Erbschaft/Nahrung – successful proof of concept of Thermo-Kinetic principles

When my grandparents (mother’s side) sold their farm near Delhi Ontario, I rescued two wagon shafts that no-one else wanted. I’ve been moving them ever since. It’s been several decades. They represent the agricultural side of my heritage.

My father was a talented musician, maker of fine stringed instruments, and a Tool & Die maker. I worked with him for five years, most Wednesday mornings, learning the basics of making violins.

This sculpture brings those two quite different concepts together. The base is made from 5 45 mm thick Maple slabs, laminated from 2 or 3 boards each. It is in the general form of a fiddle. The shafts appear to have never been used. They are probably Oak. The right shaft is fixed, the left one is hinged at the bolt. The Acrylic rod is fixed at the right and mounted on the left shaft as a short Class III lever. The incised crest in the middle is that of the Danube-Swabian cultural community.

Although a sculptural representation of heritage is a worthy project in its own right, adding movement to it increases daily value. As a thermo-kinetic sculpture, movement of the parts relative to each other can be read as a rough guide to ambient temperature.

Acrylic has in the range of 9 times the thermal expansion co-efficient of wood. As temperatures change, the Acrylic rod will expand and contract more than the wood base. This causes the left shaft to shift left and right. Since the length change is very small, the lever ratio is as high as practical. The end result is that the top of the left shaft shifts about 1 mm per degree Celsius temperature change. It’s a small change, but visible even from a distance.

All parts are coated with two coats of brushed on epoxy. This should provide environmental protection.

The weight is a 50 mm Acrylic cylinder filled with epoxy. It masses about 1 kg. The base is made from off-cuts of two of the slabs. From the ends it looks slightly like horse collars.

The sculpture is 2.65 m from ground to top, about 900 mm in width, and 600 mm in depth. I don’t know the mass, but it takes two people to move.

The name “Erbschaft/Nahrung” means “Heritage/Sustenance”.

The base is made of 5 slabs of Hard Maple, each 45 mm thick. They were individually machined on my CanCam D23 CNC machine, which has a bed capacity of 600 x 900 mm. The Donauschwaben crest was engraved using the “Project toolpath onto 3D Model” function in Vectric Aspire.

The actuator arm is an Acrylic rod. It turns out that Acrylic has three times the thermal expansion coefficient of aluminum, about 9 times that of wood. It is attached to the left shaft in a Class III lever configuration. The movement at the top of the shaft is about 1 mm per Celsius degree.

The full build process can be found here.

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