Fabricating velocity probes

[bruce]

Here is a quick pic of the one I fabricated up after being motivated by the one 86rocco sent me to play with. Haven't had time to do alot of testing with it yet but it works quite well as did the one from 86rocco.

[Mousehouse1]

Where did you find a 1/32" drill bit? Is that what size you used?

[86rocco]

I don't actually remember what size drill bit I used however, 1/32" probably pretty close. I have a set of very small numbered drill bits that I picked up at an electronics surplus place.

BTW, Bruce, whatever became of that probe I sent you? Did you pass it on to someone else yet?

[bruce]

Still sitting down on my bench.

Am I suppose to pass it along to someone else for thier "viewing"?



Edited By bruce on 1133914699

[Mousehouse1]

How do you join the two pieces of tubing together?

[bruce]

On the one I made I used 2 part epoxy a light press fit was used on the connection. The nose of the probe was fashioned from epoxy. I'm not happy with my results and plan on making another one, the one I made was more of a "lets see if it works" type project. After getting the one from 86rocco I had to see if I could make one. The bend in mine is less than 3/4". Ideally I think the material used should be something that is solderable. The tubing I used I think was inconnel? I had thought it was stainless. I picked it up at the local scrapyard, they have various small diameters of it in bundles and bundles sitting on a rack.

If there is any interest I would think about maybe making some to sell to other forum members? It has been in the back of my mind for sometime now.

[Mousehouse1]

Are the probes suppose to be a certain length?

[86rocco]

No, they just need to be long enough so that your hand holding it doesn't disrupt the airflow.

[hollywood63]

There is interest here Bruce. I tried to make one but the tubing keeps kinking on me so I gave up.
Art

[86rocco]

To bend the tubing without kinking, I heated it to red hot with a simple propane torch. I used brass because it solders easily and the reason for brass as opposed to copper is becasue copper becomes very pliable after it's been heated and cooled and so doesn't hold the bend very well.

[blown928]

So if I'm reading this right, you start with 2 pieces of brass tube, one 1/8" and one 1/16". The 1/16" tube goes inside the 1/8" tube, then you form the nose down around the 1/16" tube. Heat and roll it down? Then a bit of solder to hold them together?

Next you'd heat and bend the U (this is for a sucker probe, right? Blower probe wouldn't need the U) then drill the 2 - 1mm holes near the nose. How do you go about finishing the other end to separate the 2 tubes?

[86rocco]

I made the 1/16 tube so that it sticks out past the straight end of the 1/8" tube by about 1/2" and bent it up at angle from the 1/8", then I took a piece of 5/32" tube, cut a slot in the end about 1/16"x1/2" and slid the 5/32" tube over the straight end of the 1/8" tube with the 1/16" sticking up through the slot, then I put another piece of 1/8" tube over the end of the 1/16" tube and sealed up all the jionts with solder and/or epoxy.

[Mousehouse1]

Rocco how much of a hook should I make on the end of the velocity tube? I have a couple of them made but the first one is pretty bad and the second one if a little better. I am learning with each one.

How do you solder the 1/16 copper tube & the 1/8" tube together without getting solder in the small 1/32" holes or block off the 1/16 tubes hole? How do you trim the end of the copper tubing after you finish soldering it? If you don't trim the end do you position the copper tubing to were you don't have to cut it?

[86rocco]

Size the hook so that it'll conveniently fit inti the types of ports you'll be testing, for most automotive engine, 5/8" or so should be a tight enough bend, mine is about 9/16" wide and 1 3/8" long.

When I solder the end, I use gravity to help keep the solder clear of the smaller holes (i.e. hold the probe so the the hole are higher than the tip) and to keep the solder clear of the centre hole, I leave the 1/16" tube about 1/4-1/2 too long and trim it off after i've soldered it.

[Mousehouse1]

Rocco how do you trim off the tip without closing it off?