by Tony » Sat Jan 27, 2007 6:32 pm
Easy, just make up a whole series of very simple orifice plates. Just squares of thin gauge sheet metal with different odd sized round holes. Whatever selection of drills, hole saws, or metal punches you happen to have on hand will be fine.
Then see how much pressure your blower (or blowers) can pull through each different sized hole. Each hole size will then have a pressure reading to go with it for a particular blower. The flow can then be worked out by knowing the hole diameter and the developed pressure.
These points (one for each hole size) can be plotted on a piece of graph paper to generate a pressure versus flow curve. From that you can read directly how much flow there is at 28 inches, or any other pressure.
These simple sheet metal plates stick to the blower intake themselves by suction pressure alone, and a small diameter hollow probe can measure the pressure on the down stream side by inserting the probe through the hole. All pretty simple and easy to do. But it is an excellent way to compare various blowers and judge what you actually have, or what may be needed before constructing the actual bench.
Also known as the infamous "Warpspeed" on some other Forums.