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

[BigBro74]

That part is at the top of the thread name (DV).WHO.
Two authors that have been mentioned numerous times have written differing reasons WHY.

Build it. tried it. did that. check.

has anyone else that has commented here? flash gave a short go at it?

i'm not famous. Sucks to be me. but i asked the question, why are they testing at higher dp's and and the methodology surrounding this and what it gets you and how it is interperted. i know most say it is to see how air stays attached to the short side and such. i get all that. but is that the whole picture? and yes this part is about a testing method, not a flowbench. i dont think you can seperate the two.

Most only say what they think you can't do. negativity a-plenty. alot of "you cant do this or that". they say "prove yourself". I am not a flowbench. Besides, by the scientific method a hypothesis cannot be conclusivly proven. ever. only disproven by not obtaining the same results when replicating a test and not introducing different variables, which we all do when we test with any bench. so prove Yourself!-its impossible. in the last floating dp thread started by someone else i posted my results. I ask again, has anyone else who has posted here given this any "real" try. more than just one day in the garage.

[Tony]

Testing at higher depressions is a lot more sensitive, in that small effects in the port you are measuring become more dramatic.
Some real heroes are now reportedly testing at 120 inches !
But there is nothing at all wrong with using a 28 inch test pressure, or even testing at much less than 28 inches.

It is the method used to measure flow that is most important, not the test pressure.

There are Forum members here that for various reasons are forced to work at lower test pressures, in a practical sense, we all are limited one way or another in what we can have.

So don't let lack of available electrical power (or money) be the excuse used to justify building a floating depression bench, when with just a little more effort and understanding you can build something far better.

[Flash]

BigBro74 if you would go back to the first page and read my coment you would find that I HAVE BUILT ONE OF DV FLOATING DEPRESSION BENCHES.

Never mind i will re post it!

I When back and re read that 8 page thread again............. it was a Good One!!! Sad it ended so abruptly...........
But the next step was building and showing its merits, Good or Bad.............and the only one willing to do so........never got back to us

When i started on this flow bench Journey, it started at Mr Vizards site.
and i learn a lot there. even built one of them floating, single shop vac benches.........But it was not accurate and didn't want to do all the temp, humidity . Voltage stabilization exc. That stuffs not Cheep(AKA, HOW TO BUILD A FLOW BENCH FOR 35(?)DOLLARS) Well it's a lot more to make it accurate.......

Then i found this site, i built another bench. (I won't call it a pts bench because i didn't fallow the plans in some crucial areas and it cost me a lot of grief(and the pts members as well ) getting it to be turbulent free!
You guys were all so pation with me THANK YOU

If i had it all to do over again, it would be the "P.T.S.FLOW BENCH" done by the plans! NOT the so called 35 dollars bench.

Still it would have been nice to see some one, go down that road, of making a floating bench work,.....................

Sorry i miss read you coment but i will leave it up any ways.
Many people come to this sight with DV exitment,BUT either they give up and go a way or they build a NON floating depression bench.

I WOULD LOVE TO SEE SOME ONE TAKE THIS ROAD!
All the people on here would be more then willing to help.
Every time some one actualy start down this road......they fade away or build somthing else.

I wish some one would step up to the plate and do it.

The 8 page artical from the old forum is dead. or am i doing something Wrong???

[Brucepts]

Old forum post:

http://www.tractorsport.com/forum/viewt ... depression

[Tony]

Every time someone actually starts down this road......they fade away or build something else.

I think that is the whole point.

Once you get interested in flow benching, and start actually trying to put something together, you very quickly discover that there are MUCH better ways of going about it without adding much to the cost or complexity.

While a great many of us have messed about with floating depression at an early stage, nobody has ever used it as a final design because the shortcomings are very evident.

[coulterracn]

i asked the question, why are they testing at higher dp's and and the methodology surrounding this and what it gets you and how it is interperted. i know most say it is to see how air stays attached to the short side and such. i get all that. but is that the whole picture? and yes this part is about a testing method, not a flowbench. i dont think you can seperate the two.

I remember reading an article were Smockey Yunick stated he used 28" to flow heads because at that pressure he noticed the port responded to changes in shape, etc..

