Dismantling and Assembling of Constant Mesh Gearbox скачать в хорошем качестве

Dismantling and Assembling of Constant Mesh Gearbox

Main Parts of Constant Mesh Gearbox: The main ports of Constant Mesh Gearbox are : 1 Shafts – There are 3 shafts present in this gerabox which are : i) Main Shaft It is also known as output shaft. It is the splined shaft over which the dog clutches along with gears are mounted. Gears on this shaft are free to rotate. ii) Lay Shaft or Counter Shaft It is an intermediate shaft between the Main Shaft and Clutch Shaft. The gears of counter shaft are in constant mesh with gears of main shaft. Also the gears of counter are shaft are not free to rotate as they are directly connected to the Counter Shaft. iii) Clutch Shaft: The clutch shaft carries the engine output to the gearbox but act as input for the gearbox. It is also known as input shaft. 2 Dog Clutch: The dog clutch couples the lay shaft and main shaft by interference and not by friction. Dog clutches are used to transmit appropriate gear ratio to the main shaft or output shaft by coming in interference with pair of gears with suitable gear ratio. There are usually two dog clutches in a Constant Mesh Gear Box. 3) Gears: Gears of constant mesh gearbox come in pairs. All gears of lay shaft or counter shaft are always paired with gears of main shaft or output shaft. This paired gears of counter shaft and main shaft provide different gear ratio which can be transmitted to main shaft by engaging dog clutch with appropriate gear ratio required. Working of Constant Mesh Gearbox: When the dog clutch is engaged with different gears of main shaft different gear ratios are obtained as gears of main shaft are always paired with gears of counter shaft to form different gear ratios. If the dog clutch is not in contact with any gear of main shaft the gears of main shaft rotates freely and does not rotates the main shaft as they are connected with main shaft using bearings. The main shaft rotates only when one of the dog clutch is engaged with any of the gear of the main shaft. Reverse gear is obtained in this gearbox using the same technique that was in sliding gearbox i.e using the idle gear between main shaft gear and counter shaft gear. Different gear ratios in Constant Mesh Gearbox: First Gear: First gear is obtained in constant mesh gearbox when dog clutch gets engage by interference with the largest gear of main shaft which is in constangt mesh with smallest gear of main shaft. This gear provides maximum torque and minimum speed to the main shaft. Second Gear: Second Gear is obtained when dog clutch gets engage with second largest gear of main shaft which is in a constant mesh with second smallest gear of lay shaft. This gear provides higher speed and lower torque than first gear. Third Gear: Third gear is obtained when dog clutch engages with second smallest gear of main shaft which is in constant mesh with second largest gear of lay shaft. This gear more speed and less torque than second gear. Fouth Gear: This gear provides the highest or maximum speed in a vechile using constant mesh gearbox. This gear is obtained when dog clutch engages with smallest gear of main shaft which is in constant mesh with largest gear of lay shaft. Reverse Gear: In this gear the vechile goes in reverse direction. Like sliding mesh gearbox, an idler gear is also used in constant mesh gearbox between the main shaft gear and lay shaft gear to form reverse gear. Reverse gear is obtained when dog clutch engages with gear in main shaft which is paired with idler gear. Advantages of Constant Mesh Gearbox: 1Contsant Mesh Gearbox are quiter because helical or herringbone gears can be used in this gearbox instead of spur gears. Since the gears are engaged by dog clutches, if any damage occurs while engaging the gears, the dog unit members get damaged and not the gear wheels. What problems of Sliding Mesh Gearbox were solved by Constant Mesh Gearbox ? The Sliding Mesh Gearbox was a great success for the automobile industry as now there was a system which can provide different speed and torque needs by the vechile to face different road conditions. But there were some limitations and problems of Sliding Mesh Gearbox which were solved by Constant Mesh Gearbox. These problems are:- 1) The shifting of gears was very noisy process as spur gears were used but in constant mesh gearbox the gear shifting process becomes very less noisy as helical gears and bevel gears are used. 2) In sliding mesh gearbox, gears to be messed were in continuous rotation, so the meshing of gears can cause breakage of gear teeths or wear and tear of gears. This problems was solved by constant mesh gearbox by introducing dog clutches. 3) Shifting was not an easy task for drivers and requires special skill to change gears using double-de-clutching technique. But changing gears become easy for drivers after introduction of constant mesh gearbox