A friend and I started up a co-op game running BTW about two months back. We were both completely new to the mod, aware of its' existence for a long time but just never getting around to trying it. Our first project was to get a windmill up and running with a saw, several millstones, kiln, crucible, et cetera hooked up to it. The basics before we got into mass automation. One of the first design problems we ran into that going into the mod I didn't know that overpowering gearboxes caused them to explode. A temporary solution was devised at first, wherein we'd pull a switch down in the mill whenever we weren't currently milling something or using the kiln to power the gearbox. This got tedious pretty early on, and as soon as we had access to detector blocks, I decided to set one up to automatically disable the windmill when it started snowing. At about this time I was also starting to change over from coal to nethercoal, and had a large amount cooking in the cauldron while I had the mill powered down to install the system (REMEMBER THIS.) Now I wasn't sure exactly how detector blocks worked, and was confused when a detector block wasn't detecting snow directly in front of it when I affixed it to the side of the building. I thought that perhaps the block just didn't have a visual indicator of being on, so I hooked it up and asked my friend to stand in the windmill and look at the wiring when it next snowed. I pulled out the bow and started popping arrows into the thing trying to figure out why it wasn't triggering, and lo and behind, the detector block activated, the signal inverted, shutting the torch that was keeping the gearbox off down, and we heard an explosion from below in the mill.
It takes me a minute of looking around for creeper holes or something... then I remember the nethercoal. We run down into the mill and find that the hibachi is still intact, lighting our almost-completely wooden mill on fire and burning up all of our axles, rope and gearboxes.
Just thought I'd share this story of two guys who had no idea what they were doing losing all their crap by shooting arrows at a windmill.