Late 2024 we had a problem I'm not proud of. A run of our hand-crank multi-function emergency lights, the ones with the fold-out handle, started coming back from a Kenyan distributor. The crank would feel notchy, then jam, then the handle would spin free doing nothing.
My first guess was the dynamo motor. It usually is. We pulled twenty returned units and tested them, and the motors were fine. The little DC generators were spinning happily on the bench.
The real culprit was a plastic reduction gear between the handle and the dynamo. We'd switched to a slightly cheaper nylon for that gear without me really clocking it, and under the load of an enthusiastic adult cranking hard, the teeth wore down faster than they should. People in a blackout don't crank gently. They crank like they mean it.
So we went back to a glass-filled nylon for that one gear. Costs about four cents more per unit. We also added a tiny slip feature so that if someone really overpowers it, the handle slips instead of shearing the teeth off.
We tested the new ones to five thousand full cranks on a jig Leo rigged up from an old drill, which ran for two days straight and drove everyone in the office a bit mad with the noise.
The distributor in Nairobi got replacements for the whole batch. He wasn't thrilled about the delay but he stayed with us, which I appreciate more than I said at the time. The lesson, again, is don't quietly change a load-bearing part to save four cents.
