Water putty rocket nozzles

[dagabu]

I would start with a 1/4" throat, if you buy a carbide drill bit, you can open it up to your desired width but you can't make it smaller. Please email me with the title of this discussion so I can get your info to send this off to you.

 

Dave

[dagabu]

Oh, they are 1", the main ram is 6-1/4" plus some to hold on to.

[dagabu]

It's done, email me please yoyo. coldfire11@msn.com

[stix]

I assume a lot of pyro's must be cat lovers... oh well, back to the serious stuff.

 

 

I guess I don't understand the whole topic, why buy a drill bit from a store when the tooling made to form a nozzle is cheaper and overall better? One has to do side by side nozzle testing to see first hand how the extra work, time and money are wasted with water putty.

 

Sometimes it's useful when experimenting or making prototypes - then move to something more permanent.

Nice that you helped out yoyo with some proper tooling - perhaps you're related to Santa

 

 

I approached rocketry from the angle of melted sugar rockets, rather than black powder. The intelligent decision would have been to get BP tooling and go with 1/2" or 3/4" rockets instead, but by now I'm invested enough in sugar rockets to not want to switch quite yet.

 

Water putty isn't that expensive. A pound of rockite is 8 dollars, so quite affordable.

 

Edit: Also, black powder is very dusty and a bit more dangerous to work with than melted KNSU, which will stay within safety limits by simply underheating or over-caramelizing it (accepting a reduction in performance).

 

Very similar to where I've come from yoyo. I've only made 50 or so grams of bp which I'm yet to use in a rocket. The reason being is not having decent cardboard tubes, so I have to roll them myself - interesting as it may be, i'd prefer to get on with the fun stuff.

 

I agree with you on the safety aspect - I'm certainly a lot more cautious handling bp than r-randy.

 

Are your r-candy rockets end burners or core burners?

 

 

Is there a consensus that the divergent section is a least "useful" in directing the flow of gasses than just a blunt hole? I think it is.

 

I take it the answer is yes. - anyone?

Edited December 24, 2014 by stix

[dagabu]

I like to help where it is needed, it's good to give back.

 

Less permanent? A file, sandpaper, a drill and a dowel all are that are needed to make a former with the proper size (for you) throat. Drilling a hole by hand is not going to give repeatable results so the data is useless, you HAVE to make an investment of some kind to make the results repeatable and verifiable. Sorry but that is the way it is...

 

From a safety aspect, the only real difference (as I see it) is the ball milling of the BP v.s. cooking R-candy. Frankly, we have heard a lot of both type accidents this past year, I don't think either is safer than the other.

 

I hesitate to make a statement about how useful a convergence v.s. divergence due to the propellant differences, impulse, use of the rocket motor etc. In the case of small black powder rocket motors, there seems to be much debate as to the necessity of nozzles at all. In fact, I am making and selling nozzless tooling sets with NO convergence or divergence for lifting heavier shells.

Is there a consensus that the divergent section is a least "useful" in directing the flow of gasses than just a blunt hole? I think it is.

 

[yoyo]

Once again, thank you very much Dave. Entirely unexpected and joyous gift.

 

Stix - Search on ebay.com for 1" CARDBOARD TUBES 20 FEET Rocket Pyrotechnics 3 LB Super Strong. It looks like the seller does ship to Australia. I've ordered three packages so far. They are a tad bit heavier than preferred, but the pro is that I have yet to have a single cato with them, even after 50 tests. They are also extremely well-rolled and can be cut evenly.

 

My rockets have always been core-burners. As discussed in an earlier thread, I didn't get to nozzles for a while. Oddly enough there were more problems with end-burners, such as end-caps bursting, or not enough lift.

Edited December 24, 2014 by yoyo

[dagabu]

Once again, thank you very much Dave. Entirely unexpected and joyous gift.

