What Is Sliding Mesh Gearbox?- Parts And Working

What is a Sliding mesh gearbox?

Sliding mesh gearbox is a transmission system that consists of various sets of gears and shafts that are arranged together in an organized fashion and the shifting or meshing of different gear ratios is done by the sliding of gears towards the right and left over the splined shaft with the help of a gear lever operated by the driver.

An obsolete type of transmission or gearbox in which the gears on the layshaft are fixed to the shaft rigidly, whereas the gears on the main shaft can slide on it by means of splines but are otherwise permanent rotational mesh with the shaft. The figure below shows the arrangement of the sliding mesh gearbox.

Sliding Mesh Gearbox was the first gearbox or transmission system invented in the automobile. The first transmission system was given by French Inventors Louis-Rene and Emile Levassor who invented the world’s largest-ever transmission system with 3-speed sliding mesh transmission in 1894. The gear ratio is achieved by sliding the required gears to bring it with appropriate mating gears.

Parts of Sliding Mesh Gearbox:

The main parts of the sliding mesh gearbox are:

  1. Shafts
  2. Gears
  3. Gear Lever
sliding mesh gearbox diagram

Shafts

The shaft is generally used to transmit the power from one end to another end. There are three types of shafts in the case of Sliding Mesh Gearbox.

  1. Clutch Shaft: The clutch shaft is used to transmit the power from the engine when the clutch is in the engaged position. When the clutch shaft is rotating, the clutch gear which is attached at the end of it also rotates along with the clutch shaft.
  2. Lay Shaft: The layshaft is an intermediate shaft between the clutch shaft and the Main shaft which provides meshing of fixed gears to the movable gears to provide the output appropriately. The fixed gears are attached to the layshaft and they are in mesh with the gears of the main shaft and the gear of the clutch shaft.
  3. Main Shaft: This shaft acts as an output shaft for the transmission of power from the engine shaft via layshaft. The gears with internally splined grooves are arranged on the main shaft so that they can mesh easily with the gears of the layshaft.

Gears

Usually, two types of gears were used in the sliding mesh gearbox. They are: –

  1. Spur gear: Spur gears have straight teeth that are produced parallel to the axis of the gear. These gears are the most economical types of gear but tend to vibrate and become noisy at high speed.
  2. Helical gear: The teeth of helical gears are not parallel to the gear axis. The teeth of this gear type are at an angle to the gear axis. These gears are less noisy and have a smoother operation than a spur gear. Also, these gears have higher tooth strength and a higher load-carrying capacity.

Gear Lever

It is used to slide the gears in the main shaft to obtain the appropriate gear ratio. It is operated by the driver.

Construction and Working of sliding mesh gear box

The gear connected to the clutch shaft also rotates. As the gear of the clutch shaft rotates, the layshaft gear which is connected to the clutch shaft gear also rotates but in opposite direction. So, the layshaft rotates due to the rotation of layshaft gear that is rigidly fixed in the layshaft.

Sliding mesh gearboxes are made with spur gear. The gears in the layshaft are rigidly fixed shafts. The gears in the main shaft alone can move along the spline. The selector fork moves the gear and moves the perfect mesh with the required gear in layshaft when the gear lever is shifted.

An idler gear is provided for reverse gearing. Thus, the power that forms the clutch shaft is transmitted to the main shaft through the layshaft.

  • First gear: In the first gear, the gearbox provides maximum torque at low speed. The smallest gear on the layshaft engages with the biggest gear in the main shaft, thus transmitting high torque. First Gear is used at the time when the vehicle starts its movement in a forwarding direction.
  • Second gear: In the second gear, the gearbox provides low torque and high speed when compared to 1st gear. Second Gear is obtained when second largest gear of second smallest gear of layshaft meshes with middle size gear of the main shaft.
  • Third gear: In the third gear, the gearbox provides low torque and high speed when compared to 2nd gear. The third gear is the last gear or top gear of the Sliding Mesh Gearbox. This gear is obtained when the biggest gear of layshaft meshes with the smallest gear of the main shaft.
  • Fourth gear: For the fourth gear, the clutch shaft and the main shaft are engaged by a dog clutch, thereby the main shaft rotates at maximum speed as that of the clutch shaft.
  • Reverse gear: When selecting reverse, the direction of rotation of the output shaft is changed This is achieved by using an idler gear. The idler gear meshes between a countershaft gear (layshaft or 2nd motion shaft) and an output shaft gear (main shaft or 3rd motion shaft).

Advantages of Sliding Mesh Gearbox:

  • Since only one gear is in mess in the sliding mesh gearbox so less fluctuating loads on shafts causing less vibration and noise
  • unlike the contact mesh gearbox in which all gears are in constant mesh.
  • Its efficiency is more than a constant gearbox as only one gear is in mess, unlike the contact mesh gearbox in which all gears are in constant mesh.
  • Its manufacturing is easy as compared to a constant mesh gearbox.
  • Its mechanism is simple.

Disadvantages of Sliding Mesh Gearbox:

  • Only spur gears can be used as gears are not in a constant-mesh gearbox in which helical or herringbone gears can be used.
  • More effort is required to engage the gear as the gear has to be slide in sliding mesh gearbox, unlike constant mesh gearbox where only dog clutch has to be a slide for engagement of different gears.
  • Less life of gear as more wear and tear of gear is caused in sliding mesh gearbox due to friction.
  • It takes more time and money to replace the gears if the gearbox fails but in constant mesh gearbox only dog clutches are to be replaced at failure which takes less time and money.

Applications:

  • Sliding Mesh Gearbox is used in Alfa 12HP with 4-speed manual transmission.
  • It is also used in Fiat 6HP with 3-speed manual transmission.
  • It is also used in Mercedes 35 HP and Renault Voiturette.

