> For the complete documentation index, see [llms.txt](https://jamesbrayy.gitbook.io/atar/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jamesbrayy.gitbook.io/atar/engineering/core/types-of-mechanisms.md).

# types of mechanisms

***

#### pulley belt:

* the preferred model of power transmission over long distances.
* comprised of a looped strip from a flexible material that is used to link rotating disks.
* used to transmit power when shafts are far apart.
* direction of rotation of the driver and the follower are normally the same, but it is possible to have these rotating opposite directions if the drive belt is twisted.
* $$\text{VR}=\frac{∅*{follower}}{∅*{driver}}$$
* ![](/files/kdm8f0wreupAqLOKLf3j)

#### chain and sprocket:

* the preferred model of power transmission over medium distances.
* comprised of a system of chain links that connect via a set of sprockets.
* sprockets are toothed wheels.
* $$\text{VR}=\frac{\text{teeth}*{follower}}{\text{teeth}*{driver}}$$
* ![](/files/cls5bI6EIRI7jMbbfLpZ)

#### rack and pinion:

* rotary motion can be converted into linear motion and vice versa.
* $$\text{distance}=\frac{\text{teeth}*{pinion} \text{revolutions}}{\text{teeth per metre}*{rack}}$$

#### gears:

* the most preferred model of power transmission over short distances.
* comprised of gears that mesh with each other to transmit power.
*

```
![](/files/wrLQPTErwkatgkJbwkA5)
```

* **idler gear drive:**
  * if we add a third gear to the gear train, then the follower gear will rotate in the same direction as the driver gear.
  * this extra gear is called an idler gear.
  * the velocity ratio is not affected.
* **spur gears:**
  * the driven and follower gears rotate in opposite directions.
  * $$\text{VR}=\frac{\text{teeth}*{follower}}{\text{teeth}*{driver}}$$
* **worm gear and worm wheel:**
  * large increases in the velocity ratio are achieved with only two gears.
  * only the worm gear can be used to drive the system and not the worm wheel.
  * this system will lock into place when power is switched off.
  * $$\text{VR}=\text{teeth}\_{worm wheel}$$
* **compound gear drive:**
  * compound gears are when two gears are joined together on the same shaft.
  * compound gear drives allow us to achieve very large increases in velocity ratio in a small amount of space.
  * $$\text{VR}=\frac{\text{teeth}*{follower1}}{\text{teeth}*{driver1}} \frac{\text{teeth}*{follower2}}{\text{teeth}*{driver2}} ...$$

#### lead screws:

* **single start:**
  * used in CNC machines and 3D printers to convert rotary motion into linear motion.
  * common in actuators for precise linear movement applications.
  * $$\text{distance}=\text{n}\_{starts} \text{pitch} \text{revolutions}$$
  * ![](/files/Wd3p7LHGdTFlR2PUfkUX)
* **multiple start:**
  * used in high-speed cnc machines and actuators where faster motion is needed compared to single start lead screws.
  * common in robotics and automated systems for quick linear displacement.
  * * $$\text{distance}=\text{n}\_{starts} \text{pitch} \text{revolutions}$$
  * ![](/files/4pbEfX5skSzebOZ03DZZ)
  * ![](/files/nIJ4h0g59Nb8vFRz8miA)