Converting MD bench to pitot tube? - Converting MD bench to pitot tube?

[cboggs]

With all this discussion about the orifice plate problems, ..
has anyone thought about converting the Mercdog style
bench to an average pitot tube design??

Curtis

[larrycavan]

Hi Curtis

Like anything else, it's possible if you want it to be and are willing to put forth the effort.

Are you having particular problems sorting out your orifice bench? Don't ever be afraid to post a question. This stuff doesn't always come easy and at times it's really frustrating. The end result though, if you hang in there, is a wealth of knowledge that you get to apply to the work you do with your flowbench.

If you want some help. Just give a holler. The Wright brothers succeded and all they had were the birds and the bees to watch...come to think of it...a bumble bee is not supposed to be aerodynamically fit to fly....good thing nobody told the bee hey...

Larry

[JRM]

[cboggs]

Larry,

Thanks for the offer of help, .. I'm going to need it when this thing
is running and ready to calibrate.

My question about the Pitot tube was more of an "investigation"
then anything. Had a long discussion with a commercial flow bench
builder, .. and he doesn't like orifice plate benches and sugested I
try a pitot tube system, .. so I posted here "fishing" to see
what turned up.

At this point, .. I need the bench running for work I have in the shop, .
and don't have time to start converting it to anything but what it is.

I've used orfice plate benches for 26+ years, .. and have had good
results, ..

Now all I need is that #### inclined Manometer scale, .. and then
to start the calibrating process, .. I'll need tons of help with that.

Cheers,

Curtis

[Mouse]

Curtis,

I would think that doing that would be like trying to insert a square peg in a round hole. But as we all know, anyone with a lathe would have no problem with that. I am aware of one individual who has adapted a Flow Performance 3" flow element into an orifice bench with a 20 - 1000 cfm (+/- 1%)goal.

It depends on the original design. While orifices work best with horozontal expanses, I find that Pitot tube designs work best if you can get the settling chamber and flow element in one vertical space, which is not easy to do, since a Pitot tube element requires some lead in and a bit of lead out length. So it depends on the amount of vertical space your design offers (being tall is a plus).

The conversion I mentioned above had an advantage in that the vacuum box is a unique vertical channel design where the motors are mounted outside the channel and the inside of the channel houses the flow element.

I tend to prefer a 3 piece configuration for Pitot tube designs, where you have the Settling chamber (or Plenum), the flow element, then the air source.

John

[bruce]

::Playing the Devils Advocate::

If you have a ton of work in the shop why not just spend the money and buy a digital setup from Mouse (Flow Performance) or Audie and not worry about water manometers?

After reading all the posts on orifice calibration that are on my forum I'm wondering why anyone would build one over an averaging pitot flow bench? My averaging pitot flowbench is built with some PVC pipe and my averaging style pitots and I can say it is quite accurate and repeatable.

I messed around for a few years playing with building my own pitot bench with water manometers and I can say this I have been using the Flow Performance setup since it was in prototype mode and I'd never go back to water manometers! I only use the water manometer now for my velocity probe. The Flow Performance setup running on my old 486/25mhz laptop repeats my numbers within .5cfms from day-to-day testing. It will generate a ton of numbers on a test which can be used in various ways since the data can be imported to most any program. (I'm working on the Excel part of that now to capture my data and present it in charts and other tables) Cheap old computers are sitting around everywhere all you need is one that runs Windows 95 or better and you are set for running the Flow Performance product. Mouse has come a long way with this product since the first prototype.

[Mouse]

[larrycavan]