Continue to Site

Welcome to MCAD Central

Join our MCAD Central community forums, the largest resource for MCAD (Mechanical Computer-Aided Design) professionals, including files, forums, jobs, articles, calendar, and more.

Spring ends in Wildfire Mechanism


New member
I used pt. to pt. to define a spring. Can you change the spring ends as shown? Can't it be just squared and ground?
Hello Ceferinos,

At spring in mechanism has no geometry representation you asign only its stiffness. I am not sure what did you mean with round and square? could you be more specific?

I don't know how more specific you can get when you say spring ends. Maybe pics will help:

I'm using Wildfire and there is a geometric representation in the mechanism dynamics option. I was also able to show visually the spring reaction force using a vector representation (an arrow than varies in size as the spring is compressed).
In Mechanism, the spring depicted is an icon only. It's not geometry, and it's not a component in the assembly. You may want to create your own part to represent the spring geometry.

David Martin

Torgon Industries
If I created a spring part, will it deform just like the icon?

Can't the icon be changed to represent the actual spring ends?
No it will not deform and the infinite possibilities for combinations of ends and sizes etc. is why it is represented by an icon with no mass. It is simply a visualization tool to help understand the mathematics behind it. You can set the stiffness K and the length of the spring and in the EOM's thats all that matters. Technically you dont even need the icon but it makes it clearer to the user when you can see a spring in the places you expect them. If you want pictures create a varible spring driven by parameters and set up some relations to calculate the distance between the 2 ends in the assembly and regenerate the model after each move. the spring will update and look right but it has no use in MDO.
The requirement for a spring that looks right in an animation has always caused a lot of effort.

One 'dirty' method is to pattern a spring within a single part.

Each instance can be controlled by relations to extend or compress as required.

The distance between each instance should be bigger than your complete assembly and moved with each regeneration to be indexed into the correct frame.

The starting requirement is then, the total number of frames and the total spring travel.

Be sure not to just make the spring increase/decrease in length as the number of coils will change; the spring model should regenerate with the same total number of coils, but with a varying pitch.

The same technique can be used to make a cable follow a very complicated 3d extension / retraction in an animation.

The reason this method works is that during most animations, only the assembly positions are regenerated, not the individual part models.

The spring icon in mdo needs its bases covering to hide the lack of closed and ground ends. This of course limits the use of the icon for more accurate appearance in an animation.