 

Stix - Search on ebay.com for 1" CARDBOARD TUBES 20 FEET Rocket Pyrotechnics 3 LB Super Strong. It looks like the seller does ship to Australia. I've ordered three packages so far. They are a tad bit heavier than preferred, but the pro is that I have yet to have a single cato with them, even after 50 tests. They are also extremely well-rolled and can be cut evenly.

 

My rockets have always been core-burners. As discussed in an earlier thread, I didn't get to nozzles for a while. Oddly enough there were more problems with end-burners, such as end-caps bursting, or not enough lift.

 

That's Phil's General Store he indeed does ship abroad. Keep in m ind that Phil's tubes ere spiral wound, not convolute wound and that humidity plays a large part in the success of using hi tubes (active thread on Fireworking.com).

[stix]

dagabu, on 25 Dec 2014 - 01:42 AM, said:

Less permanent? A file, sandpaper, a drill and a dowel all are that are needed to make a former with the proper size (for you) throat. Drilling a hole by hand is not going to give repeatable results so the data is useless, you HAVE to make an investment of some kind to make the results repeatable and verifiable. Sorry but that is the way it is...

 

Don't be sorry, I agree - and that's precisely why I don't use a drill bit to create the nozzle throat, although I can understand others doing it that way for a quick thrill. Good on 'em.

 

I've always made some sort of tooling albeit a bit crude at times. I did a lot of development over about 2yrs in my spare time to come up with my methods (nozzle forming tools & r-candy). Measuring using a home made load cell and software I wrote, I was able to work my way slowly up to my final "alpha" motor (1 lb equiv). Only then did I lathe "proper tooling".

 

From that data I was able to scale up to my "beta" motor (6 lb equiv) and lathe the nozzle tooling with predictable results.These motors can be repeated reliably.

 

If I had to lathe tooling for all the tests I did, I probably would have lost interest or taken unsafe shortcuts making the motors just to get something done. Impatience & pyro don't mix well, unfortunately I suffer from both and always have to check myself.

 

 

dagabu, on 25 Dec 2014 - 01:42 AM, said:

From a safety aspect, the only real difference (as I see it) is the ball milling of the BP v.s. cooking R-candy. Frankly, we have heard a lot of both type accidents this past year, I don't think either is safer than the other.

 

I was indeed under the impression that r-candy was safer to make than bp. In my experience it's much harder to ignite than bp. What are the circumstances that have led to the accidents? Melting over a gas flame or some other unpredictable heat source?? (understandable).

 

I use a thermostatically controlled electric frypan/skillet and have never been worried that it could blow up in my face. Now you've made me concerned . Do you have any other info, or can you post the links to the incidents? I may have to review my safety gear & procedures.

 

 

dagabu, on 25 Dec 2014 - 01:42 AM, said:

I hesitate to make a statement about how useful a convergence v.s. divergence due to the propellant differences, impulse, use of the rocket motor etc. In the case of small black powder rocket motors, there seems to be much debate as to the necessity of nozzles at all. In fact, I am making and selling nozzless tooling sets with NO convergence or divergence for lifting heavier shells.

 

Yep thanks for that Dagabu, I like the idea of nozzle-less bp rockets more and more - I may be able to use my existing bates grain tooling certainly worth looking into with a lot more purpose than I had before. It seems like less mucking around, more thrust to lift larger payloads, and less likely to CATO. The only downside being less burn-time than an end burner - but each has a purpose.

 

 

Posted by STIX - 23 December 2014 - 09:01 PM

Is there a consensus that the divergent section is a least "useful" in directing the flow of gasses than just a blunt hole? I think it is.

 

Lets not confuse nozzle-less rockets, with nozzles without a divergent section (somehow I think I'm starting to ).

 

Years ago I took videos of nozzles without a divergent section, one thing that I noticed was the flame changed direction depending on the erosion at the trailing blunt edge. Surely that would be undesirable in flight? Although more so in model rocketry I suppose than pyro rockets.

