Produce Explicit Mathematical Equations from Skeletal Diagrams

A new program from Saltire can derive mechanical equations from early design models.

Saltire Software has created an exciting program called Mechanical Expressions that has the ability to convert symbolic mechanical models into explicit mathematical expressions. Using this program, engineers can analyze models using computer algebra systems (CAS), graphing, and numerical analysis.

While other engineering software can create numerical models given a mechanical system, Saltire claims that Mechanical Expressions is the first to do so using symbolic mathematical models.

As seen in the image here of a piston-crank system, Mechanical Expressions lets engineers create a skeletal diagram and assign variables such as crank radius, rod length, and crank angle. The program can then output the equation of the torque as a function of the specified variables; describing both the values of a single crank and the values of all possible cranks in a given setup.

In terms of optimization capabilities, Mechanical Expressions also has the ability to output the expressions into various CAS systems (such as Tex or MathML). It can also output the expressions in the source code of one of 9 different computer languages, which is great if you want to save that information for later analysis.

Philip Todd, President of Saltire Software, states that “Instead of using the black box approach, which only gives you the numeric response for specific input values, Mechanical Expressions gives you the mathematics of the whole design… It is the ability to capture the essence, not just of a single instance of a design but an entire design space, that makes Mechanical Expressions such a powerful and exciting tool.”

Saltire hopes that as STEM classrooms include more modeling and as curriculums continue to adapt around the latest technologies, Mechanical Expressions will become the program of choice.

Mechanical Expressions is currently in the beta testing phase of development and is slated for release in early 2014. Though if the toolkit manages to be as exciting as it sounds, I suspect we’ll be hearing plenty more about Saltire soon enough.

Image and Story Courtesy of Saltire

Written by

Shawn Wasserman

For over 10 years, Shawn Wasserman has informed, inspired and engaged the engineering community through online content. As a senior writer at WTWH media, he produces branded content to help engineers streamline their operations via new tools, technologies and software. While a senior editor at, Shawn wrote stories about CAE, simulation, PLM, CAD, IoT, AI and more. During his time as the blog manager at Ansys, Shawn produced content featuring stories, tips, tricks and interesting use cases for CAE technologies. Shawn holds a master’s degree in Bioengineering from the University of Guelph and an undergraduate degree in Chemical Engineering from the University of Waterloo.