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Mechanical power transmission

Influence of the offset on the spiral angle

Hypoid gears (screw bevel gears)

With hypoid gears, rotary motions between non-intersecting axes can be realized! With the bevel gears considered so far, the axes of the ring gear and pinion intersect at a certain point. In...
Spur gear with internal toothing

External and internal toothing of gears

With internal toothing, the center distance to an externally toothed gear can be shortened. For cylindrical gears, a basic distinction can be made between external gears and internal gears. In the case...
Herringbone toothing

Herringbone gears and double helical gears

Herringbone gears combine the advantage of helical gears (high load capacity) with that of spur gears (no axial forces). Herringbone gears In order to combine the advantage of helical gears (higher load capacity...
Helical toothing

Helical gears

Helical gears have a lower noise level and can transmit higher torques than spur gears! When it comes down to reduce noises and transmit high torques, helical gears are often used. With...
Screw gears (crossed helical gears)

Screw gears (crossed helical gears)

Screw gears or crossed helical gears are hyperboloid gears that allow the skew mating of the gear shafts! With the gears considered so far, the axes of rotation are always parallel when...
Straight-cut toothing

Spur gears (straight-cut gears)

Straight-cut gears (spur gears) are the simplest type of toothing. In a spur gear, up to 3 teeth are in mesh at the same time. If the teeth of a toothed gearwheel...
Rack and spur gear

Rack (toothed bar)

Racks (toothed bar) allow the rotary motion of a spur gear to be converted into a straight-line motion of the rack. While only rotary motions occur with conventional cylindrical gears, a rack...
Operation of a gear transmission

What types of transmissions (gearboxes) are there?

Roughly speaking, gearboxes are divided into four types: gear drives, belt drives, chain drives and friction wheel drive. Introduction Transmission are available in many different types, depending on the application, e.g. as gear...
Application of transmissions

What is a transmission (gearbox) and what is it used for?

Transmissions control the power supplied in favor of a high velocity (rotational speed) or in favor of a high force (torque)! Where are gearboxes used? In mechanical engineering there are many technical systems,...
Exploded view of a cycloidal drive

How does a cycloidal drive work?

In this article, you will learn more about the design, the advantages and disadvantages of a cycloidal drive and its application. Operating principle The animation below shows the structure and operating principle of...
Design of the cycloidal disc with an ordinary cycloid

Construction of the cycloidal disc of a cycloidal drive

Learn more about the design of the cycloidal disc of a cycloidal drive in this article. Design of the cycloidal disc Cycloidal disc with ordinary cycloid As already explained in the article "Operating principle",...
Arrangement of the pins (trundles) on the rolling circle

Lantern pinion as a special case of cycloidal gear

In this article, you can learn more about a lantern pinion as a special case of cycloidal gear. Operating principle A special case of cycloidal gearing with point tooth form is the so-called...
Line of contact of cycloidal gears during meshing

Meshing of cycloidal gears

In this article, learn more about the meshing of the teeth of cycloidal gears. Line of action The figure below shows the meshing of two cycloidal gears. The dash dotted pitch circles are...
Construction of a cycloid (epicycloid and hypocycloid)

Construction and design of cycloidal gears

The shape of the flank of a cycloidal gear corresponds to a cycloid constructed by rolling a rolling circle on a base circle. Construction of a cycloid The shape of the flank of...
Roots type blower (supercharger)

What is a roots type blower and how does it work?

In this article, learn more about the design and operation of a roots type blower and its application as a supercharger. Operating principle The animation below shows the operating principle of a Roots-type...
Manufacturing undercut during hobbing (yellow and red gear)

Undercut of gears

Undercut occurs when the number of teeth of a gear is too small. An undercut leads to a weakening of the strength of the tooth! Undercut Undercut due to manufacturing process The animation...
Meshing of a gear with a rack


In this article, learn more about the meshing of the teeth of a gear with the teeth of a rack. Introduction The fundamentals when two gears are meshing have already been explained in...
Line of action

Engaging of involute gears (meshing)

The points of contact of two meshing tooth flanks describe a straight line for involute gears (line of action or line of engagement). Line of action Due to the special design of the...
Definition of involute function

Calculation of involute gears

Involute function For the calculation of involute gears, the involute tooth flank must first be described mathematically. The figure below shows the involute belonging to the base circle with the radius rb....
Gear cutting with a hob (hobbing)

Gear cutting (gear manufacturing)

Learn more about the different manufacturing processes for cutting involute gears in this article. Gear hobbing Involute gears are often manufactured by hobbing. The cutting edges of a hob are straight-flanked and wrap...
Comparison of profile-shifted gears

Profile shift of involute gears

In the case of a profile shift, the reference profile of the gear is shifted outwards during the manufacturing process in order to positively influence the meshing. Introduction In the article Undercut of...
Involute gears

Construction and design of involute gears

Involute toothing is often used in mechanical engineering for gears, as it offers favorable meshing and is easy to produce. Introduction In mechanical engineering, the involute is used almost exclusively as a tooth...
5th step - symmetrical arrangement of the bevel gears to avoid bending stresses

How does a differential gear work?

Learn more about the design, function and application of a differential gear and the differential lock in this article. Why does a car need a differential gear? In automobiles, the wheels are usually...
Carrier of a three-speed gear hub

How does a three-speed gear hub work?

Learn more about the structure and function of the planetary gear in a three-speed gear hub in this article. Assembly and function The figure below schematically shows the assembled components of a three-speed...
Relationship between the pitch circle diameters and the number of teeth

Derivation of Willis equation (fundamental equation of planetary gears)

The Willis equation describes the motion of the individual gears of a planetary gearbox (epicyclic gear). Superposition of motions The change in speed of planetary gearboxes are no longer as easy to understand...
Planetary gear

How does a planetary gear work?

A planetary gear is an epicyclic gear in which several gears (planet gears) mesh with a central gear (sun gear). Stationary gearbox So-called stationary gearboxes are characterised by the fact that the gear wheels...
Operating principle of a belt drive

How does a belt drive work?

In belt drives, the power transmission between the driving pulley and the driven pulley is usually force-locked by flexible belts. Introduction In belt drives, power is transmitted between at least two pulleys by...
Calculation of belt length

Calculation of the belt length for belt drives

Learn in this article how to calculate the length of belts for belt drives. For the construction of belt drives it is necessary to determine both the wrap angle and the belt...
Speed distribution along the belt

Slippage of the belt in belt drives

The relative motion on the pulleys, which is always present due to the elasticity of the belt, is called elastic slip! Elastic slip When the belt rotates around the pulleys, it is exposed...
Standard V-belt (raw edge)

Types of belts for belt drives

In this article, learn more about the different types of belts and their application, as well as the respective advantages and disadvantages. Flat belts The simplest type of belt is the flat belt....
Power transmission of belt drive

Power transmission of a belt drive

In this article, learn more about the power transmission in belt drives and the necessary pretensioning force. Circumferential force in the belt In belt drives, forces are transmitted from the input pulley to...
Addition of the centrifugal forces and the centrifugal belt force

Centrifugal forces in the belt of a belt drive

At high speeds, the centrifugal forces acting on the belt reduce the contact pressure and thus the maximum transmittable circumferential force. Formation of centrifugal forces With a belt drive in a resting state,...
Stress distribution in the belt in the operating state under load

Maximum belt stress in belt drives

In this article, learn more about the maximum belt stress, which must not be exceeded, otherwise the belt will be damaged. Introduction In general, the forces acting in the belt must not exceed...
Optimum belt speed

Optimum belt speed for belt drives

At a certain optimum belt speed, a belt drive can transmit the maximum possible power. Introduction In the article Mechanical power it was shown that an object that is moved by a force...
Calculation of the bearing force

Calculation of the bearing force for belt drives

Learn more about calculating the bearing force of belt drives at a given preload in this article. Calculation of bearing force The forces acting in the belt press the belt onto the pulley...
Forces acting on a fixed pulley

Basics of power transmission in belt drives

The basis of power transmission in the belt drive is the belt friction equation according to Euler and Eytelwein (rope friction equation). Forces acting on a fixed pulley In the article How does...
Pinion and gear of a bevel gearbox

Bevel gears

In bevel gears, the axes of the gears are at right angles to each other. Bevel gears are used to change the spatial direction of rotation. Introduction In contrast to cylindrical gears, where...
Globoid worm und globoid worm gear (globoid worm drive)

Worms and worm gears

With a worm gear, high loads can be transmitted at a high transmission ratio. Operating principle A special design of the gear wheel is the so-called worm. In this case, the tooth winds...

Overview of gear types

Depending on the shape of the gears and the type of toothing, gears can be classified as spur gears, bevel gears and worms or worm gears. The figure below shows a selection...
Oil level indicator of a demolition hammer

Lubrication of gears (transmissions)

Gears must be lubricated due to the high stress (friction) when meshing with another gear. Introduction Gear wheels of transmissions are subject to wear due to sliding processes on the flanks. Therefore, the...
Gear stages of a transmission

What is a gear stage?

A gear stage is a wheel pairing within a gearbox at which the speed or torque changes! Learn more about gear stages in this article. Definition The figure below schematically shows a toothed...
Energy flow diagram of a real transmission

Mechanical power

The mechanical power is determined by the force and speed or by the torque and rotational speed. Introduction The term power (in the physical sense) plays an important role in transmissions, since they have...
Operating pitch circle diameter of gears

How does a gearbox (transmission) work?

The conversion of speed and torque takes place in gearboxes through the arrangement of gears or pulleys of different sizes. Conversion of speed As explained in the article What is a transmission...