Summary

The attached OpenSCAD Libraries will generate chassis for small robots.

There is suport for servo based drive and a top mounted servo for ping sensor scanning.

Instructions

Copy all the scad files into a common directory.
The code has been tested using ABS, printed at .3mm layer height with 1 extra shell and 50% infill.
The parameters for the size of the bot, the board size, etc. are all contained in the file newsumo.scad.
It can be setup to generate a 3D view or printable views for the top, bottom, and sides. Just uncomment the line in newsumo.scad for what you want.
The caster used is from VXB bearings: http://www.vxb.com/page/bearings/PROD/Kit7766
The screws used to assemble it are #1 x 3/8 servo hold down from JR Hobby Hadrware: http://www.jrhobbyhardware.com/shop/index.php?main_page=product_info&cPath=108_109&products_id=255
This is a premlinary release. I am still working on adding a castering wheel. Also, a version sized for an Arduino board is in the works.