Parametric Chain Link Drive Disk

I had a desire to make some small chain drives for some of my [models](http://www.techmonkeybusiness.com/art-project-articles.html), but wanted to use some classic chain link style chair rather than proper chain drive chain. I had a look on thingiverse and discovered that nobody else had made a model for this. So, after scratching around with a pencil to work out what parameters I needed, I jumped on OpenSCAD and came up with two parametric models. This one is just a disk with the chain recesses which can be easily adapted to other pulley body designs using your vertex modeller of choice. The [other](https://www.thingiverse.com/thing:2757692) is designed to crew onto a shaft and so it fitted with a neck, holes and nut slots.

The chain size and number of link pairs determines the size of the pulley. So the important variables to fiddle with are;

**Llength**: This is the outside length dimension of a single link
**Lwidth**: This is the outside width dimension of a single lin