Getting Started
Two sticks and a block of iron, gold, lead, invar, or diamond gets you a big, heavy earth-wrecking tool. Make a big hole in the ground. You'll need some materials for what comes next.
The firebox is a dead-simple metal box where, if you throw stuff inside to burn, it gets hot. You can then use the heat to do work.
The Oven performs all the same tasks as a Furnace (cooking, smelting), but much faster, and with less wasted heat. It also has a comparator override, hopper support, and all the other niceties you'd expect to let you set up redstone controlled minecart networks. Or, you know, you could just pipe stuff in and out.
Heat diffuses through anything that's heat-conductive. Copper happens to be a fantastic heat conductor, and travels efficiently along hollow tubes. This way we can make cheap heat pipes and move heat to all our machines. Or, in some cases, concentrate the heat of many fireboxes on one machine
Convection motors provide the second kind of power in Thermionics: rotary power. While heat is almost hesitant in its diffusion, rotary power is extremely proactive, moving very quickly and efficiently across longer distances. However, motors cause a large, constant power drain unless specifically shut off with redstone. Motors also react in very expected, realistic ways to changes in workloads: Heavier work slows the motor down for everything connected, and too much work locks the motor up completely!
So as you're getting started, slap a lever on that motor so you can shut it off.
Hammer mills are your ore doubler. They grind one ore into two dusts, much like other grinding machines in other mods. This machine requires rotary power, which for early-game means hooking it up to a Convection Motor. Just remember to shut off the motor when not in use! Or better yet, run a comparator out of the Hammer Mill, into a block, put a redstone torch on the block, and feed that signal to the motor. If there's nothing in the mill, the motor gets shut off.
Axles move rotary power along a straight line, up to 16 blocks. If you orient them vertically, they can also be used as firepoles for rapid, safe descents! (and you can sneak to grab tightly onto the axle and stop yourself)
Gearboxes can turn and split rotary power in any direction. They can also be used as range-extenders, supplying another line of up to 16 blocks (15 axles and another machine or gearbox). Gearboxes and axles can be pushed/pulled by pistons, slime blocks, and frames. Imagine the ways you could automate such a system!
More content is coming, so keep your machines busy. I'll try to make some Dr. Purpur (the beverage of choice for intellectuals) available soon so you can stay refreshed and focused on science!