Another newby! - General flow bench questions...

[bruce]

Note I said "donation" not purchase

Kinda like "Cliff Notes" for flowbench building . . .

But the whole intent of my post was to steer Joe towards what works and that is the plenum design bench. Along with the other "lurkers" out there who can only view this area of the forum. Because they have not become members yet to see the really good parts of the forum that all you as members get to see!



Edited By bruce on 1201699548

[Tony]

Ha-ha, yes indeed.

I have had quite a bit of involvement with university engineering student projects over the years. Some outside help is usually fine as long as the professor knows what is going on. But students trying to pass off other peoples work as their own is far from unknown.

[bruce]

Well this thread died quick? ???

[5.0joe]

All~

Sorry for the long layoff on the posts. I have been pretty busy between my internship at GE and school, trying to lock down the design for this project so I can begin construction of the flow bench. Anyways, in the last week or so, I thought about the responses and suggestions I got from all of you and browsed around the forum a bit more for ideas. As a result, I came up with a hopefully improved design, which I modeled in SolidWorks. I am attaching a Word document to this post with pictorial snapshots of the proposed flow bench layout. Each picture has a caption with it for a brief explanation. In addition, I wanted to note: each of the two chambers in the box are 18" wide, 18" tall, and 18" deep. The right panel with the PVC flange will be connected to the shop-vac(s). If you are wondering why a shop-vac, it is because one of my design objectives is "Compact/Space-Efficient." I figured by having an external vacuum source, it would save the space that another vacuum compartment would take up, and also add modularity to the system by being able to remove and put away the shop-vacs when the flow bench is not being used. The flow bench that is modeled in the attached file will be paired with a small stand on wheels. This will give the ability to have a free-standing, rolling flow bench, or the flow bench itself can be lifted off of the stand and placed on a table top if the testing area requires. Feel free to take a look at the pictures I have attached, as this may not make much sense without them. Any feedback or suggestions are greatly appreciated.

Thanks,
Joe

[Tony]

Excellent design Joe.
Simple and efficient. And as you say, the shop vac can be upgraded, or later replaced with a more powerful external blower box.

An eighteen inch cube volume should make an excellent settling chamber.
I like it.

[5.0joe]

Tony~

Thank you (big sigh of relief)! Finally, I am seeing some progress. I should start building within the next couple of weeks if this design is feasible. This site so far has been a tremendous help, more so than others because everyone on here seems to break down the theories into more understandable terms or concepts.

Thanks again!

[106-1194218389]

Joe,

I am building basically the same thing right now. My chambers are verticle, one on top of the other with the divider in the middle for the orifice horizontal. It is 24" square and each chamber is around 15" high. I also am using shop vacuums, in this case 2. With 2 shop vacs I can flow a 180 cc Dart Iron Eagle at 6". I like your idea in that back board looks like a good place to mount your inclined manometer. I am using two 2" PVC van stone flanges in the bottom chamber to mount my shop vacs to.

John

[thomasvaught-1]

I like your basic cabinet size. Similar to the SF1200 stuff.

With more capacity from a second motor cabinet you can always increase the flow/test pressure.

Tom V.

[5.0joe]

jfholm~

I actually plan on mounting the U-tube and inclined manometers on the backboard. My goal as far as flow rate is to be able to flow a maximum of 300cfm at 28". However, I am planning on using a test pressure of 10", meaning I will only need to be able to pull a maximum of about 180cfm, then convert that up to 28". Grainger has a shop-vac rated at 210cfm through a 2.5" orifice. Not sure how well this will work. If inefficiencies occur, I plan on using two of these through a Y-fitting to get that test pressure...hoping one will be adequate though.

