn into the pumping element chamber(suction stroke)
At BDC, the inlet valve closes
The fuel in the chamber can be compressed by the upward moving plunger.
High- pressure accumulator (Rail).

Pressure-control valve (DRV) :

Responsible for maintaining the pressure in the rail at a constant level.

ECU with Sensors :

Common Rail is an EDC controlled injection system
The ECU controls & monitors the complete injection process
The sensors deliver all the measured values which are required in the process

Rail-pressure sensor(RDS) :

Measures the pressure in the rail
Inputs the information to the ECU.

LPG properties

The various properties of LPG are listed below. we can check it one by one.

Properties of LPG:

It is a mixture of gases, mainly constituting Propane and Butane.
It has a simple structure in chemical terms.
It is one of the cleanest of all alternative fuels.
It is a liquid under normal pressure in ambient conditions, usually, it is found to be gaseous form.
Vaporous form in LPG is two times heavier than air and it is half of the same volume of water.
Density of liquid LPG is 0.55 gm/ cm.cube.
LPG boiling point is -42°C or-44°F.
LPG freeing point is -188°C or -306.4°F.
LPG heating value is 11920 to 11997 kcal/kg.
LPG Flashpoint is -76 degrees Fahrenheit.
Ignition temperature of LPG is 410 to 580 degree Celsius.
LPG maximum flame temperature in oxygen is 2830 degree cent.
LPG maximum flame temperature in the air is 2000 degree cent.
The gross calorific value of LPG is 11400 Kcal/kg.
It is almost colourless and odourless.
Ethyl Mercaptan is normally used as a stenching agent for an odorant purpose helps to know about LPG leaks.
LPG vapours are tasteless and non-toxic.
LPG is also caused suffocation in some closed condition.
LPG is mildly anaesthetic and can be harmful so LPG has never been used or considered safe enough for medicinal purposes.

LPG heating value

Gross heating and Net heating value for LPG :

Gross heating value in kcal/kg - 11920

Net heating value in kcal/kg - 11997

Gross heating value in kcal/nm³ - 28000

Net heating value in kcal/nm³ - 25775

What is melting point

Melting Point :

The temperature at which a given solid will melt is called the melting point.

The melting point is also called Liquefaction point.

The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure.

In theory, the melting point of a solid should be the same as the freezing point of the liquid.

At the melting point, the solid and liquid phase exist in equilibrium.

What is freezing point

Freezing point :

The temperature at which a liquid turns into a solid when it is cooled is called freeing point.

In other word, Liquids have a characteristic temperature at which they turn into solids, known as their freezing point.

Freezing point is also called the crystallization point.

LPG Freezing point

What is the freezing point of LPG?

The freezing point of LPG is -188°C or -306.4°F

LPG freeze or melt at -188°C or -306.4°F and becoming ice.

LPG freezes at a much lower temperature.

Thermodynamics definition

Definition

LPG boiling point

What is the boiling point of LPG?

The Boiling point of LPG is -42°C or-44°F

LPG boils at -42°C or -44°F and becoming gas vapor.

LPG stays in a liquid state because it is under pressure in a gas cylinder.

As a liquid, LPG looks a lot like water.

LPG is colorless and odorless in its natural state.

The boiling point of LPG depends on what proportions are Butane and Propane present in the mixture.

What is boiling point

Boiling point :

The temperature at which the liquid boils and turns to vapour is called the boiling point.

In other word, the boiling point of a substance is the temperature at which the vapour pressure of the liquid equals the pressure surrounding the liquid.

When a liquid is heated, it eventually reaches a temperature at which the vapour pressure is large enough that bubbles form inside the body of the liquid. This temperature is called the boiling point.

The boiling point of a liquid varies depending upon the surrounding environmental pressure.

For any liquid boiling point is high in high pressure than its atmospheric pressure.

For a given pressure, different liquids boil at different temperatures.

For example, water boils at 100 °C (212 °F) at sea level, but at 93.4 °C (200.1 °F) at 2,000 meters (6,600 ft) altitude.

LPG acronyms | Abbreviations

There are many acronyms for each and every full form. Let us know some of the acronyms of LPG. You can also check out the advantages and disadvantages of LPG to know more about it.

List of Acronym of LPG:

LPG - Liquefied Petroleum Gas

LPG - Low Price Guarantee

LPG - Liquid Propane Gas

LPG - Landwirtschaftliche Produktionsgenossenschaft ( East German Farmers Collective )

LPG - Low-Pressure Gas

LPG - Liberalization, Privatization, and Globalization

LPG - Long Period Grating ( Sensor )

LPG - Licensed Professional Geologist

LPG - Land and Property Gazetteer

LPG - Local Peer Group

LPG - Lesson Planning Guide

LPG - London Possible Group

LPG - Lowest Possible Gear

LPG - Lincoln Park Gardens

LPG - Light Particle Gun

Care for drilling machine

For the long life of drilling machine care of drilling machine must be required. Following points should be required to take care of the drilling machine while performing the drilling process.

Lubrication is important because of the heat and friction generated by the moving parts. For lubrication follow the manufacturer’s manual for proper lubrication methods.
Clean each machine after use.
Clean T-slots, grooves and dirt from belts and pulleys.
Remove chips after drilling to avoid damage to moving parts.
Wipe all spindles and sleeves free of grit to avoid damaging the precision fit.
Put oil on all unpainted surfaces to prevent rust.
Operate all machines with care to avoid overworking the electric motor.

Special Care :

Operations under adverse conditions require special care.

If machines are operated under extremely dusty conditions. Operate at the slowest speeds to avoid rapid abrasive wear on the moving parts and lubricate the machines more often. Under extreme cold conditions, start the machines at a slow speed and allow the parts and lubricants to warm up before increasing the speeds.

Metal becomes very brittle in extreme cold. so do not strike the machines with hard tools. Extreme heat may cause the motor to overheat. or keep on and off the operations to keep the motor running cool.

Drilling machine safety

Drilling machines are one of the more dangerous hand-operated machines so we have to take care before the accident is necessary. Safety procedures during drilling operations will help eliminate accidents, loss of time, and materials.

It is necessary that no damage is done to the operator, the machine tool and the cutting tool. To ensure this, the following points are to be remembered :

The work should not be held by hand use a holding device to hold the workpiece.
Use proper work holding device to hold the work because in drilling machine work tend to rotate along with the drill so it cause damage to the operator.
Never make any adjustments while the machine is operating.
The shank of the drill should be cleaned before it is fitted this will leads to the breakage of a drill.
Use a brush to clean away chips, not by your hand.
Keep all loose clothing away from turning tools.
Make sure that the cutting tools are running straight before starting the operation.
Never place any tools on the drilling tables.
Care should be taken to ensure whether the belt and gears are connected properly.
Keep all guards in place while operating.
Ease up on the feed as the drill breaks through the work to avoid damaged tools or workplaces.
Remove all chuck keys and wrenches before operating.
Always wear eye protection while operating any drilling machines.