Rocket dimensions

[TYRONEEZEKIEL]

After making zillions of starmines, and making zillions of stars and research, I believe I am ready to step it up a notch in my pyro arsenal.

 

I am extremely familiar with rocketry, in the sense of estes rockets, on up to high power. My dad and I make APCP all the time and build rockets very frequently. We are bothe NAR and Tripoli members, and both highpower certified. Yet when it comes to making BP motors myself, i seem to have missed something. I have made a 3/4" ID rocket about 1,5" long stick stabilized, and it flew great! Today I bought a 7/8" dowel, and a 1" dowel rod today. I roll my own tubes by getting a sheet of computer paper, cutting it long ways every 1.5" stacking the sheets together and wrapping them around my dowel rod, tighten them, and gluing the flaps down. Same method that NightHawkinLight uses in making his stinger missles.

 

Anyway, I tried the same thing but 2" long strips to make more room for fuel. Also, I increased the diameter of the rocket to 7/8". This seemed to have increased the surface area of my rockets a bit too much, and I keep catoing my rockets off the launch.. one hit my shed and catoed Normally I would rather keep testing myself, but keeping safety concerns high, I felt like it would be a good idea to get a few pointers.

 

What are a few bottle rocket style dimensions, using my same ID tubes?

I have no tooling other than a dowel and a hammer. I drill my cores with a drill press, and i use milled kitty litter for nozzles. (which get rock freakin hard by the way)

 

Thanks very much!

[Mumbles]

Your rockets are MUCH shorter than normal. The standard is 10x ID for the rockets we make so 8.75" and 10" respectively. I may also be possible your tubes are not strong enough, or you're not able to generate enough force by hand to make rockets this large (especially using wooden rammers).

[TYRONEEZEKIEL]

I know that they are very short, I was trying to go for the estes rocket engine style. I have a feeling that it is my mandrel size and depth that is throwing these rockets out of whack. maybe I should use a star composition that is a bit less energetic than my milled BP. it would make a good color too. I have been experimenting with this a bit lately, but i have just been turning them upside down in the ground, and testing thrust output and nozzle strength. Pihko AP#4 tears these rockets to shreds.

[psyco_1322]

Don't try ramming colored star comps, you'll end up with roasted hands. Most are made with KClO4, and that is not a suitable oxidizer to ram with. If its not KNO3 based, don't even consider it.

 

Also, if you have the ability to make a press, it will greatly improve rocket consistency and performance.

 

Try drilling out your nozzle to 1/3 of the ID of your tubes. So for your 7/8" and 1", try .29" (9/32"), .33" (11/32") nozzles respectfully.

 

Im sure your know that nozzles are very important to how your motor burns. I would take your dowel to a sanding belt, or the like, and put a point on your rammer. This should give you a tapered inside nozzle, which will greatly help reduce CATOs. Gasses don't like running into flat walls. An outside taper would also be good. As for degrees of taper, it should be around 30 inside, 60 outside.

 

Hope this helps a bit.

[TYRONEEZEKIEL]

so today, i made a 1" ID rocket about 3 inches long. I packed about 7/8" of kitty litter as the nozzle mix, a good 2.5 inches of 5-6hour milled BP and capped the rest off with a kitty litter bulkhead.

 

My core was about 1/3" i believe the bit was 21/60" or very close. i inverted it in a pile of sand.. and poof.. the thing launched out of the bucket of sand. I find the casing left in the street, and for once it wasn't a nozzle failure, but either a, i didn't pack my tubes correctly and had a "blow-by" where the propellant grain separated from the casing, causing too much surface area, or my bulkhead was too weak. Am I on the right track here?

[Yankie]

Your fuel is too fast to use in a core burner, try using 60:30:10 or just make end burners.

[ActionTekJackson]

so today, i made a 1" ID rocket about 3 inches long. I packed about 7/8" of kitty litter as the nozzle mix, a good 2.5 inches of 5-6hour milled BP and capped the rest off with a kitty litter bulkhead.

