usapyro Posted June 16, 2011 Posted June 16, 2011 (edited) Been looking for a good way to quickly seal the back ends of rockets off and that is the first thing I thought up... The particle size on sand is kind of big so either I need a lot of red gum or some kind of finer filler too... I searched the forums and couldn't find anything on good quick drying formulas. Normally back ends of rockets don't really need to be sealed off but I am testing a "gel" rocket fuel and quickly realized the new issues that creates... Will work on this tomorrow... Cheap idea of the moment is 75 % sand, 17 % sodium bicarbonate(cheap filler between sand grains), 8 % red gum... Will tell you how it goes! It doesn't need to withstand heat, it just needs to act as a solid pressure barrier... Pyroguide's composition's say "degrades during storage" so those won't work... (I'm a perfectionist...) Exactly why would calcium carbonate and water glass degrade I have no clue?!? ***Pyro adhesive is a form of cement, that can be used for filling cardboard tube end caps, which have first glued on tube with white glue. It is water soluble and adheres well on paper.Some recipes for pyro adhesive: #1 - #2Water glass 1 - 4Zinc oxide 1 -Calcium carbonate 1 - 5 *** Maybe someone here has some easyier idea's like "quick dry tile grout?" Kinda worried about the chemicals in those though... Edited June 16, 2011 by usapyro
Ralph Posted June 16, 2011 Posted June 16, 2011 (edited) terrible idea redgum is a crap binder this will crack and not hold up other disadvantage is it will shrink the pyro adhesive not only sets very quickly but also dosnt shrink and crack like your mix will stop posting threads about your impatience if you cant wait get a license by commercial product no drying time involved at all EDIT: the adhesive degrades in storage if not used immediately it begins to set a pyro friend of mine who uses it has devices a couple years old his plugs are still perfect Edited June 16, 2011 by Ralph
dagabu Posted June 16, 2011 Posted June 16, 2011 I am kind of confused with the first adhesive you posted, 75 % sand, 17 % sodium bicarbonate, 8 % red gum. I have no idea how this would act as a cement. I have used epoxy mixed with Glass Microspheres to make very lightweight plugs that are stronger then rammed clay. You can find them at any boat building or repair shop, eBay has them for under $20.00 for a gallon of them. -dag
DeepOvertone Posted June 16, 2011 Posted June 16, 2011 I was going to suggest epoxy mixed with a filler like sand or the above mentioned microspheres. Harbor freight sells two part epoxy for a dollar from time to time. I bought 20 packs the other day. You do have to be careful though. Epoxy creates heat during the curing process. I found that it actually gets hotter and cures faster when mixed with a filler. So I would test that while in contact with whatever fuel you are using. Just to make sure it won't ignite.
dagabu Posted June 16, 2011 Posted June 16, 2011 (edited) I was going to suggest epoxy mixed with a filler like sand or the above mentioned microspheres. Harbor freight sells two part epoxy for a dollar from time to time. I bought 20 packs the other day. You do have to be careful though. Epoxy creates heat during the curing process. I found that it actually gets hotter and cures faster when mixed with a filler. So I would test that while in contact with whatever fuel you are using. Just to make sure it won't ignite. No need, comp ignition temp is way above the runaway temp that small batches of epoxy with filler will achieve. If doing a 100g batch, I would be concerned but with a 5 gram batch of epoxy plus filler, I have no concerns at all. I agree with you on the faster curing though, 5 minute epoxy mixed 50:50 by volume with microspheres hardens in about 30 seconds in my experience. -dag Edited June 16, 2011 by dagabu
usapyro Posted June 16, 2011 Author Posted June 16, 2011 (edited) I was going to suggest epoxy mixed with a filler like sand or the above mentioned microspheres. Harbor freight sells two part epoxy for a dollar from time to time. I bought 20 packs the other day. You do have to be careful though. Epoxy creates heat during the curing process. I found that it actually gets hotter and cures faster when mixed with a filler. So I would test that while in contact with whatever fuel you are using. Just to make sure it won't ignite. Most epoxy I have ever used or seen would be impossible to mix together with sand. It's wayy too thick. I have a bunch of Gorilla epoxy. This stuff doesn't shrink while setting? It seems like it would since it warms then cools... I love gorilla products... Gorilla super glue, white glue, duct tape... That stuff rocks! White glue that sets in 15 minutes?That is what I'm talking about!!! Odd topic: All this talk about epoxy reminds me of when I was bubbling pure oxygen into epoxy when I was twelve years old in an attempt to make an oxygen/epoxy rocket engine... LOL! Never got that one to work... Edited June 16, 2011 by usapyro
usapyro Posted June 16, 2011 Author Posted June 16, 2011 (edited) stop posting threads about your impatience if you cant wait get a license by commercial product no drying time involved at all EDIT: the adhesive degrades in storage if not used immediately it begins to set a pyro friend of mine who uses it has devices a couple years old his plugs are still perfect LoL... I don't think water glass and calcium carbonate are very regulated substances... Also, there is good reason to find the FASTEST way to get things done... If you are at a club event/visiting a friend in the country/etc... Can you wait patiently for four days for a glitter comet to dry? No! You need acetone/alcohol binders that dry super fast. Just as you need everything else to be able to dry/set super fast. And yes, I also got my PVB binder now that works with glitters... Yay! I feel sorry for you, because you seem to resent the fact I like my glitters to dry as fast as my colors or something? I don't get you... Ah, it appears I just misread the instructions on the water glass stuff. It took me 2 minutes to find Calcium Carbonate retail online... I also found Sodium Silicate too... Odd... It's a liquid... Must mean it's a water binder only... Damn! Set time must be hours and hours... Edited June 16, 2011 by usapyro
