What’s so different about train wheels : Differential mechanism in trains

Have you ever wondered what keeps the train on the track? When a track takes a turn what makes the train stay on the track instead of just continuing in its direction of motion? After all, there is no steering in a train

Many of us would think that the flanges on the wheels would do the job.

But that is not the answer.

The flanges are just a safety device. If the flanges rub against the track, it gives a horrible noise and it is a huge waste of energy. Moreover, there will be wear of tracks and wheels.

The flanges are a secondary mechanism just in case the real mechanism fails  

There is an another problem connected to it: Rail wheel differential design

There is something fundamentally different in the design of differential of a train and an automobile.So, why is it different on a train?

  1.      Unlike a normal locomotive, trains have a huge body
  2.      Trains don’t make sharp turns like an automobile

Hence adding a differential would be a potential waste of resources.

So, how does it go around a corner?The answer lies in the geometry of the wheels and tracks

The wheels are tapered, conical in shape.That means they have a varying diameter at different points of contact


Suppose the track curves right,the whole wheel-set shifts a bit to the left.


The point of contact of the left wheel is at a larger diameter of the cone. While the diameter at the point of contact on the right wheel is much smaller.



As both the wheels are connected by a solid shaft both the wheels must the same angular velocity. Since velocity is a function of diameter and angular velocity, the left wheel has a greater velocity than the right wheel. This forms the differential in a train

The whole beauty of this system is that the amount of shift of the wheel set happens automatically, makes the train move on turns smoothly and keeps the train on track.

Hence the conical geometry along with the flanges ensures the train stays on the track

Power Steering

power steering

Power steering

In heavy duty (dump) trucks and power tractors the effort applied by the driver is inadequate to turn the wheels. In this case a booster arrangement is incorporated in the steering system. The booster is set into operation when the steering wheel is turned. The booster then takes over and does most of the work for steering. This system called power steering uses compressed air, electrical mechanisms, and hydraulic pressure. Hydraulic pressure is used on a vast majority of power steering mechanism today.


When the steering wheel is turned, the worm turns the sector of the worm wheel and the arm. The arm turns the road wheel by means of the drag link. If the resistance offered to turn the wheels is too high and the effort applied by the driver to the steering wheel is too weak, then the worm, like a screw in a nut will be displaced axially together with the distributor slide valve. The axial movement of the distributor slide valve in the cylinder will admit oil into the booster cylinder through the pipe line. The piston in the booster cylinder will turn the road wheels via the gear rack, the toothed worm sector, arm and drag link. At the same time, the worm sector will act upon the work and will shift it together with the distribution slide valve to its initial position and stop the piston travel in the boost cylinder. When the steering wheel is turned in the other direction, the wheels will be turned appropriately in the same sequence.


The more the steering mechanism and wheels resist turning, the more the control valve is displaced. Hence, power assistance is always supplied in proportion to the effort needed to turn the wheels.

Electronic power steering

Electrically assisted power steering is used in some cars. The assistance can be applied directly by an electric stepper motor integrated with the steering column, or the steering mechanism, or it can be applied indirectly with hydraulic assistance pressurized by electric pump. EPS attached to the rack and pinion-steering-exists in Honda-City vehicles.

power steering

Electronic power steering Improves steering feel and power saving effectiveness and increases steering performance. It does so with control mechanisms that reduce steering effort. Nissan’s Blue Bird passenger car series use an electronically controlled three way power steering. This power steering is responsive to vehicle speed, providing maximum assistance as the speed rises. The driver can also select his or her own performance from three levels of assistance that make the steering effort heavy, normal or light.




Belt Conveyors for bulk materials:

Take up Arrangement:

All belt conveyors require the use of some form of take up device for the following reasons:

  1. To ensure adequate tension of the belt leaving the drive pulley so us to avoid any slippage of the belt.
  2. To ensure proper belt tension at the loading and other points along the conveyor.
  3. To compensate for changes in belt length due to elongation.
  4. To provide extra length of belt when necessary for splicing purpose.

Usually there are two types of take up arrangements.

These are:

  1. Fixed take up device that may be adjusted periodically by manual operation
  2. Automatic take up device (constant load type)


Manual Screw Take Up:

The most commonly used manual take up is the screw take up. In a screw take up system the take up pulley rotates in two bearing blocks which may slide on stationery guide ways with the help of two screws. The tension is created by the two screws which are tightened and periodically adjusted with a spanner. It is preferable to use screws with trapezoidal thread to decrease the effort required to tighten the belt.


The main problem with the use of manual take up is that it requires a vigilant and careful operator to observe when take up adjustment is required. Perfect tension adjustment with this system is also not possible. For these reason these devices are used only in case of short conveyors of up 60m length and light duty.


Automatic Take Up:

In automatic take up arrangement the take up pulley is mounted on slides or on a trolley which is pulled backwards by means of a steel rope and deflecting pulleys. The carriage travels on guide ways mounted parallel to the longitudinal axis of the conveyor, i.e., horizontally in horizontal conveyors (Ex.: Gravity type automatic take up arrangement) and at an incline in inclined conveyors. Hydraulic, Pneumatic and electrical take up devices are also used.

