single orfice with large scale - 0-600 cfm bench

[Tony]

One scheme I had thought of using at one stage, was a rotating drum behind the flow manometer. It could be directly linked to the orifice turret mechanically.

The idea is that when you switch the flow range (change orifice size), the scale behind the manometer changes too. It would then be entirely possible to have direct flow numbers in CFM, and suitably spaced graduations behind the flow manometer.

All you need is an illuminated window so that only one scale is visible. Maybe a large diameter PVC pipe, with suitable scales. Some light sprockets or a toothed belt system could couple the drum to the orifice disc shaft.

I am sure with a bit of ingenuity a rather neat and practical system could be made, and if there are a large number of different flow ranges, it would be very convenient to use.

[larrycavan]

With FP1 electronics the readings are already in CFM, there's no conversion required. Flow range calculations are realistically 0 - 40" across the orifice so with enough motors and a 3" orifice, you've got over 700CFM of measurable flow to work with @ 40", 645 @ 28".

Electronics being the easy way out is all well and fine. After having dealt with water guages the advantages of electronics are unescapable. Still, I can't help but lean toward everyone building a bench to grasp and understand thoroughly, the function of manometers. With Rocco's spreadsheet to use as a base calculator the overall function of the system can be fully investigated. The knowledge gained from that exercise is invaluable in solving problems that crop up.

Calculating the scale requirment for a single, large range bench and the various ways to achieve it is good for the mind....

JMO

Larry C

[Scott]

I think 250 or 300cfm bench is feasable with a single orifice
and a 32" inclined, graduated down to 10 or 15 percent or 30-45 cfm as long as everthing is stable.

RRBD

[Thomas Vaught]

Tony, as far as the rotating scale goes, our carburetor flow stands at Ford were set up that way before the switched to the electronic stuff.

No shield though.

A fuild tube just ran very close to a octogon shaped rotating piece that had different scales
in cfm. If you were on range number 1 the rotating piece read from zero to say 40 cfm.
Same deal for say range 5 with might be from
200 to 300 cfm.

The deal was the stands were in a atomspheric chamber (LARGE) with dual air locks and controlled pressure and temperature/ humidity.

Why the scales worked without corrections.

The rotating piece/ flow tube was pivoted on one end and a second part allowed moving the inclination angle/ assembly for proper calibration of each bench/range (if necessary).

Tom V.

[Tony]

The idea of changing a scale by revolving a drum is far from new, it was fairly common on short wave radio receivers long before the days of digital readouts.

I like the idea of being able to correct the manometer slope slightly from range to range with individual set screws. All possible.

I also feel that building an orifice bench with water manometers is a terrific way to learn and gain a good understanding of the fundamentals. It is also a minimum cost way to get started, important for many of us here.

The electronic and software approach is undoubtedly better, and I may go that way myself eventually, but doing it with water manometers has been a great learning experience, and a lot of fun, and the results very satisfying.

[86rocco]

I've made some water manometers to go with the flowbench I'm building even though I plan to put together a digital data aquisition system almost immediately. There's something comfortingly low-tech about water columns physically moving in response to air flow and pressure that really appeals to me so, even if they end up being nothing more than a means of double checking the electronics, it'll have been time well spent.

[86rocco]

I just can across this , I thought some of you might find it interesting, especially in light of the current topic.

[highway]

I have built the single orfice, single scale bench. I took about 3 months to complete. The scale was a 3 week undertaking and very involved (stepped well and curved scale water manometer) It was not worth the effort. It worked, but after a long run it would condense water droplets in the line and not return to zero.
Then I decided to buy a FP1. Well worth the money and would have saved me 3 weeks. I have had the bench working about a month and it is very accurate. After using the FP1's different modes I decided to add a second orfice. The correction mode is right on and will expand the flow range when I can not pull 28". Special thanks goes out to John for his help.
After moving the bench to the shop and doing the final calibrations I ended up with CD's of .60 intake and .59 exaust.Hope to post some pics soon Highway

[Thomas Vaught]

Another Happy FP-1 customer

Tom V.

[larrycavan]

That's great to hear highway!

[DaveMcLain]

I think that a single range system will work just fine if you use an electronic system for measuring your depression across the orfice as is done on the setup from Performance Trends with their black box.