Steering gear Mechanism

October 7th, 2011 by daniel

We use steering gear mechanism for changing two or more than two wheel axles with respect to chassis. Commonly we have two back wheels common axis and are fixed in a direction with respect to chassis.

In automobiles front wheels are placed over front axles and are fixed at points A and B, similarly back wheels are on the back axle. When a driver takes a turn, front wheels move with respect to pivoted points and back wheels remain straight and do not change their direction.

Steering gear mechanism

So to avoid skidding on the road, it is necessary for front wheels to meet at instantaneous center I. if wheels do not intersect than skidding must be done definitely. So after getting instantaneous center, the angle of inner wheel θ must be greater than angle φ of outer wheel.

For deriving relation let us consider

a= Wheel track

b =Wheel base

c = Distance between points A and B

Considering triangle IBP

cotθ = BP / IP

Now from triangle IAP

cotφ =AP / IP = (AB + BP) / IP = AB/IP + BP/IP

cotφ =c/b + cotθ

cotφ – cotθ = c/b

So according to desire result if the value came positive then there will be no skidding.


October 7th, 2011 by daniel

Spring is a type of mechanical device which show movement in upward or downward direction or a device which can store mechanical energy. When we apply specific amount of force is applied on it under elastic limit, it will come to its original position by pushing force and this pushing force is the energy released. This energy is store in it when external force is applied. Material of the spring must be non-magnetic, electricity conductivity and has high temperature working ability. Max temperature on which springs can work is up to 1100°F.
There are many types of springs used which are following
• Helical springs
• Conical and volute springs
• Leaf spring
• Disk springs
• Torsion bar
• Special purpose springs

Helical springs

Helical spring is said to be a spiral type spring which is coiled in the form of helix. There are further two types of helical springs depending upon the direction load and these springs are
Compression helical spring is a spring which compress after the load is applied. In the result, the length of the spring reduces and energy stores it. This spring releases energy when it comes back to its original position and this force is called pushing force.
Tensile helical spring is a spring in which its length increases after applying load but after the removal of load spring returns to its original shape.
In both types load is applied parallel to spring axis. When we look this spring type depending upon the geometry it also has two types.
Closely coiled helical spring is a type of spring in which there is very less space between two turns and helix angle is less than 10° which means that each turn is almost at right angle.
Open coiled helical spring is a type of spring in which there is considerable difference between each turn. In this type helix angle is greater than 10°.

Helical springs


Conical and volute springs

Conical springs are said to be compressed conical springs and by changing their angle of helix, ending, material. These springs are available in only round shape made of high carbon steel wire. The pitch of these springs is variable and changes at every point. They are made like telescoping spring as partial and complete telescoping. In it we less active coils than total number of coils because top and bottom end coils are fixed which means that if any spring has 6 coils then it will definitely has 4 active coils used for operation.


Conical springs

On the other hand volute coils are also similar to conical springs but they have parabolic shape. The pitch of these coils is same. These springs have friction between each turn so it means that this spring best suits to vibration damper. Similarly they have benefits over helical springs so we can say that this spring is the modified form because it has more lateral stability and non-linearity of their load.


Volute springs

Leaf Springs

This type of springs has number of flat plates of varying lengths and each length hold together with clamps and bolts. We use these springs mostly in vehicles to absorb shocks produced by unbalancing of vehicle. Major stresses that are produced in this spring are compressive and tensile.


Leaf springs

Disk springs

This spring is made by conical discs and remains at the place against slipping by central bolt or tube. We can use these springs where we need high spring rates and compact spring unit.


Disk springs

Torsion springs

This spring can be in two shapes either in helical or in spiral. Helical type spring may be used where load can wind up the springs and is used in various electrical mechanisms. On the other hand spiral type is used where number of coils of spring increases as we increase load. This type is use in clocks and watches. Major stresses in torsion springs are compressive and tensile due to bending.


Special purpose springs

These springs can found in any shape like ring, rubber, air or liquid springs. The purpose of using these springs is to do special task only.

$35 tablet in India is reality

October 6th, 2011 by daniel

Popular tablets in the world market are Apple iPad at $499, HP TouchPad at $99 and recently released Kindle Fire at $199. But you will be surprise if anyone said about a tablet at $35 and comes with final $10 price tag in the market. Surprising one, but this tablet is released only in India and the name of the company is Askash. This company offers these tablets to students according to subsidized rate offered by government.

Kapil Sibal the information technology and human resource development minister said that by this tablet we reach the sky and explain it what is possible. So allow me to send a message.

The weight of the tablet is only 13 oz and has basic computing features like social networking, email, instant messaging, online banking, surfing and multimedia.

It operates on Google Android 2.2 OS and has two USB slots, Wi-Fi access, 256 MB internal memory, headphone and 7 inch screen.You can get portable phone charger units for Samsung,iPhone and other brands for under $30 on Amazon also
When this tablet launched company got excellent reaction from isolated areas in which many students are those who do not use a computer.

This tablet assembled in India and officials hope that this company would jump hardware industry to show its software strength. Officials also expressed that about 16 percent of 800 components are sourced here and 70 percent imports from South Korea, US and China.

$35 tablet in India is reality

Truss connection and supports

October 5th, 2011 by daniel

Rivet connections are used to join structural members and in practical applications we assume the connection a pin joint connection if the central line of the members is concurrent at joint. In the analysis we also consider that external forces will apply at pin connections. This condition is satisfied in most of the trusses. To know it practical application we consider a bridge truss in which the deck is laid on cross beams and these beams are supported by these joints.

In case of large trusses we use roller, rocker or some other kind of slip joints so that they can allow some extension and contraction due to change of temperature and also due to deformation from the applied load. Trusses and mostly frames in which no such condition is made are statically determinate. There are two methods which are used for the analysis of simple trusses. In both methods reactions are find out firstly by using equilibrium equations and then by applying force analysis method to find out remaining reactions, these two methods are method of joints and method of section.

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