4 Engineers Share Their Biggest Mistakes on the Job

When people ask me what it’s like working in a modern design office compared to the bygone days, I like to tell them that with computer-aided design (CAD) techniques, we can screw things up forty times faster than we could with a pencil. What used to take months of persistence and attention to detail can now be botched almost instantaneously.

People make mistakes, but when engineers make mistakes someone, somewhere is going to have to write a check. That’s why it is so rare to hear them discuss their blunders as candidly as they have in this thread from the AskEngineers subreddit.

I’ve chosen three of my favorites and thrown in one of my own at the end just for completeness.

Enjoy.

1. “I shut down the world’s largest diamond mine.”

Reddit user eskimoboytim shared a deliberately vague story about the cutting power to (presumably) Jubilee a.k.a., the Yubileyny diamond mine in Russia, which is the biggest diamond mine in the world.

I shut down the world's largest diamond mine (cut off the power) for about 45 minutes. While I do take responsibility, I was set up to fail. Actually, kind of an impressive now that think about it. So, I'm a field service engineer, and our company was asked to assist with commissioning. We didn't do any design work, we just provided hardware. Thing is when I showed up, I found that all the wiring was %$#@d. They had literally copy and pasted from another site, and it was totally wrong.
I had to attempt to redesign their whole system in two days as that was their outage time frame. I didn't finish, but they insisted on starting anyway. I warned them that we would be testing their black start capabilities. Thankfully black start worked.

That is the short story. Sorry the vagueness, would rather not give too many details.

2. “It changed cells for the next step instead and rotated/swept horizontally directly through the safety fence…”

(Image courtesy of FANUC America.)

Reddit user Ingen-eer recounted the kind of story that keeps robot programmers up at night.

I was programming a FANUC palletizing robot for a company that made large vehicle wheels (22”, 60-80 lbs each). There were two cells side by side. The idea was the bot would fill a pallet, then swap cells and work on the other pallet so the human operator could empty the full cell with a forklift. There was also a “change cells for the next wheel” button to interrupt or reset loading as needed.
We were struggling with the indexing code to get the bot to remember where it was in a sequence if it was interrupted, and to recognize if a count reset was appropriate. I pushed a piece of code I thought was right, and for a few tests, it worked.

Then we hit the “change cells next wheel” button. It changed cells for the next step instead and rotated/swept horizontally directly through the safety fence, bending and ripping it out of the concrete.

Uh, %@#$, oops.

I didn’t get fired, but I did get the support I had been quietly wishing for from the more senior programmers. I don’t do contract programming anymore.

3. “Fixed it by buying 1-inch shorter pre-WW1 rail…”

As Reddit user spikes2020 demonstrates, the smallest mistakes often lead to the biggest pains.

Poured concrete 1 inch too high in a building for railroad. Fixed it by buying 1-inch shorter pre-WW1 rail to make up the difference. They have even off the shelf plates that transition between the two.
Someone else made a big mistake and measured the rail center to center when laying out the track on a set awg. Rail is measured inside to inside. Laid rail 2 inches too narrow...

4. “Marine Corps brass was insisting that the word ‘amphibious’ implied the ability to float…”

Early in my career, I was hired on as a contract worker at large company which had just received a multi-billion-dollar order to build amphibious, eight-wheel light armored vehicles for the U.S. marine corps. We toiled for several months on the project, burning through thousands of man hours before making an unfortunate discovery: our hull design was far too heavy.

Marine Corps brass was insisting that the word ‘amphibious’ implied the ability to float and in order to make that happen, we needed to eliminate a lot of weight from the design. Out of desperation management sent out a memo to everyone in engineering asking for suggestions on how to accomplish this.

This touched off a storm of anonymous suggestions such as drilling lightening holes in the hull, filling the tires with helium and my personal favorite, painting the hull with a lighter color. Management was not pleased with this response, but hey they asked!

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