stix Posted September 13, 2015 Share Posted September 13, 2015 . . . The method you described isn't really the most reliable, because you could easilly make a mistake, plus if a small amount of gasses do leak, the first place they are coming out is the hole . . . What do you mean by "easily make a mistake"? A small amount of gas leaking out of your aluminium "twisting" rivets is not much better either. Anyway, let's not get side-tracked by methods, unless of course the issue keeps happening. What exactly do you mean by your rivets twisting - In which axis? Link to comment Share on other sites More sharing options...
Oinikis Posted September 15, 2015 Author Share Posted September 15, 2015 (edited) So I did another test. The grain was supposed to burn for 2 secs, but i combusted in less than 1. So there was an inhibitor problem. Due to that there was overpressurization of estimated over 50 Bar. due to that plugs shifted, but held majority of the gasses, but a channel formed near the nozzle, and gasses burned a hole in the aluminium. Good thing to know that it didn't cato. Of course the plugs split, rivets twisted (The inside part angles outward), even the tube bent a little.So the hopefully final problem is the inhibitors. Of course I'm matters harder for myself by using endburner grain, if I used BATES it would have been easier, and I think, successful. But anyway, I use two rolls of craft paper glued as my mold, and latter wrap tape, to seal the grain. I think the fuel doesn't stick to the paper. Also right now I'm using different fuel formula where 1/3 of sugar is glucose, and it helped with casting but still. Any suggestions? Edited September 15, 2015 by Oinikis Link to comment Share on other sites More sharing options...
chand Posted September 15, 2015 Share Posted September 15, 2015 So I did another test. The grain was supposed to burn for 2 secs, but i combusted in less than 1. So there was an inhibitor problem. Due to that there was overpressurization of estimated over 50 Bar. due to that plugs shifted, but held majority of the gasses, but a channel formed near the nozzle, and gasses burned a hole in the aluminium. Good thing to know that it didn't cato. Of course the plugs split, rivets twisted (The inside part angles outward), even the tube bent a little. So the hopefully final problem is the inhibitors. Of course I'm matters harder for myself by using endburner grain, if I used BATES it would have been easier, and I think, successful. But anyway, I use two rolls of craft paper glued as my mold, and latter wrap tape, to seal the grain. I think the fuel doesn't stick to the paper. Also right now I'm using different fuel formula where 1/3 of sugar is glucose, and it helped with casting but still. Any suggestions?Why don't you try using some liqiud bindex it will be good instead of changing ratio Link to comment Share on other sites More sharing options...
Oinikis Posted September 15, 2015 Author Share Posted September 15, 2015 It won't work, because you'll need to have a high percentage of it, and it will wreck it. Cold binders are usually used only in high performance fuels, like APCP or HTBP, where binder acts as a fuel itself. In this case sugars act as a binder. Anyway, just done a bit more reading, and turns out that with increased Oxidizer/Fuel ratio temperature sharply increases, while performance doesn't. And I always used 66.7/33.3 ratio (2/1), and didn't think about it. Now I'll try 65/35(25 sugar/10 glucose). Not only the combustion gasses should be cooler and less agressive, but it should have better casting properties, plus i'll improve the tooling. Also I think I'll try both endburners and BATES, to finally move on, because this took too long. Link to comment Share on other sites More sharing options...
stix Posted September 16, 2015 Share Posted September 16, 2015 (edited) The flame front directed to the aluminium tubing is always going to be a problem. The only end burners I've ever done was years ago. This was using 'ground down' Estes black powder motors, The Al tube was about 3mm thick and the motors burned for around 4seconds. The tube was red hot after that and some of them cato'd. That's why I like sugar rockets, the fuel burns slower than bp (I'm not sure of the temp difference though). I've found BATES grains work well - mine are actually semi-bates in that both ends are inhibited. The grain/s are a tight fit into the tube, then pressed against the nozzle and bulkhead. No where for the flame or pressure to go except out the nozzle. I would still rather cardboard tubes if I could get them. I mentioned in an earlier post about other methods of testing fuel energy and pressure. You could look at making a Scientific Bomb Calorimeter. Around 30yrs ago when I was mucking around with composite fuels (APCP) my colleague and I made a calorimeter to test the calorific value of the fuel and a similar device with a pressure gauge. The positive thing about your current tests is that you are moving forward, Cheers. Edited September 16, 2015 by stix Link to comment Share on other sites More sharing options...
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