Thought I might expand upon my post about the area around the feeder hole being so important - as perhaps some of the 'experimenters' on the forum might be interested in this one ?
A few years ago I had a crazy(?) idea to solve the problem of starvation, when a cluster dies even with stores available within a few inches - this being due to them being too cold to break cluster to move onto those fresh stores. My idea being to 'inject' a permanently available supply of sugar syrup directly into the cluster, so that they could draw upon it as needed, without having to move during extremely cold weather.
The device I dreamt-up was an inverted jar feeder fitted with a tube extending downwards several inches into to a centralised area between combs where the winter cluster was likely to form. Here's a photograph of the device I made (ignore the shrink-wrap for now):
But - when the jar was inverted, water (being used for trials) came pouring out of the tube without any hesitation. Hmmm. My 'knee-jerk reaction' to this was to assume that the hole was too big, and so shrink-wrapped a short length of capillary tube to the end of the wide-bore tube. But - even now - with a hole of some 0.5mm diameter, the water still kept jetting out. Then it would stop, bubbles could then be seen rising inside the jar, and again a fine jet of water was produced. This sequence continued until the jar was empty.
At this point, I stopped 'shooting from the hip', and sat down to figure out the principle involved. Having established that a 'suspended drop' was fundamental to the mechanism, I added a small washer to the end of the capillary tube in order to provide a flat surface around the hole, in order that the drop could become suspended there:
Mystery solved - this then worked like a charm. But - whether supplying syrup like this to a winter cluster is in reality a practicable idea ... well, I'll leave that to others to play with. British winters really aren't severe enough to give this idea a reasonable trial.
LJ