I took a triple-motor Air-Flo central vacuum, and added a separate switch and check valve for each motor. This allows instant performance comparisons for 1 versus 2 or 3 motors. Interesting results.
we learned that only so much cfm can go through that small vacuum hose. so all those vacuum motors are choked by that little vacuum hose. if you had a bigger vacuum hose say 2" you would have full airflow capability.
I note that all 3 motors are set up in-parallel. This is part of the reason that third motor is having such a poor effect on your working vacuum. Assuming all three motors are the same model, the third motor cannot produce a higher vacuum than what the model of motor is designed to produce. In order to increase the working vacuum further you would need to dispense with that third motor in parallel, bring in a fourth motor so that you can instead now connect two pairs of motors in series (e.g. 2 tangential bypass motors: the air intake of one connected to the air exhaust of the other). Each pair of series connected motors is then set up in parallel with the other pair inside the vacuum canister. You're working vacuum will be higher, allowing your CFM to greatly exceed what you got with just two single motors in parallel and without having to increase the diameter of the vacuum hose. Also, you're electricity usage will be greater. But unlike with that third single motor, now you'll have a performance increase to show for it. [Disclaimer: The above is just my opinion based on my online research of the topic. FYI: I'm in the process of slowly collecting all the parts I need to someday build my own four-motor central vacuum, which of course will provide me the opportunity to either confirm or falsify the above.] EDIT: I don't know the power requirements of the triple-motor Air-Flo machine. But a four vacuum motor setup would require a higher amperage than typical power source (e.g. ideally that afforded by a dryer receptacle, with the appropriate voltage adapter/splitter, depending...).
As soon as you lifted the motor filters I knew this was very similar to the MD silentmaster vacs. I checked on MD's website and they said these units were made as a private label for Air-Flo. I knew that bag system looked familiar! *edit* i didnt see the previous video where you explained that modern day made these as a private label. I do have a question about series and parallel motors if it is ok to contact you?
If it's the one in one of your old videos I just saw, that's a private labeled MD for sure. Doesn't sound like a dual motor unit though. Could be a Model A (single 7.2" three stage motor) or Model B (single 7.2" two stage).
