PTS Flowbench Forum

Old School wrote:
What do you want to archive by adding one extra motor and an Ampere gauge?

The idea is that with an amp meter, experience will quickly tell you at what point the house fuse or circuit breaker is about to "pop".

You can then confidently wind the wick up on your bench, and know you are getting all there is to get, without the frustration of constantly running around restoring power.

Having a bit of motor speed in reserve is a lot better than running absolutely flat out, knowing there are still a few more supply amps available, and falling a tad short of reaching test pressure.

JFHolme - thx, that's a nice & inexpensive unit. Let us know how it works when you've got it connected.

Tony - got it. Good idea! Keep 'em comming....

One more thing I need to know is if the PTS design bench uses (PVC) pipes inside, or is it open plenum/chamber design? I've seen other designs which include 4" or 6" pipes. Over here we use metric sizes and after doing some research, I would have problems finding right connectors etc...

Definitely no problem building a bench in Australia or Europe with the Forum plans, it has been done many times.
America is now the only place on the entire planet that still uses inches.

David, I received your PM, but for some reason I am unable to send you a PM in reply ???

Anyhow, the answer to your question is yes.
What you are suggesting would be a good path to follow.

Old School wrote:One more thing I need to know is if the PTS design bench uses (PVC) pipes inside, or is it open plenum/chamber design? I've seen other designs which include 4" or 6" pipes. Over here we use metric sizes and after doing some research, I would have problems finding right connectors etc...

There are no pipes in the PTS design.

More than a few have been built all over the world now. I'd venture to say half of my business is International

Tony wrote:Single stage motors will be more efficient at our pressure levels than two stage vacuum motors.
That should narrow down the search.

Been doing more research on vac motors and came across this chart. It seems to support data I've been looking at (by Domel) which tells that around 44" drop, 2-stage motors are more efficient?

We went through all this a while ago on another thread here.
I will see if I can find it again.

The only figure you should be looking at is CFM per amp at 44 inches if highest overall efficiency is your main goal.
That will get you the most airflow where available mains power is a problem.

Another aspect entirely is the pressure versus flow curve.
As flow increases, pressure always falls off with a centrifugal blower.
But as the above curves show, adding more centrifugal blower stages in series create a much steeper pressure versus flow slope.

There are two disadvantages of having a very steep pressure slope.
It will be much more difficult to set and to hold a constant test pressure with flow variations.
And if flow is suddenly accidentally blocked, the pressure can instantly rise up to dangerous levels.

The absolutely ideal flow bench blower would hold 28 inches test pressure at all flows without having to adjust anything !!!
Not really possible, but a single stage blower with very broad flat flow curve probably comes the closest to the ideal.

If I had to choose between a two stage blower and a single stage blower that both offered identical CFM per amp figures, I would go for the single stage blower every time.

Sorry that I haven't been keeping up with the posts on here. I have some experience with that meter & the results were mixed. See this thread
http://www.flowbenchtech.com/forum/view ... ?f=6&t=503

I also posted the spreadsheets that I use here
http://www.flowbenchtech.com/forum/view ... f=14&t=562

They did refund me for the second meter, but it was a hassle & cost me around $20 to send it back. I'm still using the first meter & am happy with it, I just suggest that you find a way to do a sanity check on them.

Mark