Fabricating velocity probes

[stef-1]

I made a couple of conventional j pitot tubes this weekend. One has a smaller radius than the other to get near the short turn. The old j pitot I made into another straight pitot but with an angled nose, again to get down the short turn.



One thing I learnt that may be of use to you guys, when soldering the tip I get much better results using a good soldering iron and flux cored solder. Using a torch it's easy to get it too hot and have the solder wick up the probe and come out of the static holes.
Also today, after reading the recent posts I remembered that I got some British Standards (the same as your ASME standards) on flow measurement a few years ago. After some digging around in the junk room I found them and scanned the specs for the three types of pitot probes in it. They were in BS 1042: Section 2.1 - Measurement of fluid flow in closed conduits, method using pitot static tubes.
Here they are below.







I also had this idea. Attach the impact tube to the outside of the static (at least for the end of it) so that the impact hole is right next to the static holes.

[jfholm]

I found another great source for small tubing and other parts we need for flow benches. They have all sorts of brass fittings, plastics etc. They have plastic balls for flow balls etc.

I found copper tubing here in 1/8" and 1/16" in 36" lengths and bought some to try on my velocity probes.

John

[jfholm]

I found it rather hard to bend the brass and copper tubing with the little bender from Tower Hobbies. It would go flat, stretch and crack even when I went slowly. It was also hard to drill the static holes. Thanks to Doug, he sent me a link on annealing. Heat the tubing just in the area you are going to bend and drill with a propane torch for just a few seconds until it just starts to change color and then quench it in cold water. You will then find it very easy to bend and drill.

Also thanks to Stef, if you just file a slight flat spot on the tube where you are going to drill it makes it much easier to drill also.

John

[msj442]

i had that same problem with the little tubing bender , cracking and such. i was trying to bend it to fast. i sat down one day and just watched closely to see what is was doing. i realized that the tubing actually needs to slide somewhat while your slowly rolling the bender around,on one side at least. i actually oiled the tube a little and i had a nice bend that didnt break.

jmo, max