Ventsi Posted June 16, 2011 Posted June 16, 2011 Alright it's been a while since I've looked any of this up but this is from the top of my head. The composition from Pyroguide is good one, and as far as it degrading think at least half a year of storage or more, most compositions were made for the commercial side of pyro. And as far as the set time it should be no more than a day or so since it cures more than dries. But an Epoxy/Filler would probably be your best choice. If you're loking for something more fluid go to your local hardware store and pick up some fiberglass resin, mixed up with sand it make grat plugs! For anything from rockets to small dia. mortars!
Mumbles Posted June 16, 2011 Posted June 16, 2011 You know, you can always make stuff ahead of time. This project may not be viewed in the best of light even if made and shot on site should someone get wind of it. I think what Ralph was getting as is that you could just get licensed and buy stuff ready made, a nod to your impatience. Anyway, I know what you're putting in there, but is there anything you have against adding a cardboard disk over the fuel and using hot glue or epoxy or something?
usapyro Posted June 16, 2011 Author Posted June 16, 2011 Anyway, I know what you're putting in there, but is there anything you have against adding a cardboard disk over the fuel and using hot glue or epoxy or something? I was under the assumption that the amount of pressure transferred to the back of a rocket engine through a gel was equivalent to the thrust... And that you would need a very solid barrier. This is not the case? Don't worry, my experiments over the years have never been noticed that I am aware of... The long thirty mile drives into the middle of nowhere on gravel roads are kinda fun really. Kinda necessary with these because they might be sticks of dy*****e not rockets... LoL!
Ralph Posted June 17, 2011 Posted June 17, 2011 Accidents happen from people rushing and taking short cuts like not turning off a hot glue gun as you move it over to seal some tubes with pyro composition and having it malfunction shooting sparks onto live comps, they happen from using ever more volatile solvents in a semi furnace drying box you made and having an ignition, from using recently cooked charcoal you just couldn't wait the extra few hours for it to cool down and an ember in there blows your mill up when your milling. The pyro technic comunity dosnt need any more accidents The pyro adheasive works by a double displacement reaction were calcium silicate is formed which quickly forms rock my freind who uses it makes it sound like it will hold its form pretty much instanly after its been manipulated and if you dont use the batch quickly enough much of it gose to waste
Peret Posted June 17, 2011 Posted June 17, 2011 (edited) I was under the assumption that the amount of pressure transferred to the back of a rocket engine through a gel was equivalent to the thrust... And that you would need a very solid barrier. This is not the case?This is correct, but the force the plug is exposed to is only the feeble thrust of the delay, since the cored section is long gone by the time it burns up that far. Calcium carbonate and sodium silicate is good stuff that makes a hard cement, but I found it can shrink and crack if you try and make a plug out of it. It's mainly useful for cementing tubes to things. Edited June 17, 2011 by Peret
usapyro Posted June 17, 2011 Author Posted June 17, 2011 (edited) This is correct, but the force the plug is exposed to is only the feeble thrust of the delay, since the cored section is long gone by the time it burns up that far. Calcium carbonate and sodium silicate is good stuff that makes a hard cement, but I found it can shrink and crack if you try and make a plug out of it. It's mainly useful for cementing tubes to things. Hmmm... That explains why my end burner just did a near silent cato when trying a cardboard/hot glue plug... I'm testing a fuel that is a Gel so things are a little different... Edited June 17, 2011 by usapyro
dagabu Posted June 17, 2011 Posted June 17, 2011 Most epoxy I have ever used or seen would be impossible to mix together with sand. It's way too thick. Epoxy comes in all sorts of viscosity from 600cps to 3000cps. Mixed with sand or glass bubbles, it retains 90% of its strength, does not shrink and sets up fast. Also, the bulkhead does not have to take on the whole thrust of the rocket motor, the amount of fuel on top of the spindle will contain most of the thrust and the remaining thrust will act on the plugs surface allowing the adherence of the epoxy (the grip it has on the walls) to hold it in place. Be sure to have a clean tube above the fuel, scrape the epoxy against the walls to ensure intimate contact with the walls, use glass bubbles for weight savings and to keep missile hazards down. Nobody wants to get shot in the face with an ounce of epoxied sand -dag
Mumbles Posted June 17, 2011 Posted June 17, 2011 He's talking about a gellied rocket fuel. The dynamics of force may be different from a pure solid like BP, and something like he is using which presumably would have some liquid characteristics. I could see them putting more force on an end plug.
