madmandotcom Posted January 29, 2011 Share Posted January 29, 2011 my ignitors have recently been gettng stuck in my candy and blocking the exhaust hole causing the motor to cato, how do i avoid this? Link to comment Share on other sites More sharing options...
dagabu Posted January 29, 2011 Share Posted January 29, 2011 Use Visco instead. Link to comment Share on other sites More sharing options...
madmandotcom Posted January 30, 2011 Author Share Posted January 30, 2011 Use Visco instead. i would but there is nowhere that exports to nz Link to comment Share on other sites More sharing options...
ausgoty Posted January 30, 2011 Share Posted January 30, 2011 (edited) i would but there is nowhere that exports to nz You should be able to make some secent black match. Handy to have around anyway. Give that a try. Edited January 30, 2011 by ausgoty Link to comment Share on other sites More sharing options...
madmandotcom Posted January 31, 2011 Author Share Posted January 31, 2011 ok, thanks Link to comment Share on other sites More sharing options...
WSM Posted February 1, 2011 Share Posted February 1, 2011 (edited) my ignitors have recently been gettng stuck in my candy and blocking the exhaust hole causing the motor to cato, how do i avoid this? If you're making your own ignitors, make them smaller . I've had decent luck mounting the ignitor to the launch system base so when the engine ignites, it rises away from the spent ignitor (and launcher). If you make black match, if need be for better ignition, add a small percentage of (compatible) metal powder to heat up the burning match slurry. WSM Edited February 1, 2011 by WSM Link to comment Share on other sites More sharing options...
madmandotcom Posted February 1, 2011 Author Share Posted February 1, 2011 ok, thanks Link to comment Share on other sites More sharing options...
donperry Posted February 5, 2011 Share Posted February 5, 2011 (edited) ahm, the thread title is misspelled great posts tho Edited February 5, 2011 by donperry Link to comment Share on other sites More sharing options...
Ralph Posted February 6, 2011 Share Posted February 6, 2011 (edited) still getting catos ? Edited February 6, 2011 by Ralph Link to comment Share on other sites More sharing options...
ChrisNZ Posted February 6, 2011 Share Posted February 6, 2011 Blackmatch has worked a treat for me. I usually use enough to fill the core plus another 5-10 inches depending on the size of the rocket. I'm launching 6:3:1 BP rockets though, never had any luck with sugar/etc. But yes, black match for sure. Link to comment Share on other sites More sharing options...
donperry Posted March 8, 2011 Share Posted March 8, 2011 What else can cause a cato? I know of the nozzle being too small is a common one, but what about inconsistencies while ramming.I just read a post where the poster was saying that those that are pressed are less likely to CATO than those that are hammered. anyone care to explain? Link to comment Share on other sites More sharing options...
dagabu Posted March 8, 2011 Share Posted March 8, 2011 I can tell you what others have said and what I have experienced though I have no empirical evidence that one bit of it true When hammering the fuel, the surface of the increment receives most of the pressure and sends shock waves down the grain causing the fuel to align better. I am also told that the best you can hope for is the equivalent to 2000 PSI on the comp with hammering while pressing to 9000 PSI (or loading pressure) makes a firmer and cohesive grain. So that with hammering, the grain has a bunch of hard to soft layers in the grain and the pressed rocket has a grain closer to one density. The "soft" parts of the fuel grain dont bond so well to the hard parts and cracks form on lift off from the pressure and it CATOs. To get consistent motors, I use just enough fuel to make an increment 1/2 the ID of the rocket motor. A 3# rocket gets a 1/2" increment and a 1# rocket motor gets a 3/8" increment. The best way to test this theroy is to pound a motor using one ID increments and then cut the case off, pull the fuel grain out and break it. Look where it breaks. Then use an awl and scratch it down the length, see where the awl really digs in and where it rides on the surface? The other problem I see personally (besides the nozzle) is the tube wrinkling accordion style. When the fuel starts to burn and the thrust is at its peak, the tube straightens out causing cracks and blows the tube. Link to comment Share on other sites More sharing options...
donperry Posted March 8, 2011 Share Posted March 8, 2011 (edited) That hard and soft spots does make irregular burn rate and maybe irregular pressure. Would it be better then to say use enough fuel to make less than or equal to half the ID? We could even test the theory with clay or dirt and observe the irregularities. <from paper made tube> Edited March 8, 2011 by donperry Link to comment Share on other sites More sharing options...
dagabu Posted March 8, 2011 Share Posted March 8, 2011 That hard and soft spots does make irregular burn rate and maybe irregular pressure. Would it be better then to say use enough fuel to make less than or equal to half the ID? We could even test the theory with clay or dirt and observe the irregularities. <from paper made tube> I would think that the theory would be repeatable with other materials but why? BP in infinitely reusable, grind it down and re-press. Yes, the smaller the increments, the better. It would lessen the pressure needed as well but economy is also a desirable trait and the more pressings it takes to make a motor the less motors you are able to press. Link to comment Share on other sites More sharing options...
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