I have another thread going about this but thought those in the Mech Eng field might want to figure this one out.
I was doing an ejection ground test and used too much powder. The tube is2.6" diameter and only 10.5" long and has about 5.5" of it used by e-bay and nose cone. The chute and cord take up the rest. So overstuffed is an understatement. .5 grams of BP did not do the job so the hammer mechanic in me said use more. I used 1 gram. Yes I know that is too much and told my son we would blow it out or blow it up. I did both. Chute came out like a champ. Tube blew out as well.
I have the tube drilled for 2 sheer pins but only used one. I usually only use one but drill two for symmetry just in case I need two. During the test the tube failed. Paper tube that is. The nose cone contains a brass shim to help cut the sheer pin(s).
Looking at some crude video it appears the nose cone starts to leave the tube and then the tube fails. Looking at the tube, it appears it failed at the unused sheer pin hole. The tube then tore from there then failed along the wrap.
The top edge of the tube is completely saturated in CA. The holes for the pins are also saturated with CA.
Anyone want to take a guess why it failed at the hole? Or have a mathematically supported reason?
My theory, The pin on the opposite side sheered cleanly. In fact the head is still in the tube and cleanly cut on the inside. When the nose cone ejected past the open hole the pressure found the weak spot in the tube and the tube erupted and the cone and chute and cord continued on their original path.
I was doing an ejection ground test and used too much powder. The tube is2.6" diameter and only 10.5" long and has about 5.5" of it used by e-bay and nose cone. The chute and cord take up the rest. So overstuffed is an understatement. .5 grams of BP did not do the job so the hammer mechanic in me said use more. I used 1 gram. Yes I know that is too much and told my son we would blow it out or blow it up. I did both. Chute came out like a champ. Tube blew out as well.
I have the tube drilled for 2 sheer pins but only used one. I usually only use one but drill two for symmetry just in case I need two. During the test the tube failed. Paper tube that is. The nose cone contains a brass shim to help cut the sheer pin(s).
Looking at some crude video it appears the nose cone starts to leave the tube and then the tube fails. Looking at the tube, it appears it failed at the unused sheer pin hole. The tube then tore from there then failed along the wrap.
The top edge of the tube is completely saturated in CA. The holes for the pins are also saturated with CA.
Anyone want to take a guess why it failed at the hole? Or have a mathematically supported reason?
My theory, The pin on the opposite side sheered cleanly. In fact the head is still in the tube and cleanly cut on the inside. When the nose cone ejected past the open hole the pressure found the weak spot in the tube and the tube erupted and the cone and chute and cord continued on their original path.