newbie bench questions...

[blownalcohol]

First, let me say hello to all members. I have looked around at a lot of posts and can tell I have a lot to learn....but that's okay.

Bruce, thanks for the quick response to my email. I have read a lot of early threads, but still have some questions that are probably elementary to most here, but I don't know the answers so I've got to ask.

I am planning on building a flowbench for my business. I will be flowing heads that are already over 550cfm @ 28" so I want to be able to pull at least 650cfm @ 28", possibly more.

My only experience with flowbenches was with a sf600...fully manual.. had to manually choose different ranges throughout the lift range. I flowed quite a few heads on this bench, and had been planning on just buying one like it....then I found this forum and realized that for a lot less money I can build a lot more bench.

I want a bench that is comparable to others as far as flow numbers, but really just want it to be deadly repeatable. I want to start with a known good head and be able to tell if I am improving or hurting the flow.

I have read both threads on pitot and orifice style benches and still don't completely understand the difference. I would really appreciate it if someone could make some real general descriptions of each so maybe I could have a clear picture in my head of how each works....maybe just the major differences. Please tell me if you think one is better for my application....

I am planning on using one of the pc based units. I have read enough positives on them to be comfortable going that route. The sf600 was brutal from a time standpoing...lotsa calculations & time is money in my business. At this time I don't know for sure which one to use....If anyone has some recommendations, after reading about what I am wanting, I would really appreciate the input.

I initially planned on using several vacuum motors...the price is very appealing, especially the 1234 motors at surpluscenter.
However, from reading othe threads, I noticed a pattern of several experienced builders saying their next bench would use a blower of one type or the other. That being said, I am considering this option. I have some machines in my shop using vfd's to control the spindle motors. I understand this is a good way to control the depression. I would appreciate some input on what capacity and style blower to look for. I am very familiar with roots blowers as most every engine I build has one on it. That being said, I am also very familiar with how much horsepower it takes to turn one...which is why I am thinking a centrifugal type might be a better option.
I may decide that it just doesn't make sense to spend the money as my bench will not be used a whole lot, but would like to consider all options before making my decision. Tony may be the guy for these questions....he seems like the blower guy.

I am planning on a cabinet like the sf1020 Probench. Just for comparison, does anyone know how many of the Ametek 115923 motors it uses, and an idea how many 1234 motors it would take to build a comparable bench?

I know this is a lot to read, and a lot of random questions, but I had to start somewhere.

Thanks in advance for everyone's help...I am looking forward to this project.

[Tony]

Hi Jeff, welcome to the Forum.

We flow bench freaks cover a fairly wide ranging group, and our flow benches mirror that variety.

Many of us are tinkerers on the outer fringes of amateur motorsport, and have neither the resources or the need of a serious high dollar, high capacity flow bench. But you would appear to be a very serious professional user that can genuinely justify something special.

The definite trend seems to be towards pitot style benches using electronics, and others here can explain all that far better than I can.

Orifice style benches with water manometers are still very useful, mainly because they can be built at absolute minimal cost, but are not quite so convenient to use. People here are usually biased one way or the other, and I am just a very small time orifice bench user.

So if you are prepared to spend the cash on some electronics that is an excellent decision, something I hope to do myself one day.

The other decision is what to use to move the air. Regardless of your choice, a high power VFD would be ideal to control your bench airflow, even if multiple vacuum cleaner motors are your final choice to run from the VFD.

But a centrifugal supercharger run off a suitably powerful three phase induction motor and a VFD would be much more silent, more compact, less prone to motor overheating, and probably more efficient, as well as being fairly simple to get going.

Sure superchargers need significant horsepower to drive, but a whole bunch of vacuum cleaner motors will need to develop similar total combined horsepower to do the same job. Mains amps are mains amps, and you are going to need rather a lot of them no matter what type of blower is the final choice.

My belief is that for a professional bench that is going to see constant and relentless heavy duty usage, a centrifugal supercharger will also have better long term reliability.

Vacuum cleaner motors are probably better suited to a low cost home flow bench, but I expect some here may disagree with that.

[blownalcohol]

Tony,

Thanks for your help, I am still on the fence about the style of vacuum source......

I would apppreciate anyone else's input on my initial questions.

Thanks again, Tony.

