I am looking a making a mini cyclone for my shop vac. I have seen Bob Pentz site, and he appears to have a fine plan for a full size model. Does anyone out there know where I can get a half scale model of that design. Normally I would say take it to a copier and hit 50%, but air is a bit funny in that not all air flow proerties are linear in nature, but rather geometric. I have a fear that half scaling will result in too much static loss, or too high a velocity to effectively seperate the finer dust. I am a Civil (traffic) engineer, so the fluid dynamics is a bit rusty. Any mechanicals out there who can assist. I assume that the critical design feature is the air velocity on the air ramp inside the cyclone.