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Model Forum / General / Rockets / November 2004Drilled brick nozzles
One simple (probably silly) idea for making cheap easy-to-make nozzles: drill them out from firebrick (or even tile?, stone?) with round hole-cutter with centering drill bite. What you get is piece of brick looking like Bates grain. Later then it is possible to make central hole conical. Does anybody have experience or is it just not working idea? Best, Vello > One simple (probably silly) idea for making cheap easy-to-make nozzles: > drill them out from firebrick (or even tile?, stone?) with round [quoted text clipped - 8 lines] > > Vello The stuff does not drill easily and neatly. You could form the nozzle in place from "Leak Fix" cement. The kind used to repair leaks in the basement walls. It expands when cured and will stay in place. I have made some from ceramic also, formed them soft and had them baked. Local craft shop had ceramic lessons and I enrolled and made a bunch of nozzles. Tom If you don't have access to a lathe and some graphite, this is an excellent idea! James > I have made some from ceramic also, formed them soft and had them baked. > Local craft shop had ceramic lessons and I enrolled and made a bunch of > nozzles. > Tom > If you don't have access to a lathe and some graphite, this is an > excellent idea! I've thought that there are possibilities along this line for making composite parts, if one could get some high-strength ceramic fiber, wet it out with clay "slip", and then lay it up in the desired shape and bake it... -dave w > If you don't have access to a lathe and some graphite, this is an > excellent idea! > > James Only if you're burning relatively-low temperature propellants. It might work out OK for KNO3/{Sucrose,Dextrose,Sorbitol}, but for aluminized APCP, you'd likely see substantial erosion. And no way will it work for hybrids. I use firebricks on one of my test stands on the blast deflector. The stuff actually melts and flows, leading me to believe that it would be a relatively poor material for nozzles. > > If you don't have access to a lathe and some graphite, this is an > > excellent idea! [quoted text clipped - 9 lines] > The stuff actually melts and flows, leading me to believe that it > would be a relatively poor material for nozzles. For sure I'm talking about simple single use motors. What I love is that this way nozzles come one per 5 seconds (well, there is some thinking about how to make them tight in motor case). For sure brick can't match grafite, but is it really worse then just clay? If yes, there is a lot of stone-like materials to drill, so I just have to test. KNO3 is only oxidizing stuff available here, so my choices are candy or kno3-epoxy. Really. Can't be any worse than "Durham's Water Putty". Talk about erosion. I did my first batch of pvc test motors with it a few years back. Composite ate that stuff alive. At least I was smart enough to put a steel insert throat into them, or my "a" and "n" results would have been even more questionable. I have since refined my methods. And bought a lathe to turn graphite (among other things). James > > > If you don't have access to a lathe and some graphite, this is > an [quoted text clipped - 18 lines] > KNO3 is only oxidizing stuff available here, so my choices are candy or > kno3-epoxy. If you don't have a lathe, how can you turn the bricks? Sure, you can drill out the nozzle but you need a way to shape the rest of it too, right? > If you don't have a lathe, how can you turn the bricks? Sure, you can drill out > the nozzle but you need a way to shape the rest of it too, right? Take hole-cutter of the same dia as motor casing and centering drill bite of the size of nozzle-hole you want (problem is, hole-cutters come with some standard dia centering bites so if it don't fit your design, you have to drill central hole one more time to get right dia). Shaping the inner part of nozzle is easy with $5 conical milling cutter and drill. Outer surface will stay as it is and will be glued (epoxy or clay, cement) to the casing. Remember, we're talking about simple single use motors - idea is to keep costs of tooling and materials as low as possible. Roughly: hole-cutter $10-12 (profi stuff $30), milling cutter $5 (or $10 if you take different angle cutters for inner and outer end of nozzle), brick or tile ? $1?. Hopefully hand drill is in household anyway. Best Vello Brick sounds porous and therefore inclined to deal with heat unevenly and be mechanically weak. I would think a better alternative would be to 'cast' your own, if you don't turn them on a lathe. I'm thinking something you pour in a mold that either self-sets (cures) and/or later gets fired in a kiln. Speaking of nozzles, are semi-exotic metals any help? Thinking of Titanium. It's more expensive than more common metals but you don't need _that_ much, do you? TBerk > Brick sounds porous and therefore inclined to deal with heat unevenly > and be mechanically weak. [quoted text clipped - 10 lines] > > TBerk Titanium would be a bad choice. > Brick sounds porous and therefore inclined to deal with