Sliding Mesh Gearbox – Main Parts, Working and Application

Introduction

"New is Gold" was quite rightly said, as the origins of improved technology that we use today are new innovations in the automotive sector. Sliding mesh gearbox was one of these inventions and created a very vital automotiv system, i.e. a transmission system or gearbox. But what was the idea from? What's the job of it? Just let's explore.

French inventors Louis-Rene and Emile Levassor invented the world's first ever 3-speed sliding mesh device transmission transmission, in 1894, a boom in the automotive industry. The principle is a power transmission system.

Sliding mesh gearbox is a transmission system consisting of several sets of gears and shafts arranged in an organized way, and a shifting / matching of different gear ratios is carried out with the aid of a driver-operated gear-heel by sliding gears to the right and left across the split-waft.

Need of Sliding Mesh Transmission

Introduction of an IC engine had led to the introduction of an automobile that was the replacement of the horse carriage which was used as the travelling medium by the people in early 18th century, but still the automobile was lacking behind when it came to face the challenges (turns, elevations, roughness etc.) given by the the roads as there was no such mechanism fitted in early vehicles that could provide different torque and speed ratios as demanded by the road conditions.

1894 saw the introduction of Sliding Mesh Transmission System, the first transmission system designed to deliver different speed and torque ratios to solve these road challenges.

The various problem solved by this types of gearbox are-

Fuel consumption of an automobile increased as the load on the engine is decreased or shared by the intermediate system known as sliding mesh gearbox.

Due to the varying torque ratios provided by this gearbox, the automobile vehicle is made to go to the hill stations which was not possible earlier.

Time taken to reach the destination was decreased as overall speed of the vehicle increased due to the high speed ratios provided by it.

Reverse of the car made possible with the introduction of this transmission system.

Jamming of vehicle due to the rough road conditions was solved after the introduction of the sliding mesh gear box.

Components of a Sliding Mesh Gearbox

(i) Shafts – Sliding mesh gearbox consists of 3 shafts that are-

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 organised 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.

Clutch shaft- It is the shaft that is used to carry engine output to the transmission box with the help of engaging and disengaging clutch which is mounting at the engine end, gear or a pair of gear is mounted over this shaft which is used to transmit rotational motion to the lay shaft.

Lay shaft- It is the shaft having gears mounted over its outer surface and is in continuous rotation with the clutch shaft as one gear of this shaft is always in contact with a gear on the clutch shaft, it is used as a intermediate shaft( between main shaft and clutch shaft )that provides the meshing of the gears of the main shaft in order to transmit appropriate output to the final drive.

(ii) Gears – 2 types of gear were usually used in sliding mesh gearbox.

Spur gear- This is the type of gears having straight cut teethes over its surface, straight teethes proving maximum meshing area.

Helical gear- This is the type of gear in which the teethes are cutted in angular fashion unlike spur gears this type of gears are smooth and less noisy.

(iii) Gear lever- It is the selecting mechanism operated by the driver in order to select the appropriate gear ratio, this liver is connected to the main shaft along with the selector forks.

An obsolete kind of transfer or gearbox, in which the gears of the layshell are rigidly fixed on the shaft, while the gears of the central shaft are sliding on it with a rotational mesh with the shaft but otherwise. The following figure shows the sliding mesh gear box configuration.

Construction and working of sliding mesh gear box

Boxes are made with spur gear for sliding mesh gear. The gears are rigidly attached to the shaft. The gears can be shifted along the spline in the main shaft alone. When the gear lever is moved, the selector fork shifts the gear with the required equipment in the shaft. For reverse gearing, an idler gear is given. Therefore, the control shaft is transferred through the lay shaft to the main shaft.

First gear

In the first gear, the gearbox provides maximum torque at low speed. The smallest gear on the lay shaft engages with the biggest gear in main shaft, thus transmitting high torque.

1st Gear 2nd Gear

Second gear

In the second gear, the gearbox provides low torque and high speed when compared to 1st gear .

Third gear

In the third gear, the gearbox provides low torque and high speed when compared to 2nd gear.

3rd Gear 4th Gear

Fourth gear

For fourth gear the clutch shaft and the main shaft is engaged by a dog clutch, thereby the main shaft rotates at maximum speed as that of 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 is meshed between a counter shaft gear (layshaft or 2nd motion shaft) and an output shaft gear(mainshaft or 3rd motion shaft).

Application

It is the oldest type of gearbox used in early 19s models of cars.. Some of them are-

Alfa 12HP used sliding mesh gearbox with 4 -speed manual transmission.

Fiat 6HP used 3-speed manual transmission.

Mercedes 35HP used 4-speed manual transmission

Renault Voiturette used manual 3-speed transmission.

Sliding Mesh Gearbox – Main Parts, Working and Application