Caibration Problems

[Flathead]

Hi
Have recently completed a pretty basic bench but now I am struggling with calibration. First I made up a set of plates and had them flowed on a SF600 when tested I could not get correlation between SF600 flow and what was indicated on my bench. First thought was that maybe the results from SF600 were unreliable so I then got Bruce to make up a 100cfm a 150cfm and a 200cfm when tested against one another I got the following
100/200 25% should be 50% on inclined manometer 100/150 64% should be 66% 150/200 65% should be 75%. So what have I done wrong? One thing I noted as different is that I do not have baffle plates in the chambers each side of the orifice plate could this cause problems. I have attached photos to indicate build style. Motors are ex vacuum cleaners, test pressure is controlled via air bleed using mixing bowl valves flow reversal via inspection ports. Air driver and control is on the RH side, orifice plate and test port on the left, hopefully the photos can do the rest.
Help!!
Grant

[Flathead]

Photo of completed bench.
Grant

[Brucepts]

Baffle Plate, your airflow is hitting your orifice plate as a column of air and is giving you weird readings.

[1960FL]

Flathead,

I Nice looking DIY bench, what are all the electronics in the motor Box? Would love to here more about your disign and build.

Rick

[Flathead]

Hi Bruce
Thanks
Are there any requirements for the baffles saw some talk re round or rounded ends and edges what distance away from plates is required and what sort of size.
Thanks again.

Hi Rick
Not much design mostly just build. A submersible sewage pump arrived at work in a nice 3/4 inch plywood box which I disassembled then glued and screwed back together fitting all the necessary dividers. Setup is an amalgam of internet sources Dtec for airbleed control, so my vacuum motors don't over heat, old Popular Hot Rodding article for mixing bowl valves, Wikipedia for basics and of course this site for other ideas. Of course I will be happier when I get it to produce reliable and repeatable data, thats not happening at the moment. I built the bench to help in developing a Flathead Ford V8 engine I am messing around with. The next challenge will be getting the bench to produce reliable data when fitted with a hose setup that plugs into the bottom of the bores of the engine. Do you or does anybody know of any issues around the use of this type of setup?
The electronics in the motor box are the speed controls that were part of the vacuum cleaners I have just set the speed at about halfway they will pull 28" at 200cfm which should be heaps for my purposes.
Thanks for your interest.
Regards
Grant

[coulterracn]

Grant
I have attached two pages from the book 'Air flow & How to Get It' written by Joseph DeAngelis.







This next picture is of a Model A flathead engine attached to a Big Blue.



Ray

[Flathead]

Hi Ray
Thanks I made up a similar hose set up and tried it but at that stage was having trouble with bench readings, will have to install baffles and get the bench working properly first. I guess my main concern was whether or not the length of hose had any effect on the results and what size hose was required, access to the bottom end of the flathead bores isn't great I was hoping to be able to use 3" hose?? By the way whats the Model A engine being used for. Thanks again.
Grant

[varnish]

How much pressure recovery would be in that system?

[coulterracn]

This is where I found the picture of the Model A engine adapted to the flowbench. Check out the Roof 101 cylinder head link. continue to click 'next' to see all the flow data etc...

http://www.modelaparts.net/index.html

Ray

[Flathead]

Hi
Still having difficulties with calibration. Fitted circular baffles plates with rounded edges 4 3/8 " under top deck and the other same distance under metering plate. Tested at this stage and found bench over flowing, 100 against 150 off the scale , 100 against 200 reads 95% Remade pressure taps and installed them in the corners. Previously had radiused top deck hole and meter plate hole so squared up the top one none of this made any difference still over reading. pressures are now very stable just miles off what they should be. Man this is getting frustrating thought you can't fool basic physics but my word you really can. Can somebody have a look at my inclined manometer and advise if there are any glaring problems or give me any other ideas please.

Grant