I remember hearing this story but not remembering the source. If you happen to have a source, I’d appreciate if you could send it.

In the middle of the twentieth century, electric high speed rail was spreading after the initial success in Japan’s Tōkaidō Shinkansen, the first high speed rail system. In a new installation, based on plans from the Japanese’s design, construction was almost done and testing was in progress. The engineers were concerned with some vibrations they were noticing from the overhead catenaries; as the test train went faster along the track, resonant vibrations from the catenary rubbing along the pantograph, leading to unusual wear.

When the engineers asked for documentation to see how the catenary supports were constructed, there was no useful documentation besides the spacing between poles; the engineers had build their poles exactly to these spacings. The engineers did an on site inspection, and to their horror the catenary supports were varying by inches. To them, the lack of precision and repeatability was a flaw.

In their testing, the engineers found out that the imprecision and the subsequent variations in catenary position naturally dampened the vibration through the randomness, instead of resonating due to precise harmonics being met. A consultant they talked to in this process said to “Go hit each support with a hammer,” as a solution to their problem. Eventually the engineers relaxed their standards in order to get more variation.