One thing is that nigh-impossible to automate in vanilla Minecraft is a tree farm (Wither tree farms are possible, but … really?). Many mods, however, introduce some way to do just that, either through a dedicated tree-farming mechanic or through some kind of multi-use block-breaker (i.e. see my Factorization tree farm). The original raison d’etre of the Forestry mod was specifically the automation of tree farms, for crying out loud. Rotarycraft’s solution is the Woodcutter, a machine that becomes available very early on (it uses only about 22 steel ingots and requires only the slightly modified power of a steam engine).
Now, it’s easy enough to set up a Woodcutter and just let it go. The Woodcutter has a very high chance of replanting a sapling and can even be enchanted with the Infinity enchantment to guarantee a 100% chance of replanting. Moreover, a Steam Engine or four Wind Turbines will produce the right amount of energy (16,385 Watts), so you don’t have to worry about refueling a Gasoline Engine or replacing the magnetized shaft core in an AC electric engine. But the Woodcutter requires 64 Nm of torque, meaning you’d need to use a 4:1 gearbox along with a Steam Engine or four Wind Turbines to power it, so unless you’ve already got a bunch of diamonds or bedrock dust, you’d have to find some way to replenish the lubricant (either manually or, better, by piping lubricant out to it). If you don’t want the Woodcutter to run all the time (“I’ve got four double chests of oak logs and it’s still cutting!!!”), it’s easy enough to insert a clutch between the Woodcutter and its power source (actually, place that clutch between the power source and the gearbox to save on lubricant when the Woodcutter is turned off) and then run a line of redstone dust to a lever that is somewhere more convenient for you.
There are three problems with the Woodcutter, though, that make it so that a single Woodcutter by itself is not an all-in-one solution. First, it doesn’t keep the blocks it chops down in an internal inventory but spews them to either side of itself. This is easily enough solved using a using a bunch of hoppers, a subterranean hopper cart collection system, or (better) a well-placed Item Vacuum (which itself would require another 16,385 Watts of power – unconverted, though). Second, it can only work with one tree at a time (so you need one for each species of tree). Third, it does nothing in itself to accelerate the growth of that single tree. So even with an Item Vacuum, you’d need at least four Woodcutters (or one for each species) for the beginnings of a satisfactory automated tree farm, meaning, additionally, that you’d need five Steam Engines (four Woodcutters and an Item Vacuum; an ultra-noisy solution) or 20 Wind Turbines (lots of steel, there). And even this wouldn’t work terribly fast because you’d be waiting for the trees to grow.
***NOTE***: I don’t know how I missed this, but Reika has pointed out to me that the only reason the the Woodcutters are spewing items out to either side is that they are trying to eject into an inventory below them. When such an inventory is lacking, out to the sides everything goes. What this means is that two parts of the following design are unnecessary, even if they work. Reika, in fact, called this design (in one of the finest back-handed compliments I’ve ever received): “a beautiful example of how a gap in understanding is usually the cause for RotaryCraft to appear overly complex or difficult.” Well … at least it’s beautiful.***
I have designed a simple four Woodcutter system powered by Industrial Coils, though, that solves a lot of these problems:
The redstone underneath the ground is not too difficult, but I suspect there are some who would like to see it, so Saturday I’ll post a picture-intensive explanation of the redstone that makes all of this work.
I had also designed a system that used an AC Electric Engine to power the four Woodcutters, the Item Vacuum, and an Item Pump line (to bring the harvested bits from the Item Vacuum back to a central storage area).
This system works, but I ran into a problem with two different implementations of it: somehow, something was interfering with the AC Electric Engine and causing it to lose power. I suspect it might have been the buried redstone dust (even though the line was far enough beneath the AC Electric Engine that it could not have been powering any blocks adjacent to it). It is a very cool-looking system when all put together, and I’m sure the problem I ran into could be solved, but even when it works there is a good bit energy wasted unless you turn everything on at the same time. This is because the AC Electric Engine puts out 131,072 Watts of power regardless of whether or not you’re using all that power. While the five Industrial Coils of the above-described solution have to be recharged from time to time, this is only very rarely, and only the power that is needed is used. You don’t have to worry about running all four Woodcutters to make the most of your produced energy.
The same would go for a single Gasoline Engine-powered system (65,536 Watts generated whether or not you’re harvesting all four trees). BUT, if you were to use four Gasoline Engines and four Engine Control Units to throttle down the power output of each to 16,385 Watts (at which point it’s fuel efficiency would be double!), you could control these in very much to same way as the above-described Industrial Coil system. I’ll talk about using Engine Control Units in an upcoming post.
***Follow-up*** As I noted above, Reika pointed out that the Item Vacuum is a workaround for a problem that doesn’t actually exist, since the Woodcutters will naturally eject into an inventory placed below them. So how might we take advantage of this fact? Simple. Place a chest or hopper below the Woodcutter, then use Item Pumps (or the item transport solution of your choice) to pull the items from the chest/hopper and send them to your intended destination.