[5.0joe]

Quick question: when I cut out the hole in the divider panel for the orifice, I read somewhere on the forum to cut the hole in the panel slightly larger than the orifice hole. So for example, if I have a 2.5" orifice hole, what would be sufficient for the hole cutout diameter in the panel? Also, I was originally going to construct this out of MDF, but I decided to stay away from that for the simple fact that I don't want to experiment with Formica for the first time on an important project like this. So, I think I am going to use a nice grade plywood, with a stain or nice coat of paint to finish it off. Now, after researching, it seems that 3/4" plywood seems to be the standard for flow benchs, on here at least. However, my senior design advisor at school is concerned about the finished weight of the settling chamber with a wood that thick. I keep telling her that to maintain integrity and rigidity, it's probably going to need to be that thick; also to prevent bulging or splitting of the wood when screws are driven into the edges. Is there any way I can safely get away from 3/4" to maybe 1/2" plywood without sacrifing the functionality, accuracy, and integrity of the flow bench?

[106-1194218389]

IMO I would not go smaller than the 3/4". I feel you would introduce a flex factor and I think that the flex would work on the screws, glue etc. and would cause a failure much sooner than if using the 3/4". I used Melamine, which is the particle board covered with the white surface material. I personally do not have experieence with screwing into the sides of plywood and do not know if it will split it or not as it is a layer wood. There are some advantages to using plywood though. Maybe we can get another response on plywood from one of the other guys.

John

[Tony]

Make the hole large, so that the thickness of the bulkhead is well clear of the down stream flow wake, so it is not going to interfere with the natural flow coefficient..

The edges of the hole only need to mechanically support the orifice plate, so if the orifice plate is fairly sturdy, the supporting hole for it can be made quite large.

Difficult to say really, but maybe if your material is going to be 3/4 , perhaps 3/4 inch larger all around than the orifice hole ? So 2.5 inch hole, plus 1.5 inches = 4 inches minimum. Even five inches would be practical.

That is only a suggestion, but that would be my approach.

Your flow bench will end up being unbelievably heavy, so put some very robust casters underneath.

My own flow bench is made from one inch MDF, and has a large cast iron cased air blower. The whole thing weighs in at around 1,150 bs ! It is difficult to move, even on wheels. Yours should be nowhere near that weight, but it will still end up being a lot heavier than you probably expect.

Just keep in mind the very high forces that several psi of air pressure can generate. Better safe than sorry.

[SWR]

On the case of plywood... I mentioned somewhere on the forum the safe way of using screws on the edges of ply. Pre-drill holes,just a tad smaller than the thread-stem diameter. I.e,if you bring out the calipers and measure the diameter at the bottom of the threads,pre-drill with the first smaller size drill than your measurement. That way it's small enough to not leak along the screw stem if you have a misaligned one,and big enough to not split the ply.

[5.0joe]

I think I read the post that talked about pre-drilling, and so I planned on doing that. It looks as if I will most likely go with 3/4" thick, so long as I can justify the need to my advisor. Thanks for the advice guys. Also, I plan on using Dwyer manometers (U-tube and inclined). The U-tube selection is pretty straight forward. But for the inclined, I haven't yet decided which one I will use. I was actually looking at the Mark II series (about $200 cheaper). It is only +/- 1% less accurate than the more expensive inclines. I am assuming I will probably need something that has a range of about 0"-4" W.C. if I am testing at 10". I'm sure everyone has their preferences when it comes to manometers. I'm interested to here the differences and downfalls of one particular compared to another.

[RACEPUMPER]

Hey Gang,
I'm Jim from New South Wales in Australia. I operate a performance auto shop that does everything from normal service work to building 1000+ HP race engines. About a month ago i started thinking a bit more seriously about building a flowbench so i did what most of us do and started looking online for maybe some plans or tips. I found the magazine article detailing the MSD flow bench - wow that was a decent find - pretty informative I thought!!
So imagine my surprise when I found you guys!!
My what a great forum you have. I've got the biggest black rings under my eyes from staying up late reading some of this awesome information that you people are so generously sharing.
It looks like a sure bet to buy Bruce's plans from what members are saying, can I have them emailed to me Bruce?
I'm still willing to pay such a reasonable price for them, it would seem logical to email them?

orifce or pitot? At this stage I'm considering an orifice bench

Keep up the great work

Jim