dagabu Posted June 17, 2011 Posted June 17, 2011 He's talking about a gellied rocket fuel. The dynamics of force may be different from a pure solid like BP, and something like he is using which presumably would have some liquid characteristics. I could see them putting more force on an end plug. Hmmmmm, thinking about a pressed plug or a cross support? -dag
r1dermon Posted June 21, 2011 Posted June 21, 2011 A gelled rocket fuel is going to exhibit massive fuel grain erosion. It will probably burn erratically as well, since a gel is amorphous and the chamber pressure will likely be so great on any motor with practical thrust dynamics, that you're going to experience cato's due to shifting grain geometry mid-burn. If your plan is to stuff a tube with flammable gel and ignite it in the same manner as a traditional solid booster, i don't encourage it, and i can all but guarantee your device will not function as you wish. As for the OP, id hotglue a bulkhead over the nozzle.
dagabu Posted June 21, 2011 Posted June 21, 2011 As for the OP, id hotglue a bulkhead over the nozzle. Im sorry, I dont know what the"OP" is, and what do you mean by hot gluing a bulkhead "over the nozzle"? Im sure you have a good picture in your mind, I just come up blank... -dag
stckmndn Posted June 21, 2011 Posted June 21, 2011 Im sorry, I dont know what the"OP" is, and what do you mean by hot gluing a bulkhead "over the nozzle"? Im sure you have a good picture in your mind, I just come up blank... -dag Original Poster.
dagabu Posted June 21, 2011 Posted June 21, 2011 Original Poster. Gotcha! What about the hot gluing the bulkhead over the nozzle thing? -dag
usapyro Posted June 21, 2011 Author Posted June 21, 2011 A gelled rocket fuel is going to exhibit massive fuel grain erosion. It will probably burn erratically as well, since a gel is amorphous and the chamber pressure will likely be so great on any motor with practical thrust dynamics, that you're going to experience cato's due to shifting grain geometry mid-burn. If your plan is to stuff a tube with flammable gel and ignite it in the same manner as a traditional solid booster, i don't encourage it, and i can all but guarantee your device will not function as you wish. As for the OP, id hotglue a bulkhead over the nozzle. It's not that "gelly" of a gel... It's made to the consistency that it can be pressed into a tube with hand pressure using 75% of the strength I can muster... Fun to play with, but castable mixtures are a bit better...
r1dermon Posted June 22, 2011 Posted June 22, 2011 Im sorry, I dont know what the"OP" is, and what do you mean by hot gluing a bulkhead "over the nozzle"? Im sure you have a good picture in your mind, I just come up blank... -dag assuming the intent is to seal the backend of the rocket, a bulkhead plate would have to be manufactured to conform to the outer diameter of the nozzle, and fill the space between the edge of the body. Unless im misinterpreting the OP. Google bates grain geometry if you want to learn a bit more about getting a regressive burn profile from a less aggressive burning propellent. Im interested to see a test of this gelled rocket fuel grain.
dagabu Posted June 22, 2011 Posted June 22, 2011 assuming the intent is to seal the backend of the rocket, a bulkhead plate would have to be manufactured to conform to the outer diameter of the nozzle, and fill the space between the edge of the body. Unless im misinterpreting the OP. Google bates grain geometry if you want to learn a bit more about getting a regressive burn profile from a less aggressive burning propellent. Im interested to see a test of this gelled rocket fuel grain. Gotcha, your still speaking Model Rocket lingo, gotta remember that. -dag
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