Tips to choose optimal gear for the paticular situation ...

In this series of discussions,we have so far discussed transmission system and it's attached sub systems. finally we will have to look at Tips that given smooth very efficient operation to utilized power consumption of vehicle.

Why we need to change gear?

1.To change speed level of the vehicle.

2.To change the power level.

how we select suitable gear for the situation?

1.considering efficient fuel consumption


2.considering only fastest movement.

what can control fuel consumption

 1.accelerator position

what control's speed and torque for particular engine power instant

1.clutch position

2.gear level

relationship of output power and speed


power = engine power(accelerator position) x gear level x clutch position..........................(1)

speed = engine speed(accelerator position) x gear level x clutch position............................(2)

accordingly the mode of desires we have to chose it in our interest.
 

Firstly will discuss basics of the vehicle transmission system(VTS)

What is Transmission System(TS) ?

TS is gear train which is used to change the speed of the vehicles,connected between engine and wheels(deferential)

Figure 1 : Diagram of the vehicle power transmission system

Psychically transmission system consist of pairs of meshing gear wheels and its input connected to engine via clutch(next couple of blogs we will learn,for this instant we will keep in mind clutch is a device which can connect or isolate the gearbox from engine(power source, especially the time period changing gear).output is connected to driving wheel that used to drive vehicle.

Gear	RPM	Ratio
1st	1295	1:0.432
2nd	1913	1:0.638
3rd	2510	1:0.837
4th	3000	1:1
5th	3278	1:1.093

 Table 1: standard gear ratio(when assuming gearbox input shaft rotates 3000 RPM)

Figure 2: Gear box cross section      Figure 3: Schematic diagram of gearbox

here you can understand how coupling,connecting wheel to supply rotational energy

Power(N.m/s,W) = Torque(N.m) x Rotation speed(rad/s)

In Table 1 you can just understand, in first gear, gear ratio is 1:0.432 as long as I/P of gear box rotates 3000 RPM then output rotates 1295 RPM ,considering formula if speed reduce the handling torque will increases so, in first gear ,low speed and high torques application means can pull more load compare with 2nd gear as long as considering standard gear ratio.

Figure 4:Meshing the gear wheels

basically what you have to understand just look at figure is both wheel has teethes, when one gear wheel is rotating, at the meshing point,teeth of other gear wheel is pulled by rotating wheel teeth, therefore both rotates but direction of rotation is counter sides.

next will think one round rotates of rotating gear at meshing point it pass all its teethes and also that number of teeth were pulled out.

suppose let's take rotating wheel has N1 teeth and driven wheel has N2 teeth 

• 1 round of wheel 1 mesh N1 teeth
•  N2 meshing of wheel 2 gives 1 round of rotation
• N1 meshing of wheel 2 gives N1/N2 round of rotation  

that how gear trains gives variable speeds.

Types of gear wheel,categorized according to teeth geometry

1.Spur gears

2.helical gears

3.herringbone gears

here classified used these types according to requirements

spur gears helical gears herringbone gears degree of power transmission  good better best direction of power can be transmitted only parallel both parallel and perpendicular only parallel

Table 2: types of gears

 Figure 5:Spur gears

 Figure 6:Helical gears

 Figure 7:Herringbone gears

 Gear changing and Clutch engagement

its performed by shifting mechanism of the gear wheels and meshed another set which has a deference gear ratio in it.
need to isolate gear wheels from driver when changing is done,therefore its used clutch which operate based on frictional plates principle.

then gear wheel which is to be meshed are firmly handled by gear changer and after all clutch is to be engaged slowly to supply power for drive driven wheels via gear box.
in reality clutch and gearing give continuous transmission.clutch has a continuous gear ratio due to its slip(slip changing slowly,when engaging slowly).

 Clutch

 Figure 8: Clutch assembly

Fly wheel directly fixed to crank shaft(engine),clutch disc is fixed to gear box input shaft
very substantial,clutch disc can move horizontally and while rotation can transfer with no slip,clutch disc has linear which has a ability to contact firmly with flywheel surface, when pressure plate apply horizontal force and also when pressure plate released then clutch disc return from flywheel, isolated power source from rest.that is how working it.

there are different types of clutches

1)centrifugal clutch(automatic transmission system mostly used)

2)cone clutch

3)belt clutch

4)dog clutch

engaging force can be supplied by different method

1) manual (manual transmission)

2) hydraulic/pneumatic piston(automatic transmission)

3)electromagnetic forces(motors or solenoids)

please comment here any clarification and grammar mistakes whatever in it(all are open to discuss )