justanotherpyro Posted July 1, 2006 Posted July 1, 2006 The initial guide thing is very true. Its how the model rockets work and they don't have a guide stick . A pipe several feet long is how I launched my cheesy,unbalanced ground bloom rockets .They do look pretty though, especially with the color change.
ActionTekJackson Posted July 1, 2006 Posted July 1, 2006 Alrighty, finally got a good workin mix for the 4th (one anyway). This Rocket kicked off July 1st, at 12 am. It's not actually a straight BP rocket, it's a BP, Sugar/KNO3, Mg hybrid mix, with a 15g cylinder payload of flitter stars with a whistle break. The rocket itself is 3/4" ID x 3 1/2" Long. I kept with a 3/8" Nozzle and a full core. Mg/BP/Sucrose Hybrid with Flitter Payload
d4j0n Posted July 1, 2006 Posted July 1, 2006 I have heard arguments both ways, square is best, round is best, and it makes no difference. I always used round on my end burners. Now I always use square sticks on the core burners. So I am unable to say which works best. I do have a 1lb core burner with a round stick here, I will post its video when I light it. As well as with a few others 1 lbers with square sticks. But I must say, there is more mass on a square stick then of an equal diameter round stick. Because you can imagine a round stick inside the square one, the square just has edges. Maybe that has something to do with it. It is written somewhere (some book I forgot) that you can attatch kraft wings to the end of thin round sticks. I'd imagine such a method would give the best performance and also be most material efficient. Only downside would be that the wing would have to be pretty thin unless you use an angled ramp to launch the rocket.
_DB_ Posted July 2, 2006 Posted July 2, 2006 Very nice rocket there, ActionTekJackson! I love the tail it produced. Mind sharing those ratios for your hybrid mix?
ActionTekJackson Posted July 2, 2006 Posted July 2, 2006 Well, I can tell you the process that I got it to work, however, I'll need some time to actually recreate it so it can be made consitently. I took a batch of KNO3/Sugar mix, and divided the total batch weight in half and added that much Mg (was alot). This however, will not fly (makes and excellent fountain though). So I proceeded to make the mix faster by adding BP (which I can't use straight because they will CATO). If I were to guess I'd say follow what I said at the begginning and add the same weight BP as you did Mg. I'll do some testing and figure it out for sure after the 4th. Remind me though.
_DB_ Posted July 2, 2006 Posted July 2, 2006 Will do. I was just asking out of curiousity as I cannot try this mix out for myself since I don't have any Mg.
ActionTekJackson Posted July 4, 2006 Posted July 4, 2006 Oooh.... yes.... The latest addition to our 4th show. Just thought I'd share this. 3/4" x 3 1/2" Hybrid Rocket with 15g Flash payload :-D3/4" x 3 1/2" Hybrid w/flash Payload
al93535 Posted July 21, 2006 Author Posted July 21, 2006 Well, I lit up three rockets tonight. Only one made it into the competitions though. Why you ask? Well I had two CATO's!! I was weighing out my RP and noticed my scale's readout was going crazy. The grams were jumping up and down. I smacked it a few times but to no avail, so I used it to weigh out my batch of RP anyways. Well, turns out I had too much kno3 in there. I am just glad I found out before I used anymore from that batch! But I am really sad this rocket didn't fly! It was my first double break on a rocket! Oh well, I will just have to make another. http://www.apcforum.net/files/doublebreakCATO.wmv Just goes to show you, just a few grams off and boom! And yes the scale went to scale heaven, or scale hell shall I say. Ahh, another one coming from ebay.
ltf Posted July 21, 2006 Posted July 21, 2006 LOL it came out nice.. like some weird starmine cake..Sorry about the English.ltf
leosedf Posted July 21, 2006 Posted July 21, 2006 Very nice colors btw. I still cannot decide what's best for me. End burners or core burners?Anyway i'll try to construct end burners this weekend since i need them to go high enough!Whithout payloads i think
Silverturk Posted July 21, 2006 Posted July 21, 2006 Maybe its best to ask here... Which rocket will reach the highest altitude, end burner or core burner?I have tried some end burners now, and to give it a higher thrust I´m using a smaller nozzle. Does that have any disadvantage compared with an core burner?
BigBang Posted July 21, 2006 Posted July 21, 2006 You can't just say a core burner, or an end burner, will give the maximum altitude. It all depends on the design of the rocket, the type of propellant used, the burntime, ect... In most cases, the longer the brntime, the higher the achievable altitude. On the other hand, if you have a heavy rocket, an endburner might not have enough thrust to get it to any altitude. For heavy rockets, a coreburner will give a higher thrust to give it enough momentum to get to altitude. It just depends on what you application is to what motor configuration you should use.
leosedf Posted July 22, 2006 Posted July 22, 2006 What about using an End burner with a small core (2-3cm) for the initial start?Will it work?
Pont Posted July 22, 2006 Posted July 22, 2006 Isnt any rocket with a core even if it isnt through the whole grain a core burner. I always thought end burners had no core, indentations etc
rocket Posted July 22, 2006 Posted July 22, 2006 I think that is the case how can an end burner be, well call an end burner if it has a core even if it is 2-3cm. I would think that the grain would keep burning in the general shape of the core.
