<< Click to Display Table of Contents >> Navigation: Getting Started Tutorials  MechDesigner > Tutorial 18: Math FB > Step 18.3: Acceleration: Find the RadiusofCurvature of the Cam 
A plot of a curve's RadiusofCurvature is a good example because RadiusofCurvature needs the Velocity and Acceleration Equations for the X and Y coordinates.
We must symbolically differentiate the Velocity Equations, given in Step 18.2, to find the Acceleration Equations.
Remember, MechDesigner does these calculations automatically with GearPair. We are doing this with a Math FB only as an example of how to use the Math FB.
Before we can plot the RadiusofCurvature for a 2DCam, we must add a CamData FB


We can see graph for the RadiusofCurvature is nonsense. 
Differentiate the X and Y Parametric Velocity Equations for the EpitrochoidCurve with respect to Θ. These are the two Parametric Equations for the X and Y Velocity Components: PXacc = (a+b) * cos(Θ) + ( (a+b)2 * h * cos((a+b) * Θ / b) ) / b2 PYacc = (a+b) * sin(Θ) + ( (a+b)2 * h * sin((a+b) * Θ / b) ) / b2 As before we must replace: a with p(0) ; b with p(1) ; h with p(2) ; Θ with p(3) In the Math FB they are: –((p(0)+p(1))*cos(p(3)))+((p(0)+p(1))^2 * p(2) * cos((p(0)+p(1)) * p(3) / p(1)) / p(1)^2) ((p(0)+p(1)) * sin(p(3))) + (( p(0)+p(1))^2 * p(2) * sin((p(0)+p(1)) * p(3) / p(1)) / p(1)^2) 
These are the 6 equations for the two outputconnectors As entered the Math FB: •Equations 1, 2, 3: Position and Velocity, and Acceleration Equations for the X axis •Equations 4, 5, 6: Position, Velocity, and Acceleration Equations for the Yaxis

We can now see the the plot for the RadiusofCurvature is as we expect. How can we check that the result is correct? We can check the results if we add a Circles to the BasePart with a radius equal to the values given in the graph. 