incline manometers scales

[Psi_man]

[color=#000000]Hello every one,

I was planning on machining some incline manometers scales for myself, but it seems like a lot of people need them and if I set up a CNC machine to do one, I might as well make 15.

I just need some help with the design.

How much vertical rise? 10

[bruce]

Nope not stepping on my toes at all. I'm open for anyone helping others out on the flowbench quest. I never setup this forum so I could sell parts, so if I can can advertise here so can others . . . what little $$$'s I make from selling parts goes towards paying my web hostings fees to keep this forum alive

[84-1074663779]

Psi_man.

The slope of incline does not effect the flow percentage scale graduations in any way, and neither does the type of fluid. The actual bore of the tube will not effect accuracy either. If there is pressure to raise the fluid to a certain height, tube bore can be anything you want to make it. A fatter tube displaces more fluid, but does not effect how high the fluid rises.

The two things that do really matter are tube straightness and keeping it properly level. If the tube bows, the fluid will still go to the right height, but that may not then correspond to the markings along the scale.

A vertical manometer can be quite a bit off vertical and the accuracy hardly changes. A low sloping manometer tube will be effected greatly. It might be best to bolt a long very gently sloping manometer permanently to the wall, rather than being able wheel the whole flowbench around over an uneven floor.

There is probably a point of diminishing returns with making a sloping manometer very long. The graduations may be further apart, but actually reaching the expected accuracy and resolution may not be that easy in practice.

[fchp]

I'm very interested. If you decide to make them, let me know.
phinishline@yahoo.com

[2seater]

I tried a few different materials for the tubing in the manometers and I finally settled on Teflon tubing, 1/4" od x .031" wall thickness. It is not clear but is translucent and colored fluid can be seen through it very easily. I am using Marvel Mystery Oil @ .830 sp.gravity, which works well, doesn't freeze, is cheap and seems to dampen oscillations in the readings a bit. For support I dado cut a groove in a hardwood board , slightly undersize for the tube diameter so it can be pressed into place and it is screwed to the wall. The Marvel oil has pretty good film strength and other materials would cause the reading to recover relatively slowly and slipperiness of teflon has helped the response time. I did try smaller diameter tubing, and that worked okay for high inclinations, but in my high resolution, low rise manometer, the response was very slow. My suspicion is the surface tension of the fluid causes a need for a minimum tube size of some sort to respond correctly. In the quest for best accuracy, I modified the Excell spreadsheet formula for rise in the manometer, to add the ratio of the well size to the tubing i.d. In my case the ratio is 502:1, so the spreadsheet adds 1/502 x the rise to the inches of rise in the manometer. Picking nits I guess.

[Psi_man]

Well, the shop I work at just got swamped with work, so it will be a little while before I can get this job in a machine. I'll keep you guys up dated.