One of the key objectives of the Spartan Project is to make a design that has specific dimensions. Many people have built machines, including myself, that used Patrick Hood-Daniel's bearing trucks or "Bearing Rail Assemblies (BRA)". These were a great step forward because of their simple design and use of inexpensive bearings. They had the disadvantage of not being easily adjustable, which caused the builder to have to cut the actual MDF parts of the machine to an arbitrary size to cause the proper fit. They also had the side effect of requiring the use of a 45-degree chamfer bit, which I found to be uncommon and not easy to borrow, which adds cost to the build.
Here are some ideas of linear motion systems that could be used, along with some of my opinions on pro's and con's. I'd like to discuss what options we have, which would be best to use (and why), and begin to come to a decision on which will be incorporated into the final design.
"Bearing Rail Assemblies":
Pro's: Simple to construct, use inexpensive rollerskate bearings
Con's: Limit adjustability, require purchase/use of special 45-degree chamfer bit, strength is limited by small number of threads holding through thin aluminum angle
Pro's: Very simple to construct, adjustable, requires no special tools, allows for a design with specific dimensions
Con's: Expensive (adds $200-300 to the build)
Square-tubing BRA's: As seen on Peter Chick's site... http://www.chickfamily.net/blog/
Pro's: Use inexpensive rollerskate bearings, may provide necessary adjustability
Con's: Require careful construction and possibly the use of a jig or drill press
Commercial linear slide bearings:
Pro's: Easy to construct
Con's: Very expensive