Aug 31, 2011

ABS - an Excellent safety feature in many modern vehicles

An anti-lock braking system (ABS, from German: Antiblockiersystem) is a safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up (that is, ceasing rotation) and therefore avoiding skidding.
An ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces for many drivers; however, on loose surfaces like gravel or snow-covered pavement, an ABS can significantly increase braking distance, although still improving vehicle control.

Stopping a car in a hurry on a slippery road can be very challenging. Anti-lock braking systems (ABS) take a lot of the challenge out of this sometimes nerve-wracking event. In fact, on slippery surfaces, even professional drivers can't stop as quickly without ABS as an average driver can with ABS.
The theory behind anti-lock brakes is simple. A skidding wheel (where the tire contact patch is sliding relative to the road) has less traction than a non-skidding wheel. If you have been stuck on ice, you know that if your wheels are spinning you have no traction. This is because the contact patch is sliding relative to the ice (seeBrakes: How Friction Works for more). By keeping the wheels from skidding while you slow down, anti-lock brakes benefit you in two ways: You'll stop faster, and you'll be able tosteer while you stop.

There are four main components to an ABS system:
Speed sensors
Pump
Valves
Controller


For complete Article Click HERE

Antilock brake diagram

Power steering

The term power steering is usually used to describe a system that provides mechanical steering assistance to the driver of a land vehicle, for example, a car or truck. The power steering system in a vehicle is a type of servomechanism.
For many drivers, turning the steering wheel in a vehicle that doesn't have power steering requires more force (torque) than the driver finds comfortable, especially when the vehicle is moving at a very slow speed. Steering force is very sensitive to the weight of the vehicle, and nearly so much to its length, so this is most important for large vehicles. In a vehicle equipped with power steering, when the driver turns the steering wheel, she or he feels only a slight retarding force, so a vehicle equipped with power steering can be driven by any healthy driver, even when the vehicle is being parked. This is because the power steering system furnishes most of the energy required to turn the steered wheels of the car.
Most power steering systems in cars and light trucks today are hydraulic (that is, the force to turn the wheels is provided by a hydraulic piston, which is powered by high pressure hydraulic fluid), but in some cars and trucks, the steering force is provided by an electric motor.

Power-Steering-System


For an article about Hydraulic Power steering click HERE

Solar-powered refrigerator

Solar-powered refrigerators are most commonly used in the developing world to help mitigate poverty and climate change. By harnessing solar energy, these refrigerators are able to keep perishable goods such as meat and dairy cool in hot climates, and are used to keep much needed vaccines at their appropriate temperature to avoid spoilage. The portable devices can be constructed with simple components and are perfect for areas of the developing world where electricity is unreliable or non-existent. [1] Other solar-powered refrigerators were already being employed in areas of Africa which vary in size and technology, as well as their impacts on the environment. The biggest design challenge is the intermittency of sunshine (only several hours per day) and the unreliability (sometimes cloudy for days). Either batteries (electric refrigerators) or phase-change material is added to provide constant refrigeration.


Contents:

Aug 29, 2011

Six Stroke Engine



The six-stroke engine is a type of internal combustion engine based on the four-stroke engine, but with additional complexity intended to make it more efficient and reduce emissions. Two different types of six-stroke engine have been developed since the 1990s:
In the first approach, the engine captures the heat lost from the four-stroke Otto cycle or Diesel cycle and uses it to power an additional power and exhaust stroke of the piston in the same cylinder. Designs use either steam or air as the working fluid for the additional power stroke.[1] The pistons in this type of six-stroke engine go up and down three times for each injection of fuel. There are two power strokes: one with fuel, the other with steam or air. The currently notable designs in this class are the Crower six-stroke engine, invented by Bruce Crower of the U.S. ; the Bajulaz engine by the Bajulaz S.A. company of Switzerland; and the Velozeta Six-stroke engine built by the College of Engineering, at Trivandrum in India.
The second approach to the six-stroke engine uses a second opposed piston in each cylinder that moves at half the cyclical rate of the main piston, thus giving six piston movements per cycle. Functionally, the second piston replaces the valve mechanism of a conventional engine but also increases the compression ratio. The currently notable designs in this class include two designs developed independently: the Beare Head engine, invented by Australian Malcolm Beare, and the German Charge pump, invented by Helmut Kottmann.

Diff Types of Six-stroke Engines:


The M4+2 engine working cycle animation

DTS-i and ExhausTEC technologies used in bikes by Bajaj Auto.


What is DTSi?