 

My core was about 1/3" i believe the bit was 21/60" or very close. i inverted it in a pile of sand.. and poof.. the thing launched out of the bucket of sand. I find the casing left in the street, and for once it wasn't a nozzle failure, but either a, i didn't pack my tubes correctly and had a "blow-by" where the propellant grain separated from the casing, causing too much surface area, or my bulkhead was too weak. Am I on the right track here?

 

 

So it sounds like you're drilling your cores. This can be done but keep in mind consistency will be very difficult this way. Its very easy to damage the grain by drilling. Also, how thick are your tubes? Its possible your fuel is too fast for your tubes, I put it that way because you are making your own tubes, so try doing a little overkill on a few tubes thickness. Also, what size increments are you ramming that 2.5" grain? If its too large it won't compact properly, leaving gaps for the flame to propogate into and give a sudden spike in pressure, causing a CATO. If you can take some pictures.

[psyco_1322]

If the tube survived, as in its not thin pieces all over your yard, than its not the cases fault. It is possible that all the fuel got pushed out of the case and through the bulk head. I would say your hammer isn't big enough, find a larger one...no seriously. If your rockets blow up, get a bigger hammer.

[TYRONEEZEKIEL]

So. i need to pack my grains harder. that makes sense. because once i had a case rupture while i was ramming, and i unrolled it to find the nozzle and propellant grain still stuck together and solidified. They separated really easily, and the BP crushed in my hands. the nozzle didnt.

 

So if i smack it harder, it will become stronger?

[ActionTekJackson]

So. i need to pack my grains harder. that makes sense. because once i had a case rupture while i was ramming, and i unrolled it to find the nozzle and propellant grain still stuck together and solidified. They separated really easily, and the BP crushed in my hands. the nozzle didnt.

 

So if i smack it harder, it will become stronger?

 

Yea, psycho has a great point there. I ram my rockets just about as hard as I can using a rubber mallot (its hell on the mallot, need a new one every year). Though if your case split during ramming you might want to get or make some kind of a sleeve. I am really interested to see what your tubes look like though.

[psyco_1322]

If at all possible, ram with a solid hammer, not a rubber mallet. Dan Thames showed me that a few years ago. The rubber really absorbs the blow and does not consolidate as well as a solid hammer. He uses hammers with replaceable faces, and uses a plastic face. A plain metal hammer will work too. Ram them as hard as you can with out splitting the case, a slight bulge in the tube at every increment is right on the line of splitting tubes. You can ram the clay portions a little hard and cause them to bulge the case intentionally. This will make them smash into the tube walls and it will be more difficult for them to "pop" out.

[TYRONEEZEKIEL]

I just followed that exactly. and it worked perfectly. my stick was about an inch too short, as the CG was just at the nozzle. it flew out of sight..

 

I have always used a solid metal hammer, i was just worried about splitting my case. If i ever saw any bulging i would toss it out and start over.

 

 

also, how would I make a ram safe report to go in these rockets?

 

 

thanks for all of your help

[Seymour]

A salute is usually added by first drilling a passfire hole trough to top of the clay until it reaches the top of the fuel grain. You can then add Flash to the remaining unfilled tube and attach a cap, or you can attach pre-made salute to it. Other effects can be added too this way, and nothing other than clay and fuel needs to be rammed.

[Arthur]

Most of the old fashioned text books suggest that bugger rockets need slower compounds, Try slowing the compound a little. From Weingart -If it rises too slowly add more nitrate, if it bursts before ascending add more charcoal.

Lancaster suggests adding coarser charcoal to bigger rockets.

[TYRONEEZEKIEL]

wouldnt leaving an open passfire hole with loose packed flash cause an early break since the fuel can burn from both ends?

[Seymour]

What do you mean? Once the passfire is reached it is boom time. No more delays, bang.

 

If you want a delay, you ram an increment of a slow burning composition on top of your fuel, and below your clay. This is almost always done on core burners, and is done less frequently with end burners.

 

I'm not sure what you mean by the fuel burning from both ends. The fuel will burn from any end it can, but usually all but one are inhibited!

