Constant Mesh Gear Box
Constant mesh gearbox is a kind of Transmission where all or most of the gears are always in mesh with each other, instead of a sliding-gear transmission, in which engagement is obtained by sliding a few of the gears along a shaft into mesh. In a constant-mesh manual gearbox, Equipment ratios are selected by small Clutches that connect the many gear sets to their shafts so that power is certainly transmitted through them. The following diagram shows the set up of a constant mesh gear box
Construction and functioning of a constant mesh gear box
Constant equipment mesh gearbox employed helical gears for power transmitting. The gears are rigidly set in the lay shaft. The gears in output shaft rotates freely without engaging with shaft, hence not transmitting power. The gears in both shafts are at all times meshed together.
To engage the gears with output shaft dog clutch is used. the dog clutch is definitely shifted by the seletor fork transferred by gear lever.To provide reverse gearing a idler gear is used.
When the gear lever is pushed, the apparatus selector fork pushes your dog clutch. The dog clutch engages the gear and the output shaft, thus power from lay shaft right now transmitted to result shaft.
CONSTANT MESH GEARBOX
A constant mesh transmission is that a kind of manual transmission where sliding gears from the sliding mesh gearbox is replaced with the constantly meshed combines of gears as well as the new shifting devices named dog clutches sq . measure introduced which assists in transmittal the desired output to the the majority of shaft by creating connection with the acceptable couple of the meshed gears.
A constant mesh transmission typically includes 4 forward speeds and 1 reverse manual transmission configuration.
Why will we wish Constant Mesh Transmission?
The introduction of initial transmission system i.e. sliding mesh transmitting was an excellent success in cars trade as currently there is a system which might offer needed torsion and quickness ratios want by the vehicle to face the road challenges however still there were several vital problems with this gear that raised the query on its efficiency and responsibility. the issues long-faced were as follows-
The shifting of gears wasn’t an easy task because the shifting needed a particular technique that wasn’t in any respect everybody’s cup of tea, a talented driver was needed for driving such vehicle, the special technique needed being Double-de-clutching.
Note – Double-de-clutching- it’s the technique since the name indicates that needed dual engagement and disengagement of clutch for shifting one gear.
f i.e. once driver must shift the gear he preliminary presses the clutch pedal and create the apparatus to the neutral, than once again he releases the clutch pedal and accelerate so as to extend the speed of the lay-shaft to ensure that the meshing of relevant gear will take place, save for he presses the clutch pedal and produce the apparatus lever to the desired equipment and unleash the clutch pedal and at last the desired gear is obtained.
Since the gears should be meshed square measure in continuous rotation with a totally different speed compared to the meshing of those gears will cause breakage to the gear teethes or continuous wear and tear is there.
The shifting of gears could be a terribly clamant method.High maintenance is needed as slippy and meshing of gears causes resistance to wear of shafts and gears.
MAIN PARTS
Clutch Shaft.
Lay Shaft or counter Shaft.
Main Shaft.
Dog clutch.
Gears.
There are various kinds of gears with both spur and helical gears like:
Clutch gear.
First gear.
Second gear.
Reverse gear.
WORKING PRINCIPLE:
In Constant Mesh Gearbox gearbox, all gears of the primary shaft are in constantly meshed with the corresponding gears of the layshaft or countershaft. Too dog clutches are given on the main shaft: one between the clutch gear and the second gear; and the additional between the first gear and invert gear. The main shaft is made splined and all the gears are absolve to move on it. Dog clutches can slide on the main shaft and rotates with it. All the gears on the countershaft are completely fixed with it.
When the left dog clutch is made to slide to the left with the help of the apparatus shift lever, it meshes with the clutch gear and the top speed gear is obtained. When the still left dog clutch meshes with the second gear on the main shaft, the next speed gear is achieved. Similarly, by sliding the right-hand dog clutch to the left and correct, the first speed gear and reverse gear are obtained respectively In this kind of gearbox, because all the gears are in continuous mesh, they are safe from being broken and unpleasant grinding audio does not take place while engaging and disengaging them.
