Seemed to me that there is a lot of black magic thinking about air flow in dust collection systems and no scientific basis used for designs of small shop or home evac systems.
Being that in my trade I am rather familiar with air flow, sizing of ducts, fans, outlets etc. The WYE's and TEE's, the differences between the fittings used, and air measurement, as well as gas and fluid measurements I would have figured that there should be something out there regarding Vacuum systems, but there is very, very little.
Busy Bee's site had a little bit on them, and particle drop out on slopes, using smooth pipe as much as possible, all stuff learned via the college of hard knocks.
Well, the use of a simple manometer is useful for checking designs of air flow, finding restrictions, and a host of other design weaknesses. So I started searching with the word manometer and dust evac systems, etc. Key word being manometer. You can make one very simply with a U-tube, or a gauge or even electronic measurement now a days.
Found this a real joy to my heart, as someone has taken the time to check out the real world. You might find it interesting and also a way of fine tuning what you have an optimizing it.
Acknowledgements My introduction to the problems with dust collection came from Jim Halbert in the mid to late 1990s when he freely shared his knowledge on airflow, cyclone design, and measurement in articles and innumerable forum posts. At the time I was happy with my dust collection system and mostly just glanced at Jim's efforts. I admired and felt sorry for him because many of his posts got attacked and mired in controversy. He consistently told people they believed garbage advertising hype and needed to do some of their own measurement.
Suddenly I landed in the hospital with respiratory problems and my doctors said no more woodworking until I cleaned up my shop. With lots of research including the university where I have taught engineering for over three decades, I kept finding much of the best information on small shop dust collection came from Jim Halbert. By then he had long given up posting, so I did lots of digging through the various woodworking forum archives and finally contacted him directly. He was kind enough to share his dust collection information, design and testing articles and web pages.
Have fun with it, and also a healthier life.