MONIAC · The hydraulic economy

Preparing the hydraulic circuit…

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MACHINE RUNNINGRECIRCULATING FLOW · GRAVITY 9.81 m/s²00:00

01 / OPERATE THE MACHINE

Time scale

Spawning stopped

Drag SOURCE into a tank or pipe, or select Move source and click a location. Source: 680, 120.

Spawning rate120/s

Maximum particles per simulation second · waits if blocked

Return pump65%

Motor power · 0% switches the pump off

02 / ADJUST THE SLUICES

03 / TRY A DISTURBANCE

Change a valve and watch the delay travel through the machine.

04 / OBSERVE THE FLOW

Dye particles by circuitHighlight a single particle

Particle limit

Income / consumptionGovernmentInvestmentForeign balancesTracer

Turn a brass knob to adjust its gate. Drag SOURCE to move the emitter. Drag inside a tank to stir. Space pauses.

RETURN FLOW0 particles/s

PARTICLES IN CIRCUIT0 particles

TRACER RETURNS0 laps

ELAPSED SIMULATION0 s

Inside the machine · physics, economics and historical references

THE PHYSICAL MODEL

Every ball is a persistent particle with position and velocity. Gravity accelerates it; contact constraints keep it inside the glass and prevent particles from passing through each other. Inelastic contacts and drag dissipate motion. Adjustable sluices are colliding solid plates, and the return pump supplies work to the particles in the intake and return pipe.

The simulation uses a fixed 1/120-second step and a scale of 110 pixels per metre. Slowing time changes playback speed, not gravity. Flow meters count particles crossing outlets; they do not generate the flow. The circuit starts empty with spawning stopped. Start spawning adds particles at the movable source; Stop spawning leaves existing particles circulating. Reset clears the circuit and stops spawning. Reaching the selected particle limit also stops the emitter; a blocked source waits for room without overlapping particles.

READING THE ECONOMY

Income loses taxation (T), then saving (S), while household expenditure passes through the consumption circuit (C). Imports (M) feed foreign balances. Government spending (G), investment (I) and exports (X) return stored balances to the circulating flow. Closing an outlet retains particles upstream, with a visible delay elsewhere in the loop.

Knob and slider percentages are physical gate openings, not prescribed economic shares. Turn a knob clockwise to open its gate or anticlockwise to close it; dragging vertically from its centre also works. Focused knobs accept arrow keys, Home and End. The knobs and sidebar sliders stay synchronised. Actual outflow depends on the available head, neighbouring particles and the gate. Foreign balances form a finite closed reservoir here, so exports can run dry. Colour identifies the last side circuit visited; the pump resets the dye to income.

ABOUT THIS RECONSTRUCTION

Bill Phillips built the first MONIAC in 1949. The original represented monetary flows with water, and financial balances with tank levels. This is an interactive, simplified reconstruction of that principle, with a rearranged circuit for visibility. It is a discrete particle analogue of water, rather than a calibrated fluid solver or a reproduction of every Mark II linkage and economic equation.

Historical references: Reserve Bank of New Zealand · demonstration and explanation; Chris Bissell · MONIAC history and Mark II diagram (IEEE, 2007).