Amplitude and Frequency

This section explores the Gearing FB. The Gearing FB dialog-box has parameters to specify similar functionality to a 'Belt and Pulley'.

The Gearing FB applies a basic mathematical function to transform input values at the input-connector to output values at the output-connector.

There are three Parameters in the Gearing dialog-box.

See also: Add Gearing FB.

tog_minus        The Crank at a speed that is different to the MMA









To drive a 'crank' at other speeds, or even backwards (clockwise), connect a Gearing FB, between the Linear-Motion FB and the Motion-Dimension FB.


There are two 'Cranks' in the image to the left.


Left-side Crank: Its motion is given by the motion-values at the output-connector of the Linear-Motion FB. This increases linearly from 0 to 360, and repeats. Thus the Crank will rotate Counter-Clockwise.


Right-side Crank: Its motion is determined by the Linear-Motion AND Gearing FB1s-red . Edit the Gearing Ratio in the Gearing FB dialog-box  to -1.  The output will be -360 to 0 and repeat. Thus the Crank will rotate Clockwise.

tog_minus        Cranks on Cranks – video1






We can add a crank to a crank.


Shown here is an Epicycloid Curve called the 'Deltoid' – it has a shape like a delta. To do this:

1.Connect two Parts end-to-end with Pin-Joints, the first Part to the Base-Part
2.Use Motion-Dimension FBs fix the initial angle of the two Parts.
3.Drive the first Part with a Linear-Motion FB – it is a 'Crank'.
4.Make the second Part half the length of the first Part
5.Drive the second Part, with a Gearing FB, and edit its Gearing Ratio to '-3'.
6.Use a Trace-Point to show the Deltoid. The deltoid curve is the trace of the point at end of the second Part.

Note: You can easily replicate this motion with a Gear-Pair.

tog_minus        Use the Gearing FB to change a Motion's Amplitude AND Frequency

There are three ways to use Gearing Function-Blocks:

To amplify (or attenuate) the magnitude of a motion
To increase (or reduce) the frequency of a motion
To change the magnitude and frequency of a motion



Here, we connect a Motion FB to the Gearing FB.

For example:

Linear-Motion FB range = 0–360º
Motion FB range = 0–100mm
Gearing Ratio = '3'...

...the slider motion = 'Base-Value + 300mm'

The Gearing FB increases the AMPLITUDE of the Slider.



Here, we connect the Gearing FB to the Motion FB.

For example:

Linear-Motion FB range = 0–360º
Gearing Ratio = '3',
Input to Motion FB: range 0–1080º
Output from Motion FB range = 0–100mm every input of 360.

Thus, slider completes its motion 3 times in one cycle of the Master-Machine-Angle.

Note - if the Gearing FB is '–ve', the input to the Motion FB is 360 to 0, thus the Motion becomes reversed.



To change the amplitude and frequency of a motion, connect a Gearing FB before and after a Motion FB.

Help Files for MechDesigner and MotionDesigner 11.1 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd