Sir Yun wrote:i know a mechanical bleed is simple to make but i kind of think it is sort of wastefull to dump several hundred cfm (powered by your hard earned money), heat up to the room and drive you nuts with the noise
Definitely agree with this.
I cannot think of any advantages of a mechanical control over electrical, especially as motor speed control modules are now so cheaply and readily available. Maybe forty years ago, but not today.
Also known as the infamous "Warpspeed" on some other Forums.
I would agree with the motor controller ideas today vs the mechanical bleed.
One comment: With individual motor control you would be adding a bleed circuit so that you could run the proper number of vacuum motors at full capacity for the flow and then trim the actual depression across the system using the mechanical valve to LOWER the depression by opening the valve and bleeding off suction to the measurement orifice and tested part. There would be a slight change in the room temperature due to the lower motor speed of the one vacuum motor controlled by the motor controller vs running at max output like the other motors.
I tried running one motor direct and only one on the controller, no mechanical bleed. And as I expected that works as well, although it is harder to adjust.
It's basicly a electromechanical valve that way. I do not know if the load on the one controlled motor is higher.
It is just what happens when you mix different vacuum motors as well. The weakest link controls the box
Maybe you do not need to control all the motors, but just one or two.
So say 16 motors. split into three banks of five motors with check valves, and just power on/off switches.
then one motor with controller.
Run all banks flat out for high lifts and high bulk flow, then use a bank less for a mid,and low lift flow.