The DTSi (Digital Twin Spark ignition) technology from Bajaj could potentially revolutionise motorcycling in the country. The company may well want to replicate the technology in its other engines as well. This technology, which is also being patented by Bajaj Auto, boosts the performance of the engine, while simultaneously cutting emissions.

The DTSi technology incorporates twin sparkplugs at either ends of the combustion chamber for faster and better combustion. Single sparkplug meant slower burning of the air-fuel mixture and sub-optimal combustion chamber characteristics. This is the heart of the new technology from Bajaj. But, its benefits are fully realised only after it is combined with a computerised direct ignition (CDI) system and new generation throttle response system.

The digital CDI in the new Pulsar, which features an advanced eight-bit microprocessor handles the spark delivery. The programmed chip's memory contains the optimum ignition timing for any given engine rpm, thereby squeezing out the best performance characteristics from the combustion chamber. Working together with the Throttle Responsive Ignition Control System (TRICS III) supposedly also delivers the optimum ignition timing for varying load conditions.

Bajaj has also developed a new third generation TRICS III to complement the new ignition system. The TRICS system controls the ignition based on throttle use. Depending on the needs of the motorcycle rider, whether for cruising or a burst of acceleration (such as for overtaking), the ignition requirements changes; especially useful in city riding conditions.

Based on the level of throttle opened, a magnetic field opens or closes the reed switch, which, in turn, is connected to the Digital CDI. The CDI then switches to the desired Ignition Advance Timing Maps (pre-programmed timing from the eight-bit processor). This helps the engine achieve an ideal ignition spark advance for every throttle opening and engine rpm level.

Current motorcycle and scooter engines have a single spark plug that ignites the air and fuel mixture inside the combustion chamber. As a result, the rectangular combustion chambers in most motorcycle engines have a certain degree of unburnt air-fuel mix, since the flame front arising from the sparkplug does not reach all the corners of the combustion chamber.

This loss of unburnt air-fuel mix leads to lower power and fuel efficiency. After Bajaj Auto perfected the technology for adding a second spark plug to the engine and the engine management systems to go with it, it decided to first put the new technology to work on the Pulsar.



What is ExhausTEC?

ExhausTEC stands for Exhaust Torque Expansion Chamber, a technology patented by Bajaj.

The technology involves use of a small chamber connected to the exhaust pipe of the engine to modify the back-pressure and the swirl characteristics, with an aim to improve the low-end performance of the bikes.

The ExhausTEC technology is claimed to be highly effective in improving the low- and mid-range torque.

What does this Torque Expansion Chamber do?

We should first have an idea of what “Torque” is and what it does to a motorcycle.

Torque is the “twisting force” that rotates the wheels of a motorcycle.

It is torque which is responsible for moving/accelerating at slow speeds. More torque  at slow speeds means that acceleration or pick up at slow speed will be good.

The Torque Expansion Chamber (TEC) improves the scavenging (exit process) of the  exhaust gases and is also designed create a pressure difference inside the exhaust  pipe. This pressure difference inside the exhaust pipe creates a vacuum which helps to  pull in additional air-fuel mixture at low engine speeds and thus improves the engine  torque at low revs without compromising the mid or high engine revs.

The benefit of the feature is that good pick up is available right down from slow  engine speeds and therefore there is less need for changing gears in stop-go traffic  conditions.

Aug 28, 2011

>>  click here for download a case study of
Crank shaft failure analysis

Clutch, Discbrake, steam boiler line diagrams


Clutch




Basic Disc Brake






Steam Boiler






Brake system

Aug 27, 2011

How its made - Rolls Royce


How a Rolls Royce Phantom is made.
Click on the below links for pics of a SOLAR ENERGY CENTER
Album1

Indian car manufacturers logos


 

Clutchless multi-speed gearbox


Look, no clutch

Multi-speed transmission changes gear without interrupting torque

Who

Transmission specialist Zeroshift has devised a multi-speed gearbox for electric vehicles (EVs) that needs no clutch: a damper inside the gear hubs and electronic control of the motor make ratio changes seamless. Having more than one gear ratio and the ability to shift without interrupting torque means the motor runs at higher efficiency, extending range and batteries’ life expectancy by up to 10%.

