Roadapple Posted October 31, 2010 Posted October 31, 2010 I have been using standard formula for 4oz rockets. I was told that I have to change the ratios for a 3# rocket. The formula that I was given was: Potassium Nitrate-16, mixed Charcoal-12 and Sulfur-3. Is this O.K. or is there a better recipe out there.
dagabu Posted October 31, 2010 Posted October 31, 2010 Road, There are so many great answers to this question and I am sure that you will get a lot of input but let me help a little in asking some questions so that the answers will fit a little better: 1. What kind of tooling are you using on the 4oz rockets? 2. What is the spindle length?3. What is the ratio of nozzle to ID, i.e. 1/2" ID, 1/4" nozzle opening, 2:1.4. Do you use a nozzle or are you using nozzleless rockets?5. Do you pound or press?
Eric70 Posted November 2, 2010 Posted November 2, 2010 Roadapple, If you are talking about core burner rockets, typically the fuel used in smaller rockets will be too fast for the bigger ones and cause cato or nozzle blowout. However, if you press them rather than hand ram them, it seems that from reading posts at Passfire that you can get away with faster fuel because with pressing you get a consistent consolidation of the increments. As Dag says we could use more details of what you are dealing with and there are many different great answers out there. I wouldn't call my answer great, it's a budget effort, hand-rammed (pounded) but it works for me. For 3# black powder core burners I have been using the following mix: 13 oz KNO36 oz charcoal2.5 oz sulfur The KNO3 is a fine powder, the charcoal is from hardwood and fine and the sulfur is rubbermaker's straight from the container. The ingredients are thrown in a big ziplock bag, sealed and gently flipped around for 5 minutes, screened 3 times and ready to use. I was using 15 oz KNO3 and 3 oz sulfur but it was blowing out my 3# nozzle half the time. This is the mix I used for 8 oz and 1# core burners. After I dropped the two down I have not had a problem and the rockets seem to fly just as high but not like they are "redline" and on the verge of blowing up.
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