Redrocketman Posted April 17, 2017 Posted April 17, 2017 I'm not going through all the numbers that have already just been thrown down , but in relation to your question Stix, with the same amount of fuel which would have more alititude, I know without any hesitation my 312gm I class PVC deLavell nozzled motor would have at least double the altitude of a 312gm nozzleless 'sandwich roll' motor!!!!
stix Posted April 18, 2017 Posted April 18, 2017 . . . What exactly are the basics? Truth be told, there are none. This is not a traditional propellant, use the method that resonates with you, dont let my opinion or anybodies keep you from finding your way. Well I guess what I meant by the "the basics" is "not over-complicated". Any unnecessary extra step introduced to a process will, by its very nature of being there, introduce another point for a possible failure of that process or system. I'm not going through all the numbers that have already just been thrown down , but in relation to your question Stix, with the same amount of fuel which would have more alititude, I know without any hesitation my 312gm I class PVC deLavell nozzled motor would have at least double the altitude of a 312gm nozzleless 'sandwich roll' motor!!!! Not sure what you mean Red, seems like your referring to a different thread regarding scaling??
dagabu Posted April 18, 2017 Posted April 18, 2017 Yes, that is always invariably true. However, you are including a bigger variable when inserting Taffy candy into a tube with huge air pockets. No matter what method you choose, you still have to address those air pockets whether it is using grated candy or poking pins into the grain etcetera.
JMan Posted April 19, 2017 Posted April 19, 2017 (edited) Honestly I have a couple pumps straight out of a fridge freezer and ac unit (idk which is best probably ac) and a couple rubber mats for o rings and I think I can rig up a nice vacuum chamber with gloves to test that out because right now I need it in a vacuum for two reasons 1.) test to see how well air pockets are taken out (before during and after packing)2.) see if maybe the water boils off in a vacuum instead of boiling it off at high temps and if so how fast and how dry is the fuel I'm really excited for this because I honestly cannot find these tests done anywhere on rcandy they should both work (although I'm not to sure how dry it will get like this) but if anyone does know of an experiment like this please let me know Edited April 19, 2017 by JMan
stix Posted April 19, 2017 Posted April 19, 2017 (edited) Yes, that is always invariably true. However, you are including a bigger variable when inserting Taffy candy into a tube with huge air pockets. No matter what method you choose, you still have to address those air pockets whether it is using grated candy or poking pins into the grain etcetera. Well that may be true if you are simply pouring hot melted r-candy into your mold or inhibitor sleeve - you may/will get voids. Poking pins into the grain - really? If it ever gets to that point, then best to come up with an alternate casting method. @JMan Sounds interesting what you are doing. So what is your current method for making r-candy? Edited April 19, 2017 by stix
JMan Posted April 19, 2017 Posted April 19, 2017 (edited) @JMan Sounds interesting what you are doing. So what is your current method for making r-candy?My current method is recrystallization. Get my pot and scale put it on and zero it. Add 40 g of water. Add 35 g of sugar. Add 65 g of kno3. Cook at 160 c (370 F?) untill test burns of samples no longer "boil" before burning. I think what I'm going to try is placing 4~10 in long pvc into a vacuum. In this tube will be the negative mold for the core. Stand it up and fill it with the disoloved mix. Pull the vacuum and hope that the water gets low enough pressure that it "boils" or vaporizes (if it does actually boil I might have to regulate the vacuum to keep it clean and not splash) hopefully that will condense the fuel down to a smaller amount (maybe 1~2 inches depending on how much water is added/taken away) and it can be pushed out as a nice solid air free bates grain. Hopefully Edited April 19, 2017 by JMan
Mumbles Posted April 19, 2017 Posted April 19, 2017 Good luck with your experiment. I don't want to get you down, but I don't think it's going to work. Evaporating things like this in a vacuum are more likely to create a sponge of fuel instead of a grain, even more so if the water is actually boiling. The way to get smooth surfaces and solid layers is generally slower evaporation. That said, I'd love to be wrong.
JMan Posted April 20, 2017 Posted April 20, 2017 (edited) Evaporating things like this in a vacuum are more likely to create a sponge of fuel instead of a grain, even more so if the water is actually boiling. The way to get smooth surfaces and solid layers is generally slower evaporation. What do you mean "sponge of fuel"? Porris or springy or what? I'd understand that all the water might not escape because at that point it's not the solution in water it's water in the solution. But that's why it's an experiment right? I've tested the pump and it keeps a perfect seal and creates about -.1 Mpa so it should create a nice gental evaporation with out disturbing the fuel too much. Anyways it might take a while to set it up and get real results but I'll keep you updated through the whole process (should I start a new thread for this if so chem or rocket?) Edited April 20, 2017 by JMan
Mumbles Posted April 20, 2017 Posted April 20, 2017 I will admit, my version of boiling under vacuum is probably different that most. I use vacuum to remove solvents all the time working in a chemistry lab. When they boil, they really boil. What I meant to say is that the actual boiling, mostly due to bubbling of solvents, tends to create voids due to rapid gas escape. This is exacerbated by sticky things, and solvents that like to hydrogen bond like water. Like I said, I'd love to be wrong though. If I'm looking at that correctly, -0.1mPa is around 6mmHg/torr so actually relatively low. Keep us posted.
JMan Posted April 20, 2017 Posted April 20, 2017 If I'm looking at that correctly, -0.1mPa is around 6mmHg/torr so actually relatively low.It's just a guess right now I was looking at a phase diagram of water and that's just about where water starts to boil. I don't have a gauge or much of a set up yet I just put water in the vacuum and it's just barely making bubbles, but I don't think it's dissolved oxygen because it keeps it up untill it chills a tiny bit. But if it is it won't be that hard to find a slightly better pump or change the oil in this one (i don't know if an oil change would make it run better?)
