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Caps blowing off/shooting fuel help.


x8quicksilver8x

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I've made 5 rockets so far and 3 of them that had promise are launching all the fuel out through the clay caps. Now while it is actually some what awesome my intentions are a rocket not a sugar bullet :P

 

Note: My next test I'm planning to use a PVC cap with PVC glue and the second test a threaded end glued with PVC cap but going to take extra precautions for I'm afraid it might decide to detonate...here's my designs maybe it's not the pressure but something else I might be doing.

 

Setup and materials.

 

*3/4" diameter PVC 5" lengths.

Scoring both ends with razor aprox. 3/4 inch depth.

 

*I'm using Durhams water putty as caps 3/4 in depth drying over a day

 

*For nozzles I'm using a high brass end of a *empty* 12 gauge shotgun shell with the primer drilled out and glued into PVC it fits very snug and offers a 1/4 " hole - I know this is un conventional but it's very promising these shells do not budge and seem to withstand heat. (I have also used Durhams putty for nozzles)

 

*I'm using recrystalization for fuel and hammering it down hard... have experimented with several portions of kn/su with same results

 

* drilling middle of fuel all the way to the top (to the clay) with 1/4 bit

 

*I'm igniting with a 100 ft extention chord with clips on a thick stainless steel wire using 18v battery and have experimented with wire at different depths in fuel core.

 

So my problem is containing my fuel and caps..every thing else seems to functions as its supposed to.

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It sounds like you are almost there. Water putty sets in 15 min but may take a week to "cure", also it may help to glue a scrap piece of pvc pipe in the end against the putty. Just cut a 1/4" piece and trim it until it fits inside the pipe. Also I would avoid drilling all the way to the header plug, this should reduce the forces exerted on it.
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Thank you :) I was thinking maybe coring it half way would help as well. I know for a fact if I could keep a even burn and my rocket contained I have more thrust than I could ask for...or maybe just a pipe bomb...I like using the shot shell and adopting PVC cap as well cause it reduced set up time.

 

I might post a video later of my last test. My fuel shot out at 1000 ft per second it was absolutely awesome and a step further in the right direction I am just ready to get airborne and then be able to upgrade to the bigger and better.

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X8, that is a wise decision to start with a short core. When testing a new motor I start short then extend the core in each progressive motor until I achieve a failure, then back it off one size. This works well for most fuels but sugar fuel can get tricky due to various factors causing inconsistency. As long as you develop a consistent fuel every time the variations can be limited.

I wish I could go back in time to the first time I made a successful sugar motor. I was dancing around like an idiot(All hail Jason, conqueror of the mighty sugar rocket) pure elation. I've been a rocket junkie ever since, and always trying to out do myself with every new design.

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After being involved in home made out I for over 15 years and being on the various forums for much of that time, it seems many people have problems with sugar rockets and that they are a bit temperamental. Also, pvc has some pretty big draw backs as you can't be very close to them because of the danger of shrapnel, they don't degrade and are polluting, and they don't give which makes getting a plug to hold more difficult.

 

Maybe look at black powder rockets and cardboard tubes? They have some of their own difficulties but once you are set up they are pretty easy to make, especially in the smaller sizes. Then once you get them working you can start putting headers on and explore a lot more of the pyro world.

 

But I agree, once you get that first rocket up, it's an awesome feeling and can definitely get you hooked. I had 2 or 3 failures and then figured out smaller increments and I still remember that first one that took off like a bullet and was almost instantly out of sight in the daytime and the intense loud whoosh as it left earth. Anyways, keep working on them and you will get there and maybe research this forum and try to look at some of the benefits of different rocket designs that may be easier and more consistent once you're tooled up.

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One of the problems with PVC is that it expands as it heats. If the tube expands faster than the plug then the plug will loosen and maybe fly out.

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