 

Perhaps what is lost in thrust having the divergent section (due to subsonic velocity) is gained in stability?

 

Now come on Dagabu, surely in the back of your mind you see some benefit in having the divergent section. Afterall, why else would you kindly make tooling for yoyo that included it?

 

 

Once again, thank you very much Dave. Entirely unexpected and joyous gift.

 

Stix - Search on ebay.com for 1" CARDBOARD TUBES 20 FEET Rocket Pyrotechnics 3 LB Super Strong. It looks like the seller does ship to Australia. I've ordered three packages so far. They are a tad bit heavier than preferred, but the pro is that I have yet to have a single cato with them, even after 50 tests. They are also extremely well-rolled and can be cut evenly.

 

My rockets have always been core-burners. As discussed in an earlier thread, I didn't get to nozzles for a while. Oddly enough there were more problems with end-burners, such as end-caps bursting, or not enough lift.

 

Thanks for the info yoyo. At this stage I don't need a lot and will likely roll my own unless a member bulk buy to Oz can be arranged.

 

In regard to end-burners or core burners - Having a nozzle will increase the pressure and therefore burst endcaps or the nozzle if they are not secured properly. Conversely, not having the fuel burn fast enough and/or too large a nozzle will result in not enough thrust. A weak casing could result in CATO, a stronger casing could result in even bigger CATO'S or bring success. It's a matter of finding the "sweet spot" within safety limitations.

 

I've found the "sweet spot" to be reasonably wide providing you are consistent with your fuel and methods.

 

Cheers.

 

[EDIT] Nothing's perfect.

Edited December 30, 2014 by stix

[Col]

if they are both top fused I dont think the nozzled will have a higher peak pressure than a nozzleless. Assuming the whole core is ignited in both cases. The nozzled motor will maintain a higher average pressure if the nozzle doesnt erode.

The nozzleless has a bit more fuel and a bit less dead weight (clay) to hoist and less dead weight to come back down

[dagabu]

"Now come on Dagabu, surely in the back of your mind you see some benefit in having the divergent section. Afterall, why else would you kindly make tooling for yoyo that included it? ;)"

 

I am sure we can argue the pros and cons till the Wallabies come home but the reality of divergency is that any payoff from using a divergent nozzle has to be carefully considered. In the case of R-candy in J size motors and with graphite nozzles, you can expect amazing gains from proper geometry but after exhaustive research by hundreds of us HP rocketry guys over the decades, smaller motors (under 1") start to suffer from scaling issues as the gasses being exhausted remain the same size no matter the rocket or nozzle size.

 

The hard truth is that the particles exhausted are of a known size and just cannot scale all the way down to many of our rocket sizes.

 

I sent the tooling off to Yoyo because he wants to research and exhaust all options with this style of casting, we all can gain some insight from his trials. Plus, I love to help, I am a servant at heart and a manager by trade.

[Mumbles]

We're starting to get off topic here a bit. It's a little difficult to compare nozzled to nozzleless since they tend to use different fuels. Nozzleless can accept a faster fuel. If I had to put money on it, I'd agree with you Col and say with the same fuel, they'd achieve the same peak pressure (approximately), but nozzled would maintain a higher average pressure. With their respective optimized fuels, I think it'd be hard to say that nozzleless would not achieve a higher peak pressure since they tend to use a much hotter fuel.

[Col]

I didnt find much in it when i compared identical hot fuelled (top lit) motors with a nozzle and nozzleless.

[dagabu]

Hello,

 

For anyone who uses Rockite, Durham's water putty, or some other variant for rocket nozzles, how do you make them properly symmetrical and straight? I'm uQsing a conical cake mold, and too often the nozzles come out with a very slight tilt which is immediately noticeable during launches.

 

Any suggestions would be appreciated.

 

Question already answered, the natural progression IMHO is to discuss why use castable nozzles if no bates style grains are being used and then move on to the potential benefits/detractors.