With my limited success with non-metal casings and my recent influx of cob casings I decided to try using chopped match heads as the filler for cobs because I know other people have gotten it to work.
After the failure of the first one I made at the 2002 party using two part epoxy to seal the fuse hole I purchased a different two part epoxy paste to try. I made two cobs using whole match heads and two using match heads chopped up a bit. The fuses were then inserted and the paste was spread around the opening and left to dry.
The devices with the paste tube:
Testing:
My test chamber was dismantled so I used an old Class C aerial shell mortar buried in the dirt. The cobs were dropped in after being lit, and dirt was piled over the whole thing quickly. All four failed to explode, the recovered casings showed everything went out the fuse hole, with some (probably most) match heads remaining inside the casing. This wasn't very exciting, so I got one of my last two cobs that had the last of my decent powder in it. This one blew apart the tube very nicely and the casing fragmented, while the others failed to do any damage at all. There was no noticeable difference in the chopped match heads and the whole ones.
Damaged tube with three of the cob casings:
This time I made four cobs again using whole match heads. Two were fused similarly to the last four, but the fuse holes were sealed better. The next two had fuse holes drilled in the side, M-80 style. They were filled, glued, then fused.
Match cobs #2:
Testing #2:
The cobs were tested the same way as last time, in a buried tube. The end fused ones again failed, just shooting out the fuse hole. The first side fused cob blew the tube in half, but not nearly as well as the bottle rocket powder cob from the previous day. The casing was still in one piece, split open. I got a new tube, and the next cob did the same thing, blowing the tube in half and the casing in one piece, split down the middle. Definitely an improvement over the last few!
Blown open tube with cob casing:
Conclusions:
I know other people have gotten match head cobs to work fine with normal fusing so maybe my glue isn't good enough. The side fused ones work well however, so I'm happy with that. The next tests will use bottom fused cobs to hopefully get more power/noise and avoid the awkward shape of side fused devices.
The next tests were with two end fused cobs filled with whole match heads. A hole was drilled in the bottom for the fuse and then taped over to fill the casing through the top, which has to be drilled out a bit also to fit the match heads inside. Once the casings were full, the opening on the top was sealed with the same expoxy paste used in all the other tests on this page. Once that was dry they were fused, and the fuses glued in place.
The two bottom fused devices:
Testing #3:
The first cob was tested the same way as all the others, inside a cardboard shell tube underground. It worked as intended, and the damage to the blown apart tube looks better than that caused by the side fused cobs.
End fused cob #1:
The next cob was a bit different. I decided to put it in something other than a shell tube because I'd seen enough of those blown apart by now. I put it in a small metal container, lit the fuse and buried it. The fuse was pointing up (same as the last test) with the epoxied-shut opening pointing down. The cob shot up into the air a couple feet through the 8 inches or so of soft dirt and landed nearby. The casing showed that it blew out the sealed opening rather than bursting the container like the last one.
End fused cob #2:
Conclusions:
The first one worked perfectly, so I'm not sure why the next one didn't. Perhaps it was not glued as well, but they seemed pretty similar when I made them. I will test this design a bit more and decide between this or side fused.
Four match head filled cobs were made this time, two bottom fused using the same glue as all the others, and two fused normally with a new glue I got called "Fast Steel". Both Bottom fused cobs shot out the end like the 2nd bottom fused test (above). Both normal-fused with the new glue shot out the end as well.
Conclusions:
Looks like I'll be sticking with the side fused design...