﻿ MechDesigner Reference & User Interface > 2.2 Mechanism-Editor > Mechanisms > Machine elements > Add Pulley

#### Terminology:

 Pulley : A rotating-Part. It is a wheel with teeth around its circumference. The teeth engage with a Belt. The angular motion of the Pulley and the linear motion of a Belt are related by the radius of the Pulley. The number-of-teeth and the Tooth-Pitch control the radius of the Pulley. There are two types of Pulleys. Type 1: Driving Pulley : You define the angular motion of the Pulley - the motion of the Driving Pulley controls the linear motion of the Belt. Type 2: Driven Pulley : The linear motion of the Belt controls the angular motion of the Driven Pulley. Belt : It is a Timing-Belt (we do not show you the Teeth on the Belt). The Belt does not slip relative to the Teeth on the Pulleys. The shape of a sketch-path represents the path of the Belt. The motion of a Motion-Point on the sketch-path represents the motion of the Belt. The sketch-path needs one Arc for each Pulley. A Pulley must rotate about the center-Point of the Arc.

#### Kinematic State before you do Add Pulley.

 Type 1: Driving-Pulley: The rotating-Part is kinematically-defined. Type 2: Driven-Pulley: The rotating-Part is not kinematically-defined.

#### Kinematic State after you do Add Pulley.

 Type 1: The rotating-Part is kinematically-defined. It is a Driving-Pulley. The motion of the Pulley, its number-of-teeth, and the tooth-pitch now control the motion of the Motion-Point along the sketch-path (the Belt). Type 2: The rotating-Part is kinematically-defined. It is a Driven-Pulley. The motion of the Motion-Point along the sketch-path (the Belt), the Tooth-Pitch and the Number-of-Teeth on the Pulley now control the motion of the Pulley.

### Kinematics-Tree of Pulley

Driven-Pulley

 It is a Pulley-Rocker in the Kinematics-Tree after you do Add Pulley. A Path-Joint is a child to the Pulley-Rocker.

Driving-Pulley

 It is a Part that is kinematically-defined in the Kinematics-Tree before you do Add Pulley. For example, a Driving-Pulley in the Kinematics-Tree is a Rocker.

### Prepare to do Add Pulley (TYPICAL)

#### Preparation 1: Add the sketch-path for the Belt.

Sketch-loop as the path of the Belt.

Preparation 1: Add a sketch-path to represent the path of the Belt.

The sketch-path should include only Lines and Arcs. Usually, add Tangent constraints between each Line and Arc. Do not add equal constraints to the Arcs. The sketch-path is usually a closed sketch-loop. It is usually helpful to fully define the geometry of the sketch-path.

 1.Mechanism-Editor: Edit the Base-Part (usually) or Part 2.Part-Editor: Add a sketch-path with Lines and Arcs to represent the path of the Belt. You need one Arc for each Pulley. 3.Part-Editor: Add Tangent constraints between each Line and Arc 4.Part-Editor: Add a dimension to the radius of each Arc. (Do not add Equal constraints between Arcs)

If the rotating-Part is a Rocker: (for a Driven-Pulley)

 5.Part-Editor: Add a Line from the center-Point of the Arc that is the rotating-axis of the Rocker / Pulley

You need the Line to add a Motion-Dimension FB to the rotating-Part.

A Line for a Motion-Dimension FB

#### Preparation 2: Add the Motion-Path FB to the sketch-path

Preparation 2: MOTION-PATH FB

Add ONE Motion-Path FB to the sketch-path.

 1.Click Kinematic FB toolbar > Add Motion-Path FB. 2.Click a sketch-element in the sketch-path

The Motion-Path FB is in the graphics-area.

A Motion-Point is at the start-Point of the sketch-element you click.

#### Preparation 3: Add Rotating-Parts for the Pulleys

A Pulley is a Driving-Pulley or Driven-Pulley. It is a rotating-part.

rotating-Part for a Driving-Pulley

Preparation 3A: Type 1 - Driving-Pulley

A Driving-Pulley is a rotating-Part that is kinematically-defined.

Add a maximum of ONE Driving-Pulley to a Belt.

 1.Add a Rocker with its Pin-Joint at the center-Point of the Arc with a Line (see Preparation 1: 5, above) OR 1.Add Parts to the model, in which there is a rotating-Part with its Pin-Joint at the center of the Arc in the sketch-path of the Belt - and it is kinematically-defined.

rotating-Part for a Driven-Pulley

Preparation 3b: Type 1 - Driven-Pulley

The motion of the Belt and the Pitch-Circle Diameter control the motions of Driven-Pulleys.

The rotating-Part is not kinematically-defined before you do Add Pulley.

 1.Add rotating-Parts to be Driven-Pulleys, with a Pin-Joints at the -Point of each Arc with a Driven-Pulley.

There are four elements to select in the Command-Manager

STEP 2: Click the four elements

 1.Click a Pin-Joint at the center of a rotating-Part*. 2.Click the Motion-Path FB. The Part-Editor opens 3.Click the dimension that controls the radius of the Arc. The Part-Editor closes 4.Click the rotating-Part* that has a Pin-Joint (see 1) at the center-Point of the Arc (see 3)

* If the rotating-Part is :

is kinematically-defined - the motion of the Pulley moves the Belt (Driving-Pulley).

is not kinematically-defined - the motion of the Belt moves the Pulley (Driven-Pulley).

STEP 3: Complete the Command

 5.Command-Manager: Click in the Command-Manager.

Result:

 The schematic of the Pulley shows in the graphics-area. •Use the Motion-Path dialog to edit the Tooth-Pitch and length of the Belt. The Pulley has an integer number-of-teeth. •Use the Pulley dialog to edit the number-of-teeth on each Pulley.

1 x Driving-Pulley (Purple)
1 x Driven-Pulley (Magenta)