PTS Flowbench Forum

I think I mentioned earlier that I do have a Flowquik unit and I will be glad to sell it at a much discounted rate. Somethings to keep in mind:
It comes in different models, or did come in different models. There is a single tube 2" model (which was the only one at first), then there was a dual 2" tube version (the one I have) and a 3" tube version. The dual tube and 3" tube were released to help for high flow heads because the single 2" tube version had issues when flowing high flow heads.

Now on the flow straighteners that are in the ends of the tubes, where they are positioned makes a difference in the flow readings. I know from experience! I was flowing a head and inadvertently turned on the vacuum and sucked a rag down the flowquik tube. This pushed the flow straightening element down the tube right next to the flow element itself. I did not notice and when I flowed the head I had amazing gained 35 cfm. I though man am I good and went bragging all over town about how damn good I was. One of my friends put the head on his bench and told me I was 35 cfm happy. I went back and started looking at my flowquik and noticed the flow straightening honeycomb was pushed down the tube. I pulled it out a little at a time and flowed each time and watched the flow go back down a little at a time. This seemed to be more noticeable at the higher lifts when there was more airflow.

Let me know if you want it and I will sell it to you

John

PS though you will probably still be able to build a PTS bench cheaper

One of the things which always surprises me is the effort people make to improve port flow is seldom seen in flowbench internal flow. It's perfectly OK to have multiple 90 deg bends, dramatic volume changes, sharp edge corners, etc- as long as it fits in a 2 x 4' floor footprint! It would be interesting to see how much fan Hp this philosophy uses up compared to applying a "conservation of momentum" design strategey.

Tony made a good point about a sharp edge orifice having a predictable CD if the upstream air was largely undisturbed. This would be the case if you were flowing it on the outside of the bench in a quiet room. But, how big does your orifice box have to be to absorb an incoming jet? Imagine you're standing in front of someone with an electric leafblower. He turns it on, you hold your palm in front of the jet and back up until you no longer feel it. How far would that be- 4ft, 6ft, 8ft? Whatever the distance, that's the minimum size of the orifice enclosure to assure an undisturbed flow with an incoming jet from an electric leafblower- and a multimotor bench at full power will likely be at least comparable.

I appreciate the responses, will be back later with more- Thanks!

Main.

Not sure what you are doing, designing a bench or subtly trying to question the design of an orifice style flow bench? But if you study the orifice in any book for it to work PROPERLY, In a box, in a tube, in a pipe, in a shoe. IT HAS TO BE SUBJECT TO FULLY DEVELOPED FLOW!. (Laminar Like Flow) thus the air straightener. PVC pipe is anything but consistent on its ID and shape it is mend to flow something else that leads to the septic tank. These minor defects cause changes in the boundary layer and thus create turbulence (Tumble and Swirl) within the pipe. good for some masses non good for our air. The flow straightener does this close enough to the orifice to allow the orifice to see good air.

In the PTS style bench the settling chambers are large enough to allow for the air to reorganize prior to entering the orifice. The main reason we use a baffle plate is to eliminate or an least minimize the chance for direct air flow to interfere with the orifice flow. I would ask that you try this experiment take your leaf blower in the house go to a bedroom open the window move the dresser in front of the doorway about three feet in. Then have you r wife stand in the hall with the leaf blower pointed at the back of the dresser from say 5 feet away, now you go stand at the window and tell me if you feel the air from the leaf blower blowing on you or just air moving out the window?

Lets see your design and get to building this orifice in a tube.

BTW you will most likely not need and air straightener if you put a settling chamber up stream from you orifice in a pipe and only limit the pipe length before the orifice to no more than say 32".


Rick

A little over 20 years ago, I helped a friend build a bench (He's a professional head porter). He had a requirement that the head be placed at eye level, as he wanted some relief from stooping over like the Hunchback of Notre Dame for much of the working day. The settling box was placed seperately from the blower box, with 4" PVC pipe joining them under a bench. We sized the box for 16 motors (delusions of grandeur!), started with 2 motors, later increased to 8.
All motors were seperately switched, and one was one a variable-speed control for airflow trimming. I don't believe he's ever used more than 6 motors at one time.

