# Hammer Throw

> An independent browser reimplementation of the World Athletics hammer throw. Three or
> four turns of a tethered 7.260 kg head on an inclined plane, then a release whose
> optimum angle the engine derives from its own mechanics instead of assuming 45 degrees.

Single page, no server, no account, no network calls. WebGL renderer hand-written for this
build; no third-party library is loaded or bundled.

## What is modelled
- The turn phase: the head orbits a circle of radius R in a plane inclined by beta, driven
  by the thrower's torque through a wire that leads the head, and pulled back by a
  pendulum term of effective gravity g*sin(beta).
- The release: the velocity is the orbit tangent, whose elevation can never exceed the
  plane inclination and equals it exactly a quarter turn past the low point.
- The flight: a non-aerodynamic steel sphere, integrated with fourth-order Runge-Kutta
  against a choice of drag models.
- The rules: World Athletics Book C - C2.1 Technical Rules, TR 25, TR 32, TR 36 and TR 37,
  including the sector test, the measurement floor, the cage strike rules, the cut to eight
  after three rounds and the TR 25.22 countback.

## Headline result
The ballistic optimum from level ground is 45 degrees. Release height moves it to 44.48;
air resistance to 44.00; and the coupling between release speed and plane inclination - the
largest of the three - to 41.55 degrees. The twelve men's finalists at the 2017 World
Championships released at 41.28 +/- 2.52 degrees. The model was never fitted to a release
angle.

## Findings recorded on the page
- World Athletics TR 36 specifies no MINIMUM length for a hammer, only a maximum.
- TR 32's sector-laying note ("12 m apart at 20 m") is a chord, not a perpendicular width.
- Wikipedia mis-states the length limit as applying to the wire, and as the same for both
  implements.
- The 2017 London release parameters only fly their own published distances in a vacuum.
- Sedykh's published world-record release parameters fly about 4.6 m too far.
- Two published estimates of the drag loss differ by nearly a factor of two.

## Files
- index.html, styles.css
- js/hammer.js    the engine: rules, turn dynamics, flight, competition
- js/mesh.js      hand-built geometry with outward-wound triangles
- js/render.js    the WebGL renderer
- js/glmat.js js/provenance.js js/storage.js js/ui.js js/app.js
- CREDITS.txt LICENSE.txt

## Not affiliated
This is an independent reimplementation of a sport. It is not affiliated with, endorsed by
or connected to World Athletics, and it represents no real athlete.