T-nozzle from a caulking gun with plastic hose seal
T-nozzles were introduced to the water rocket world by Scott Chestnut. A description how it works can be found in Brad Calvert's Water Rocket Book.
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Long ago, Brad's drawing (click on the picture or here) showed me how a T-nozzle without machining could be built. I made one, but it worked only up to pressures of 3 or 4 bar. At higher pressures, the T-nozzle was fired out the bottle neck after leaving the launch tube. |
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After several experiments I came up with this: a clear plastic hose
instead of Brad's rubber washer seal. The blue tape is added for better alignment
in the bottle neck.
Assembly is similar to Brad's. The red nozzle plug can be screwed to the nozzle tip. The launch tube piece presses onto the left end of the hose piece, the nozzle is pulled (hard) with the red screwdriver as a handle into the hose. Put the hose in hot water before assembly - it gets much softer then. |
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T-nozzle, assembled. In use, this piece sits INSIDE a bottle and cannot
be removed without special tools.
This T-nozzle worked fine up to 6 bars. Adding some tape to the rim (before assembly!) makes it work until 8 bar! |
T-nozzle in use |
I used this T-nozzle in RUMMA2. A 2.8 mm
opening was too small (too little thrust), the water was not used up yet
at apogee! So it helped accelerate the descent instead - not what I wanted.
Since I cut it open to 3.5 mm diameter, it has a nice long thrust phase; the water exhaust is quite audible, the air exhaust even more and gives the rocket a good forward kick. T-nozzles are real fun! |