[jason pohlman]

hi, jeff. i'm also new here and planning a bench just about like this.i will be using products from flowperformance.the plan is to use the fp1 to control they're pwm valve.this will contol the depression of the bench. i already have a pro-charger centrifigal blower.it is a p1sc-2 which is rated at 1200 cfm.not sure what kind of power this will require but i'm going to start with a 7.5hp motor from an old air compressor.from some of the posts i read here, i believe controlling depression by bleeding off excess air flow would be better than using the rfd.if you have'nt yet,i would recommend looking at the flowperformance web sight.check out the flow elements, i'm going to use the 2.5" for my pitot bench.looking to flow 600cfm at 40".good luck with your build!

[head_tech]

hi jeff,

Im also new here and planning a bench and have wondered if a roots type blower would be the way to go, i have had a bit to do with roots type blowers like yourself, hopefully i to can learn a bit more from reading your thread. i have decided to go with a orifice style bench as this seems the cheapest option to me and im on a budget. It would be good to watch your project unfold

[Tony]

Jason,

A VFD will be able to control pressure and flow of a centrifugal supercharger over a very wide range. Surge is unlikely to be a problem because the "boost" pressure will be relatively low. Any actual surging will not be violent enough to be a problem and will probably go completely unnoticed . If it is objectionable, than a manual air bypass valve that can be run either open or completely shut, will entirely eliminate any surge.

Surge is mainly a problem where the air blower is run flat out at maximum speed all the time, and the air is just throttled. A VFD is a much nicer solution, as it dramatically cuts down noise and power consumption, as well as all but eliminating any surge tendency.

head_tech,

A big roots blower should work fine, but beware of the massive pressure spike that would result from a sudden accidental total flow blockage. A safety pressure relief system directly across the blower would be an absolute necessity. An fine air filter screen right on the blower intake might be a good precaution too. A twisted rotor blower would be best, the two lobe designs may pulse fairly significantly.

[Shawn]

Hi,
I was in a similar situation. I currently have an SF600 that just doesn't quite have the capacity that i need to do what i wanted. After researching it for well over a year now, I decided on a pitot style bench over a LFE or larger superflow style orifice bench. Here's the reason's that lead me that direction.
The pitot doesn't require range changes. It utilizes an averaging pitot,or tube, inside of a piece of pvc for measuring flow. To me this is an advantage in time, like you stated earlier. It's much easier to build, only need tubing that you can buy from your local hardware store. Bruce, the site host, builds the averaging pitot's at a price that can't be beat. With an FP1 for data, you can have a complete bench that is computer controlled for a very reasonable price.
A LFE style bench was more than I wanted to spend, and data aquisition is critical to accuracy.
I decided against normal vacuum motors. After figuring out what it was going to take to run the amount of them I need, and the amp draw, I went with a self contained centrifugal blower. Here's the company I got it from-

If you would like, I have the vacuum curves for the 70 and 100 series blowers. I don't have a way to post them here. Maybe I can email them to Bruce so everyone can see them.
These are very nice units and will be more than what you need to get the air you want.
I also bought a VFD from AC Tech at what I thought was a pretty resonable price to control the motor/blower speed for depression. There are a bunch of reasons that the vfd is a good idea, some of which have been posted above.
With anything there are pro's and con's to all of the styles, but for what your looking to do, and not really having a need for high resolution of results bellow 150cfm, I think you'll find the same thing that I did.
My new bench is about half way complete, so I don't have exact results yet, but I do have a friend that completed his and has nothing but good things to say about it.
Hope this helps.
shawn

[Thomas Vaught]

Hello Jeff,

Quote:

"First, let me say hello to all members. I have looked around at a lot of posts and can tell I have a lot to learn....but that's okay.

It actually comes pretty fast these days with the large database of info provided my the members in the past.

Quote:

"Bruce, thanks for the quick response to my email. I have read a lot of early threads, but still have some questions that are probably elementary to most here, but I don't know the answers so I've got to ask.

I am planning on building a flowbench for my business. I will be flowing heads that are already over 550cfm @ 28" so I want to be able to pull at least 650cfm @ 28", possibly more.

My only experience with flowbenches was with a sf600...fully manual.. had to manually choose different ranges throughout the lift range. I flowed quite a few heads on this bench, and had been planning on just buying one like it....then I found this forum and realized that for a lot less money I can build a lot more bench.

So you already understand the data-taking process and the basics of the SF-600 so you are much farhter along vs most initial posters.

Quote:

"I want a bench that is comparable to others as far as flow numbers, but really just want it to be deadly repeatable. I want to start with a known good head and be able to tell if I am improving or hurting the flow.

Agree. With the instrumentation out there today the bench will be repeatable. How it compares with a given bench is open for debate.
The "plates swapping" process posts showed that. If you have read that post a lot of the benches were within a few numbers (depending on the range they were on) but if you were off
1% which is what all professional benches advertise that would be 5.5 cfm on your 550 cfm heads. I personally think you would be closer than that with electronic data collection.

