OT. WAY OT, Engineering Problem. Need some help Options

[jfort]

My son and I have a real problem and we need some help. My son is a licensed blaster. He has been asked to stimulate oil wells with dynamite. I am trying to help him. In short, we will fabricate a "torpedo." Currently, we are thinking of using a 5' length of 1.5" PVC with the down end made into a point. The torpedo will be filled with 2 sticks of dynamite and filled with as dense a sand/gravel as we can find. It will be dropped down a 5" pipe filled with water. It is estimated that it is 640' to the bottom. Can you help me calculate how long it will take the torpedo to reach the bottom? (We need to make sure it gets to the bottom before the fuse ignites the dynamite!!) I am sure the efficiency through the water, drag, is an important and not known for sure variable, but perhaps there is a range that would get us close enough.

Any guidance or leads would be most appreciated.

[hcdmueller]

Why not use commercially available shock tube as your line? The shock tube has a pretty high tensile strength. If you are nervous about that you could dual prime and just zip tie or tape the two strands shock tube together.(I recommend this for the redundancy) With a little bit of testing you can determine if the shock tube will support the weight or if you need a separate line to reinforce the setup. The reels of shock tube can be bought already setup with a cap.

There is no depth limitation on the cap it if is sealed in the torpedo device you are making. Just make sure that the the torpedo is sealed properly.

I am glad you decided to avoid the det cord as it can act funny if to much tensile stress is placed on it over a long distance possibly causing misfires.

I would actually recommend against using the time fuse as it has a tendency to burn differently in a confined space. The pressures that it will be exposed to at 640' can also have an effect on burn time.