construction and working of constant mesh gearbox

Constant Mesh Gear Box
Constant mesh gearbox is a type of Transmission where all or the majority of the gears are always in mesh with one another, instead of a sliding-gear transmission, where engagement is usually obtained by sliding a few of the gears along a shaft into mesh. In a constant-mesh manual gearbox, Gear ratios are chosen by small Clutches that connect the various gear sets to their shafts so that power is certainly transmitted through them. The following diagram shows the arrangement of a continuous mesh gear box
Construction and operating of a continuous mesh gear box
Constant equipment mesh gearbox employed helical gears for power tranny. The gears are rigidly set in the lay shaft. The gears in output shaft rotates freely without engaging with shaft, thus not really transmitting power. The gears in both shafts are often meshed together.
To activate the gears with output shaft dog clutch can be used. the dog clutch is definitely shifted by the seletor fork transferred by gear lever.To provide invert gearing a idler equipment is used.
When the gear lever is pushed, the apparatus selector fork pushes the dog clutch. The dog clutch engages the gear and the output shaft, therefore power from lay shaft now transmitted to output shaft.
CONSTANT MESH GEARBOX
A constant mesh transmission is a form of manual transmission where sliding gears from the sliding mesh gearbox is replaced with the constantly meshed combines of gears and also the new shifting products named dog clutches square measure introduced which helps in transmittal the required output to the most shaft by creating connection with the acceptable couple of the meshed gears.
A constant mesh transmission typically comes with 4 forward speeds and 1 reverse manual transmitting configuration.
Why will we want Constant Mesh Transmission?
The introduction of initial transmission system i.e. sliding mesh tranny was a great success in cars trade as currently there was a system which can offer needed torsion and quickness ratios want by the vehicle to face the road challenges however still there have been several vital issues with this equipment that raised the query on its performance and responsibility. the issues long-faced were as follows-
The shifting of gears wasn’t an easy task since the shifting needed a special technique that wasn’t in any respect everybody’s cup of tea, a talented driver was necessary 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 double engagement and disengagement of clutch for shifting one gear.
f i.electronic. once driver must shift the apparatus he initial presses the clutch pedal and create the gear to the neutral, than once again he releases the clutch pedal and accelerate so as to extend the rate of the lay-shaft to ensure that the meshing of applicable gear will occur, save for he presses the clutch pedal and generate the apparatus lever to the required equipment and unleash the clutch pedal and finally the required gear is obtained.
Since the gears are to 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 deterioration is there.
The shifting of gears is actually a terribly clamant method.High maintenance is necessary 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 given on the primary shaft: one between your clutch equipment and the next gear; and the additional between your first gear and reverse gear. The main shaft is manufactured splined and all of the gears are free to move onto 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 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 next gear on the primary shaft, the next speed equipment is achieved. Similarly, by sliding the right-hand dog clutch left and right, the first speed gear and reverse gear are obtained respectively In this kind of gearbox, because all of the gears are in constant mesh, they are safe from being damaged and unpleasant grinding audio does not happen while engaging and disengaging them.
Constant mesh gearbox is used for the smooth functioning of an automobile. They are used to increase the rotating push (Torque); this is accompanied by a decrease in speed. It is a type of manual transmitting. The invention of earliest manual gear system could be traced back again 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 provided point of time.
In technical terms, it could be thought as a gearbox in which all of the gears are at all times in a state of mesh. The gears stay fixed at their primary positions. The gears will remain engaged at all times. Find out more about its construction, working, advantages, drawbacks and applications in this post.
Construction:
It is made up of following components:
1. Counter shaft or Lay Shaft:
This shaft is in direct contact with the clutch and the main shaft. Keeping in mind according to the gear ratio, the rate of the counter shaft could 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 gear.
2. Main shaft:
This shaft operates the speed of the vehicle. The power is made available to the main shaft through the gears from the counter shaft. That is done relative to the gear ratio.
3. Dog clutch:
Dog clutch is special feature of constant mesh gearbox. It is used for the coupling of any two shafts. That is performed by interference. Utilizing a dog clutch, numerous 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 apparatus ratio is more than one, the main shaft will work at a speed that is slower than the counter shaft, and vice versa. The set up of both reverse, in addition to forward gears, is present.
Working:
Forward gear selection:
From the input shaft, the power starts flowing and is split into four parts. Each component goes to one of the output gears, namely first, second, third and 4th. Gear ratios can be obtained for each of these. This is often done by the correct sliding of dog clutch over the teeth of the chosen gearwheel. After this the path of the energy flow completes. This happens because of the locking movement of the output shaft.
Reverse gear selection:
The power 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 changes the path of the rotation. In the case of forwarding direction equipment selection, the output gears will rotate in a path opposite to the input gears. But in the case of reverse gear selection, the rotation is certainly in the same direction as the input shaft.
The steps are taken up to change any gear in the constant mesh gearbox system:
1. The first rung on the ladder when one really wants to change the gear will be the pressing of the clutch. After this comes the neutral state of the automobile to be performed. Proper optimization of the engine’s speed is necessary.
2. After the neutral gear, one moves forwards to the first gear. The first equipment. This process is known as dual clutching. Inefficiency in executing the above steps might result in a harsh and gnashing sound.
Advantages and Disadvantages of Constant Mesh Gearbox:
Advantages:
The first and foremost benefit of the constant gear mesh is the utilization of helical gears. The double helical gears and the helical gears are really beneficial owing to their quieter operating capabilities
There are many conditions which might cause harm. In the case of constant mesh gearbox, any harm is suffered completely by the dog clutch teeth. One’s teeth belonging to the apparatus wheels remain intact. This is simply not the case for sliding mesh gear box.
The other gear boxes are noisy and create an undesirable din.
Disadvantages:
It really is less efficient than the others due to higher mesh teeth. Skill is required for it.
The dual clutch mesh is required. This is necessary to have the spinning motions of the shaft.
Application:
Some of the vehicles which use this type of gearboxes are farm trucks, motorcycles, and heavy machinery.
In this kind of gearbox, all the gears of the main shaft are in constant mesh with the corresponding gears of the counter shaft or lay shaft.
Two dog clutches are given on the primary shaft i.e. one in between the clutch equipment and the second gear, and the various other between the first gear and the reverse gear.
Your 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 and when the left hand dog clutch is made to slide left by means of the gear shift lever, it meshes with the clutch equipment and the top speed gear is obtained. When the still left hands dog clutch meshes with second equipment, the next gear is obtained.
Similarly, by sliding correct hand dog clutch left and right, the 1st 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 will not take place while engaging and disengaging.