Automatic take up has the following features:

  1. It is self adjusting and automatic
  2. Greater take up movement is possible

For the perfect conveying of materials, adding a resistance with the peripheral forces on the driving pulley of a belt conveyor is important. Some of the resistances are:

  1. The inertial and frictional resistance due to acceleration of the material at the loading area
  2. Resistance due to friction on the side walls of the skirt board at the loading area.
  3. Pulley bearing resistance applicable for other than the driving pulley
  4. Resistance due to the wrapping of the belt on pulleys
  5. Special resistances include
  6. Resistance due to idler tilting
  7. Resistance due to friction between material and skirt plate
  8. Frictional resistance due to belt cleaners
  9. Resistance due to friction at the discharge plough

Special resistances are usually small. Here the resistance due to idler tilting and skirt resistance is ignored. There being no discharge plough the resistance due to plough is ignored. For belt speeds greater than 3 m/s, the edge clearances are applicable.


Automatic transmission


In this fast moving and leisurely world it is important that we look at the automation of gear systems in car. With the development of technology it is now possible to shift gears in car automatically making human life more comfortable than before.
An automatic transmission also called auto, self-shifting transmission, n-speed automatic or AT, is a type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually.

Like other transmission systems on vehicles, it allows an internal combustion engine, best suited to run at a relatively high rotational speed, to provide a range of speed and torque outputs necessary for vehicular travel. The number of forward gear ratios is often expressed for manual transmissions as well
the most popular form found in automobiles is the hydraulic automatic transmission. Similar but larger devices are also used for heavy-duty commercial and industrial vehicles and equipment. This system uses a fluid coupling in place of a friction clutch and accomplishes gear changes by hydraulically locking and unlocking a system of planetary gears. These systems have a defined set of gear ranges, often with a parking pawl that locks the output shaft of the transmission to keep the vehicle from rolling either forward or backward. Some machines with limited speed ranges or fixed engine speeds, such as some forklifts and lawn mowers, only use a torque converter to provide a variable gearing of the engine to the wheels.



Brain Wars | Episode 3 – Open lockers


A very rich celebrity decides to safeguard his wealth in a very
innovative way. He buys a cupboard having 10×10 indentical lockers
(numbered from 1-100) having single key. He passes through all the
lockers in numbered order and opens all of them. Then he goes to the
first locker and locks every alternate lockers till he reaches the
100th locker. Then he again goes to the first locker and opens every
third locker such that if the locker is already opened he closes it.
Simillary for the fourth pass he opens/locks every fourth locker and
continues the process for 100 passes. At the end of the 100th pass he
is left with few open lockers and uses them to keep his wealth. In
rest of the lockers he installs laser alarms so that even a wrong
selection of locker by the thief would lead him behind the bars. So
fellas do you have enough force to identify those wealthy lockers?

Continue reading Brain Wars | Episode 3 – Open lockers

Brain Wars | Episode 2 – Light years?


Let’s say ISRO discovered life on a planet which is 40 light years away from Earth. So it sent a spacecraft to verify the discovery. The spacecraft can travel with a maximum speed of 70 lightyears/year ( using a Wormhole!) and any change in speed is instantaneous (i.e. time lost in acceleration and deceleration is negligible). At the midway crew members realized that they were traveling at the speed of 20 lightyears/year and decided to speed up the spacecraft. How fast do they need to travel the rest of the course to have an average speed of 40 lightyears/year? Given the speed limits of the spacecraft is it even possible?!


Its impossible to have an average speed of 40 lightyears/year.

Continue reading Brain Wars | Episode 2 – Light years?

Brain Wars | Episode 1 – Shortest possible time [puzzle]


A family of four members (Father, Mother, Daughter and Son) set up a camp near the bank of a river. At midnight they discovered that the forest behind them has caught fire and is rapidly approaching them. The only choice the family has got is to cross the river (they have a boat which can carry a maximum of two members). All the family members know how to row the boat but with different speeds (Father, Mother, Daughter and Son can row to other side of the bank in 1min, 2min, 5mins and 10mins respectively). The pairs must row at the speed of the slowest person. Also the boat cannot cross the river without a person on it. Given the limitations what is the shortest possible time in which the entire family can safely cross the river?

Continue reading Brain Wars | Episode 1 – Shortest possible time [puzzle]

Gravity explained using Einstien’s Theory of relativity

    General theory of relativity is the geometric theory of gravitation  published by Albert Einstein. General relativity generalizes special relativity and Newton’s law of universal gravitation,  providing a unified description of gravity as a geometric property of space and time.

Here is a simple model explaining Einstein’s theory : Continue reading Gravity explained using Einstien’s Theory of relativity

CNC Routers are costly. This startup brings the most cost effective router in the market.

In this surge of startups in Indian market Radiance team approached a core mechanical startup named ‘Ethereal Machines’. In this video the co-founders of Ethereal machines are sharing the journey of their startup, what odds they faced while building the company and have shared their experience.

See video interview below:
Continue reading CNC Routers are costly. This startup brings the most cost effective router in the market.