Originally Posted by
LeeWay
The rails are about 1/2" tall and maybe 5/8" wide. The trucks are about 2" by 2.5" and sit maybe 3/8" proud of the rail. Then add the 1/4" plate and it all fits snugly inside the 5" by 1.5" aluminum channel. This is architectural channel, so has square corners rather than radiused like structural stuff. It doesn't really matter though.
I think 30 mm rail is way overkill, however, it would certainly be solid. A single truck that size would be fine.
I used two on each because I had them. These are probably 20mm rails or there about.
I built in a little extra travel in my machine, so I still get full 4' by 4' easily. Maybe two inches longer and 1" wider. Putting the grinder as close as possible to the torch helps with this.
Both are within 5" and are offset maybe 2.5" from each other.