quandary: which type of flow bench to build?

[Tony]

Welcome to the Forum Ron.
Software for the DM is included in the price, and future software upgrades are entirely free and downloadable from the internet as they become available.

The reason for the surprisingly low cost, is that many members here just enjoy helping other Forum members to build their own flow benches without having any personal profit motive.
What we have been able to achieve as a very friendly self help group has been truly remarkable.

[ron thorne]

More questions while I await the delivery of pts plans:

1. If I decide later to flow at higher depressions than, say, 36", ("This is not a high depression flow bench") what modifications could I do in the construction of this bench to enable that (i.e. heavier materials, etc) ?

2. Looks like the surplus center (16-1446 & 16-1448) are an economical alternative (won't flow as much as more expensive motors), but will take more amp capacity? Which used vacuum cleaner models have the best flowing motors?

3. Would my application (lift limited to .400" and VERY restricted modifications to oem stock low flowing heads) benefit from higher flowing depression (over 36")? In other words, are high depressions only useful in larger flowing less restricted applications?


Thanks, Ron

[Tony]

Bear in mind that 28 inches of test pressure is almost exactly one psi, or 144 Lbs per square foot of air pressure.
The forces on the bench panels can very quickly add up to many thousands of pounds.

Another difficulty with building a very high test pressure flow bench will be the amps and the horsepower required to generate sufficient airflow at much higher required pressures.

Building a thirty inch 500 to 600 CFM bench is a realistic goal, and quickly runs most of us right up to the limit of the brick wall of available electrical power.
Experience of many people suggest it's also a pretty good balance of flow versus pressure to test with.
A 100 inch 200 CFM bench, or a 10 inch 1,500 CFM bench may be much less useful.

When you have assembled a pile of likely vacuum motors, the best approach might be to do some testing to weed out the best ones from the junk.
The magic figure you are looking for is highest CFM flow per amp, at the back pressure the motors will be running at when installed, which will be 44 inches (28 inches test pressure + 16 inches measurement orifice drop)

You will discover there are huge differences in motor efficiency when measured at 44 inches of back pressure, and size or cost is not a good indication of efficiency.
In the end its the limit of available power that stops most of us, and good motors can easily produce perhaps twice the CFM of some crappy motors at the power limit.
Take your time and choose motors wisely.
Your efforts and your patience will be well rewarded.

[ron thorne]

Tony, I don't think anyone could have answered my questions any better! Thanks.