Brake broke
Not me but a mate (why do the stupidest ones start with that? It really wasn't me, but I'd hesitate to call the guy a mate) once decided to repair the leaky air brake unit on a truck we were using.

Now, for those that don't know, the air brakes on lorries (that "TSSSSCHH" when they stop at lights) use compressed air to hold the brakes *off*, with a big strong spring holding the brake *on*. Think how hard you have to press the brake on a car for an emergency stop, and now imagine how strong the spring needs to be to do this for a truck...

Four bolts, the air pipe and a little pin for the linkage, and he's got the brake unit off. It's one of those things you see beside the back wheels of trucks, about the size of a soup pot. It's mostly full of spring. I did mention the big strong spring, didn't I? Between the "lid" and the "pot" is a rubber sheet which keeps the air in, and this had split. Genius-boy decides that this can be stuck back together with silicone sealant. To do this, he's got to take the "lid" off the "pot". So they're held together with a metal band around the rim, held tight by a bolt. Out comes the bolt, off comes the band, and it pops apart but is held in place by the big nut in the middle.

The big nut that hold in the spring. I did mention the really big, really strong spring, didn't I?

So, he starts to undo the nut. While standing right in front of the unit. Another mate saw him doing this just as the nut was holding on by its last half-turn, and shouted at him to get out of the way. As Genius-boy turned to see who was shouting, the nut popped off, and lid, diaphragm, and great big spring shot across the workshop and out the door, missing him by a hair.

Length? It buried itself 200 yards away...
(gordonjcp, Thu 20 Dec 2007, 13:46, Reply)