Hey everyone, before I say anything let me just tell you that during all of these "launches" I was in a rural area far away from anyone, and I took the proper safety precautions to make sure nobody could get hurt. I recognize that the line between rocket motors and bombs is very thin and I have been very careful to not endanger anything or anyone.
About 8 months ago I took an interest in rocketry and wanted to make my own rocket from the ground up. Starting with the motor, I decided that following Grant Thompson's sugar rocket tutorials would be a great and easy way to start. These motors use R-Candy as a propellant, packed clay for an end cap, and 3/4" PVC for a body. I closely followed the tutorial and the first test launch worked flawlessly. I made a couple more after those worked just as well. Then I launched my first homemade rocket and it worked perfectly! After that I decided to try adding in an ejection charge for a parachute, but then the rocket motor end cap gave out. After that, I went back to testing a couple motors with no ejection charge and got varying results, but most just giving out and doing the same thing. I got frustrated and gave it a rest for a little while since I got bored. Recently I have got back into it and started taking things a little more serious. I have made over 10 motors, doing different things for each of them. I scored the inside of the PVC to give the clay end cap a better grip, I packed the powders harder, and softer. Regardless, all of the motor's end caps gave out every time. Yesterday, I decided that clay would just not cut it. I purchased some PVC caps and PVC cement to cap the ends of the motors after I put the clay in. I drilled in a 7/32" hole in the clay and PVC cap to make the nozzle, and drilled all the way into the propellant to give the rocket a core (like I always have). When I test launched the motor, it went about 20 to 30 feet, then completely exploded, meaning I accidentally made a pipe bomb instead of a rocket motor. I used SCH 40 PVC which is rated for 480 PSI. Could someone please tell me how this could happen? I thought for sure that a 7/32" nozzle would allow the exhaust to escape quick enough not to surpass 480 PSI. I also don't know how it could have worked in the past with only clay, yet now the PVC can't even withstand the pressure.
P.S. I know using PVC for rocket motors is frowned upon, but I'm just trying to get the hang of things before I come up with my own designs.
Edited by loganater, 21 July 2018 - 07:20 PM.