justhininabouti Posted January 10, 2012 Posted January 10, 2012 I'm just starting to get into making rockets. I like the attention they get when they are used to lift a shell. I am getting my motors dialed in, and am about to start building what I'll need. I've read that straight clay nozzles expand/contract with humidity, and are not recommended (By some) for rockets that will not be used for a period of time. Because of my situation, I will need to keep these motors around for some time. My question is this, what opinions do you have about straight clay nozzles/Plugs? What do you use for your nozzles/plugs? How well do they store? Thanks guys
dagabu Posted January 10, 2012 Posted January 10, 2012 (edited) Justin, I have been making nozzled rockets for a while now and after using a dozen different clay mixes for nozzles, I can say what I do like and what I don't like about different clay mixtures but you ultimately will have to try a few and see for yourself what works best for you. I have listed a few of the mixes and what I though of them below. 1. Kitty litter, red bag, Walmart brand a. I screened it so that I would be using 8 mesh ans smaller grains since it would bridge in slammer tooling. Resulted in a shiny, variegated nozzle with poor erosion characteristics. In my home tests, even with a LPI of 12,000, I could not get it to consolidate hard enough to make for an acceptable nozzle. 2. Bentonite clay from Continental clay, non shrinking pottery clay b. I mixed mixed it with 1% candle wax and heated it to 250° F for an hour and mixed it well. This also gave shiny nozzles and it was much harder to the finger nail and gave acceptable erosion characteristics. The clay nozzle however had the tenancy to get blown out under high pressures or with normal loading pressures. The smooth clay had no ability to grip the walls of hard tubes. 3. Hawthorne fire clay, 80 mesh grog and bentonite pottery clay, waxed a. Mixed in even proportions, the fire clay gave the nozzle the erosion resistance needed to maintain the nozzle throat even in high thrust motors. The 80 mesh grog bites into the walls so hard that even with a screw driver, I can not get the clay off the inner walls of hard tubes after forming a nozzle. The pressure needed to make the nozzle is the same as the rest of the rocket takes to press the fuel. The bentonite clay fills in the mass in-between the fire clay and grog, it gives a shiny appearance and hard to the touch when pressed. I will continue to use the mixed clay but I did take a bit of time off from using it as it does not play well with aluminum or stainless steel spindles so I had to wait until I had a Navel Bronze spindle before I went back to using it. Grog cuts deep scratches into soft materials and even stainless steel would grab the mix so hard that the nozzle end would crack off when removing the finished rocket from the tooling. Waxed nozzles seen to store fine with no absorption of humidity once pressed but should be kept in a sealed bucked as a powder until needed. -dag Edited January 10, 2012 by dagabu
VintageRacer Posted January 10, 2012 Posted January 10, 2012 Straight Fresh-Step cat liter or similar with a touch of graphite is all I use now. Once your motor is made put a piece of metal foil tape on the ends, store as you would anything else. Skip the grog which will only tear up you tooling. Your nozzle is only going to be used once, period, so don't make it more difficult than it's needs to be. DanB
mabuse00 Posted January 10, 2012 Posted January 10, 2012 At the moment I use pure betonite with 5% graphite. Erosion is not severe but there is always some. I don't want to use grog because I'm afraid to wear the tools early with that stuff. In my opinion the wax is not nessecary - as long as your motors are stored in a dry place with a constant humidity level.
justhininabouti Posted January 10, 2012 Author Posted January 10, 2012 (edited) My tooling is aluminum, so the grog sounds bad. Is the graphite used to reduce the wareing of the nozzle or as a lubricant? How do you think the pottery clay would be on my tools? Edited January 11, 2012 by justhininabouti
Blackthumb Posted January 11, 2012 Posted January 11, 2012 I'm back to cheap WMart kitty litter and 30 wt motor oil. Grind and screen 10-30....only had one blowout in the last 50 - 60 units....use in 1/2 to 3/4 nozzles...
