DIFFERENCE BETWEEN WELDING AND BRAZING EXPLAINED !!

Welding and brazing are the metal joining process.Type of joining process to be applied for joining two parts depends on many factors.

WELDING :

>Welding is a process in which both the participating metals are metaled and re solidified to complete as one metal. Proper melting of mating parts is a basic criteria to result a sound weld.

BRAZING :

>In case of Brazing both the participating metals are not melted but a third metal of lower melting point is used to be filled in between the two. The solidification of this third metal results the joining. 

>The filler metal is drawn into the gap between the closely fitted surfaces of the joint by capillary action.

>The design of the joint should incorporate a minimum gap into which the braze filler metal will be drawn.

Comparison between welding and brazing :

S.No	Welding	Brazing
1	Welding joints are strongest joints used to bear the load. Strength of the welded portion of joint is usually more than the strength of base metal.	Brazing joints are weaker than welding joints. This can be used to bear the load up to some extent.
2	To join, work pieces need to be heated till their melting point.	Work pieces are heated but below their melting point.
3	Heat cost is involved and high skill level is required.	Cost involved and skill required is lower than welding.
4	Mechanical properties of base metal may change at the joint due to heating and cooling.	mechanical properties may change at joint but it is almost negligible.
5	Temperature required is 3800°C in welding joints.	Temperature may go to 600°C in brazing joints.
6	Heat treatment is generally required to eliminate undesirable effects of welding.	No heat treatment is required after brazing.
7	No preheating of workpiece is required before welding as it is carried out at high temperature.	Preheating is desirable to make strong joint as brazing is carried out at relatively low temperature.

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DIFFERENCE BETWEEN CRANKSHAFT AND CAMSHAFT EXPLAINED !!

Crankshafts:

The crankshaft is an engine component that converts the linear (reciprocating) motion of the piston into rotary motion. The crankshaft is the main rotating component of an engine and is commonly made of ductile iron.

All major components of the engine like piston,connecting rod etc. are supported by this shaft.

Construction Of Crankshaft:

A crankshaft is simply the same as an eccentric, except the eccentric is a much smaller diameter than the shaft itself Crankshaft length mainly depends on number of cylinders are present in engine .Firing order also considered while designing the Crankshaft .

Location :  Crankshaft is located in crank case . On Crankshaft, Connecting rods and pistons are mounted. The crankshaft rides on bearings which can wear down over time. The bearings support the crankshaft and also the rods which connect the pistons to the crankshaft.

Applications :It actually part of an engine where the power is available , and this power is transferred in the form of torque to clutch and thereby  gearbox and wheels.The main function is to convert liner motion of the piston to useful rotary motion.

Camshafts:

Camshaft is a part of engine which is responsible for opening and closing of exhaust and inlet valves.As the engines work they need to breathe out exhaust gases and take in fresh air ( charge) for the next cycle to take place . All these processes need to take place at a designated time with respect to each other. These processes are timed through opening and closing of valves and actuation of fuel pumps through a actuating mechanism which is triggered by movement of the crankshaft. The camshaft comes into picture here. The Crankshaft drives through a belt or chain drive the camshaft on which the inlet,exhaust, fuel pump cams are fitted for each unit when the crankshaft rotates it in turn rotates the camshaft which precisely actuate the valve and fuel pumps.

Construction Of Camshafts:

 A camshaft is a long bar with egg-shaped eccentric lobes, one lobe for each valve and fuel injector.

The relationship between the rotation of the camshaft and the rotation of the crankshaft is of critical importance. Since the valves control the flow of the air/fuel mixture intake and exhaust gases, they must be opened and closed at the appropriate time during the stroke of the piston. For this reason, the camshaft is connected to the crankshaft either directly, via a gear mechanism, or indirectly via a belt or chain called a timing belt or timing chain.

Location : Depending on the location of the camshaft, the cam operates the valves either directly or through a linkage of pushrods and rockers. Direct operation involves a simpler mechanism and leads to fewer failures, but requires the camshaft to be positioned at the top of the cylinders.

Applications :This shaft receives the power from crankshaft  (1:2) and operates the engine valves through cam and follower mechanism(generally mushroom headed follower is used to reduce friction b/w cam and follower).

KNOW WHY GEARBOX IS NOT USED IN ELECTRIC VEHICLES !!

Internal combustion engines generate usable torque and power in a narrow band of engine speeds. To accelerate the vehicle, multispeed transmissions step that down, in varying gear ratios, to keep the engine in its power band. Keeping the engine in its power band also proves to be the most efficient and durable. An engine, in first gear, can easily accelerate a car to 30 mph, but would also shake itself to bits attempting to accelerate to highway speed. Likewise, that same engine would hardly be able to accelerate from a stop in 6th gear.So,we require gearbox in case of internal combustion engines because usable torque and power is generated in a narrow band of engine speeds.The variation of torque is very high at different engine speed range.

In case of electric vehicles, electric motor-generators (MG) generate 100% of their torque at very low speeds, DC MGs near stall (zero rpm), and AC MGs around 1,000 rpm, as a general rule. As rpms increase, torque falls off at a fairly linear rate, at the same time that power is increasing. Toyota Prius, for example, the MG generates up to 300 N•m of torque around 1,500 rpm, trailing off to about 50 N•m at 6,000 rpm. At its most-efficient, 93%, the MG is pushing only 100 N•m at 2,250 rpm, perfect for cruising. In any case, a multispeed electric vehicle transmission is unnecessary because even 100 N•m is plenty of torque at cruising speed.Torque is necessary for acceleration, the most of which is generated near stall. Power is necessary for cruising, the most of which is developed at high rpm.

At lower speeds we need high torque which electric motor generates but in case of engines it is not so.This is shown in the graph above.The curve is almost linear in case of electric vehicle which shows that torque is almost same for wide range of operation.