Technology

Development of the concept is under way using Zeroshift’s proprietary gear-shifting system. The innovation could enable manufacturers to downsize EVs’ electric motors, keeping them running longer at the medium loads and speeds where peak efficiency of more than 95% is possible. For drivers, that could mean more performance, greater range and longer lasting batteries.
Zeroshift’s concept prevents any torque interruptions during ratio changes and does not require a clutch, issues that have so far deterred EV manufacturers from fitting multi-speed gearboxes. Current EVs instead use a single-speed transmission, but the motor then spends more of its time outside of its optimum efficiency range.
The improved efficiency offered by Zeroshift’s concept could also extend EVs’ in-service battery life. Current range limitations often lead EV drivers to drain the cells to the maximum allowable level of discharge in order to reach their destination; the deeper cycling affects batteries’ life expectancy. Improving the motor efficiency uses less of the energy stored for a given journey, easing the discharge-recharge cycles and reducing recharge time.
The company’s technology replaces the synchromesh in a conventional manual gearbox with paired interlocking rings that change ratios without interrupting the torque. To provide the required levels of shift refinement, Zeroshift’s concept uses electronic control of the electric motor or motors to match the shaft speeds and an integrated passive damper system within the drive hub to isolate any vibrations. 
The combination of sealed pockets of silicone fluid and mechanical compression springs make shifts virtually unnoticeable to occupants.

Application

Zeroshift is developing its compact transmission with several vehicle manufacturers. The company is also working with consultancy firms and manufacturers on the integration of its technology into the next generation of seamless layshaft automatic transmissions for hybrid medium-duty trucks, buses and passenger cars.
Bill Martin, Zeroshift’s managing director, says: “Our studies suggest that by using a compact, multi-speed transmission and a smaller electric motor, manufacturers can gain an operating efficiency of up to 10%. You can use that 10% to improve EVs’ range or reduce the size, weight and cost of battery packs.
“The benefits of Zeroshift’s transmission would be greatest for electric delivery vehicles, where the compromises in efficiency are greatest. To be able to pull away fully laden on hills requires low gearing, but the motor then runs too fast and too inefficiently on the highway.”

The Lathe Animation


Aug 6, 2011

Objective Solving Tricks (GATE)



Most of time students complain that they couldn’t complete their objective paper; they were struck in one or another problem and wasted a lot of time. Some says that their guess went wrong and marks were deducted due to negative marking, some could not read paper completely and missed some easy questions etc.
I’ll like to stress that objective paper solving is different from subjective paper. You don’t need to study extra for objective questions but practice little bit.
Your guess in solving objective can bring you in difficulty but some intelligent/educated guess can add valuable marks to your score. Most of time objective questions have some hint in the form of multiple choices for the question.
Following can be used as guidelines for solving objective paper:

General Tips
 Keep the structure of GATE in mind(25 Quest 1 Mark each, 30 Quest. 2 Marks each with 4 common data questions and 4 Linked Questions).
 Plan your time. Allow more time for high point value questions; reserve time at the end to review your work, and for emergencies. I'll suggest following sequence, but you can keep as per your choice: 2 Marks question, Common Data Questions, Linked questions and then single mark questions.
 Look the whole test over, skimming the quesitons and developing a general plan for your work. If any immediate thoughts come to you, jot them down in the margin
 Start with the section of the test that will yield the most points, but begin working with the easiest questions to gain time for the more difficult ones and to warm up.
 Work quickly, check your timing regularly, and adjust your speed when necessary.
 Avoid reading into the questions. When you find yourself thinking along the lines of "this is too easy; there must be a trick..." mark the question and move on to another.  Interpret questions literally.
 Mark key words in every question. To help find the key words, ask yourself WHAT, WHO, WHERE, WHEN, and HOW?

Multiple Choice Specific Tips
 Remember in GATE each question will have four choices for the answer, only one is correct and wrong answer carry 33% negative marks
 Read the question (without reading choices) very carefully.
 Mark important key words and look for special key words like not, but, except , or, nor, always, never, and only . Mark these key words. E.g.
Ques The number of leaf nodes in a rooted tree of n(n>0) nodes, with each node having 0 or 3 children is:

Important words to mark in this are, "n>0" and "or"
The number of leaf nodes in a rooted tree of n(n>0) nodes, with each node having 0 or 3 children is:
Many times we miss words like "or" and whole question in changed.
 If you can think of answer before reading choices, keep it in mind before reading choices
 Compare with choices and select the best suited answer.
 Most of times choices are made to confuse. If there are two or more options that could be the correct answer, compare them to each other to determine the differences between them.
 If there is an encompassing answer choice, for example "all of the above", and you are unable to determine that there are at least two correct choices, select the encompassing choice.
 Make educated/intelligent guesses - eliminate options any way you can.
 Multiple choices can provide direct short cut to get correct answer, especially in numerical problems.


Best Wishes for GATE-2012 Aspirants... Do Well... :)

( In Assosiation with ARTA Mech Rangers blog)

NTPC Placement Papers Collection



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