Constant mesh gearbox is used for the smooth operating of a car. They are accustomed to increase the rotating force (Torque); this is accompanied by a reduction in swiftness. It is a type of manual tranny. The invention of earliest manual equipment system can be traced back to the nineteenth century. There are multiple equipment ratios present which provides various torque and acceleration ratio. Additionally, the reverse mechanism can be present. This manual transmissions which are developed lately contain all the gears mesh at any given point of time.
In technical terms, it could be defined as a gearbox in which all of the gears are often in circumstances of mesh. The gears remain fixed at their primary positions. The gears will remain engaged at all times. Find out more about its building, working, advantages, drawbacks and applications in this post.
Construction:
It is made up of subsequent components:
1. Counter shaft or Lay Shaft:
This shaft is in direct connection with the clutch and the primary shaft. Keeping in mind according to the equipment ratio, the rate of the counter shaft may be much less that the speed of the engine. The gear ratio can be explained as the ratio of the teeth of driven equipment to the teeth of the driver gear.
2. Main shaft:
This shaft operates the speed of the automobile. The power is made available to the primary shaft through the gears from the counter shaft. That is done relative to the gear ratio.
3. Dog clutch:
Dog clutch is particular feature of constant mesh gearbox. It is utilized for the coupling of any two shafts. This is performed 
by interference. Utilizing a dog clutch, various gears can be locked to the result and input shafts.
4. Gears:
The main work of the gears may be the transmission of power between the shafts. If the apparatus ratio is more than one, the main shaft will work at a swiftness that is slower than the counter shaft, and vice versa. The arrangement of both reverse, and also forward gears, is present.
Working:
Forward gear selection:
From the input shaft, the energy starts flowing and is split into four parts. Each component goes to among the result gears, namely 1st, second, third and 4th. Gear ratios can be acquired for each of them. This is often done by the correct sliding of dog clutch over one’s teeth of the chosen gearwheel. After this the road of the energy stream completes. This happens due to the locking motion of the output shaft.
Reverse gear selection:
The power will flow from the input shaft to the reverse gears. The energy is after that transmitted from the reverse gear to the invert idler. The idler wheel changes the direction of the rotation. In the case of forwarding direction equipment selection, the result gears will rotate in a direction opposite to the input gears. However in the case of reverse gear selection, the rotation is certainly in the same direction as the insight shaft.
The steps are taken to change any gear in the continuous mesh gearbox system:
1. The first step when one really wants to change the gear will be the pressing of the clutch. After this comes the neutral condition of the vehicle to be performed. Proper optimization of the engine’s speed is required.
2. After the neutral gear, one moves forward to the first gear. The first equipment. This process is known as double clutching. Inefficiency in performing the above methods might result in a severe and gnashing sound.
Advantages and Disadvantages of Constant Mesh Gearbox:
Advantages:
The first and foremost benefit of the constant gear mesh is the usage of helical gears. The double helical gears and the helical gears are extremely beneficial due to their quieter operating capabilities
There are many conditions which can cause harm. In the case of continuous mesh gearbox, any damage is suffered entirely by the dog clutch teeth. One’s teeth belonging to the apparatus wheels stay intact. This is not the case for sliding mesh equipment box.
The other gear boxes are noisy and create an undesired din.
Disadvantages:
It is less efficient than the others due to higher mesh teeth. Skill is necessary for it.
The double clutch mesh is required. This is necessary to have the spinning motions of the shaft.
Application:
Some of the vehicles which use this kind of gearboxes are farm trucks, motorcycles, and large machinery.
In this type of gearbox, all the gears of the primary shaft are in constant mesh with the corresponding gears of the counter shaft or lay shaft.
Two dog clutches are given on the main shaft i.electronic. one in between the clutch gear and the second gear, and the various other between the first equipment and the reverse gear.
The dog clutch can slide on the shaft and rotate with it. While, all of the gears on the counter shaft are rigidly fixed with it.
As so when the left hands dog clutch was created to slide left by means of the gear shift lever, it meshes with the clutch equipment and the very best speed equipment is obtained. When the left hands dog clutch meshes with second gear, the next gear is obtained.
Similarly, by sliding right hand dog clutch to the left and right, the initial speed gear and reverse gear are obtained respectively.
In this kind of gearbox, all of the gears are in constant mesh and hence for this reason, they are safe from being damaged and irritating grinding sound does not happen while engaging and disengaging.
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