patrick_g
Elite Member
HomeBrew2, If the bend is a ways from the end and you fill the tube well past the bend you don't need to do anything to contain the sand. Some prefer damp sand. For really small diameters I think finer sand is better but for larger diameters course sand is OK.
An interesting insight into the behaviour of sand (granular material in general) is to fill a pipe (1/2 inch or 3/4 or ... in diameter and a foot or so in length) nearly full of sand. Cover one end with a piece of freezer foil or Saran Wrap or Kleenex held in place with a rubber band around the pipe. Secure the pipe in a vise or other really secure arrangement with the covered end pointed down and not touching anything.
Now insert a rod (metal prefered as wood may get smashed up too easily) and with a big hammer pound the living daylights out of the dowel to try to force it to shove the sand out of the bottom of the pipe. If you secure the pipe really well (you can weld a couple lumps to the sides so it can't slide through the vise jaws) and the vise is secure and strong you can use a sledge hammer or electric demolition hammer or a 100 ton hydraulic press.
The rod (dowel) should be a fairly close fit to the ID of the pipe. 3/4 rolled steel (hot or cold) fits a 1 inch tupe pretty well. If the rod is too small it will penetrate into the sand too easily instead of pushing the sand (the objective.)
For the arm chair experimenter who has no patience for real experiements... here is the results:
The sand, the pipe, and the dowel (hammer a bit too) gets hot. This accounts for the energy input. You can not push the sand out of the tube. The sand randomizes the applied force and the net result, if you pound it hard enough, is to heat the apparatus significantly and to expand the diameter of the pipe just below the top level of the sand. Some of your downward force, when randomized, is converted to radial, or nearly so, force which shoves out on the tube expanding it. Virtually no force is propagated down the tube through much sand depth which explains why you can "CAP" the end with Kleenex held by a rubber band and not be able to knock it off.
Pat
An interesting insight into the behaviour of sand (granular material in general) is to fill a pipe (1/2 inch or 3/4 or ... in diameter and a foot or so in length) nearly full of sand. Cover one end with a piece of freezer foil or Saran Wrap or Kleenex held in place with a rubber band around the pipe. Secure the pipe in a vise or other really secure arrangement with the covered end pointed down and not touching anything.
Now insert a rod (metal prefered as wood may get smashed up too easily) and with a big hammer pound the living daylights out of the dowel to try to force it to shove the sand out of the bottom of the pipe. If you secure the pipe really well (you can weld a couple lumps to the sides so it can't slide through the vise jaws) and the vise is secure and strong you can use a sledge hammer or electric demolition hammer or a 100 ton hydraulic press.
The rod (dowel) should be a fairly close fit to the ID of the pipe. 3/4 rolled steel (hot or cold) fits a 1 inch tupe pretty well. If the rod is too small it will penetrate into the sand too easily instead of pushing the sand (the objective.)
For the arm chair experimenter who has no patience for real experiements... here is the results:
The sand, the pipe, and the dowel (hammer a bit too) gets hot. This accounts for the energy input. You can not push the sand out of the tube. The sand randomizes the applied force and the net result, if you pound it hard enough, is to heat the apparatus significantly and to expand the diameter of the pipe just below the top level of the sand. Some of your downward force, when randomized, is converted to radial, or nearly so, force which shoves out on the tube expanding it. Virtually no force is propagated down the tube through much sand depth which explains why you can "CAP" the end with Kleenex held by a rubber band and not be able to knock it off.
Pat
