What Are the Types of Gear Flashcards

Spur gear- it’s a gear that is made with straight cut teeth, one so it is not able to slip off when in contact with another spur gear, and second of all it permits 1.5 to 2.5 gear teeth to mesh at a time. All gear teeth lie parallel to the centerline, or axis, of the gear. The only problem with their strength is that they can become very noise. That is why they are found mostly on heavy-duty trucks

Helical gear- is a gear that is cut at an angle to the gear axis. Because of the way it is cut, it allows them to mesh more gradually with each other (2.5 to 3.5). There is however some problems that comes with them because how they are shaped. Each gear pushes against its shaft parallel to its axis. Special bearings are needed to protect the gearbox from this type of axial, or thrust, loading. This intern creates more friction than a spur gear

And because of the way the spur gear and helical gear’s teeth are they are considered external gear, but can also be internal gears. A internal gear may mesh with a smaller external gear design to rotate as it travels around the inside of the internal ring gear. This type of external gear is called a pinion gear because of its smaller diameter. When an external gear meshes with an internal ring gear, both gears rotate in the same direction, but when an external gear meshes with another external gear, the gears rotate in opposite directions.

Bevel gear, this type of gear is kind of like a spur gear and how they have straight cut teeth. The only differences between the two are how they are cut at an angle to the outside gear surface. Special gears used in a differential, called spider gears, are a common example of the simple bevel gear. Also are used to change the direction of rotation.

The last gear is named a hypoid gear, its gear teeth are curved much like a spiral bevel gear. The differential uses a this type of gear to provide a change in the direction of torque and for gear reduction (torque increases) to the rear drive wheels. The reason for that is because of its strength, gradual tooth engagement, and quieter operation. The pinion gear is offset below the centerline of the ring gear, because of the offset it allows the driveshaft to be positioned lower in the vehicle, reducing the size of the hump in the vehicle’s interior.

1. Explain gear ratio. Gear ratio by definition is when one gear turns another, the speed that the two gears turn in relation to each other is gear ratio. Which are expressed relative to the number one, that fall into three categories direct drive, gear reduction and overdrive. To figure that equation out u have to take the number of rotations the drive gear must make in order to rotate the driven gear through one revolution. To obtain the answer u have to divide the number of teeth on the driven gear by the number of teeth on the drive gear.

1. How is gear reduction achieved? It’s by dividing the number of teeth on the driven gear by the number of teeth on the drive gear, just like u would to find the gear ratio. The only difference in a gear rational is that the driven gear which has three times more teeth which make it slower than the drive gear which is fast. That would mean that the drive gear must travel three complete revolutions in order to drive the larger driven gear through one rotation. Gear reduction can also be named under drive as drive speed is less than, or under, driven speed that’s why it is used in the lower gears of a transmission. First gear in a transmission is called “low” gear because output speed, not gear ratio, is low. Low gears have numerically high gear ratios. That is, a 3:1 gear ratio is lower gear than those with a 2:1 or 1:1 gear ratio. These three ratios taken in order represent a typical up shift pattern from low gear (3:1), to second gear (2:1), to drive gear (1:1).

. Ratio always ends in one with a colon in between. Therefore, the first number is less than one if it is an over drives ratio and greater than one if it is a gear reduction ratio.

1. How is gear overdrive achieved? It’s achieved when a driven gear like the example in the book has 8 teeth and must turn faster than the drive gear which has 24 teeth making the gear ratio 0.33:1. What that means is it will take the driven gear to turn three times for each turn of the drive gear so the driven gear is said to overdrive the drive gear. Overdrive ratio of 0.65:1 and 0.70:1 are typical of those used in automotive applications. This is very similar to what a gear reduction condition is. Therefore, the first number is less than one if it is an overdrive ratio.

1. What is the purpose for an idler gear? The purpose for the idler gear is so it can sit between the driven gear and the drive gear and control what direction it wants it to go. For without it, the drive gear and driven gear would only be able to rotate in opposite direction. A good example of this is when the driver wants to go in reverse a floater or idler gear is placed in between the two and makes then go in reverse. It does not affect the final drive ratio, gear ratio or the speed between the drive and driven gear.

Bell housing, it’s a bell-shaped housing and it’s what is attached between the engine and the transmission. Front bearing retainer sometime called a quill supports the clutch throw out (release) bearing and sometimes houses the front grease seal. A separate casting called the extension housing is usually found in the rear of the transmission, and the case for the center of the transmission is called the transmission case. The input shaft or sometimes named main gear, clutch gear or main drive pinion is splined to the clutch disc. The output shaft or main shaft is splined at the end. The output shaft transmits engine torque to the drive shaft (propeller shaft) through a yoke and universal shaft. The last part of the transmission is called a countershaft (also called a lay shaft or cluster shaft) is made of gear that are called cluster gears or counter gears that provide the other set of gears necessary to achieve the changes in gear ratios. The countershaft is another shaft inside a transmission/transaxle which provides another set of gears to produce the necessary gear ratio.

Question 9

Quesion 10

It permits a shift to be made without gear clash. The parts of a typical synchronizer include the synchronizer sleeve, hub, and ring.

The input shaft and the countershaft are rotating if the clutch is engaged (clutch pedal up) but no torque is being transmitted through the transmission.The speed gears are diven by the cluster gears, but roate freely, on the output shaft. The output shaft may turn if the vehicle is moving or coasting, but no engine torque being transferred through the transmission.