WSM Posted January 16, 2012 Posted January 16, 2012 (edited) My tooling is aluminum, so the grog sounds bad. Is the graphite used to reduce the wareing of the nozzle or as a lubricant?How do you think the pottery clay would be on my tools? The graphite helps prevent chemical reduction of the nozzle clay, caused by corrosive exhaust gasses and as a plus, is a lubricant too. So yes, it helps prevent nozzle wear. Which pottery clay? Are we talking about moist, pliable clay or dry, powdered fireclay materials? In pyrotechnics we usually use the dry powdered clay products. Many use bentonite clay and bentonite has issues. It can absorb a lot of moisture unless treated with oil or wax. The preferred bentonite is calcium bentonite (most of the bentonite we see is sodium bentonite). Fireclays from ceramic suppliers are preferrable to bentonite (in my opinion) and are used to make firebricks. Kaolin (white china) is a type of high temperature fireclay. Fireclay is gentler to your tools and if treated with wax and a little graphite added may make an ideal nozzle material. I've also used boiled linseed oil in my nozzle mixes. If you add it, wait a month before using the mix. It takes several weeks (longer in cool weather) for the linseed oil to air-polymerize but when it does, it goes plastic under pressure and flows around the clay grains and into the paper fibers (and even graphite grains) and bonds incredibly well. If you want to use boiled linseed oil but don't care to wait so long; thin the linseed oil with a little Coleman fuel (with a couple drops of Japan drier added). That will cut the polymerization time down to a few days, depending on the temperature. If you want to add wax to fireclay (or kitty litter or whatever ceramic nozzle material you choose), place the weighed amount of clay in a stainless steel mixing bowl and into an oven set at 300oF for half an hour to warm it thoroughly. With gloved hands, remove the bowl of hot clay and pour the weighed, melted wax over the clay and stir it all together till uniformly mixed and set aside to cool. When cool the clay won't look different but it will perform beautifully as a nozzle and erosion will be greatly reduced if not eliminated. Better rockets through chemistry . WSM Edited January 16, 2012 by WSM
allrocketspsl Posted January 17, 2012 Posted January 17, 2012 roll your own tubes that way the tube is just right for nozzels,the harder the tube the harder to get it up against the wall to hold tight,cant remember a top plug or nozzel blow out
justhininabouti Posted January 17, 2012 Author Posted January 17, 2012 The graphite helps prevent chemical reduction of the nozzle clay, caused by corrosive exhaust gasses and as a plus, is a lubricant too. So yes, it helps prevent nozzle wear. Which pottery clay? Are we talking about moist, pliable clay or dry, powdered fireclay materials? In pyrotechnics we usually use the dry powdered clay products. Many use bentonite clay and bentonite has issues. It can absorb a lot of moisture unless treated with oil or wax. The preferred bentonite is calcium bentonite (most of the bentonite we see is sodium bentonite). Fireclays from ceramic suppliers are preferrable to bentonite (in my opinion) and are used to make firebricks. Kaolin (white china) is a type of high temperature fireclay. Fireclay is gentler to your tools and if treated with wax and a little graphite added may make an ideal nozzle material. I've also used boiled linseed oil in my nozzle mixes. If you add it, wait a month before using the mix. It takes several weeks (longer in cool weather) for the linseed oil to air-polymerize but when it does, it goes plastic under pressure and flows around the clay grains and into the paper fibers (and even graphite grains) and bonds incredibly well. If you want to use boiled linseed oil but don't care to wait so long; thin the linseed oil with a little Coleman fuel (with a couple drops of Japan drier added). That will cut the polymerization time down to a few days, depending on the temperature. If you want to add wax to fireclay (or kitty litter or whatever ceramic nozzle material you choose), place the weighed amount of clay in a stainless steel mixing bowl and into an oven set at 300oF for half an hour to warm it thoroughly. With gloved hands, remove the bowl of hot clay and pour the weighed, melted wax over the clay and stir it all together till uniformly mixed and set aside to cool. When cool the clay won't look different but it will perform beautifully as a nozzle and erosion will be greatly reduced if not eliminated. Better rockets through chemistry . WSM WSM - Thanks for the reply. I've settled on the pottery clay/wax/graphite mix for the short term. Although I have to give the linseed oil a try when I get some time. allrocketspls - At this point in my venture I'm going to have to stick to store bought tubes. I may give rolling a try, but there are too many variable right now to add another learning curve to the mix Thanks everyone for the helpful advice.
allrocketspsl Posted January 18, 2012 Posted January 18, 2012 WSM - Thanks for the reply. I've settled on the pottery clay/wax/graphite mix for the short term. Although I have to give the linseed oil a try when I get some time. allrocketspls - At this point in my venture I'm going to have to stick to store bought tubes. I may give rolling a try, but there are too many variable right now to add another learning curve to the mix Thanks everyone for the helpful advice. I know what you mean mate your right later down the road once you've mastered the rocket
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