udpate doc

README.md

@@ -38,6 +38,46 @@ Here's the back of that:
 
 ![allup](/images/backside.png)
 
+## Kinematic Bits
+
+Currently the set assumes 3/8" HDPE, 8x22x7mm bearings, NEMA23 Motors and 9mm Wide GT2 Belts
+
+Version for 1/4" HDPE, 5x11x4mm bearings, NEMA17 Motors and 6mm Wide GT2 Belts.
+
+See [cad/assembly/elements/](/cad/assembly/elements) for kinematic elements, and [cad/assembly](/cad/assembly) for one-machine made with these elements.
+
+Motor and XY Constraint:
+
+![motor](/images/kunits-motor.png)
+
+XY Constraints, with preload adjusting and without:
+
+![xy-adjust](/images/kunits-xy-adjust.png)
+
+![xy](/images/kunits-xy.png)
+
+YZ Constraints ('out of plane'):
+
+![yz](/images/kunits-zy.png)
+
+**Assembling in Rhino**
+
+![basically](/images/kunits-basic.png)
+
+or
+
+![units xz](/images/kunits-before-form.png)
+
+filling in
+
+![one](/images/kunits-one.png)
+
+![two](/images/kunits-two.png)
+
+![three](/images/kunits-three.png)
+
+![four](/images/kunits-four.png)
+
 ## Hardware Notes
 
 - needs more clearance on belt-side