A "floating pressure drop" type flowbench - By David Vizard

[Tony]

The Vizard floating pressure drop bench depends ENTIRELY on the airflow from the vacuum cleaner motor.
If that varies your readings will vary as well.

All other types of flow benches work in an entirely different way, and the problems associated with varying air temperatures, varying mains voltage, and varying blower outputs have either no effect at all, or an effect that can be measured and compensated for.

The PTS flow bench is entirely ratiometric, and is totally immune to any of these changes without any compensation needing to be applied.

If you crank up the blower to create a known repeatable test pressure on the PTS bench, the bench will always read exactly the same and be totally repeatable under any changing air or voltage conditions.

How does that work ?

You feed the same exact air first through what you are testing, and then through your measurement orifice. You measure the pressure drops across each.

It does not matter what the air quality is, because the same exact air flows through both, they will ALWAYS have the same RELATIVE pressure drops.

And because you have very precisely set the test pressure across what you are testing, the pressure drop across the measurement orifice will always repeat, rain, hail, or shine.

The Vizard method is hopeless, because everything changes all the time.
Measure the same port six days running, you will get six different pressure drop numbers, even though you have changed absolutely nothing in the test setup.

When you start making changes, the tests numbers will be all over the place, and nothing will repeat, not a good way to do any serious airflow testing.

[1960FL]

Well I guess the PTS is $50 more for a start because that's what the plans cost. To me DIY is also about self design or open source..
If someone wants to give me the PTS plans for the same price as the DV plans cost me ($0)then I'd build that one as well..
So how do you compensate for a voltage drop?

Ace

First off Welcome aboard, Second if you are one of DV's lemmings here to defend DV and the F-D bench save yourself the energy.

Now on to flow benching if free is what you are looking for 150% of the information to build one hell of a flow bench is here in the TWO forums, archive link at the top of the main page and this current active forum. If you come across a post on the archives that should of had a picture in it and it is missing please PM me and i will try to find pic and or fix the post. Bruce's plans are offered up very quickly here as many have gone the rout of building there own design and struggling through there design issues and hove gone on to build a PTS Bench as it is a proven design (Like Cliff Notes). Bruce runs this forum out of his own pocket no advertising no fees just good people adding value. If you read the Flowbench 101 and then maybe the Wikipedia information everything is there to build an orifice bench from scratch and no one here will discredit it they will just help you all they can to see you build a viable piece of test equipment.

I say work on a design post it in Members projects of another area and lets get started.

Rick

[Tony]

Rick is spot on.

The bench plans you can buy from the Forum are the result of several years of testing and long discussions on the Forum by many very clever and experienced flow bench people.
There are members here that do flow bench testing for a living, or are professional engineers.

Bit by bit the knowledge and experience has grown from suggestions, experiments, and the combined personal experience of Forum members, and every single bit of it is available step by step in thousands of posts spread over several years.
None of us here could have achieved all this on our own, but as a group effort by many contributors, progress over time has been both continuous and spectacular.

There is no secret knowledge, it is all right here free and available for anyone to read and research, if you have the time to read through the many many years of relevant posts and topics on flow bench design.

The fifty dollars will save you a great deal of time and effort searching the forum, and the money goes entirely to support the costs of keeping the Forum open on the internet.
There are regular bills that must be paid to keep the Forum alive, and it is all done through donations and the small charge for the Forum plans.

Contrast that with Mr V's commercial money making site, that is crawling with fairly garish and intrusive advertising.
You won't see anything like that here.
V's site is a money making enterprise, as are his books and his lectures, that is what he does.

We here are a bunch of flow bench and petrol head enthusiasts that help and support each other freely through a common interest, without any profit motive or self interest.

You will notice something else here too, we are a very friendly, polite, and well behaved Forum, always have been.
Which is pretty unique on the internet.

[Brucepts]

You know I had some really good replies for this post . . . but, decided it's not worth it

Anyways my plans are 23-24 pages long allow you to build one serious flowbench not some shop vac setup for $10 to $1000 like others on the internet are selling. You can build a flowbench that will rival(?) or be better(?) than the commercial flowbenches you can buy for $$,$$$'s

As Tony stated no advertisements here although my website hits would generate a pretty good income and I probably could give away plans! But, then everyone would have to look at ads all the time and personally that sucks to me! Sure everyone else feels the same way.

I ask for donations and get a few from time to time, plans sell quite well and most who buy end up building a flowbench at some point and are quite happy, don't see a lot of discussion on getting a PTS flowbench on this forum or other forums working either?

