Parametric Chain Link Drive Disk

I had a desire to make some small chain drives for some of my models, 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 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 link
Lthickness: This is the diameter of the link “wire”

N: The number of chain link pairs around the pulley. Please note this is pairs of links not the number of single links.

Pwidth: Width of the pulley main drum which the chain recesses are cut into.

There are a bunch of other parameters that you may wish to tweak too;

Ptol: Is the printing tolerance. It is used to provide a bit of space around the chain profile so that chain will fit into the recess despite a bit of spread from the extruded plastic.
PtolThk: This is a printing allowance for the "radially" orientated link thickness. This allows a bit of extra on either side of the link slot so any sagging of the printed filament can be easily removed or at least won't interfere with the link sliding into the slot.
Wclr: On either side the the tangential link is a cutout slot. This parameter just controls the size of this slot.

Hopefully this is all clear enough.

I feel the model will work well for larger chains where the printing tolerances are less of a factor in the final printed shape.

I trust this will be useful to you.