Ore handling and burden

A shaft furnace does not eat ore. It eats burden, which is crushed iron ore blended with lime flux, and it eats fuel, and the two go into the shaft as separate layers. Burden is made in one block, the Burden Maker, and charged through another, the Tall Hopper.

Making burden

The Burden Maker is two hoppers over a shared basin with a sliding gate between them. It has no mechanical power port, so it can be built before any axle exists, and it is the only source of Blast Burden.

Vessel	Takes	Holds
wide hopper	crushed iron ore	512 units
narrow hopper	lime	205 units
basin	the finished burden	1152 units

Right-click adds one item, ctrl plus right-click adds a stack, and an empty hand takes it back out. Nothing is locked and nothing is spent until the gate is opened. Opening the gate, at the centre cell of the base on the open side, drops both hoppers into the basin at once as one batch. The basin must be empty before the next batch drops: that refusal is the only batch boundary the machine has, and it is what keeps two loads from averaging into each other.

Ore is admitted by material role rather than by item code. The base rule is any item whose path starts with crushed-iron; rows in assets/iiex/config/materialroles.json add crushed-hematite, crushed-magnetite and roasted-crushed-iron when Industrial Story is loaded and crushed-ore-hematite, crushed-ore-limonite and crushed-ore-magnetite when Expanded Matter is. Flux is game:lime and nothing else. Crushing itself is vanilla's: a pulverizer turns nuggets into crushed ore. Scrap iron bits are not ore and do not crush; they are cupola charge, and go back round as cast iron. See Iron and its grades.

Grade

Burden carries one quality, its flux fraction, and the grade is stamped onto the item that leaves the basin so the furnace can report what it is being fed.

Grade	Flux fraction of the batch
under-fluxed	up to 0.03
standard	0.03 to 0.08
over-fluxed	0.08 and above

Bands are inclusive at both ends and scanned in order, so a boundary belongs to the earlier band: 0.03 reads under-fluxed and 0.08 reads standard. About one part lime in twenty is standard. The burdenmaker's block info names the grade the two hoppers would make before the gate is opened.

Fuel is not part of the grade. Fuel is charged as its own layers and metered at the raceway, so it is not a quality the burden item carries. See Coke and fuel.

Charging the shaft

The Tall Hopper is a two-cell tank the player fills at the mouth. It holds 128 units, which is one burden stack, drips 8 units per second into the column the furnace nominates, and has no on/off toggle: a loaded hopper drips until it is empty. It holds one material at a time, which is how a round is laid.

A shaft's charge is measured in bands. One band is 2 items, a block is 16 bands, so one block of shaft holds 32 items of any material. Two rules do all the bookkeeping:

1. Fuel may be added to a column only above the last burden, never beneath it.
2. Each load fills the lowest columns first, so the stockline self-levels.

Charge appears in the shaft as Charge blocks, one per block of column height. They are windows onto the furnace's own columns, not containers. Right-clicking one with an empty hand takes one band off the top of that column, whichever window was clicked. Breaking one splices that block's units out of the column and drops them, one stack per material and grade, which is the recovery route for a chilled furnace whose cold charge sits at the bottom of the shaft out of reach of a take.

Adding charge by hand through the pile blocks is not implemented. A held stack does nothing.

Step by step

1. Build a Burden Maker from any burned-brick colour except fire and clinker.
2. Fill the wide hopper with crushed iron ore and the narrow one with lime, reading the grade off the block info until it says standard.
3. Open the gate, then reach into the basin and take the burden out.
4. Build a Tall Hopper over the furnace shaft.
5. Fill the hopper with coke and let it drip until it is empty.
6. Fill it with burden and let that drip.
7. Repeat steps 5 and 6, coke under burden, round after round, until the shaft is full.

What goes wrong

The basin refuses the gate. The basin still holds the previous batch. Take it out first.

The hopper charges nothing. A hopper standing over a cell that is not a furnace shaft has no machine to ask what is chargeable, so it accepts nothing. A hopper over a firebox furnace, such as the coke oven or the reheating furnace, is the same case: those machines have no charge columns, so the hopper would hold its load for ever. Fireboxes are charged by clicking the bed directly.

Burden laid on a burning furnace sits there cold. A new layer with fuel in it catches and joins the fire; burden on its own does not. Lay whole rounds and the case never arises.

The furnace will not light on a deep heap down one side. Ignition is positional: what the fire waits for is a complete bottom course across the whole shaft, not a quantity of charge. The hopper's lowest-column-first rule produces that on its own if the rounds are laid whole.

A lean charge cannot be blown. How much coke is in the column sets how much pressure the blast needs, because the fuel layers are what the air gets through. See Furnaces and heat for the numbers.

Another ore mod's crushed ore is not accepted. Adding it is a row in materialroles.json, not a code change. The real hazard with an ore mod is not the furnace but the crushing recipes: two mods that patch the same vanilla nugget-crushing recipe collide, and that collision has bricked installs and opened duplication loops in the older mods. Adding the same kind of content is safe; patching the same recipe is not.