Constant Mesh Gear Box
Constant mesh gearbox is certainly a type of Transmission where all or the majority of the gears are always in mesh with one another, as opposed to a sliding-gear transmission, where 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 construction and working of constant mesh gearbox clutches that connect the many gear sets to their shafts so that power is 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 transmission. The gears are rigidly set in the lay shaft. The gears in output shaft rotates freely without engaging with shaft, thus not transmitting power. The gears in both shafts are constantly meshed together.
To engage the gears with result shaft dog clutch can be used. the dog clutch is shifted by the seletor fork relocated by gear lever.To provide invert gearing a idler equipment is used.
When the apparatus lever is pushed, the gear selector fork pushes the dog clutch. The dog clutch engages the gear and the result shaft, hence power from lay shaft today transmitted to output shaft.
CONSTANT MESH GEARBOX
A constant mesh transmission is that a form of manual transmission in which sliding gears from the sliding mesh gearbox is replaced with the constantly meshed combines of gears as well as the new shifting gadgets named dog clutches square measure introduced which helps in transmittal the required output to the many shaft by creating contact with the acceptable pair of the meshed gears.
A constant mesh transmission typically includes 4 forward speeds and 1 reverse manual tranny configuration.
Why will we want Constant Mesh Transmission?
The introduction of initial transmission system i.electronic. sliding mesh tranny was an excellent success in vehicles trade as currently there was a system which might offer needed torsion and rate ratios want by the vehicle to face the street challenges nevertheless still there have been several vital problems with this equipment 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 special technique that wasn’t in any respect everybody’s cup of tea, a talented driver was needed for generating such vehicle, the special technique needed being Double-de-clutching.
Note – Double-de-clutching- it’s the technique because the name indicates that needed double engagement and disengagement of clutch for shifting a single gear.
f i.e. once driver must shift the apparatus he preliminary presses the clutch pedal and generate the gear to the neutral, than once more he releases the clutch pedal and accelerate in order to extend the swiftness of the lay-shaft to ensure that the meshing of applicable gear will take place, save for he presses the clutch pedal and create the apparatus lever to the desired equipment and unleash the clutch pedal and finally the desired gear is obtained.
Since the gears should be meshed square measure in continuous rotation with a completely different speed than 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 main shaft are in constantly meshed with the corresponding gears of the layshaft or countershaft. Too dog clutches are provided on the main shaft: one between the clutch equipment and the second gear; and the various other between your first gear and invert gear. The main shaft is manufactured splined and all of the gears are free to move onto it. Dog clutches can slide on the primary shaft and rotates with it. All the gears on the countershaft are permanently fixed with it.
When the left dog clutch is made to slide left by using the apparatus shift lever, it meshes with the clutch gear and the top speed gear is obtained. When the remaining dog clutch meshes with the second gear on the main shaft, the second speed gear is achieved. Likewise, by sliding the right-hand dog clutch to the left and right, the first speed gear and reverse equipment are acquired respectively In this type of gearbox, because all the gears are in continuous mesh, they are safe from being broken and unpleasant grinding sound does not occur while engaging and disengaging them.
Continuous mesh gearbox can be used for the smooth functioning of an automobile. They are used to increase the rotating pressure (Torque); that is accompanied by a reduction in rate. It is a kind of manual transmission. The invention of earliest manual gear system could be traced back again to the nineteenth century. There are multiple equipment ratios present which gives various torque and swiftness ratio. Additionally, the reverse mechanism is also present. This manual transmissions which are developed recently contain all of the gears mesh at any given point of time.
In technical terms, it can be thought as a gearbox where all of the gears are often in a state of mesh. The gears remain fixed at their initial positions. The gears will stay engaged all the time. Find out more about its construction, working, advantages, drawbacks and applications in this post.
Construction:
It really is made up of following components:
1. Counter shaft or Lay Shaft:
This shaft is in direct connection with the clutch and the primary shaft. Remember according to the gear ratio, the swiftness of the counter shaft may be less that the swiftness of the engine. The gear ratio can be explained as the ratio of the teeth of driven equipment to the teeth of the driver equipment.
2. Main shaft:
This shaft operates the speed of the automobile. The power is manufactured available to the primary shaft through the gears from the counter shaft. That is done in accordance with the gear ratio.
3. Dog clutch:
Dog clutch is particular feature of constant mesh gearbox. It is used for the coupling of any two shafts. This is carried out by interference. Utilizing a dog clutch, different gears can be locked to the output and input shafts.
4. Gears:
The main work of the gears may be the transmission of power between your shafts. If the gear ratio is more than one, the primary shaft will work at a velocity that is slower than the counter shaft, and vice versa. The arrangement of both reverse, in addition to forward gears, is present.
Working:
Forward gear selection:
From the input shaft, the power starts flowing and is divided into four parts. Each part goes to among the result gears, namely initial, second, third and fourth. Gear ratios can be acquired for each of these. This could be done by the proper sliding of dog clutch over the teeth of the chosen gearwheel. After this the path of the energy movement completes. This happens because of the locking movement of the result shaft.
Reverse gear selection:
The energy will flow from the input shaft to the reverse gears. The power is after that transmitted from the invert gear to the reverse idler. The idler wheel will change the path 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 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 modify the gear will be the pressing of the clutch. After this comes the neutral state of the vehicle to be achieved. Proper optimization of the engine’s speed is required.
2. After the neutral equipment, one moves forwards to the first gear. The first gear. This process is known as dual clutching. Inefficiency in executing the above techniques might lead to a harsh and gnashing sound.
Advantages and Disadvantages of Constant Mesh Gearbox:
Advantages:
The first and foremost advantage of the continuous gear mesh may be the utilization of helical gears. The double helical gears and the helical gears are 
extremely beneficial owing to their quieter operating capabilities
There are various conditions which can cause harm. Regarding constant mesh gearbox, any harm is suffered completely by your dog clutch teeth. The teeth belonging to the gear wheels stay intact. This is not the case for sliding mesh gear box.
The other equipment boxes are noisy and create an undesirable din.
Disadvantages:
It is less efficient compared to the others due to higher mesh teeth. Skill is required for it.
The double clutch mesh is required. This is required to have the spinning movements of the shaft.
Application:
A few of the vehicles designed to use this type of gearboxes are farm trucks, motorcycles, and weighty machinery.
In this kind 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.e. one in between the clutch gear and the next gear, and the additional between the first gear and the reverse equipment.
The dog clutch can slide on the shaft and rotate with it. While, all of the gears on the counter shaft are rigidly set with it.
As so when the left hands dog clutch is made to slide to the left by means of the apparatus change lever, it meshes with the clutch equipment and the top speed equipment is obtained. When the remaining hands dog clutch meshes with second gear, the next gear is obtained.
Similarly, by sliding correct hand dog clutch to the left and right, the initial speed gear and reverse gear are obtained respectively.
In this type of gearbox, all the gears are in constant mesh and hence for this reason, they are safe from being damaged and irritating grinding sound does not occur while engaging and disengaging.