Quote:

"I have read both threads on pitot and orifice style benches and still don't completely understand the difference. I would really appreciate it if someone could make some real general descriptions of each so maybe I could have a clear picture in my head of how each works....maybe just the major differences. Please tell me if you think one is better for my application...."

I personally like the sharp edged orifices but it is a known fact that any orifice has a sweet spot in the performance curve. SF knows this and designed and calibrated the bench to be in those sweet spot locations. The pitot tube deal may not have this issue with electronics but I have seen errors using liquid manometers. I work for Ford and the bench we have at Ford in our research lab is a venturi bench. It was used
as the "Standard" for the plate study basically because it cost 100 times more than any typical bench. LOL! It is still a 1% bench as the calibration devices we check against are +/-.5%
devices.

Quote:

"I am planning on using one of the pc based units. I have read enough positives on them to be comfortable going that route. The sf600 was brutal from a time standpoing...lotsa calculations & time is money in my business. At this time I don't know for sure which one to use....If anyone has some recommendations, after reading about what I am wanting, I would really appreciate the input."

As you figured out you can do a lot better vs the older SF-600 bench but that is still a quality bench. The 1020 bench is better mostly due to the electronics.

Quote:

"I initially planned on using several vacuum motors...the price is very appealing, especially the 1234 motors at surpluscenter.
However, from reading othe threads, I noticed a pattern of several experienced builders saying their next bench would use a blower of one type or the other. That being said, I am considering this option. I have some machines in my shop using vfd's to control the spindle motors. I understand this is a good way to control the depression. I would appreciate some input on what capacity and style blower to look for. I am very familiar with roots blowers as most every engine I build has one on it. That being said, I am also very familiar with how much horsepower it takes to turn one...which is why I am thinking a centrifugal type might be a better option."

The 1020 bench uses 12 or the 115923 Ametek
Lamb 2 stage vacuum motors (110 volt motors wired in a 220 volt circuit.

Quote:

"I may decide that it just doesn't make sense to spend the money as my bench will not be used a whole lot, but would like to consider all options before making my decision. Tony may be the guy for these questions....he seems like the blower guy."

Use vs money is always a concern. The better the bench the more you will use it and the more other people will recomment your bench to others. The use may go up drastically!

Quote:

"I am planning on a cabinet like the sf1020 Probench. Just for comparison, does anyone know how many of the Ametek 115923 motors it uses, and an idea how many 1234 motors it would take to build a comparable bench?"

See above: 12 of the 923 motors. The 1234 motors may pull the same cfm but not at the same depression. 12 motors of either type will suck a lot of power. A sf-1200 I have used pulled over 80 amps on each leg of a 220 circuit.

Quote:

"I know this is a lot to read, and a lot of random questions, but I had to start somewhere.

Thanks in advance for everyone's help...I am looking forward to this project."

Personally I would look at the centrifugal blowers or the roots style. Friends have built benches using both but in each case they had access to three phase power. If you are a business I assume you will have the same access. Same deal for the controllers.

Look her for good blower systems if you do not want to build your own.



The X-40 blowers are what you want.

Tom V.

[jason pohlman]

hello,thomas how fast will the vfd respond?i was under the impression it would be slow.i'm not familar with one of these units.also will these require three phase?ofcourse i may need to go with three phase anyway, if the 7.5 motor won't work for me.guess i will do some more searching on this!the sweet spot you talk about on these bench's?i used a superflow300 for a few years and on bigger stuff the numbers just did not look right.it would repeat but it seemed the farther you got above about 320 cfm it would not give acurate numbers.i know that no two benchs are the same but i could take a head off of our bench that flowed 380 and put it on a friends sf600 and it would go 420.the numbers below 320 seemed to compare pretty well with the sf600.i guess maybe i was out of the sweet spot? hey,jeff i did not mean to hijack your thread.it's just this is right in line with what i'm doing as well.

[jsa]

[Thomas Vaught]

Jason,

A SF300 and a SF600 are very similar as they both use some common orifice sizes. The SF600 also uses two more motors (8) vs the 6 for the SF300.

The SF300 uses red .826 Specific Gravity fluid in the common Dywer #246 inclined manometer and the SF600 uses a blue fluid with much
higher Specific Gravity in the 1.91-1.92 range.

This higher specific gravity fluid makes any useable range 50% bigger.

