Demo

Millrace — Overshot Gristmill Simulator

The Bugged Dev

@thebuggeddev · 14.2K followers

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Sep 30, 2026

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A fully interactive 3D overshot gristmill simulation built in an afternoon with Claude Opus 5.5. You see a cross-section diorama — water jets from a sluice gate, fills 36 buckets on a 4.8m wheel spinning at 6.7 RPM, and a gear train steps that up to 120 RPM to grind 120 kg/h of flour. A live physics panel shows flow rate, torque, shaft power, and efficiency curves in real time. Toggle section, explode, wireframe, and names views. The sim runs at ~45% efficiency — close to a real mill's 60–80%.

Real hydraulic physics: sluice gate opening and head height drive jet speed, flow rate, and bucket fill — all calculated live with the actual formulas shown
Gear ratio chain from 6 RPM wheel to 120 RPM millstones is fully simulated, with a runner speed pattern chart showing the millers' optimal 110–130 RPM band
Multiple 3D view modes (section cut, explode, wireframe, names) let you inspect every part of the mechanism

“Spent an afternoon with Claude Opus 5.5 figuring out how a watermill actually works Eventually we got the whole mechanism working, from water filling the buckets and turning the wheel to the gears stepping 6 rpm up to 120 rpm and the stones grinding grain. It is not perfect yet. This wheel is running at around 46% efficiency while a real one typically reaches 60 to 80%. Still, pretty close, ig?”
— @thebuggeddev

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