8.5 Mill Spillway

The Weldon Mill water wheel inspired me to take a crack at an effect I've wanted to try since practically forever. I'd wanted to make an animated waterfall around 75-100 N Scale feet tall, but that's obviously not an option for a layout of this size. The spillway is essentially a 16 N Scale-foot-tall waterfall.

This little project, which I began on 3 September 2020, was an interesting challenge. At first I built a complex device based on the principles I'd devised for a 100-footer. It didn't work. I tried a few variations on that theme. They didn't work. Ultimately what did work was unexpectedly simple—the KISS principle to the rescue. But although the mechanism is quite simple—particularly when compared to the original design—it still took many tries at every step of the way to achieve success. Nothing I did worked the first time.

First, I made a frame from ⅛-inch sheet styrene. I drilled the sides for roller bearings that press-fit in place. Then I sandwiched a drum made of 1" PVC pipe in between a fender washer and a gear, on a ¼-20 bolt. Because the PVC pipe is smooth and slippery, I created a rubberized surface by bonding lengths of elastic band to it with CA.

Next came the profile plate. This part serves three purposes: it shapes the water belt to the trajectory of the falling water; it has a graphic that shows through the belt to simulate the increase in the volume of white water as it descends; and it also provides spring tension on the water belt to keep it tight against the drum. I made it from 0.020" sheet styrene bent roughly to a parabolic shape. I created a graphic of fuzzy, irregular tapered streaks and printed on label material, then laminated it with clear plastic to protect the image and provide a smooth surface on which the water belt can slide.

The sharply-curved end of the profile plate simply rests on a styrene tube installed across the top of the frame; a pair of retaining blocks behind the tube hold the profile plate in place with no need to bond it to anything.

The water belt is simply clear Scotch tape wrapped around the drum and profile plate about 6-8 times, with the adhesive facing outward. This was the single most difficult step: I made probably a couple dozen belts before I got one of the right size with a minimum number of blemishes. Once that challenge was met, I installed the geared drive motor, and with the motor running, I dry-brushed on thin, irregular lines of white acrylic paint as the belt moved.

I then applied thin, wispy tendrils of fiber (plain old pill bottle cotton). It's surprising how little was required, because its purpose is to simulate mist, not water; indeed, I removed most of what I'd initially applied. Finally I sprayed the water belt with clear fixative, again with the motor running, to hold the cotton securely in place and to help keep it clean (a trick I learned when I was making static waterfalls back in 1975), as well as to seal up any remaining exposed tape adhesive.

I completed the effect on 5 September 2020.

The final step was to fabricate the stone walls on the sides, which I made from old Chooch castings. Using a paper template, I carefully cut the parts to fit the shape of the falls. (The odd shape of the piece below right provided extra stone that would be trimmed back prior to installation.) I sanded the edges facing the fibers until they were silky smooth to prevent snagging, and after painting and weathering, I sprayed these areas with clear gloss both to make them look wet and to further smooth the surfaces. To avoid any surprises, I permanently installed the stone parts on the frame while the waterfall was running.

Then I made a pile of talus rubble at the base of the falls, bonding the rocks in place individually with CA, followed by generous amounts of gloss medium tinted lightly with acrylic white paint for a translucent effect. The last detail on the talus pile was a tiny strip of wispy cotton glued to the top edge of the talus pile to help blend it into the descending water.

The final touch was a temporary threshold, until such time as the upper waterway gets modeled. It's just a piece of plastic baggie with a tattered edge laminated to a thin piece of black styrene with a similar tattered edge. The tattered plastic baggie conforms to the irregular water flowing under it, adding tiny changing glints, and also makes the black styrene look super-glossy.

The unit is ready for installation.


Originally I was going to make a fairly large spillway based on Taylor Mill in Derry, New Hampshire (top) but shaped like the second image above. However, the proximity of the firefly meadow forced me to go much smaller, which was fine by me because it provided the opportunity to make the spillway more rustic, and the discharge more waterfall-like.

I also made sure to gather some stone wall references. Note the moss growing near the wet areas, and how wet talus is nearly black.

Environmental Sound

As with the cricket sounds that will accompany the fireflies, it was only natural to provide rushing water sounds for the spillway. Once again, my work with the jazz music for Phil's led me to some very economical MP3 players, which will allow me to select my own water sounds to play. The sound has a secondary purpose: to help mask the noise from the motor drive, which is pretty substantial. I'll install the speaker directly behind the falls.

Also See...

"How to build a waterfall," Model Railroader magazine, December 1975, p. 81.

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