PTS Flowbench Forum

I have been using my home made Flow Bench with the Audie setup for years and it's time to do better than 28". I could really use the advice from you guys who have already gone down the road. I like the PTS box and will be using it for a base to build on. I would be glad to post pictures of the build as well in hopes of avoiding common pitfalls that some of you have already experienced. I started out building my Home Theater in this uninformed manner and unfortunately eclipsed the knowledge base in short order and had to figure it out myself, talk about a steep learning curve, sheesh.

I have plenty 220/240 power, when I built my engine room I installed a 50A dedicated breaker for the new flow bench.
I would like to pull as much vacuum as posible 60-80" or more if possible.
I mostly do small 4cyl heads

Motor recommendations?
Motor Controller?
Suggestions for software / hardware to use with High pressure with Pitot Tube capabilities? Don't like the Audie, I have Performance Trends on my Dyno currently.
Design change recommendations other than building a stiffer box for high pressure?
Best orifice type or style to use?

I would like it to be as idiot proof as possible with auto weather corrections and port mapping capabilities. Please be patient as I don't really even know what questions to ask at this point.

Thanks in advance!

Hi Rick, welcome to the Forum.

Almost any two stage vacuum motor will reach 96 inches, so the choice really depends more on what is available in your part of the world. Apart from cost, the figure to look for is CFM per amp at your chosen test pressure plus design orifice drop pressure (probably 80 + 16 inches total).

Motor controller, PTS motor controller would work fine when fitted with a suitable range pressure transducer which is not a problem. Likewise Bruce can supply a 100 inch digital manometer.

Orifice will be no different to a low pressure bench, you can stay with the 16 inch design pressure drop orifices that Bruce can supply.

You don't wish to discuss 5 square feet per ton flow bench panel loading, so I won't venture there.

Cool thanks, that's a perfect start. I have ordered the plans from bruce and this is the motor I am looking at from Lighthouse.

122093-00
240 volt
Long Life
Brushes.

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

Your motor choice looks good.

What you are testing at eighty inches is obviously going to flow a lot more air than when tested at only twenty eight inches. A typical "normal pressure" flow bench should deliver about 12 CFM per amp at 220 volts with good motors.
Your high pressure bench might possibly end up with about 5 to 6 CFM per amp, and its going to need to reach about roughly 70% more CFM flow than a "normal" bench.

Power availability is what in the end stops most of us, so I hope you have some very serious power available to run this.

First off what CFM do you plan on testing at that high of depression? CFM drops as depression increases.

You are going to need to reinforce the cabinet build to pull those kinds of depression!!

That motor will not fit into the smaller 600cfm cabinet design it is to tall and sits to close to the front motor chamber board to allow good cooling. Stick with the Ametek 115923's

Do not buy any parts or cut any wood until you have your design worked out

Tony wrote:Your motor choice looks good.

What you are testing at eighty inches is obviously going to flow a lot more air than when tested at only twenty eight inches. A typical "normal pressure" flow bench should deliver about 12 CFM per amp at 220 volts with good motors.
Your high pressure bench might possibly end up with about 5 to 6 CFM per amp, and its going to need to reach about roughly 70% more CFM flow than a "normal" bench.

Power availability is what in the end stops most of us, so I hope you have some very serious power available to run this.

I suppose the first attempt at a high pressure unit will be a bit of an educated guess to start with and luckily I am not limited when it comes to power, I have 400A 3 phase in my backyard shop.

Brucepts wrote:First off what CFM do you plan on testing at that high of depression? CFM drops as depression increases.

I don't know, right now I am getting right at 150 CFM at 28"

You are going to need to reinforce the cabinet build to pull those kinds of depression!!

Yes, I will adjust the plans to suit.

That motor will not fit into the smaller 600cfm cabinet design it is to tall and sits to close to the front motor chamber board to allow good cooling. Stick with the Ametek 115923's

Did I order the wrong plans? Do you make one more suitable for what I am doing?

Do not buy any parts or cut any wood until you have your design worked out

Yes sir, I will probably redraw them in AutoCad (for strengthening) before I cut anything, thanks!

Is there a formula to go from 150CFM at 28" to say 80" at ??CFM?

Thanks

Pressure requirement increases square law with flow.
If you increase pressure from 28 inches to 80 inches that is x2.857.

Square root of that is 1.690.
As I mentioned previously you are going to need about 70% more flow to test a given port at 80 inches compared to testing at 28 inches.
Your motors are only going to deliver very roughly half the flow at 96 inches as at 44 inches.
As Bruce says, higher test pressures become very costly in terms of both motors and electrical power.

It would take twice as many motors to reach similar flow, and 2.86 times as many motors to attain that additional required seventy percent. So in rough round terms THREE TIMES as many motors and amps to test a port at 80 inches compared to testing at 28 inches.

Increasing the internal volume of the bench to fit more and larger motors may be possible, but that is going to run you smack into the five square feet per ton structural loading problem. I suppose anything is possible, but this is going to be a real challenge.

Great, thanks Tony. I'm not really worried about the exact depression and am more concerned with more real world flow so the higher the depression the better, this coupled with the fact I am flowing very small (horrible) ports makes me optimistic. If the first attempt does not meet my expectations I will certainly have a better knowledge base for the next one with.