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.

[davep]

I believe that terminal velocity will be reached quickly enough that once that is calculated it should be used for the entire fall. The pipe diameter is sufficiently large that the "torpedo" should not experience undue drag (some yes). I'd add vanes to try and give the "torpedo" some spin.

650 feet of magnesium wire might make a good fuse.

You could do a test prior to the actual blast. Attach 100 feet of wire, and let it drop (with a dummy warhead of the same mass/density). Time the 100 foot fall for each ten feet. If the rate of decent becomes constant, then use that rate. Retrieve the dummy.

[Todd Enlund]

The pipe diameter is sufficiently large that the "torpedo" should not experience undue drag (some yes).

I agree, but the pipe diameter is sufficiently small that there will be friction every time that the "torpedo" hits the tube. In 640 feet of production tubing, there will be 19 joints that the "torpedo" could hang up on. Not likely, but possible.

I'd add vanes to try and give the "torpedo" some spin.

I'm not sure what you'd gain. I don't think it would add sufficient stability to prevent the "torpedo" from hitting the sides, but it would provide additional points to foul the "torpedo".


The consequence of premature detonation is probably ruptured production tubing, and would pose a problem...


I still agree with Gary. I'd be testing my ass off.