Ok, here's the mod -- using stock, inexpensive McMaster stainless steel bead chain.
http://www.mcmaster.com/nav/enter.asp?partnum=3606T19&pagenum=1389http://www.mcmaster.com/nav/enter.asp?partnum=3606T33&pagenum=1389
Here's what I'd suggest for installing in a narrow spout, like the Hario. Bend the end coupling as indicated above-right, so that its width slightly exceeds the ID of the spout you're installing in. Press the piece into your spout, relying on the springiness of the thing to hold it in place. Other methods come to mind.
Based on
B|J's dimensions, this piece may work well with the Hario. I'll send some o' this stuff to 'im for assessment.
The mod does two things. First, it helps the user direct the water with more precision, because the "final control point" can be lowered directly into the dripper, and is independent (with infinite degrees of freedom) of the water pot's orientation. Gravity ensures a consistent, perfectly vertical water path. Second, it both reduces and renders more consistent the water's pour velocity by bridging the distance between spout and grind with a water path that slows flow by introducing turbulence and drag, giving the water a "terminal velocity" independent of chain length. For fun, I poured water down a two foot length of this chain, and noted satisfying latency with typical pourover pour rates.
It might also be considered a feature that this mod still allows for a faster pour when, during brewing, it's desirable -- something not true of the otherwise salutary "stuff the bamboo skewers into the spout" approach. Note in the last photo, though, that this technique does obstruct flow somewhat when installed as indicated in tubular spouts -- perhaps a happy median.
It works pretty well. There's an optimal length for the chain, but I don't know what it is yet. I'm sure it will vary depending on equipment used and technique preferences. If it's too long, abrupt pot motion (steady, there!) can induce mild swinging action -- though the water flow quickly dampens such motion (awesome pun). It doesn't occur if your hand's steady. I suspect the end connector/cotter pin connection provides more free-swinging potential than the chain linkages themselves, so I'll likely anchor this thing back in the spout a ways with a stainless screw, obviating the cotter pin and eliminating that swing point. It will also create a bit of an arc in the chain, better paired with pour trajectory.
I've considered installing a stainless washer at the low end of the chain (as a kind of "landing pad"), to disperse the water at
lowno velocity. There's some playtime yet to have with this.
