PTS Flowbench Forum

Doing some searching of the forum I saw some old posts about using a spreadsheet to determine how many vacuum motors are necessary by plugging in the CFM specs, but I couldn't find the actual spreadsheet. I am looking into the feasability of using these inexpensive vacuum motors for my build:

http://www.surpluscenter.com/Brands/Pan ... 6-1448.axd

So if I were looking to get 600cfm @28" out of my flow bench how many should I get?

Thanks,
Bob

13 to 14 of them to possibly get to 600cfm @28"

Base your flow numbers off of 44" to get a rough idea of how many motors you might need. 28" test pressure plus 16" differential across the orifice plate.

So those motors flow 47cfm @42.4", I figured around 40-44 @44" as a rough idea of what you might expect.

Motors are the heart of your flowbench getting 600 cfm is going to cost some $$$'s.

If you want to go with a lower cfm those motors will work fine and a few people here have used them in builds.

Best to buy some motors with a higher flow rating per amp imho, try to keep the max amps as low as possible for the airflow you need

5.7" diameter through flow single stage motors are most suitable for a PTS build imho, and I would aim for at least 65CFM @44" per motor to avoid needing a huge quantity of them to flow 600@28" (+16 DP, 44" total at the motor)

Max power supply amps is a big factor when choosing motors along with reliability

Here is the motors I bought for my bench Domel Vacuum Cleaner Motor 496.3.720-2 - they are rated at 114 cfm @ 44"H2O. I bought 8 of them. They are amp hogs at 14.4 amps each. I am going to wire 2 of them in series so they I will have 4 banks at 240 volts. I had to have a 60 amp circuit put in my house to handle it. They first four motors were $104 each then I found 4 more for $59.00 each. If you look around and really dig on the internet you should be able to find a good deal on them.

John

ok thanks guys, makes perfect sense. The Domels look interesting but I want to stick with 220V motors to keep amperage requirements reasonable. My shop is already wired for a 60A 220 for my TIG welder. Really the max I'm looking for is around 450 cfm but having that extra headroom with many vacuum motors would mean they won't be working too terribly hard. Having some cheap spares is nice too.

Just did a Solidworks sketch and it appears I can get 15 on the blower plate but I imagine I'll have to use heavier plywood for it since the motors will have to be spaced closely.

Just wondering if the less expensive motors are going to be a lot noisier. I expect ear plugs will be in order when running the flowbench if I decide to go with these motors.

Thanks,
Bob

One thing to keep in mind is you can wire them in series to get your 220 volt usage and keep the amps down. That is what I am going to do. That way even though they are 14.4 amps each wiring them is series keeps it to 14.4 amps per two motors. So for 4 pairs you only need 57.6 amps and that would only be if you had no load wide open.

John

Bruce wrote
Motors are the heart of your flowbench

Bruce has given you Real Good Advice

If it were me I would not take a short cut any where on a flow bench Build

http://www.centralvacuummotor.com/flowbench.htm