I eventually found a solution that utilized the law of cosines and law of sines to relate all the variables in a way that would help. I only needed to generate four points to create the basic geometry of a tooth then I could rotate it N times around the center and be done. What finally helped me was thinking about the problem as a vector problem. I hacked at it for days and was able to make some progress but would then get stuck trying to simplify the equations enough to be implementable in javascript. I could fully constrain the sketch in Fusion 360 so I knew that I had enough information to solve this problem. I figured out how to statically display SVG in a simple page then went about the actual generation of the geometry. Much of it was way over my head but I did discover that I was able to natively embed SVG on the web using HTML5 which got me started in the right direction. I started by trying to dissect how worked.

I wouldn’t call myself a computer scientist but I’m pretty stubborn, reasonably nerdy, and know my way around a few programming languages. I was going to make a web based timing pulley generator, just as Matthias Wandel and Abel had done for involute spur gear generators. I decided it was time to bite the bullet and give back to the community as so many others had. I created a parametric model in Fusion 360 that worked but the software would crash half of the time when updating parameters. That then lead me to this lovely diagram.Īt this point, I realized that I didn’t want to be hand-making geometry in CAD for every pulley. I struggled to find any official documentation of the MXL pulley specifications and eventually discovered that most of the geometry could be found buried in the technical downloads of companies that sold pulley hobs. It can’t be that hard … right?Īfter a while mucking around in Adobe Illustrator and Fusion 360, I was in over my head.

So I figured I would just make the geometry myself. What I discovered was that these suppliers only sold timing pulleys in limited tooth counts and their CAD geometry wasn’t always great – lots of missing fillets. I thought I could just jump on McMaster or SDP-SI, download some free CAD files, and export the geometry. So heck – why don’t I just laser cut some pulleys!? And I didn’t trust myself to get the specs right on my first try. And I kind of wanted them to be transparent. And I needed them in very special configurations like hubless and hex bored. I was going to need to buy a lot of timing pulleys. I had decided on the MXL standard to minimize the size of my project but quickly ran against a cost hurdle. This post describes the inception of, and my work on, the Timing Pulley Generator Tool.Īs I was working on a DIY clock project, I quickly became aware that I was going to need lots of timing pulleys.

Gear template generator matthias wandel