make a needle valve

[Ayay]

This uses a stainless bicycle spoke, 6mm copper tubing or a 'T' piece, and a bit of soldering with tin solder or silver brazing alloy.

needle valve design.jpg

Points to note:
There is no seal except for the threads at the top. A watertight seal is not essential as long as the brass nut is above the head; that is the highest level that the liquid can dam up to. In a reflux still it would be the level of the reflux outlet, and in a pot still it is the level in the lye arm where liquid runs back into the still if the valve is closed. (In case you want a valve in a pot still that is?)The height 'H' can be lengthened to get more head.

The outlet hole where the needle seats into must be a little smaller than the diameter of the needle. A standard bicycle spoke is 2.0mm, so the outlet hole needs to be 1.8mm. I think there are thicker spokes available for bikes, and even motorcycle spokes, so a bigger outlet hole can be used. I have found that a 1.8mm hole is enough for a steady dribble, I guess about 2 Litres per hour max - no promises though!

The needle point does not have to line up perfectly with the hole that it seats into - as long as you never open it far enough for the tip to get out of the hole, it will find it's way back in when you close it again. The length of spoke is springy and flexible.

The 'T' piece or tap handle at the top of the spoke must be soldered on to the threaded end. Careful to not let the solder run too far down the threads. If tin soldering eg with a soldering iron, the handle can be thicker so that a small hole can be drilled for the spoke end to fit into.

I have made a needle valve that uses the principles of the above design, but it is built into an existing bigger tap as a tap within a tap. Pics here: http://homedistiller.org/forum/viewtopi ... 3#p6772593