<aside> đźš© Inversion is a classic technique to solve design problems that involves exchanges functions and behaviours between conventional systems or components.
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This method is typically used when trying to innovate by changing existent classes of interventions.
An inverted design is one in which key functions or behaviours have been “inverted” or swapped between systems or components of existing designs. Sometimes, the result of such inversions produce significantly innovative new interventions, especially when existing designs are based on well established embodiments, assemblies, and systems.
Consider a simple wood saw (which was invented before the meat saw). In operation, the wood is held still, and the saw is passed over it to cut it. Both the horizontal and vertical motions of the saw relative to the wood are carried out by the saw.
In a butcher's meat saw, on the other hand, the meat is held on a tray and passed by a fast-spinning, but stationary, rotary saw. In this case, the horizontal motion is performed by the saw, but the vertical motion is performed by the meat.
That is, for the wood saw, the saw moves through the wood which remains stationary. For the meat saw, on the other hand, the meat moves while the blade remains stationary.
The exchange of the vertical movement between two main components of the saw systems is a classic example of design by inversion.
A common wood saw (Wikimedia Commons).
Typical electric butcher’s saw / food slicer. (source)
<aside> đź’ˇ Exercise for the reader:Â What are the benefits of this design inversion?
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Originally, manual typewriters had hammer-like keys that sat in a stationary cradle. The “carriage” moved both horizontally (to move from one character to the next in a line of text) and vertically (to move from one line of text to the other).
However, as typists became more proficient, they were able to type faster than the manual hammer keys could respond. The keys would strike one another often as a result, and get stuck. Furthermore, the carriages of manual typewriters were large and heavy and required significant human effort to reset to the start of the line (”carriage return”) and advance to the next line (”line feed”).
The IBM Selectric typewriter was one of the greatest typewriter innovations, by merit of the application of design by inversion. In this case, the horizontal component of movement was transferred from the carriage to the keys.
A typical manual typewriter. (Wikimedia Commons)
An IBM Selectric typewriter. (Wikimedia Commons)
This was made possible by the development and use of lightweight plastics to form a ball, on which the various characters were embossed. Pressing a key on the keyboard caused the ball to rotate and align the correct character with the ribbon and paper on the carriage. The ball then struck the paper through the ribbon (just as a manual typewriter would) to leave an imprint on the paper. The ball could execute this action about 10 times faster than a manual hammer could.
As a result, typists could type nearly twice as fast, while making fewer mistakes, and having to exert themselves less both physically and mentally.
<aside> đź’ˇ Exercise for the reader: What other technologies were needed to let the Selectric succeed? What other specific benefits accrued to users as a result?
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The embodiment of a movable “print head” in the Selectric typewriter also became an essential aspect of virtually every computer printer made subsequently.
A long time ago, brakes for trucks and other heavy vehicles were normally released and depressing the brake pedal engaged them, just as in automobiles.
This is obvious and intuitive.
However, there was a problem: when the brakes failed, the vehicles would lose control. Imagine a truck on a highway being unable to stop for a traffic jam as a result of brake failure.
The solution, still in use today, was to invert the problem. In modern braking systems for heavy vehicles, the brakes are engaged unless the engine is running and all pressure sensors indicate nominal operation. In this case, when the vehicle is operating normally, the brakes are forced to release by a hydraulic or pneumatic mechanism. If there is a failure of the braking system, then the brakes will automatically engage, stopping the vehicle.
In this case, the inversion is functional. The function of the old braking system was to be off unless engaged by the driver; the function of the new braking system is to be on unless released by the driver (in combination with the brake sensors and engine).
