This blog covers the day to day progress of water rocket development by the Air Command Water Rockets team. It is also a facility for people to provide feedback and ask questions.

Monday, April 28, 2008

Our First FTC pressure tests

We did our first T-8 FTC pressure test this weekend. Over the last two weeks we made up a 15 mm nozzle and an end cap that fit exactly inside the FTC. The nozzle is a standard 15mm Gardena style nozzle but one that comes with a threaded section. We made an adapter that allowed us to screw in the nozzle. The adapter has two grooves in it, one to hold an O-ring that seals against the FTC and the other allows the tube to be shrunk to stop the nozzle from flying out. We wrap some wire over the shrunk groove to keep the nozzle in place.

The inspiration for this retention setup came from Urie's water rockets. They have good photos of the nozzle and a good description of the technique.

When we tried to shrink the nozzle end by heating it with a blow torch, we forgot the fact that other parts of the FTC were also going to get heated. *doh* We ended up buckling a part of the FTC near the nozzle. Since this was only going to be a pressure test we didn't really care. Mind you when we were sealing up the end cap we filled the FTC with water, and that went a lot better.

The burst pressure was 190 psi (13.1 bar). The nozzle and end cap stayed in place so we were happy about that. This FTC is really thin walled compared to another length of FTC we got from Damo quite a few months back. The next test will be to wrap some of the glass strapping tape around it and see how much more *crossed fingers* it will hold.

You can see on the left edge where the FTC split.


Dominic L. said...

Where do we leave general questions and where can we se our reply?

George Katz said...

You can ask here, or send us a direct email: at gmail dot com.