What Is Sliding Mesh Gearbox?- Parts And Working

What is a Sliding mesh gearbox?

A sliding mesh gearbox is a transmission system that consists a series of different gears and shafts arranged together in an organized manner, so that shifting or meshing 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 gearbox or transmission in which the gears on the layshaft are rigidly fixed to the shaft, while the gears on the main shaft are allowed to slide on it by means of splines but are otherwise permanent rotational mesh with the shaft. The diagram below shows the layout of the sliding mesh gearbox.

The sliding mesh gearbox was the first gearbox or power transmission system invented in cars. The first transmission system was introduced by French inventors Louis-Rene and Emile Levassor, who invented the world’s largest transmission system in 1894 with a three-speed sliding mesh transmission. The gear ratio is obtained by sliding the required gears to bring it with appropriate mating gears.

diagram below shows the layout of the sliding mesh gearbox.

Parts of Sliding Mesh Gearbox:

There are three main parts of the sliding mesh gearbox are:

  1. Shafts
  2. Gears
  3. Gear Lever

Shaft

Shafts are usually used to transmit power from one end to another. There are three types of shafts for sliding mesh gearboxes.

  • Clutch shaft: The clutch shaft is used to transfer power from the engine when the clutch is engaged. When the clutch shaft rotates, the clutch gear attached to its tip also rotates with the clutch shaft.
  • Layshaft: The layshaft is the intermediate shaft between the clutch shaft and the main shaft that meshes the fixed gear with the drive gear to provide the proper output power. The fixed gear is mounted on the base shaft and meshes with the gear on the main shaft and the gear on the clutch shaft.
  • Main shaft: This shaft acts as an output shaft to transmit power from the engine shaft through the layshaft. Gears with internal spline grooves are located on the main shaft, so they mesh easily with the gears on the spindle.

Gear

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

  • Spur gear: Spur gear have straight teeth that are parallel to the axis of the gear. These gears are the most economical type of gear, but they tend to vibrate and make noise at high speeds.
  • Helical Gear: The teeth of a helical gear are not parallel to the axis of the gear. The teeth of this type of gears are at an angle to the axis of the gear. These gears are quieter and work smoother than spur gears. Also, these gears have high tooth strength and high load bearing capacity.

Gear Lever

It is used to slide the gear on the main shaft to get the proper gear ratio. Operated by a driver.

Construction and Working of sliding mesh gearbox

A gear connected to the clutch shaft also rotates. As the clutch shaft gear rotates, the layshaft gear also rotates, which is connected to the clutch shaft gear, but in the opposite direction. Therefore, the rotation of the layshaft gear, which is rigidly connected to the layshaft, causes the layshaft to rotate.

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The sliding mesh gearbox is made of spur gears. The layshaft gear is a fixed shaft. Only the main shaft gear can move along the spline. The selector fork moves the gears and moves the gear lever to fully engage the desired gear on the gear in the layshaft.

An idler gear is equipped for reverse gear. In this way, the force 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 speeds. The smallest gear on the layshaft meshes with the largest gear on the main shaft to transmit high torque. 1st gear is used when the vehicle starts to move forward.
  • Second gear: The gearbox in gear 2 offers less torque and more speed than gear 1. The second gear is obtained when the second largest gear of the second small gear on the main shaft is meshed with a medium-sized gear on the main shaft.
  • Third gear: In the third gear, the gearbox provides less torque and more speed than gear 2. Gear 3 is the last or top gear of the sliding mesh gearbox. This gear is obtained when the largest gear on the shaft meshes with the smallest gear on the main shaft.
  • Fourth gear: For the fourth gear, the clutch shaft and the main shaft are connected by a dog clutch, and the main shaft rotates at the maximum speed of the clutch shaft.
  • Reverse gear: Selecting the reverse gear changes the direction of rotation of the output shaft. This is achieved by using an idler gear. The idler gear meshes between the countershaft gear (layshaft or second drive shaft) and the output shaft gear (main shaft or third drive shaft).

Advantages Of Sliding Mesh Gearbox:

  • With only one gear involved in a sliding mesh gearbox, there is less load fluctuation on the shaft, resulting in less vibration and noise.
  • Unlike contact mesh gearboxes, all the gears are in the constant mesh.
  • Unlike constant mesh gearboxes where all gears are always meshed, they work better than constant gears because only one gear is meshed.
  • Easier to build than constant mesh gearboxes.
  • Its mechanism is simple.  

Disadvantages Of Sliding Mesh Gearbox:

  • Constant mesh gearboxes in which can use helical or herringbone gears, do not have gears, so only spur gears can be used.
  • The gears have to slide in a sliding mesh gearbox, so it takes more effort to engage the gears than in a constant mesh gearbox where only the dog clutch needs to slide to engage the different gears.
  • Sliding mesh gearboxes cause more gear wear due to friction, and as a result, gear life is reduced.
  • In case of gearbox failure, gear change requires more time and money, but with constant mesh gearbox, only dog ​​clutch needs to be replaced in case of failure, saving time and money.
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Application:

  • A sliding mesh Gearbox is used for the 12HP Alfa with a 4-speed manual transmission.
  • 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.

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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.

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