[hondo]

another useful tool for pressing rockets is a piece of pvc pipe that is close in ID to tube OD, then cut a slit lengthwise in the pvc that helps you get your rocket motor out once it pressed with fuel , slide your tube insde the pvc get plenty of hose clamps and put them over the pvc pipe one end to the other and tighten them down, which help to keep from splitting your rocket tube does that me since

[TYRONEEZEKIEL]

I think i havent been packing my rockets hard enough, or consistently that when ignited, the flame finds a weak spot and/or airpocket, and burns around the sides, rather than endburning correctly. That would explain my problem with blowing my fuel grain out of the top.

[psyco_1322]

Well if you got one to fly good with some harder blows thats great. Try it a few more times and see if you have consistency.

 

Are you wetting your fuel with anything like mineral oil, Vaseline, or wax? I have only had trouble with propellant sticking to the tube walls when using fuels that have oils mixed in. I have had some troubles with sugar propellants, but thats another story. If its just straight bp, it should ram rocket hard.

 

Like hondo said, with your size of rocket, your might want to make a simple PVC sleeve with hose clamps. This will let you ram as hard as you want and will not split your case. Its the same thing I am currently using to press rockets anywhere up to 9000psi on the propellant.

 

For attaching headers you just drill about a 3/16" - 1/4" hole in your clay bulkhead. Some people have preferences on where to drill the whole, but in all reality, it doesn't matter. Make sure the hole goes through the clay and slightly into your fuel. Sprinkle a pinch of fine bp in the hole and on top of your clay plug. Attach your header. I use a bead of hot glue around the edge of the tube, and sometimes a extension tube that just slips over the motor if I need more room for the header fuse to sit. Prime the fuse on your header or use some sort of super fast paper fuse (3 stranded black match in paper stuff).

[TYRONEEZEKIEL]

Today, i made a beautiful rocket. it was 2" long with a 7/8" diameter. nozzle was about 3/4" thick with just under a 1/4" mandrel that was barely into propellant grain. my bulkhead was just under the same size as the nozzle, maybe half the size. and i drilled maybe a 1/16" or smaller passfire hole in the bulkhead which was packed with BP. I then added another layer of BP on top of that, with about 3 primed 1/4- 1/2" stars taped on top. My rocket balanced with its stick just at the nozzle.

 

I lit it and watched it take off out of sight. the stars were barely visible, granted it was a blue sky, with blue stars, go figure. anyway, it was what I've always wanted.

 

I tried the same exact thing, except i added just a bit longer stick, and my mandrel seemed to be off center a bit.(I think this was my problem) this time upon ignition the rocket went about 10' up, then spiraled horizontally (luckily) away from me.

 

So, now that my nozzle and bulkhead are staying in place, its just a matter of stability.

 

whats next?

[firetech]

Core burners do not need to be balanced the way an end burner does because of their quick take off, but its better to be on the longer side. It might take a bit of experimenting for you. I balance core-burners and end-burners at the nozzle when the stick is about 30 deg. from vertical. Works like a charm. I've also heard the stick should be ATLEAST 7x the length of the engine.

[TYRONEEZEKIEL]

That would make perfect sense. My rod was certainly not 14" i am sure of that! that could very well caused for a curved trajectory.. Also, instead of hand drilling the nozzle with a cordless drill, would it be better to use a drill press, or is there much difference. I would imagine the perfect perpindicular angle would help.

[firetech]

A cordless drill will work just fine. Just try and get it as perpendicular as possible. Even if the nozzle is slightly off 90 deg. you won't notice a difference. I have recently acquired a drill press, they make some jobs MUCH easier. I suggest getting one.

BTW, the sticks I use on my rockets are very light and thin so they must be very long to correctly balance the rocket. They provide a lot of drag which is essential during flight.

[TYRONEEZEKIEL]

I do own a drill press and i will start using it from now on.. My sticks are pretty light too.

 

When I get some free time soon. (Lord willing) I will get outside and make a working rocket that Chuck Norris would be proud of.

[Updup]

so if i'm right a rocket should be balanced right at the nozzle AFTER the stick is glued on? and if the stick is longer than the balaceing point does that really matter?