Do people ask "V" how to get a PTS Flowbench running? But, people come here all the time for us to help them get other people's flowbench designs working? Humm, what do we ask for that? Nothing we pretty much tell people how it is and why it doesn't work or help them get it working. The core forum members here are the guys who do this and enjoy helping others.

The "V" plans are a few posts in a forum? Does that give you enough to get it working for free? If it does would we be talking about here? Think if you called or emailed "V" he'd help you out? He wants you to buy his books or attend his seminars as Tony stated.

I sure am not making a living at this off what I sell, I make money yes but I also put my "sweat equity" into drawing up a set of plans which are constantly in design mode as new things come along. They are professional as I have a background in drafting, they are not drawn backwards (buy someone else's plans and you will understand lol), they are clear and concise, they can be modified by the end user if need be and use simple hand tools to build.

You want to build a flowbench? I'll send you a set of plans, you get them and you think they will work for you, pay me what you think they are worth to you? I've sent parts (sometimes worth more than a few $$$$'s) to members here to help them get their flowbench going so they could make money to pay for the parts I sent them! Most of them I only know through a user name here, I took them at their word and guess what? Nobody screwed me yet!

This past year I would venture to say that 8-10 guys from here started or added to their own business after building a PTS Flowbench. Think "V" sent out a free book or let someone into a seminar for free or allowed someone to pay afterwards?

Things that make you go hummmmmmm . . . . yep lots of free plans out there, just look at all the posts here asking about'em . . . . BTW Welcome to the forum we are a fun bunch here and we are truly here to help you get a working flowbench!!!!!!

[AceR]

Ok, first of all I'll deal with the DV thing. Do I have his publications? Yes, Did they give me a good base of knowledge to start with in my trade ? Yes . Would I give him my left testicle.. No
That's where my association with him ends, If I figure one of his publications is worth getting because I may pick up some knowledge then I'll get it. If not I'll simply pass it up. His are not the only publications I buy.
If he want's to sell his knowledge well that's fine by me, but in the land of the free it seems to really piss some people off.
1960FL.. I remember reading how you claim he ripped off the floating bench design that was in another book. Just out of interest when was that book first published because the earliest I can find is 1981. That's quite a few years after DV used this design to do BMC heads at home. Then aging I could be wrong.
When I went to do a Tig welding course years ago I had to pay the teacher for his knowledge, that's how he made a buck, that's how I learned from his experience, and that's how the world works.
Anyway, that's about all I'd like to say about him on a personal note.

I will also point out that in the book he has that shows this flowbench, the information to use it is incomplete.. he does not tell you how to plot that graph using the calibration plate..as well as some other factors.
He gives you the basic concept but that's about it and in my opinion it should have been a lot more in depth. So it's a fail in that department.
As DV has spent his life testing other peoples concepts then I figure it's only fair that I test one of his.

For what it's worth I'm simply interested in the concept, not in promoting someone ( unless they want to pay me) hehehe

Now as to Tonys answer on the vacuum changes, your not stabilizing the motor speed , but your setting the same base test depression with a mechanical bypass valve. But what happens when you set it at say 28" and your screwing around with the probe etc and your wife decides to turn on the AC , run the washing machine as well as the dryer. The motors slow a little and then without noticing the water is at 26".
Well you just go back and reset the valve, easy, but you still had the same problem as what will happen with the floating bench.
This is the first problem to address. Stabilize initial testing depression.

It would also be worth noting that when this bench was used with a single vacuum cleaner it was getting used on a head with a 1.31 valve that flowed around 120cfm( or maybe even less) when ported about as far as it could go in the late 1950's or whatever year it was. ( well before my time)
Somehow I don't think plugging mums vacuum cleaner into a head that's going to flow double that figure is going to be a good idea. No matter what system your using.
This is the second problem to address. Amount of vacuum source and MAX MIN depression figures.

I'm sure there will be more but like any science experiment you need reduce your variables.

[AceR]

Bruce, thanks for the welcome .. I will point out that I have been a member here for over a year and a half.. long time reader , short time poster.

[Tony]

Now as to Tonys answer on the vacuum changes, your not stabilizing the motor speed , but your setting the same base test depression with a mechanical bypass valve. But what happens when you set it at say 28" and your screwing around with the probe etc and your wife decides to turn on the AC , run the washing machine as well as the dryer. The motors slow a little and then without noticing the water is at 26".
Well you just go back and reset the valve, easy, but you still had the same problem as what will happen with the floating bench.
This is the first problem to address. Stabilize initial testing depression.

