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 OK, It works.....now what? 
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Joined: Wed Mar 30, 2011 8:26 am
Posts: 15
Finally got my bench up and running, but I would really like to get real CFM numbers now. (I assume this is how this goes.... I get portion working and it just makes me want more)
Here's the bench. It seems to work great, I set the incline to 16" from 0% to 100% and draw 16" on the U-tube and numbers seem to look right (just guessing here really).
Attachment:
photo 1 (800x600).jpg


Here is how I made the bottom of the bench- Shop-Vac on right side, Ball valve to set depression, Added an O-Ring to the union so that is seals on both sides of the sheet metal plate with the orifice cut in it. Inclined scale looks at pressure on either side of the plate.
Attachment:
photo 2 (800x600).jpg


Here it is with the plate removed.
Attachment:
photo 3 (800x600).jpg


My question is this: Can I just buy a set of Bruces calibration plates and cut the outside to a round shape to fit my union (replace my crude hole-sawed sheet metal)? If I did this, could I assume that 100% on my bench is what the plate is rated for at the pressure?
Perhaps I am over simplifying??

Fire away with your input and feedback on my bench, I look forward to hearing what you think.


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Thu Apr 30, 2015 1:03 pm
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Joined: Fri Jan 08, 2010 10:36 pm
Posts: 1171
Location: Maryland
slufkin

Quote:
My question is this: Can I just buy a set of Bruces calibration plates and cut the outside to a round shape to fit my union (replace my crude hole-sawed sheet metal)? If I did this, could I assume that 100% on my bench is what the plate is rated for at the pressure?
Perhaps I am over simplifying??

Fire away with your input and feedback on my bench, I look forward to hearing what you think.



First do not hesitate to PM Bruce and ask if he will make you some specific sharp edge plates to fit your needs (machined round), this could be enhanced by buying some calibration plates along with it. :mrgreen:

You are not over simplifying but I do see a few issues that may come into play with your calibration, one, when you are using an orifice in a pipe you will have to add correction to the flow including the Beta Factor, Two you do not have much straight area before the orifice so you my get funny readings as flow has not fully formed (Laminar) and last since you do not have any settling chambers the manometers may get a little bouncy.

All just food for thought,

Great job and I love someone that takes a challenge and runs with it.

Rick


Thu Apr 30, 2015 3:06 pm
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Joined: Wed Oct 30, 2013 8:10 pm
Posts: 93
Hi,
Looks good and very close to my first testbench. However, there is a couple of things you could change in your design.
The bend and your depression adjustment is too close to your plate. The minimum between the bend and the orifice is about 50 cm.
The reason is the flow is not straight to the orifice and the vena contracta is an oval, and this will in turn result in that you will not get a constant cd value for your orifice at different pressures. This can be verified by measuring the flow at different depressions. If you use 10 inch all the time,and calibrate your bench to 10 , its not an issue. But dont convert to 28, the result is not compareable to numbers achieved using real 28 inch.
The beta factor is a constant from the dimensions of your tube and orifice, and it will not change.
The head must be at least the same 50cm from the bend, otherwise you get different flow numbers depending on what side the valve is that you are flowing.
This is easily tested. Put an orifice on the left side flush with the bench tube and do the same on the right side, if flow shows same, the distance is ok.
Your orifice is good enough, you just calibrate your bench using a known plate. The key here is the calibration, and not the look of the plate.
f.ex a 32mm orifec flows about 113@28. Once you have done your calibration stick to it, the changes is the important thing, not the exact values. With your design you are able to get consistant readings.
Remove the tube between the vac and the bench. When the depression changes, the risk is that the flexible tube will result into oscillation (wowing i call it), and you get inconsistent readings.
/kimi


Mon May 04, 2015 6:33 pm
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Joined: Wed Oct 30, 2013 8:10 pm
Posts: 93
Hi,
Ups, doublepost :)


Mon May 04, 2015 6:34 pm
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Joined: Fri Jan 08, 2010 10:36 pm
Posts: 1171
Location: Maryland
SLufkin, Any update on your project?

Rick


Sun May 31, 2015 7:29 pm
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Joined: Wed Mar 30, 2011 8:26 am
Posts: 15
Nothing new to report.
Been too busy now that summer has set in. We go tour charity Truck and Tractor Pull behind us now so I may be able to free up some time soon.


Mon Jul 27, 2015 12:24 pm
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Joined: Wed Mar 30, 2011 8:26 am
Posts: 15
I have not made any progress with getting real CFM #'s, but I did find the limits of my shop-vac, so now I am embarking on the buildup of a new "box-o-suction" with 8 vacuum cleaner motors. Once I can pull 16" on my test carburetor, I will return to the question of getting real numbers.

How do you guys hold the vacuum cleaner motors in place on the plywood board?


Wed Nov 09, 2016 11:54 am
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Joined: Fri Jan 08, 2010 3:35 pm
Posts: 1664
Location: Pennsylvania
slufkin wrote:
How do you guys hold the vacuum cleaner motors in place on the plywood board?


You can get fancy or simple, use some type of seal or sealant on the face of the motor and then some type of hold-down on the backside. I simply ran strips of MDF across the back of my motors, don't get to wild with tightening them down or you can crush the face of the motor housing into the fan blades.

Not the best picture to show my hold-downs but you can see the strips in this picture

Attachment:
assembly-23.jpg


This was a customer bench I built using steel plates to hold the motors in place.

Attachment:
build2.jpg


I'm working on getting these made in aluminum and adding them to the PTS Parts at some point just been dragging my feet on adding new products right now.


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Thu Nov 10, 2016 8:54 am
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