My bench is coming apart.

[Mousehouse1]

I have had to many problems with trying to find leaks and not being able to get over 350cfm out of my bench. When I had to remove the rear panel I destroyed the side panels doing it. I installed some aluminum rails and used weatherstripping to seal everything. I know the rear panel isn't leaking but I am not so sure about the side panels. I also know that the orifice disk is leaking between a few of the ranges. I am going to redo it when I take the bench apart. I have a few questions I would like to have answered.

1. How would you change the orifice disk and what would you do?
2. How would you change the side doors and what would you use? I installed some 6" deck plates but they are not air tight. Tom are all deck plates created equal? The two I have aren't that good in my opinion. I would like to install a few more in the new bench I am building but if they don't seal any better then the ones I have I don't want them.

How can I build a single orifice disk setup? If I can find a good deck plate I would like to install one in the front of my bench so I can change ranges/orifice disks. That would solve one of my problems.

If I go with another orifice disk like the mercdog design what would you do to solve some of the leakage problems between ranges?

Larry, John, Tom and Chad have been a great help with my current bench. My bench is about the same as Chads and I can't get mine to do half of what his does.

I am still going to keep the mercdog style bench but what would you change if you were going to redesign it?

I am going to pull the sides and orifice disk out of the bench probably next week.

Thanks in advance for any help you can give me.

[larrycavan]

Martin

Before you rip it apart, take a minute and think about everything.

If the flowdisk is leaking between ranges. It's definitely easy to pinpoint.

If the edges of the side panels are damaged from getting the original back off, that's repairable too.

I have no experience with those deck plates you purchased but I'll wager they're curable as well. They might just need better gaskets.

Let's approach the cabinet sides first.

You can remove the back panel and install extensions. The key to making it work is to make sure the edges are even when you're finished.

Basically, you'd just cut some 4-6" wide panels and mount them inside the back of the cabinet. Put one on each side, one along the top, one along the bottom and one on each side of the center divider board. Leave a couple of inches protruding from the rear of the bench to secure your rear panel to.

Get the cabinet in order and then approach the disk. You have a removable top and front panel. Replacing or modifying the disk won't be difficult.

Larry

[Mousehouse1]

I have the back of the bench sealed and it doesn't leak. I used 1 1/2" wide aluminum angle and attached weatherstripping to it. It worked great. You gave me the idea in one of your emails. I just don't like the side panels in their current condition. They work fine but look like crap.

I just don't see why the bench won't flow over 300cfm. I can get over 36" but can't get over 300cfm.

I just put tape over the exhaust deck plate for now so it is sealing better. I installed a new pressure tube with holes in the end and relocated it to the new top chamber. I also built a new top chamber with baffle. All of this seems to have helped but I still think the big problem is the orifice disk. To get my bench calibrated to the FP1 I have to adjust the cd numbers to .30-.40. According to John that is pretty low.

[Nick]

I bought some cheap deck plates off ebay. (4 $20) They are not near the quality of the Becksons. The Beckson has a thread all the way around on the lid. The cheep ones I bought have four tabs covering only about 50% of the lid. The Beckson lids are also more ridged. The cheap ones have AAA, that is made into a W on the bottom of the lid. I think they are made out of PVC. They both have O rings but the cheap ones have ridges where the O ring seals. I was able to make them seal with Vaseline on the O ring and the thread, maybe that might fix it temporally. I think I will chuck these and buy the good ones. I guess that's what I get for tring to save a buck. Hope that helps.

Just curious, what size orifice are you flowing through?

Nick

[Mousehouse1]

Nick I use the 1.270 for leakage, 2.330 for exhaust and the 3.068 for intake. At least that is what I had plan on using. I also bought the cheaper deck plates and they aren't made very good. I plan on buying a few of the beckson's and that should cure one of the problems.

I hate not being able to do something. That is why this thing is driving me nuts. Once I get a few things straightened out this bench should be ready to rock and roll.

[gofaster]

After seeing all of the posts regarding the difficulties involved in using the rotating orifice plate, I decided not to fool with it. I am going to use a square plate with stoppers.
I think I can eliminate the mixing bowl flow control valves by substituting deck plates in those spots. It is beginning to look like a deck plate advertisement, as I am planning to put deckplates in several places on the sides of the bench to access the flow control plates, the stoppers from the front and rear of the plate (put them in from the back on exhaust tests), and also for the vent doors. The deck plates are fairly inexpensive, so I bought several types from various sources so I can determine which ones will work the best. I am seriously thinking about using the ones with the extra wide sealing flanges everywhere. That will necessitate putting dummy females inside the bench to store any opened plates on the exhaust side.
Substituting the deck plates for flow control valves is possible (I believe) in my case because I am using a depression control on the motors (Audie).
As far as lube on the O-rings, that is a given. They make a special o-ring lube, but it's name escapes me at the moment. I use vaseline or lubriplate on the o-ring on my test stand, as well as on the valve guides and stems and on the head gsaket.

