The same principle applies to truck mounts as well. A sapphire 370 will have exactly the same water lift as a 870. The difference is the blower on the 870 will produce considerably more CFM or airflow, enabling longer hose runs or dual wanding. The problem with portables is that we are limited by the amperage we can get in an average household. In the US it is common to find 120 v. 20 amp circuits. In Canada we are limited to 15 amp circuits except in some new buildings. Old single power cord portables used to use 1-13.8 amp 7.2 inch vac motor and a diaphragm pump from 50-100 psi taking 1.1 amps. Then someone figured out that they could take 2-8amp, 2 stage vac motors, run them in series and create more water lift than the old 7.2 and still take the same amperage. Then the war was on. All kinds of configurations came out with 2 cord machines both in series and parallel with bigger vac motors and bigger, higher pressure pumps. In reality, for a portable to be efficient, we need about 136 inches of water lift which is about 10 inches hg. On a single cord machine you will get this at around 100 CFM, enabling you to use a 1.5 inch short vac hose around 15-20 ft. As the machines get larger and more powerful, you can longer and larger vac hoses but they still have their limitations. As far as etms go, you have to allow for pressure drop on your pump. The longer the hose run, the more amperage you need to keep your pressure up.Is this a portable argument?
Actually I didn't know all that....Ed, you must think we're all a bunch of idiots. Putting vacuums in series is done to increase lift, especially with small 2 stage vacuums. When in series, the amperage draw of the first vacuum drops by about 20%, allowing you to install a pump on the same circuit with out blowing circuit breakers. Yes, the rear vac motor will wear out sooner than the first one because of the hot air passing through it but these vac motors are cheap and easily replaceable. You cheated when you sucked up the bearing. On the first test, you had the the vac hose sealed to the floor before you turned the machine on. No wonder there's no cfm. The hose is sealed. No air is passing through it. On the second test, you had the machine on already and you angled the hose to the bearing. No kidding it sucked it up. You always need a balance of lift to cfm. Putting 2 8 amp 2-stage vac motors in parallel won't work very well because there is not enough lift, even though you have more airflow. Putting 2 13.8 amp vac motors in parallel produces enough lift and has tons of airflow. Even better are the newer 6.6 and 8.4 inch 2 stage vac motors. More lift and airflow at the same amperage as the old 5.7 and 7.2 equivalents.
To demonstrate lift vs airflow, all you had to do was crack the hose a little during the first demonstration. You didn't have to hook up your mx2. Sorry Ed, sounds like a sales pitch to me.Ron;
Thanks for the comment. However, no I didn't think "you were all idiots", only jImMy! (Just kidding of course)
One major correction however, to your comment; the machine (vacuum motors) were turned on when demonstrating both Lift & Air Flow. It demonstrates that a sealed vacuum requires Airflow in order to move pick up. We also indicated that in every system one will have both but the question is; how much. Air flow helps create a certain amount of lift. But, lift does not create airflow as demostrated. I believe that Ametek would agree with this video knowing them as well as I do.
In regards to putting 2-vacuum motors in parallel, (in this case, 2-8.4) we have been doing that for 43 years running the distance with success.
In the end, however, this was an honest demonstration and not a "sales pitch" in order to explain these two different principles. It was not intended to necessarily change everyone's belief and/or opinion if they chose not. But, it was fun doing it and hope that we have contributed to this fine board.
Thanks again, Ron, for your view point.