I've had the pleasure to witness Larry M flow heads for a friend. He flowed at a higher test pressure and the data was converted to 28".

28" has become the industry standard to compare flow data which is used in most engine simulation software.

Ray

[Tony]

Yes it has become a historic standard, and that is probably a good thing.
But there is no reason why testing cannot be done at much higher or much lower test depressions.

Building a high pressure bench is not to be taken lightly.
It is not just the high blower horsepower and enormous electric current, but the bench itself needs to be built strong enough to withstand the pressure.

Twenty eight inches is very nearly 1psi, or 144 Lbs per square foot.
A four foot by three foot panel has 1,728 Lbs of air pressure trying to burst or crush the bench.
Is particle board, glue, and a few wood screws up to 1,728 Lbs of force ???
Sure, if you build it right.
But building 4x3 foot panel for a hundred inches of test pressure would create a force of 6,1714 Lbs !!!
Serious stuff indeed.........

[1960FL]

Build it. tried it. did that. check.

Jason,

As i have said numerous times Show us, You have played with the concept you have posted words I have seen no pictures and i have seen no data that can correlate this device to conventional flowbench data.

Your point continually seams to be to push the concept of DV's so called F-D device and not for the progress of flow testing as a whole. One can test at any pressure within the capabilities of ones bench be it LFE, Pito, Orifice in a pipe, or Orifice but they all have one thing in common a Reference element. The term depression means nothing more than "Test Point" one can test at any pressure 1" 10" 100" it is only limited by the power of the bench. A flow bench by nature is a COMPARATOR! it's primary purpose is to show changes in flow against itself (Repeatable), it secondary purpose is to do this at some standard. My point is that the industry has struggled continually with the Standard and most of us here at FBT believe in ASME ans NIST and that the sharp edge orifice gives us a traceable standard to compare each others work on a level playing field (See Chads posts on the SF 600) . My issue is not that the F-D cannot show change in ones work it is and will be until someone shows me different Cannot be mathematically correlated to flow on an Orifice Bench or any standard.

The extrapolations and inferences of this device are like saying I am 5' 11" and where a 38" pant and he is 5' 11" and wheres a 38" pant so thus we must both weigh the same.... NOT!

BTW

I am still waiting for the "Why use a floating DP bench" vs. a standard orifice bench and also "names of well know head porters who are using a floating DP bench?

That part is at the top of the thread name (DV).WHO.

I could be mistaken but I do not believe he is considered a well know head porter so lets do us all a favor and move this topic away from HIM as this Forum in not here to promote his good it is about Flow Benches and Flow Devises.

What i have learned so far is that no one here disagrees with testing at different depressions now lets move on to the rest of it.

Last 28" is a rounded number to 1 PSI and this primarily came from Smoky's research and several points, His bench was capable of flowing up to 120" but he found his most consistent and biggest results on the dyno when testing and making improvements at 28" on the flowbench, his final justification that i have read is or maybe i have the cart in front of the horse, was that in dyno testing at peak torque the manifold pressure was at or very close to 28" on the motors he worked on.

Rick

[BigBro74]

Thank you Ray for answering my question! I respect LM's work highly and was reading about it before i came here.

on my new bench i am incorperating a flow control of sorts so i can test airspeed at standard dp's.

Flash, i agree all that stuff isn't cheap. Thanks for the encouragement.

although i have to say, so far i have tried to see how much i can get the thing to be off by throwing the temp and voltage into another realm. did a test recently in my 10 minutes of spare time on my old box bench (hey thats not a cube is it ,lol). it was 50 degrees colder and voltage was 4v less. same plate as before. at low flow it was off by quite a bit (~40 cfm @ 28",or + 12% measured @~40" wc). at half flow about +3% (~160cfm, measured @~22"). at full flow(~300), around 2%, and that was around 10" dp.

its not a good test as there are 2 variables, but something to do all the same. I would like to seperate the two in the near future for a good test.

it all just what boiled down to the thing being off about 5 cfm (extrapolated cfm)the whole way. and that is on the cheap setup originally proposed.

[Flash]

Flash, i agree all that stuff isn't cheap. Thanks for the encouragement.

I'm looking forward to this progress