From the testing I have done so far, it seems to be very repeatable, within around 1-1.5cfm variation @ 200cfm testing a port, taking it off the bench, put it back on, test again etc.. I havent calibrated it to a known orifice yet, but I have a mates test orifice from his SF600 so I will calibrate it to that.
The adapter for the heads to sit on is 1" acrylic with replaceable bores to match the bore size of the heads being tested. I am making these in 5mm increments to start with from 75-110mm I still need to machine the adapter for rubber O-rings to seal it to the bench and the slide in bores will have an o-ring top and bottom to seal them to the adapter. I am going to make slide along plates for common heads to make them quick and easy to centre over the test adapter.
The blower box currently has 12 240v, 1000W vacuum motors which are switched in 3 banks of 4. I still haven't done the control panel for the motors etc so after reading about variacs on here I will try to get hold of one to control one bank of motors for the depression adjustment. I just organised 12 new ametec motors, but the ones I currently have will do until the new ones arrive, I will make a slightly different blower box when they do with an internal overpressure bleed off. The blower box is easily removeable, only held in by 2 small angle brackets.
I just bought 2 linear actuators, one will open and close the bleed off gate valve for depression adjustment and the other will pull and push the alloy plate that changes the direction of flow from intake to exhaust. They will both be controlled by momentary toggle switches so there wont be any need to wind knobs or pull levers. This is probably a bit of a waste of time, but I think it will look pretty cool.
The air flows across the bench and up into a 500x500x500 plenum with a radiused entry into it directly below the test adapter. Test pressure is picked up in the top right corner of the plenum. I made the plenum as big as possible to try to settle the air flow before it flows out through the head. the test pressure seems to stay nice and stable once you set it. Although the flow quik unit will calculate readings at 10" or 28" test pressure, I think it is probably more accurate to reset it at each .050".
I also made up some step plate feeler gauges for opening the valves, I'll put some pics in the thread about valve opening.
From what I have tested so far, a full test from .050 to .750 takes about 5 minutes per port, I just need to open the valve, set the pressure and hit a button and it's there in the computer. The only problem I had was the valve being pulled open at .050" lift but a bit stronger spring fixed that.
Here are some photos I took the other day when I had it pulled apart to finish it off and laminate it. (by the way, I picked up the laminate at a second hand building supply shop for $22 a sheet brand new, it was $240 for the same stuff from the kitchen places).
Sorry for the veeery long post!
once I have the bench all back together and tidied up I'll take some more pics of it including the switch panel. pipework, electrics etc..