Originally a pitot tube flow sensor was used, but then he switched to an orifice in order to better compare flow numbers with others. We used a PVC slide valve to mount the orifice plates, which worked very well. The valve was a screw- together type which allowed disassembly to change the O-ring seals, we replaced the original plastic slide with aluminum orifice plates. Calibration was done on a Superflow, we never noticed any weird variances with orifice size up to 2".

If I had to do this today, I'd replace the settling box with a length of 6" dia PVC pipe about 12" long, run into a 6" elbow. We had a panel- type K&N filter under the 6" dia hole in our original settling chamber, this feature I'd keep (I don't think "settling chambers" actually settle much, if you want to break up turbulence, use a flow conditioner). After the elbow, I'd start a conical transition at no more than 4 deg slope to the 4" orifice section. 4 deg is the max divergence before flow starts to separate at speeds we're interested in, according to some wind-tunnel design data I saw a few years back. When you're operating in the blow-thru test mode for exhaust testing, a diffuser
is necessary for efficient pressure recovery, on the vaccum test mode, a 4 deg entry is much better than the typical reducer fitting. Next would come the flow straigtener, then the orifice, followed by 24" of pipe, then the blower box. If the vacuum source is a single blower with the intake exposed to the pipe, a flow straightener is necessary to prevent the air column from rotating, otherwise, you can likely do without. (Now Bruce can get out that machete he's been sharpening and start hacking away- turn about is fair play).

I called Audie to see if they went to an orifice element, the answer was no- they don't like changing measurement elements during flow testing. Their recommendation for ultimate accuracy was LFE- somewhat pricey for most at ~ $4000 each.`

I am going to start flow testing on my friend's bench, and have started making up a PD valve. I'm going to be updating the data collection to electronic/computer support, back in the late 90's, we spent about $700 on the best analog equipment we could afford. I'll be back Mon with more.

If you do some tuft testing, to explore how air actually flows into an orifice mounted on a flat surface, you will find most of it flows radially inwards along the surface.
Air does not rush straight towards the hole from directly above, as might seem more logical.

That is the reason for mounting the orifice centrally in one wall of a large "box" settling chamber, and placing a shielding baffle plate directly in front of the orifice.
It assists the air to do what it naturally wants to try to do.

Directing air, even perfectly flowing laminar air directly towards the orifice from along a pipe is going to disrupt natural flow.

Let's consider what happens to an orifice in a box under blow-thru conditions (easier to visualize). When we first apply flow upstream of the inlet side, pressure in the box will rise as the incoming air loses velocity and expands, in agreement with Bernoulli's theorem. Air will begin to flow thru the orifice, and pressure in the box will begin to decrease. If the orifice is smaller than the incoming jet, an equilibrium will be reached between interior pressure and outgoing flow, but the interior pressure will be slightly higher than that outside the box. Inside, you will have a region of organized flow between the inlet and orifice, surrounded by (more tomorrow, my post got cut off (timed out?) and I'm out of time, dammit! Jfholm- Pm me regarding the Audie.

my post got cut off (timed out?)

HMMM we do not have sessions on the forum... Maybe you should draft your posts in Word then cut and past.

Rick

Don't know what's happening exactly, it seems if you exceed a certain time, you're automatically logged out, and lose your post. I'm going to try posting/editing as I write instead of waiting till the end...

Let's start at "Inside, you will have a region of organized flow between the inlet and orifice, surrounded by a "tube" of recirculating air trapped within the confines of the box. It's similar to what you'll see in a river- downstream flow is out in the main channel, eddies and backflow close to the banks. "Orifice in a box" looks like "orifice in a tube"- it seems quite doubtful the ideal sideways flow into the orifice will occur in a box that's not room-sized.

Rick mentions placing a baffle before the orifice to prevent the incoming jet from the settling box from disrupting orifice inflow. This is a great example of "settling boxes" not settling much of anything- the jet from the bore adapter simply reforms at the exit of the settling box. When the jet hits this wall, the flow will have to boil up over it and fall down the other side. When a moving fluid drops abruptly from a higher elevation to a lower one, a cavity forms between the flow and the drop. This cavity is occupied by a turbulent roller of constantly changing size. What we end up with is a highly turbulent, pulsating flow directly in front of the orifice. You'll get the same effect if you hang the baffle from the top, side, whatever- forcing the flow to make a 90 deg turn will generate lots of turbulence in an area you really don't want it in. If you think I'm being overly dramatic, just make one wall of the box transparent, add smoke or streamers, and enjoy the show. The turbulence caused by PVC pipe irregularities will be minor by comparison.

