Di2 is Shimano’s electronic gear-changing system for mountain bikes. It’s a rear derailleur that uses battery power to move the chain between gears. The battery pops out for recharging, which presents a potential problem for the forgetful. Imagine loading your bike up, driving out to your trail of the day, then finding that the battery is sitting in the charger in your garage. To prevent this situation, cyclist and 3D printing enthusiast Chris Heerschap (whose work we looked at here) designed this dummy battery and reminder flag for the Di2: “The dummy battery is geometrically identical to the Shimano battery, but also has a flexible leash with an attention flag which hangs outside the derailleur to help you remember that there is no battery installed. “Having a dummy battery also helps to maintain the water resistance of the derailleur, since the battery is part of the derailleur’s water proofing. This way if you remove the battery from the bike but then want to wash the bike, this dummy will help keep the derailleur water resistant.” I find these kinds of mnemonic devices interesting as a design category. You also might call it idiot-proofing, and it makes me think of a common problem in the tractor-owner community. Modern tractors come with a ROPS (rollover protection system), essentially a tall roll bar. These roll bars are typically taller than the average American garage opening. This means you have to remember to fold the ROPS down before you try driving into the garage. More than a few owners have forgotten the ROPS is up, and damaged their garage doors or headers. Some people hang signs that they can’t miss… …while others attach brightly-colored flags to their ROPS. After the pull out of the garage and set the ROPS up, they remove the flags and hang them from the garage door. While there’s no official name for this category of mnemonic, idiot-proofing design, there is a close companion in the engineering world. The Japanese call it poka-yoke, which loosely translates as mistake-proofing. An example of this are cables that have shaped connectors, so that you cannot insert them upside down.
If you had to name this category, what would you call it?
Poka-Yoke: Idiot-Proof Design
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