[Mousehouse1]

Gofaster what are you going to make the plate out of? Where are you going to get the stoppers and what sizes do you plan on using? I might consider something like that as well. I am trying to figure out if I can use a single plate with the orifice in the middle and just change them out when I want to change ranges.

[Jesse Lackman]

I've been following this saga and it has got me puzzled (some would say that is a normal state of mind for me) anyway you are saying the bench will pull 36" @ 300 cfm on a port you know flows more than that but the reading will not go over 300 cfm?

You have probably posted it but what does the bench read with a big calibration orifice on the test fixture?

In my opinion the bench's ability to pull the 36"- but not show the correct flow points directly at a problem with flow differential across the orifice plate - the pressure differential across the orifice is the basis of the flow reading.

There could be two reasons for this; there is a problem with reading the actual pressure before and after the orifice; or, there is air flow bypassing the orifice disk/ orifice disk mounting board somewhere, somehow.

Any airflow between the blower chamber and the test fixture that doesn't go through the orifice in use would cause the flow reading to be low.

Cabinet leaks to atmosphere in the orifice chamber/test fixture would show up as an inability to pull/push 36" @ 300 cfm, plus the cfm would be higher than it should be.

Cabinet leaks from the blower chambers to atmosphere would show up as an inability to pull/push high vacuum/pressure or high cfm, but should not affect flow readings.

Cabinet leaks between the blower chambers and the orifice chamber that bypass the orifice would lower the flow reading.

So, IMO, I'd zero in on what is messing up the differential pressure readings across the orifice, either airflow is bypassing the orifice, or, if it is not a leakage problem, a problem with the orifice differential pressure reading itself.

Can you get to the orifice disk and seal it good in one location to test for leaks between ranges?

But don't bank too much on me, I'm the one who abandoned the orifice for a pitot and still am not sure how I'm going to do it.

[gofaster]

In response to Mousehouse1's question about my stopper plate plan,

I intend to use 1/8" aluminum for the stopper plate, and coat it with Nituff, a hardcoat anodize process that we've had great success with on other projects. It's less than 0.001" thick and is very hard, with great wear and abrasion resistance.

Using the orifice size calculator, I determined the following five sizes would get me where I need to be:
2.91" ..... 607.6 cfm
2.38" ..... 406.4 cfm
1.69" ..... 204.3 cfm
1.19" ..... 101.4 cfm
0.84" ..... 50.6 cfm

I've purchased rubber stoppers at the local ace hardware, and they have a pretty good selection. If they don't have them they are available on the internet. This site lists stoppers up to 127mm (5").



I haven't decided whether it is best to make the orifice holes nominal sizes or calculated sizes. (Example: 2.38" calculated or 2 3/8" nominal). I can do either one with good accuracy on my mill, or (even better yet) have my son make them on one of his CNC machines.

Any input from other forum members will be appreciated.

[Thomas Vaught]

I see that you assumed a Delta P across the orifice of 28"

A typical bench with a 246 durablock manometer assumes a 6"
delta P across the orifice. If you had blue (1.91 sg) fluid in the manometer the DP would be about 13.85" effectively.

Are you sure that you are not mixing up a test pressure across
a head or carb of 28" or even a calibration checking plate (tested
like a head on the bench) at 28" vs the delta p across the orifice itself?

A 28" delta P across the flow bench measurement orifices will require a lot of motors.

You understand my questions?

Thanks

Tom V.

[gofaster]

Hi Tom,

I am not sure I understand your questions. Or should I say I'm sure I don't understand.

My manometers were all ordered with red gage oil. I believed that I needed them for the initial set up, leakage testing, and calibration of my bench. After that is done, I'll hook up the Audie ProFlow data acqiusition and depression control. and I can disconnect the manometers if I feel like it. Though I think I still need a VM for pitot tube (velocity) tests.

I am setting the bench up to use twelve Ametek 115923 motors.

My intentions with the stopper plate plan were to use single and combined orifices to transition through the cfm test ranges in a way similar to changing ranges on my SF-110. I figure I should be able to test up to 1,000 cfm.

Judging by your post, apparently I have a gross misunderstanding of something.

I know I have a confusion problem, but I don't know how to explain it.

