Rain lamp parts

Fiber

General

Left: Top ends of the strands. Right: Bottom ends of the strands.

Thickness

TJ reports that his rain lamp uses 30 pound test eagle claw clear fishing line, which can be obtained at Wal-Mart. I measured one of the strands on a new Wal-Mart rain lamp with a micrometer and found the diameter to be 0.022 inches, which corresponds exactly to the 30-pound fishing line that TJ mentioned. However, my own rain lamp uses 40 pound fishing line, according to a micrometer measurement I made on that. Possibly larger rain lamps use thicker fishing lines. At any rate, clearly the typical range of rain lamp fibers is 30-pound to 40-pound fishing line.

Both the Wal-Mart store and the shopping mall sports store I visited carried no higher than 30 pound line. I had to go to a boating/marine supply store to find lines up to 50 pound. Here is a summary table of the line weights I saw at the boating supply store (12-26-05).

One spool should provide far more than enough length for a single lamp. I calculated my 32-strand rain lamp to have a fiber length of only 12.8 yards, and even the shortest line length in the above table is about 30 times that long.

I definitively determined the size of fishing line on my rain lamp by using an inexpensive micrometer I bought at a pawn shop. (New micrometers cost about $25.) Just place a dry strand into the gap on the micrometer, and screw the micrometer's bar closed.

The fishing line thickness can be measured by a micrometer clamped to the line.

As you can see in the photograph below, the reading fell between 24 and 25, which means between 24/1000 and 25/1000 inches, or .024 and .025 inches. Refering to the fishing line chart above, note that .024 inches is the diameter of 40 pound fishing line, which would be the size of fishing line my rain lamp would need as a replacement.

Closeups of the clamped line and the micrometer reading (24/1000ths of an inch).

Number of strands

Other

I've never seen or heard of a rain lamp with a fiber that wasn't made of clear nylon, but in theory I would think metal wires would work. In fact, metal would introduce some interesting possibilities for rain lamps, such as for allowing vibrations (for a musical instrument?), electricity flow (maybe for electrically-trigged fluorescent mineral oil?), sensors to measure drip rate, or maybe other uses and effects.

Weave patterns

Of course you could make any weave pattern you wanted, including some very exotic ones. With a completely free hand in rain lamp design, some exotic variations might be: cylinders with "waists" like in Disneyland's rain lamp, cylinders with wavy cylinder "surfaces," flat sheets (planes) instead of cylinders, intersecting planes (that pass through each other), intersecting waisted cylinders, strands running through a hole in the centerpiece, multiple shelves within the cage area with each shelf dispensing oil separately, multiple layers via multiple concentric circles of holes, no centerpiece at all and a plane of holes instead of a circle of holes, stiff molded strands in helical patterns, strands that cross and touch, strands that split and/or merge, strands with tapered diameters so that the droplets change speed in certain regions, motorized templates that slowly modify the fiber configuration, strands whose bottoms aren't fastened and can swing freely, strands strung with different tensions that can be played (with gloves!?) like a harp, etc.

Some rain lamps come with weave patterns that are vertical.

Since the strands are usually clear and could basically function as fiber optic cables, this leaves open a lot of theoretical lighting possibilities, too, such as each stand having a different colored light, or the colors slowly changing across all the strands, or small cuts in the strands to cause points of light to occur at strategic locations. Like haiku poems, just a few parameters in a simple system can lead to a world of wonderful variations. The possibilities for rain lamps have barely begun to be explored.

Spouts

Spouts, dry.

Spouts, dripping.

The tops of the spouts look like rivets.

My guess is that these spouts are custom-made for rain lamps, and would be very difficult to replace, without butchering another rain lamp. There is an extremely large number of commercial nozzles available for every purpose, but I believe it would be very difficult to locate exactly this type and size of nozzle, and it would also be difficult to machine one from scratch. Since there are only about four fishing line sizes available, nozzle diameter is the most critical dimension in the entire rain lamp for correct functioning. Therefore be careful not to lose any of the spouts!

Spout channel diameter

The known, directly measurable diameters are:

• diameter of 40-pound fishing line = 0.024 inches
  
• diameter of the outside of the spout = 0.120 inches
  

Idealized cross section of a spout with a strand of 40-pound fishing line inside.

Note that the outer spout diameter is exactly 5 times the fishing line diameter, i.e., 0.120 / 0.024 = 5.00. Therefore exactly five 40-pound fishing line diameters will span the length equivalent to the outside diameter of a spout. The above measurements also mean that a second fishing line, even 40-pound or 50-pound, can easily share the same spout as the first line.

Since I lacked extremely small calipers (do they even exist?), the only easy way I could determine the approximate size of the mineral oil passage was to insert shafts of different diameters into the bottom of a spout to see which shafts would fit inside. The results of these experiments are shown below.

These experiments narrow down the size fairly closely. The remaining passage diameter must be in the range of 0.063 to 0.067 inches, or 0.065 +- 0.002 inches.
This implies the diameter of the spout channel when empty is 0.089 +- .002 inches, or a range of 0.087 to 0.091 inches. If this channel corresponds to a common drill bit size, then a number in the above range should match one of the following sizes.

Unfortunately, there is no common drill bit size that falls within the range of my calculated inner spout diameter. The closest common drill bit size is 3/32 inches. This adds credence to my theory that these spouts were custom made for rain lamps.