FAQs.

What are the advantages of sliding mesh gearbox?

Advantages of Sliding Mesh Gearbox: Its efficiency is more than a constant gearbox as only one gear is in mess, unlike the content mesh gearbox in which all gears are in constant mesh. Its manufacturing is easy as compared to a constant mesh gearbox.

What is the difference between sliding mesh and constant mesh gearbox?

the differences between a sliding mesh gearbox and a constant mesh gearbox are that the gears used in the constant mesh are helical whereas in sliding mesh they were spur. the layshaft is also always connected to the main shaft, meaning the gears always mesh.

What is a gearbox mesh?

A constant mesh gearbox is a type of transmission in which all forward gear pairs remain engaged. In a constant mesh gearbox, all gears are in the mesh all the time. The constant-mesh gearbox is a type of manual transmission in which the gears are meshed or fixed to their positions.

What is the disadvantage of sliding mesh gearbox?

These are some disadvantages of Sliding Mesh Gearbox: The Mechanical Efficiency was very low in the case of Sliding Mesh Gearbox. The driver requires considerable skill for changing the gears because the gears of the main shaft and layshaft are away from each other.

What is a sliding gear?

Sliding gear is a power-transmission system in which any given pair of gears is engaged by sliding one axially into mesh with the other.

What type of gear is used in sliding mesh gearbox?

Sliding mesh gearboxes are made with spur gear. The gears in the layshaft are rigidly fixed shafts. The gears in the main shaft alone can move along the spline. The selector fork moves the gear and moves the perfect mesh with the required gear inlay shaft when the gear lever is shifted.

How many types of shafts are sliding mesh gearbox used?

The shaft is generally used to transmit the power from one end to another end. There are three types of shafts in the case of Sliding Mesh Gearbox.

Who invented the sliding mesh gearbox?

The idea of a transmission system is given by French inventors Louis-Rene and Emile Levassor who invented the world’s first-ever transmission system with 3-speed sliding mesh transmission in 1894 which was the boom in the automobile industry.

How do I know my gearbox type?

Open the driver’s side door and find the white card on the side of the door that is filled with small black lettering. This card contains specific details about the year the car was made, its transmission, engine specifications, and other details.

Does Double clutching do anything?

Not only does double-clutching allow you to put the transmission in first gear while you’re already moving, but it can also serve to extend the life of your synchronizers.

What are the merits and demerits of synchromesh gear box compared to a sliding mesh on constant mesh type?

  • No need of double-declutching as in case of constant mesh gearbox.
  • Smooth engagement of higher gears due to the synchromesh device.
  • Less noisy as helical gears are used.
  • Less vibration.

Can we use helical gear in sliding mesh gear box?

Disadvantages of Sliding Mesh Gearbox: Only spur gears can be used as gears are not in constant mesh-like constant-mesh gearbox in which helical or herringbone gears can be used.

What are the differences between sliding and constant mesh gearbox?

The differences between a sliding mesh gearbox and a constant mesh gearbox are that the gears used in the constant mesh are helical whereas in sliding mesh they were spur. the layshaft is also always connected to the main shaft, meaning the gears always mesh.

What is the main difference between sliding mesh gearbox and constant mesh gearbox?

ParameterSliding Mesh Gear BoxConstant Mesh Gear Box
ConstructionIt consists of spur gearIt consists of helical gear
The main shaft gears are not in mesh constantly with the countershaft gears, which can slide and mesh.All the gears on the main shaft are in constant mesh with the corresponding gears on the countershaft
Selector fork unit is used in this gearbox for engaging the gearA dog clutch unit is used in this gearbox for engaging the gears
Torque TransmissionLowHigh
SizeThe size of the gearbox is largeThe size of the gearbox is small compared to the sliding mesh gearbox.
ApplicationIt is the oldest type of gearbox used in motor vehicles.Constant-mesh gearbox has been used in 2&3-wheelers.

What are the advantages of constant mesh gearbox over sliding mesh gearbox?

Because the gears in a constant-mesh gearbox are constantly meshing, it’s less likely to damage the gear teeth, and there’s typically less wear on the gears. If a driver makes a “bad” change in gears, any damage that may occur will be limited to the dog clutch.

What gears are used in sliding mesh gearbox?

Sliding mesh gearboxes are made with spur gear. The gears in the layshaft are rigidly fixed shafts. The gears in the main shaft alone can move along the spline. The selector fork moves the gear and moves the perfect mesh with the required gear inlay shaft when the gear lever is shifted.

Why spur gears are used in sliding mesh gearbox?

The gears of the main shaft slide over the shaft to mesh with the appropriate gears of the layshaft so that the required gear ratio is obtained. Spur gears have straight teeth that are produced parallel to the axis of the gear. These gears are a most economical type of gear but tend to vibrate and become noisy at high speed.

Is a helical gear stronger than a spur gear?

Helical gears are more durable than spur gears because the load gets distributed across more teeth. Hence, for a given load, the force will be spread out better than with a spur gear, resulting in less wear on individual teeth.

What are the limitations of sliding mesh gear box?

Disadvantages of Sliding Mesh Gearbox:

  • The Mechanical Efficiency was very low in the case of Sliding Mesh Gearbox.
  • The driver requires considerable skill for changing the gears because the gears of main shaft and lay shaft are away from each other.

Which shaft is splined in sliding mesh gearbox?

Main Shaft- It is the shaft used as an output shaft in a sliding mesh over which the sets of gears with internally splined grooves are arranged in an organized fashion. The outer surface of this shaft is made splined so that the gears can easily slide over this shaft in order to mesh with the appropriate gear.