That is very true. The test pressure can also creep over time as the motor windings change temperature, even if the mains voltage is perfectly stable. The ideal solution to this problem is of course, the Forum developed automatic electronic test pressure controller, which many Forum members are now using.
This will constantly and automatically correct for even the slightest test pressure variation, and hold the test pressure as steady as a rock. This allows you to concentrate on other things beside constantly having to check and constantly tweak the test pressure to bring it back to exactly where it should be.
It also automatically holds a constant and very precise test pressure as you adjust your valve opening increments from one lift measurement point to the next lift measurement point, over the full entire flow range of the bench.

Of course, none of this is even possible with a floating bench.
You just have to live with and accept whatever wild errors and random changes occur from one measurement reading to the next measurement reading, which may be minutes or even years apart.

[1960FL]

AceR,

Welcome,

1960FL.. I remember reading how you claim he ripped off the floating bench design that was in another book. Just out of interest when was that book first published because the earliest I can find is 1981. That's quite a few years after DV used this design to do BMC heads at home. Then aging I could be wrong.

What you do in a closet when no one is looking is your business. I have been in this industry for many years and own most of Mr. Vizards books probably paid for a few of his projects. Mr. Dalton did not publish his Practical gas flow until the late 1980's He too a Britt was reiterating what he did in the 60's and 70's not when he published a book. The facts are Bernoulli plaid in the air flow arena before them all.

As for when my X wife turned on the oven to cook, the PTS digital DM will sample at several hundred times a second then average hundreds of these samples to display the reality on the screen, How do i know this? I write the code, O'h and did i mention support is Free on the DM and the home made water gauge if you choose to build one of those too. You see here on the forum we love flow benches but are not to fond of self promotion, i did notice there was a very lengthy thread on David Vizard in the advanced tech section on Speed Talk, those guy's might know how this device works.

BTW it is John Dalton Practical Gas Flow, and once you read it you will see it was not something he came up with in the 80's. He too played with Mums vacuum as a kid.

Vizzards concept of variable depression comes from Taylors book volume 1 Thermodynamics, Fluid Flow, Performance first edition published MIT Press in 1960 the other reference that discuss dynamic flow are both Lighty "Internal Combustion Engines" 1939 McGraw Hill and Obert "Internal Combustion Engines Analysis and Practice" International Textbook Company 1950 but Charles Taylor at MIT put it to the Test. BTW My first addiction is Technical Books


Rick

[AceR]

What you do in a closet when no one is looking is your business.

Yeah.... you see, you've really sort of lost me here from the start.
The best you have with the whole "who knew what from who " thing and "when" is just speculation on your part.
Hardly enough to stick the knife into someone when posting I"d think.
I work in the custom car field and I hear that stuff all the time, this guy stole an idea from that guy.. I saw that idea 50 years ago, on and on it goes.. To me it's usually just sour grapes of some sort..
Now I know that this forum has good material in it and is the best on the web but you should also keep in mind that if you have a web site that also sells products you make then this in itself is "self promotion".. Look at the post above, your telling about the valve, how good it is ( which it is) and your promoting it. It's not on a huge scale like some people but it's still on the scale.
I've also seen you guy's on other forum directing people here .
Garage Journal is an example, 3 posts advertising this site, then no more.Those posts were purely designed to funnel people here. Even those old farts called you a spammer. That is a case of self promotion as well .. But hey, as I said before I don't have a problem with that.
So please don't piss on my back and tell me it's raining..
I don't want my posts to center around DV from now on. If you want yours too then we simply wont have anything to talk about.
Lets also not forget who the FD bench is aimed at as well as those publications.

[Tony]

you should also keep in mind that if you have a web site that also sells products you make then this in itself is "self promotion".. .

The products promoted on this site sell for little more than the cost of the parts plus shipping, and the effort required to make the whole thing possible as a service to other Forum members.

How about you providing some of your custom car parts supplied and shipped completely free around the world to anyone that wants them ?

Custom car parts should be entirely free and available to anyone, and you should be the guy that does all the work and puts up all the money to give all of us what we are all perfectly entitled to have......

I want a free set of flared guards for my Lamborghini, painted canary yellow, and I want them shipped to Melbourne Australia at your own personal expense immediately.
Any objection to that is just pure selfishness and greed on your part.

I want my guards, and I expect a flawless paint job, and it is your responsibility to give me what I want entirely free without delay.