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Posted:
Mon Apr 11, 2005 12:34 pmby cboggs
Tom,
Sent you an e-mail about the scales you had made for
the 246 durablock, ..did you find them?
I assume they need the blue gauge oil for a 12" scale VS the 6" scale??
Or, .. is it OK to use a 6" scale????
Curtis
curtis@cboggs.com
Posted:
Mon Apr 11, 2005 10:56 pmby Thomas Vaught
The Super Flow 600 uses the same Dewyer 246 durablock manometer as the one you have but with blue 1.91 fluid.
The Super Flow 300 used the same 246 manometer but with the
.826 fluid.
Going from the .826 fluid to the 1.91 fluid increases the range by 50 percent.
The SF benches had the following ranges:
SF 300 #1 = 25 cfm SF 600 #1 = 37 cfm
SF 300 #2 = 50 cfm SF 600 #2 = 75 cfm
SF 300 #3 = 100 cfm SF 600 #3 = 150 cfm
SF 300 #4 = 200 cfm SF 600 #4 = 300 cfm
SF 300 #5 = 300 cfm SF 600 #5 = 450 cfm
SF 300 #6 = 400 cfm SF 600 #6 = 600 cfm
in each case the orifice holes were the same diameter, they
just changed the fluid to allow 50% greater readings.
Example:
50 cfm time 1.5 = 75 cfm
200 cfm times 1.5 = 300 cfm etc.
I measured the orifices on the 300 and the 600 one time and they were the same.
The sizes were .857, 1.227, 1.770, 2.507, 3.059, and 3.490
The flow readings for the 600 chart showed the flows to be:
35.5, 71.5, 151, 299, 451, 604 cfm
You do the orifice size vs the flow and the discharge co-efficients were:
.593, .583, .593, .584, .592, .609
Quite a bit different from the typical assumed .62 number typically
assumed.
Tom V.
Posted:
Tue Apr 12, 2005 7:02 amby bruce
I'm not sure I understand how you come up with the Cd's that you did?
Please do not take this post as thwarting discussions on this forum. The forum is here for the free exchange of information on flowbench designs but;
Please limit posting of "reverse engineering" of commercially sold flowbench information. I'd prefer not to have someone call me up from a company and talk to me about info passed along on this forum.
As a side note coming from a pitot style bench person, with all the discussion on accuracy of the orifices why not just build a pitot bench? Simple and accurate no need to worry bout Cd's, just an air correction factor that can be done in a spreadsheet along with your readings and out comes your cfm's.
Some PVC pipe a set of averaging pitot tubes, build a couple of flow elements to cover the various ranges you need and you are all set . . . or better yet pickup Mouse's FP1 setup in the long run you will be ahead of the game in the time/cost saved with figuring out the orifices. You will have an accurate repeatable (I have found down to a 0.5cfm difference) flowbench that you can finally do some testing on.
Edited By bruce on 1113305012
Posted:
Wed Apr 13, 2005 6:45 pmby Thomas Vaught
Quote:
"Please do not take this post as thwarting discussions on this forum. The forum is here for the free exchange of information on flowbench designs but;
Please limit posting of "reverse engineering" of commercially sold flowbench information. I'd prefer not to have someone call me up from a company and talk to me about info passed along on this forum. "
"Reverse Engineering" implies that you have no knowledge of the
concept and are stealing the design from another company.
I was simply posting the relationship between keeping a common orifice and by changing the fluid specific gravity being able to get
accurate readings at 50 percent higher flows with the same inclined
manometer.
The same applies for the co-efficients of discharge for the holes.
You have a known hole size, you calculate the assumed airflow
based on that hole size at a specified pressure drop and then compare it to the stated calibration value. Any difference between
the "ideal" flow and the reported flow is either in the creation of the orifice hole or the bench lay-out. Assuming that the bench lay-out
is not changing then the difference is the discharge co-efficient
change. By trial and error with the cd, you can get pretty close to the reported flow.
What does that really do for you? Very little as each orifice will be different in flow even with the same hole diameter and the hole
must be calibrated against other benches or a "standard" unless
you are just doing comparative flow testing.
I have had a couple of days to cool off after your original post.
I am very good friends with the head technical guy at the bench company you are so worried about and that company has used my ideas in the past on their stuff.
I was told they had no problem with "magazine" type benches as it got people involved in flow testing and they assumed at some point the person (if they were serious) would buy their product anyway.
My experience has been that that has been true in all cases.
Tom V.
Posted:
Wed Apr 13, 2005 7:25 pmby bruce
My post was not meant in any way as a personal attack and if it was taken that way I apologize for that.
But, look at my side of the screen once, here I sit with a forum that allows free flow of information on flowbench design. In this day and age corporations hire vast amounts of lawyers to protect what they sell. I surley don't want to be on the receiving end of that wrath! I'm not some big corporation, I'm an everyday person who has an interest in learning what I can about the world around me. The forum is here for that purpose.
I stand corrected . . .
Posted:
Wed Apr 13, 2005 8:22 pmby Thomas Vaught
Bruce, first off, I accept your apology.
Second I want to thank you for hosting the flow bench forums over the years. A great deal of discussion has transpired over that time
and I sincerely believe that it has helped many people construct their first bench or a different bench based on the ideas and suggestions
put forward here.
There is a lot of great talent here and I try and mention the forum in my discussion with my friend. He like I believe that all knowledge should be shared as much as possible. That was also the thought behind the patent system. You can use an idea almost immediately
(by paying a royality over a several years) vs having the idea hidden forever. All people benefit from the idea that way.
There is "Reverse Engineering" happening in some of the other
locations of the world with no patent protection, so manufacturers
do try and limit somewhat the complete idea.
The simple bench that most enthusiasts would construct on this forum has been around since the 70s and the patent protection
is long past.
Thanks again for your support of the forum.
Tom Vaught