Complementing the wheel will be an artificial (but hopefully natural looking) stream. While it is intuitively obvious that a natural stream does not power our wheel, the mind has a way of ignoring the obvious and blissfully contemplates an old gristmill grinding corn in the Ozarks. Let us be practical: very few plants in our garden are indigenous but our instincts find them beautiful none-the-less.
The Water Wheel
Perhaps the most seductive sound in a garden is the gurgle of running water. Water features come in many varieties but for me, the motion of a giant water wheel is hypnotic. The Lookout project (see Project List) upon completion literally cried out for an attached wheel. The scale of the Lookout called for a minimum wheel diameter of 8 feet.
My wheel needed to match the feel of the Lookout - - substantial and sturdy, if not overbuilt (for strength and longevity). The first decision is how many spokes? Some designs consist of four, more common is eight, but mine would have twelve. As with any design, a compatible ratio of functionality and aesthetic beauty is the goal. My spokes called for some soft arcs with accents to draw the eye. A little trigonometry is required to make the angle cuts and sizes required to achieve the 8’ diameter wheel. Accuracy is paramount to avoid subsequent wobble and out-of-balance results.
After come-a-longs, ropes, and pulleys lowered the wheel onto a makeshift sled, the tractor and I towed the assembly to the Lookout. The same type rigging secured the wheel in place on its pillow blocks.
To establish a favorable rotation speed, some builders incorporate large friction brakes on the shaft to slow down the action. My wheel uses a more high-tech approach. As the shaft turns, a belt drives a second small wheel with equally spaced sensing screws around its circumference. A tachometer counts the screws as they rotate and interprets the RPM of the wheel. If the RPM falls below an acceptable speed, additional water is metered out to bring the wheel back to the set point. Thereafter, reducing the water flow allows it to slow back down. The result: a nice slow and constant rotation.
The next decision is the number of blades which catch the water. The more blades, the greater the weight of water to turn the wheel, and the smoother the wheel will rotate. My wheel has 36 blades. The thickness of the wheel should be in proportion to its diameter; 17” wide seemed to be about right. 2 x 12 boards establish the sidewalls and dictate the depth of the blade cavities.
A big wheel like this is heavy, perhaps 400 pounds. The axle must be strong enough to carry the weight without deflection. My axle is 2” in diameter x 4’ long supported by sturdy pillow block bearings to greatly diminish friction.
Twelve spokes on each side of the wheel are sandwiched at the center with ¼” x 16” round steel plates. A special set of hubs lock the wheel to the axle. Threaded rods tie all the plates together to maintain the wheel width.
Additional spokes of copper tubing in the interior of the wheel and wire rope on the outer circumference were my idea of aesthetic beauty. Neither provides any functional support to the wheel.