When I talked to Performance trends, (I run their software on my SF-110) they told me I could do all my testing in the highest range and disconnect the manometers from the FlowCom. I have not been able to bring myself to do it. I still test with the mano's hooked up, and I always keep my tests in an orifice selection range that keeps me in the 75% or greater area on my inclined manometer.

If this information helps you understand where I am coming from, maybe you can straighten me out.

I have read everything I can find on the subject, and there are some texts where I can't get past the math or the use of language even though it's written in English.

At this point in my life I place a high value on education (which I have almost none of) and have some regrets that I spent the years that I should have been in school, blasting around the clay and dirt tracks of three states. (Probably wouldn't change it if I could, though)

I know how to use a flowbench, and I know how to use what I see on the bench to improve a port. There were questions I wanted to ask Harold Bettes at the seminar, but couldn't figure out how to put them. Still can't.

[gofaster]

Tom,
I think I am beginning to see what you mean. I'm thinking that the orifices have to support a particular cfm range at 28". The delta p across the orifice is what I need to determine the correct orifice size.? I need to play with the calculator , some paper and the spread sheet when I get a little bit of time. I thought I understood before, but I have it all mixed up.
Thanks,
-Jim

[Nick]

Ok, someone correct me if I'm wrong. Here's how I understand It. If my test pressure is 28in and my incline scale rises 12.27in, then I have to pull 40.27in of water on the motor side of the orifice. to show 100% of that orifice range.

So if the orifice is 2.5in in. then it will flow 296.8 cfm at 100% on the incline scale (12.27in vertical rise).

Now if my calibration plate is 1.5in, the orifice is 2.5in and I am using 28in depression it should flow 161.4 cfm or 55% on the incline scale, or 3.71in pressure difference across the orifice.

So the motor side would be 31.71in of water and the test side would be 28in of water if they were measured separately.

I hope I am not confusing anyone, It makes sense to me.

Nick

[Thomas Vaught]

Jim,

Nick is pretty close on his explaination.

I will try and walk you through the flow process as far as the pressures go. I will be talking about the Flow measurement orifice as Orifice "A" and a Calibration Orifice as Orifice "B"

We are doing an intake test. We are doing a calibration test. The calibration orifice size is 75 cfm.


Air from the room goes into the Calibration Orifice
"B" which is being tested at a 28" H20 delta P across that orifice (Just like a head).

From that orifice the air goes through the flow measurement orifice "A" which is designed to have a full scale delta P of 6" with a Dwyer 246 Durablock manometer with red .826 fluid.
The orifice diameter is chosen so that full scale is 100 cfm. The fluid on the manometer reads 75%
of the scale. We say we have 75 cfm of air going through the calibration orifice.

Just for conversation sake lets assume the delta p
is some value less than the 6" H20 needed to reach the 100% mark. Like 4.5" H20

So the motors have to pull the air through the 4.5" delta P orifice and through the 28" delta P across the calibration orifice. The motor has to be capible of at least 32.5 total depression at 75 cfm of flow.

If you bolted on a 240 cfm calibration orifice and had a 300 cfm measurement orifice at near the same 32.5 total depression you would read 80% on the Percent scale. (240/300=80 percent)

In both cases the total depression stayed about the same but the total flow went up due to the larger calibration orifice and measurement orifice
diameters.

For you to have a delta P across the calibration orifice of 28 inches H2O is normal. For you to have a delta P across the measurement orifice of 28"
would not require the motors to be able to pull
56 inches of water at the same flow.

The MSD bench was designed for about a 12 inch H20 measurement orifice depression. I do not what the Mercdog depression is. I do know that the SF benches are designed for 6 inches H20 delta P across their measurement orifices when using the red .826 fluid.

Hope this helps.

I am glad you are using great motors, a lot of them, and the stopper system with the deck plates!!!

Just like my bench.

Tom V.

[Nick]

The Mercdog incline scale is 28in long, on a 26 degree incline, if my math is right that's 12.27in rise.
That is where my numbers came from.

The well is not calculated into the scale, so I'm going to use one 1000 time bigger, or about 4in. (1/8 tube) Water is the fluid.

Also the spread sheets that came with it, allow you to make the orifices any size you want. The leakage and c.d. can be adjusted in the sheet. I don't like the Mecdog MSD design, but I do like the spread sheets.

I hope to finish mine next weekend. I'll post some pics if all goes well.

My next thing to test is to see if the rubber stoppers will stay in at 12in of water. I want to flow both ways through the orifice plate. My biggest one is 2.5in. So that should only be about 2.5lbs of force (4.9sqin area x .5lbs @12in water). If it will not stay in, I'll just add another port on the other side of the orifice plate.

Nick