PVC pipe has certain other qualities. It doesn't leak, and a tube equalizes stresses much better than boxlike shapes- which is why pressure-resistant items like cannon barrels and submarines tend to be totally tubular. For flowbench construction, it means no painting, no painstaking joinery, no leak chasing. You don't have to glue the joints- just run a bead of silicone round the cuff after the pipe is inserted, and cut it with a razor if later disassembly is required.

So far, Ive not heard any compelling reasons to abandon my wicked tubular ways, which have served my friend well these past 20+ years- he's made a lot of horsepower with his bench. I think a lot of your visitors are resistant to buying a set of plans when flowbench construction info is widespread nowdays- times have changed. Just about anything can be made to work, after a fashion, and you won't convert these people to customers by telling them their ideas are wrong (even if they are totally whacked out). What the handymen are really looking for is something they can't make themselves, and can't be downloaded for free- computerized data aquisition and data management. People don't want to squint at manometers trying to interpret flow readings, and customers aren't impressed by a couple lines of handwritten data. Expectations are higher today.

Now the companies that serve this market are into the "system" approach, where both hardware and software have to be bought from one company, and you need to spend ~ $1000 to to get a functional system. This is OK for business users who need out-of-the-box performance, and can write the cost off as a tax expense. This market has gotten smaller in the past few years due to economic issues, and trying to enter it against companies who've had 20 years to gain position will be a hard row to hoe. I would think about making a digital manometer/software package that would more versatile and less costly than Superflow, Audie, or Performance Trends. If your manometer will plug and play with the "Big 3" software, and your software will play with their hardware, AND offer options like high-depression flow measurement, floating depression, fixed depression, beta ratio selection, the Big 3's customers wil start getting interested. If it costs $100 less, the Big 3 will begin to have a problem with customer retention. The experimenter crowd will also show interest, as you'd be the only game in town catering to their needs. Development in this direction will likely be much more rewarding than selling plans.

Are you really questioning my business model????

If you read my forum and archive forum you can find all the info anyone needs to build their own flowbench of any design for minimal costs . . . it's been done, I give that info away for free it just takes your time to find it by reading.

The PTS Design rose out of that need to save time and money to achieve a very professional flowbench. I have had many build the PTS design on the "cheap" well below ~$1000, it's upgradable so you can start out with 2 motors and add more as need be. I do not need to be "plug and play" with ANY of the BIG 3 as you call it as they are really not that "BIG of a 3" anymore if you didn't take notice. Personally, I do not want to be like or involved with any of the BIG 3! I would venture to say they are not selling near as many products as they once were. (They sure do like trying to figureout why my ranking is high in the search engines though)

Anyone can have a Professional Flowbench sitting in their shop using my products that will rival if not work better than any of the "BIG 3" so called machines!!!!!!!!!!!!! This has been proven by more than a few individuals over the years.

Somehow, I think the PTS Design works quite well and I have no need to defend it against anyone else's product on the market, my happy customer's speak for my products!

With ~12,000 webhits a day here I think I'm doing ok against those "BIG 3" LOL

BTW I AM ONE OF THE COMPANIES THAT SERVE THE MARKET SO WE ARE NOW "BIG 4"

Well Maine,
I can see it is a waste of time trying to convince you of what the rest of us here know to be true.
Go ahead and do it your own way.
If you are completely happy with the results, that is all that really matters.

There are many ways to skin a cat.
But over many years, Forum members have through trial and error and hard work, slowly raised the level of knowledge and experience to a point where we can now openly challenge the products of the big dollar commercial flow bench manufacturers.

It is a bit like drag racing.
As the years pass, the performance level increases, through sheer hard work and experimentation.

Thanks for your input maineSS. I too have wondered about the plate effects on the stream. So I shall take the time to test that out.
I guess you could call me one of those handymen. I will say this, when I read posts I could not car less who posts them or what motives etc they may have. I look and the information within that post and then I decide if it contains theories that I have not considered. You have mentioned a couple of things that have interested me.