I'm using Audie's 2" and 3" flow tubes. There's a pic on Audie's site of a similar setup but with all the plumbing exposed. I chose to build it all into a cabinet. Due to the length of straight tube Audie recommends either side of the 3" flow tube, plus the large radius bends, the finished product ended up pretty big! Cabinet is 7 feet long and the top of the bench is just short of 4 feet high - including the casters.
I switch between the 2" and 3" flow tubes by opening and closing the relevant gate valves...
I also purchased Audie's Vacuum Motor Control. Originally I planned on incorporating a sliding bleed-off valve to dump excess pressure but the Motor Control works great and makes for an easier build :;): Adjusting flow following each valve lift increase is super quick and easy. Although the unit is designed to work at 60Hz, it's working fine here in the UK at 220v/50Hz
To deliver consistent and accurate valve lift figures I 'modified' a digital micrometer.
The bench is fitted with 6 x Ametek vac motors. Repeatability is excellent - certainly well within the 1% figure quoted by Audie.
Pitot tubes came from Performance Trends and I use them in conjunction with a Digitron digital manometer.
