Gearboxes
What type of gears are used for reverse in a manual gearbox?
'Spur' Cut or 'Straight' cut gears have teeth projecting radially. These are used for the reverse driver,driven and idler gear. Spur cut gears are generally low speed gears and can be noisy. Reverse gears are not in constant mesh and do not have any synchro mechanism, therefore the output shaft must not be turning when reverse is engaged. This is a very simple type of gear and is only used on shafts that are parallel to each other.
What type of gears are used for forwards gears in a manual gearbox?
Foward gears are constant mesh gears.This means they are always contacting each other. Forward gears are 'Helical' cut, this is when the teeth on the gear are angled. Helical gears are used for high speed applications and transmission of large power outputs. Helical cut gears are not as noisy as spur cut gears.
What is the purpose of a synchro mesh unit and how does it work?
The purpose of synchro unit is to engage a free spinning constant mesh gear to the output shaft. A synchro mesh unit consists of a Baulk ring, Synchro hub and Slider(Dog Clutch). As a gear is selected the slider pushes the baulk ring against the chosen gear, using friction the baulk ring synchronises(speeds up or slows down) the gear speed with the input shaft. As the two gear speeds synchronise the slider moves to engage the free spinnning gear with the output shaft.
The purpose of the baulk ring is to synchronise the gear with the output shaft. Also to stop the slider from engaging the gear before it is synchronised.
How do you check a Baulk ring for seviceability?
When checking a baulk ring for servicability you must check the dog teeth for wear. You must also check the ridges inside the ring that keep the ring lubricated while synchronising the gears.
A variety of bearings are used in different gearboxes. But most common are Roller, Thrust bearing, Needle roller and Caged roller bearings. Different bearings are used for different applications depending on the load that it will be placed under.
Give an explanation of a Gear Ratio.
A gear ratio relates to the speed at which two gears turn. A 1:1 gear ratio has a drive gear that turns the driven gear at the same speed, for example a gear with 25 teeth driving a a gear with 25 teeth. A 2:1 ratio would be a gear with 50 teeth driving a gear with 25 teeth. It is possable to have a ratio involving more than two gears.
This is well researched work with good explanations.
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