Redrocketman Posted April 20, 2017 Posted April 20, 2017 Ok Jman!! Next thing!! I'll go bit by bit so u don't drown!! No matter what ur kno3 must be dried, it's so hygroscopic no matter what it will suffer from moisture absorption. Big performance drop. Weigh out, sprinkle on a small baking tray n put in the toaster over on only 70 degrees Celsius for 20 mins. Now when u grind it ull near need a good respirator it will chop so fine n dusty!! I had 4 nozzleless core burners just sit there and for a bit was stumped. That's what it was!! I just made a 400mm X 40mm with 12mm core. I'll tape it to a trusty tomato pole & let it rip n film it. I'll show u how they should go - fu$^@ng hard n high!!!! And there crap compared to real motors!!!!
JMan Posted April 23, 2017 Posted April 23, 2017 Ok so my pump works fine and boils the water but I can't for the life of me find a vacuum chamber to put a pipe in (I've thought about just connecting an end cap directly to it and having the cast be the vacuum chamber) but I want to see what's going on in there how well done it is if it's boiling over anyone got suggestions?
lloyd Posted April 23, 2017 Posted April 23, 2017 (edited) 'Normally', the vacuum chamber (bell jar) is not penetrated... the pipe enters through the base plate against which the jar seals. Lloyd Edited April 23, 2017 by lloyd
Redrocketman Posted May 1, 2017 Posted May 1, 2017 (edited) Jman, PM me ur email address or Facebook name and I'll go though it in much finer details with pictures to make it easier to seeCheers red Edited May 1, 2017 by Redrocketman
EliTheClasher Posted June 21, 2017 Posted June 21, 2017 I am not allowed to make a new topic on the forum, so I guess I have to post my issues here. I am making a KN03-Sugar rocket, and I am using a dry fuel composition (not cooking the fuel). My mix is 66/33 KN03-Sugar, but the fuel doesn't burn. I did a test burn, and the lit areas simply bubbled and it looked like it had no potential whatsoever. Do I HAVE to cook the fuel, or will a dry mix be ok? (I am fine not cooking if I have to sacrifice a little power). Possible Issues: Ratio Wrong KN03 not ground up enough, or wrong source (stump remover) Igniting the composition the wrong way Thank you for your time and I really appreciated any suggestions!
Mumbles Posted June 21, 2017 Posted June 21, 2017 How are you mixing? You may want to think about adding a catalyst. Besides the performance benefits, they also has the added advantage of often being colored to assist in determining when the fuel is totally mixed.
EliTheClasher Posted June 21, 2017 Posted June 21, 2017 How are you mixing? You may want to think about adding a catalyst. Besides the performance benefits, they also has the added advantage of often being colored to assist in determining when the fuel is totally mixed. I am simply grinding the KN03 with mortar and pestle, then adding the sugar. I mix it in two cups taped together for at least 30 minutes so I know the mix is good. Maybe wrong source of KN03? I am using Spectracide stump remover.
EliTheClasher Posted June 22, 2017 Posted June 22, 2017 I am simply grinding the KN03 with mortar and pestle, then adding the sugar. I mix it in two cups taped together for at least 30 minutes so I know the mix is good. Maybe wrong source of KN03? I am using Spectracide stump remover.Is this a good option, or do I have to use a blender?
lloyd Posted June 22, 2017 Posted June 22, 2017 If you're using a mortar and pestle, keep your loads VERY small. For the best 'grind' (finest particles), you need to had no more KNO3 in the mortar than will coat the walls of the mortar about 0.050" thick. Lloyd
EliTheClasher Posted June 22, 2017 Posted June 22, 2017 If you're using a mortar and pestle, keep your loads VERY small. For the best 'grind' (finest particles), you need to had no more KNO3 in the mortar than will coat the walls of the mortar about 0.050" thick. LloydThanks! I figured this may be the issue. It seems like my burn still should be more intense than a few bubbles... Maybe a blowtorch is a bad method of ignition?
lloyd Posted June 22, 2017 Posted June 22, 2017 (edited) No... if it doesn't burn in one (VERY FAST) "poof", it's poorly-incorporated powder. Are you sure that stump-remover doesn't have a flame-retardant added? (nope... just looked it up... 100% KNO3, according to the MSDS) So, incorporation is your problem. Lloyd Edited June 22, 2017 by lloyd
EliTheClasher Posted June 23, 2017 Posted June 23, 2017 No... if it doesn't burn in one (VERY FAST) "poof", it's poorly-incorporated powder. Are you sure that stump-remover doesn't have a flame-retardant added? (nope... just looked it up... 100% KNO3, according to the MSDS) So, incorporation is your problem. LloydThanks for all the help!
lloyd Posted June 23, 2017 Posted June 23, 2017 Eli,I know this might be insulting (*but don't take it that way*). I just want to make sure you are measuring your proportions by weight, not by volume. Some have made that mistake, in the past. Lloyd
EliTheClasher Posted June 23, 2017 Posted June 23, 2017 Eli,I know this might be insulting (*but don't take it that way*). I just want to make sure you are measuring your proportions by weight, not by volume. Some have made that mistake, in the past. LloydYou know... I'm not insulted. I had been doing that I am ordering a very accurate gram scale and that will make the composition much better. That is my main error so thanks so much!
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