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Cold Propellant Leak

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chronister

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Hi. I have an Estes cold propellant rocket that seems to be leaking around the black rubber stopper where it fits onto the fueling adapter. I think maybe the rubber is too old. Has anyone encountered this problem before, or know of a suitable replacement part?
 

Leo

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I haven't experienced that so far. I think it will be difficult to find a rubber replacement because as far as I call tell it's made specifically to fit into the Coldpower nozzle.
 

chronister

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I was able to make a duplicate of the original part using PVS mold-making material. The rubber stopper actually seems to be holding pressure now. But I noticed there is still a slow leak somewhere, and when I put it in water I found the remaining leak is coming from the pressure relief vent on the motor. Is that normal? It's slow enough I might be able to attempt a flight but not sure it will work. If it's pressurized just partially and then sits for several seconds the parachute will pop out. I haven't tried higher pressure ...

Also, the fuel line keeps popping out. But I think that's because I got silicone in the place where it fits into the fueling adapter. Shouldn't have done that.
 

chronister

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Can this problem with the relief vent be caused by using the wrong propellant? I'm using an airbrush propellant can, which is isobutane/propane. It doesn't seem to spray out any liquid the way I imagine it should. Only gas seems to be going into the rocket.
 

Leo

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... But I noticed there is still a slow leak somewhere, and when I put it in water I found the remaining leak is coming from the pressure relief vent on the motor. Is that normal? ...
Yes, that is normal. That little hole is, among other reasons, for venting to signal that the engine is full of propellant. When that happens you should see a vapor cloud of gas escaping. That's when you launch the rocket.

Also, the fuel line keeps popping out. But I think that's because I got silicone in the place where it fits into the fueling adapter. Shouldn't have done that.
Not good. Clean it with isopropyl alcohol or similar. That tube needs to fit in securely.

Here is a video of my first ever Coldpower launch. You don't have to pump the fuel in like I did in the video. Just fill the engine for a constant 2 or 3 seconds which should give you enough time to place the parachute inside the rocket and add the nose cone. Then continue filling up the engine until you see the vapor coming out the vent hole.

[video=youtube;3-qyxefizfQ]https://www.youtube.com/watch?v=3-qyxefizfQ[/video]

You might want to check my Coldpower section for instructions and info: Link
 

chronister

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Leo, thank you for the information, the video, and the excellent web site with examples of cold propellant rockets! I was able to successfully fly the cold propellant motor in the test rocket that I built. The first couple of flights, the parachute came out, but didn't open. The final flight went perfectly with the chute popping open near apogee. What do you think is the best way to fold the parachute to increase the chances it will open?
 

chronister

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By the way, I have a mold now and I can make more of the rubber stoppers if anyone else needs one.
 
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