The SF300 ranges are 25, 50, 100, 200, 300, and 400 cfm

The SF600 ranges are 37.5, 75, 150, 300, 450, and 600 cfm. (50% greater). Hole sizes of the orifices are very close if not identical.

SF supplies a calibration sheet for each bench based on using a series
of calibration orifices and that is (as you know) posted on each bench.

The bench is calibrated to test the chosen part at 25" of test pressure
with a maximum of 6" delta p across a given orifice. That was modified
for the sf600 bench to 25" test pressure and a "adjusted" equivalent manometer reading of 13.5" (when using the 1.91 SG fluid).

If you use Rocco's excel spreadsheet and use the pressure conversion portion of the sheet at 300 cfm@ 6" H20 to get a 50% increase in flow through the orifice (450 cfm) the equivalent test pressure would be 13.5" of H20. That delta Pressure is what the SF600 flow orifice is seeing at full scale (100%) on the incline.

Hope that helps. If not someone else might be able to explain it better.

Tom V.

[blownalcohol]

Thanks for everyone's input!

After many hours of research, I feel more confident in beginning to make some decisions regarding the style of bench I am going to build.

I have decided to go the pitot route...I really like the thought of not changing orifices to complete my flows.

I am 90% certain I will go with the FP1 with their depression control. I have spoken with John at length about what I want to do, and he impresses me. In addition, I have read nothing but good things about his products. The only thing I want to make sure of is the software side. While I have some experience with Excel, I do not have the time nor the desire to configure my own screens / programs. For this I am looking at Larry's software....Larry, if you could tell me a little about it I would really appreciate it.

I am still on the fence about the vacuum source. I can see pros and cons for each. My biggest concern is the expense involved in purchasing a commercially available centrifugal blower with it's drive motor, and a vfd....as well as having to design my own method of reversing airflow from intake to exhaust. Not an extremely difficult thing to do, but I can see it becoming relatively time consuming & time is something I am running short on these days. By going the vacuum motor route I can use the proven plans for a vacuum chamber with the reversing disc....Audie's.

Shawn, if you get a chance, I would like to hear about your sonic system. Did you go with the 70 or the 100, and which hp motor did you choose as well. Also, you mentioned a friend who I think has used this same set-up. If you could elaborate on how it performs, as well as how y'all are handling the reversing I would appreciate it. I would like to get more info on someone who has successfully implemented one of these style blowers before making my final decision.

Thanks again for everyone's input.....and please keep'em coming!!!

[riga team]

Hi Jeff. Once tried of blower and any more there will be no desire on 4-5-6-8 - ..... vacuum cleaner Motors . Using a regulator of a phase together with FP1 pressure of the test it will be automatically sustained: and noise and heat will be much less. Pleasant silence , easy work. ANATOLIJ

[Tony]

There seem to be three very different solutions to the flow reversal problem.

Provide two test holes in the bench top. One blows, the other sucks. Flow through the whole bench (and especially the flow measurement device), will always be in the same direction. This will be by far the simplest and easiest system to build. The internal flow paths inside the bench can be optimised and need work really well in one direction only. Completely reversing the flow direction always opens a can of worms.

Some type of flow reversing valve system located within the bench. This will likely be the neatest and most convenient to use. But it can introduce design complications that can lead to flow dynamics differences in either flow direction, unless it is very well designed and constructed.

Separate the blower box from the flow bench entirely, and just swap around the external air connections manually in seconds. Something simple like a box on casters with the inlet on one side, and exhaust on the other. To reverse the flow, just uncouple it from the bench and turn it around. The blower box could also be located remotely, or behind a wall to reduce noise. This modular approach also provides a convenient future upgrade path.

[jason pohlman]

hey,jeff as for as reversing flow through the bench here is my idea. using pvc pipe plumb from the inlet of the blower to one leg of a y fitting.from the outlet of the blower plumb into the other leg of the y and then from there on to the pitot tube. my thoughts were to use 4 of the rv type gate valves to control air flow through the bench.there will be 2 valves on each leg,i hope this makes sense one going to atmoshere to either vent the air when testing the intake side of heads or providing an inlet path when testing the ex. side of head.then the other set of valves would be to control which way the air moved through the bench.the valves can be controlled buy a small air cylinder inside the bench. there is a link somewhere on this sight to a company that carries these small cylinders. i think they were around 50.00 but it was double acting and could be set up so when it closed one valve it would open another.you can attach a valve to both ends.they also had small 4 port air valves that would look like a toggle switch when mounted.so if my thinking is correct with the flip of switch it would control these cylinders and change the bench from blow to suck.i hope this makes sense to everyone,i "think" it does in my head anyway!