heat unevenly > and be mechanically weak. [quoted text clipped - 4 lines] > I'm thinking something you pour in a mold that either self-sets (cures) > and/or later gets fired in a kiln. But this will be in many times more time. There are different materials to try, stone floor plates at first. > Speaking of nozzles, are semi-exotic metals any help? Thinking of Titanium. > It's more expensive than more common metals but you don't need _that_ > much, do you? > > TBerk Melting point: iron - 2750 F, steel - 2500 F, titanium - 3034 F. Not big gap, but sure titanium nozzle will be lighter. What I can't know is the thermal stability of titanium. Titanium is melted and welded in vacuum, due "extremal reaction with oxygen in high temperatures"(Google). Price must be not too high - but no idea about retail shops:-) Vello > Speaking of nozzles, are semi-exotic metals any help? Thinking of Titanium. > It's more expensive than more common metals but you don't need _that_ > much, do you? > > TBerk Go ahead with titanium! Look http://www.azom.com/details.asp?ArticleID=233 > Go ahead with titanium! Look http://www.azom.com/details.asp?ArticleID=233 Wouldn't work with anything but KNO3+Sucrose or cooler. APCP composites, bi-props, and hybrids generally burn hotter than the melting point of titanium (1600C). And most titanium isn't pure, it's alloyed with other materials like iron, aluminum, etc. Which often lowers the melting point. It doesn't say what these particular nozzles are for, but it wouldn't surprise me if it was for an RCS system with relatively low throat temperatures (or they're regen cooled--but it doesn't look like that in the cited article). Graphite really is the material of choice for the amateur experimenter, and it *can* be machined without a lathe. In fact, graphite machines quite well generally, so the suggested method of using a hole saw to cut out slugs would work modestly well.  SignatureMarcus Leech Mail: Dept W669, M/S: 04352P16 Advisor Phone: (ESN) 393-9145 +1 613 763 9145 Internet & Security Services Nortel Networks mleech@nortelnetworks.com > > > [quoted text clipped - 20 lines] > the suggested method of using a hole saw to cut out slugs would work > modestly well. Isn't graphite too expencive for single use motor? > Isn't graphite too expencive for single use motor? Not necessarily. Depends on the size of the motor. Also, you can use a graphite throat section that is submerged in some cheaper metal, but EDM graphites of the cheaper grades would be ideal for single-use nozzles, even if they're full-width up to 54mm or so. Graphite is very often available on the surplus market quite cheaply, and even new material is now conveniently available at modest prices (www.graphitestore.com for example). Aerocon often carries surplus material, and their new material is also quite reasonably priced (www.aeroconsystems.com). SignatureMarcus Leech Mail: Dept W669, M/S: 04352P16 Advisor Phone: (ESN) 393-9145 +1 613 763 9145 Internet & Security Services Nortel Networks mleech@nortelnetworks.com You are right, but my original idea was to "compete" is class of paper/PVC motors with clay nozzles and candy propellant. Drilled is easier and stronger. But, sure, it is not for comparing with more expencive solutions - more to give easy access for young boys. And young boys interested in rocketry we want - it is first time in 2000 years now granddads can talk to kids that when they were young they had technologies in use we don't have today. Best Vello > > Isn't graphite too expencive for single use motor? > [quoted text clipped - 12 lines] > material is > also quite reasonably priced (www.aeroconsystems.com). << Go ahead with titanium! Look http://www.azom.com/details.asp?ArticleID=233 Cool! Looks like a big, high tech version of an Aerotech Medusa nozzle. I would have thought titanium would burn, though. > << Go ahead with titanium! Look http://www.azom.com/details.asp?ArticleID=233 > > Cool! Looks like a big, high tech version of an Aerotech Medusa nozzle. I would > have thought titanium would burn, though. Do anybody know what they use in military/professional (apart of hi-tech composite materials)? Wolfram? > Do anybody know what they use in military/professional (apart of hi-tech > composite materials)? Wolfram? Usually a tungsten(wolfram)/tantalum/niobium alloy. The SSMEs use such an alloy, and the engine and nozzle are made as a "tubing bundle" thousands of tubes of the correct profile, welded together into a leakproof combustion chamber. [possibly faulty memory here, so bear with me]. The H2 enters somewhere around the middle of the divergent section and flows back towards the injector in the combustion chamber. So they're using *both* a refractory metal alloy, and regenerative cooling to keep the chamber from burning itself to bits. It does have to sustain 8 minutes of total screaming hellfire, and it has to be able to do it multiple times. SignatureMarcus Leech Mail: Dept W669, M/S: 04352P16 Advisor Phone: (ESN) 393-9145 +1 613 763 9145 Internet & Security Services Nortel Networks mleech@nortelnetworks.com |
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