The Kind of CAD Improvements that Save You Time
In writing updates for “the book” this time through, Alin Vargatu, the technical editor who has added more to the book than any previous tech editor, pointed out that I had missed a couple important enhancements. One of those turned out to be the Chain Pattern. I had an example in the animation chapter of a chain using an old method that required 98 mates and a couple dozen duplicate parts. I was able to reduce that to just two parts and a Chain Pattern. The short video, in gif form, is shown below, and also shows a cool in-context method for animating a spring. I just wanted to show something that saved me personally a lot of work. You might say “That wouldn’t save me any time because I wouldn’t have made the 98 mate version to start with”. Well, yeah, you might be right, but on the other hand, having a small animation that shows a spring and a chain working together might be just the thing that you need to put your technical documents together and make a concept that would be difficult to put into words much easier to demonstrate.
I keep teasing that coaster brake bike, and I’m getting close on it. Here is the chain from that model.
Notice I included some realistic droop in the chain. And I got the motion to work, although I didn’t make the wheel spin. To get the chain synced with the pedals, I used a gear mate and a flexible subassembly, and another gear mate to link the rear sprocket with the front sprocket in the correct ratio. No actual contact required. The teeth on both sprockets are not sized to match the chain perfectly, but it still works. And I used the SolidWorks included video screen capture to make an AVI, and an online avi-gif converter to make a gif to put in the blog. Details details. And dedication and resources.
Aside from the problems with my model, when you get up close, SolidWorks requires the chain to follow a planar path. On a bicycle, especially a derailleur bike, this never happens, there is always some out-of-plane-ness (side to side flex) of the chain. But maybe that will come at a later date. For now, functioning chains are a cool thing.
Thanks for the article Matt. I missed you in Huntsville! 😉
I know this might sound rude but what is the purpose of all that? I mean what design problem is solved doing this? Is it just to show what you can do it? But really shouldn’t do. If your manager saw you doing this he’d question why you are doing this and how long it took? (You know, are you screwing around?)
IMHO-
There are other tools for kinematics that are better suited to solve these problems then attempting to do this in a CAD tool.
What usefulness are you questioning? The droop of the chain is useful for design of the length. The animation is just animation. CAD users are always putting on dog and pony shows. Why does anyone create an animation. I don’t think I was trying to solve a problem, just demonstrating functionality.
What is the function used to animate the spring???
The Spring is made from a sweep along a straight line using the “twist along path” option to make a helical sweep without a helix, and the end of the straight line path has an incontext relation with the chain, so as the chain moves, the spring changes size.
Very cool Matt…I’m going to give it a try!!!
Cool animation. Another suggestion is to use a rack and pinion mate between a sprocket and the seed link, to synchronize the movement between the chain and sprocket.