TheSidewinder Posted July 22, 2006 Posted July 22, 2006 All the end-burners I've seen DO have a very short core, but that's just to allow secure fusing. But you can make the core almost any length you want. If you have a way to graph the thrust curves, you'll see what longer cores produce. Amateur rocketeers do this a lot, I believe. Fully cored engines have a very high initial thrust, which then drops off (in a variety of curves, depending on several factors) to a point where the graphline is nearly "level" for a time period, until it drops off when the motor is exhausted. Fully non-cored (endburner) motors have a relatively slow-rising initial thrust to a nearly level line for the burn duration. Playing with the core length makes the thrust curves fall somewhere between those two extremes. You can tailor the thrust to suit your payload. Hope that helped... M
Silverturk Posted July 22, 2006 Posted July 22, 2006 Two motors, one designed to be an end-burner, the other one is a core-burner, is filled with the same ammount of black powder.Which one will reach the highest altitude? Somebody said that a motor with the longest burntime will go highest, but at the same time, a heavy rocket will need to have a core to produce higher thrust to make it leave the ground. That makes me think that a core-burner will give higher thrust and then go higher than the end-burner. Am I thinking wrong?
Givat Posted July 22, 2006 Posted July 22, 2006 Its just my logic, but gases are emitted from the burning of BP. In the End burner rocket you got more BP than the core burner so in total more gases are emitted from the end burner and more gases = more thrust. Of course this is my logic and there are many factor to determine wich will go the highest.
d4j0n Posted July 22, 2006 Posted July 22, 2006 I can't seem to get my 2oz end burner to work. I'm using a 3/32" nozzle thats 1/8" into the grain. Is that how end burners are supposed to be? or should it be closer to a half ID into the grain? The rockets don't even move (I gently stuck it into soft green grass/dirt, can't find my launch tube). I'm using alder bp milled for 5 hours with 5% 325 mesh flake Al added.
justanotherpyro Posted July 22, 2006 Posted July 22, 2006 Two motors, one designed to be an end-burner, the other one is a core-burner, is filled with the same ammount of black powder.Which one will reach the highest altitude? Somebody said that a motor with the longest burntime will go highest, but at the same time, a heavy rocket will need to have a core to produce higher thrust to make it leave the ground. That makes me think that a core-burner will give higher thrust and then go higher than the end-burner. Am I thinking wrong?There isn't a specific answer to your question. There are way to many variables. I think I know what you are going after though. If the motor was as light as a feather, and the only thing that would effect altitude was a core, then a rocket without a core would go higher. Rockets weigh a good amount. So if you have an end burner vs a core burner, then its possible that the end burner wouldn't even lift it. It would just be a reverse fountain. Whereas same rocket design with a core will lift it. In this case the core burner obviously went higher because the end burner didn't even budge it. The basics are strength of propellant. You have to vary propellant to the weight of a payload while sacrifcing altitude, which is where cores come in so that you can lift a payload. Example ( 100% made up) 10g propellant uncored can lift 5g payload to height of 100ft10 g propellant cored can lift 15g payload to height of 40ft
ADP9 Posted July 22, 2006 Posted July 22, 2006 Here's a couple pics of my rocket i plan on shooting later. http://img108.imageshack.us/img108/6452/1000872ir5.jpg http://img131.imageshack.us/img131/9504/1000873wl1.jpg It's an endburner with pressed BP as a propellant. I'm currently making another with the following comp: 75 parts KNO3, 20 parts Pine Charcoal, 10 parts Sulfur, 8 parts KClO4 which will be pressed. The payload is a sweet aerial shell weighing about 40g BTW.
Silverturk Posted July 22, 2006 Posted July 22, 2006 So a motor that gives a lower thrust but for longer time will go higher than a motor with higher thrust and shorter burntime? btw, ive recently tried to put a motor on a scale to see how much thrust it makes. The motor is a complete end burner, I just drilled 2-3 mm into the black powder, and then I filled the nozzle with loose BP and pressed it. It gave about 500g under a second and then 300 for another second untill it was finished. The motor itself wheight about 30 gram (10 g propellant, 12mm ID 3mm nozzle)I´ve also tried with 2.5mm nozzle. The motor CATO:ed, leaving only pices of my scale-board. LoL
ADP9 Posted July 22, 2006 Posted July 22, 2006 Haha I've always been curious as to try that without the cato of course ha. I'm sure there is some device out there that could measure thrust a little more easily. Here is my second engine that I just finished making. (next to my first one) It has a bored 1/4th in. nozzle with a core about 1.5in into the rocket the rest is an end burner. Can't wait to see how they perform. http://img97.imageshack.us/img97/921/1000877ml7.jpg
justanotherpyro Posted July 23, 2006 Posted July 23, 2006 I have an idea for determining altitude. Fishling line on a pully spool type of system with the end of the fishing line attatched to the bottom of the rocket stick. Rigging up a spring scale in reverse ( figure it out ) could then determine thrust as well theoretically.
d4j0n Posted July 23, 2006 Posted July 23, 2006 An easy way to determine altitude is to hang a weight on the center of a protractor, attatch a straw to the protracor as a sighting device, and use it to guage the angle of the highest point of the rocket flight. Measure distance from launch, use some simple trig, and you should have the height. Your fishing line might just melt in the exaust.
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