Setting-out logic

These are geometry. A passing figure is not a specification compliance.

Logic

Slope is rise over run. 0.15 m in 3 m is 5%, 2.86°, and 1 in 20. Use slope.

A step reports pitch and 2R+G. Rise 180 mm and going 250 mm is 35.8° and 610 mm. The 550–700 mm band is a cited comfort check, not an Approved Document K approval. Use stair rise and going.

A simple circular curve has tangent R tan(Δ/2) and arc RΔ in radians. Radius 200 m and deflection 40° give tangent 72.79 m and arc 139.63 m. No transition. Use horizontal curve.

Gear output speed is input speed times driver teeth over driven teeth. 1,450 rpm, 20 driving 60, is 483 rpm. Torque from a perpendicular force is force times radius: 500 N at 0.25 m is 125 N·m. Shaft power then follows if you have speed. Use gear ratio, torque and shaft power.

Setting-out screens

A slope is rise over run, reported as a percentage, a ratio and an angle. A circular curve gives a tangent and an arc from a radius and a deflection. A stair gives an angle and a 2R+G figure from a rise and a going. Each is geometry.

The curve worked case is a 200 m radius and 40°, tangent 72.79 m, arc 139.63 m. That is not a coordinate. The stair worked case is 180 mm and 250 mm, about 35.8° and 610 mm. That is not Approved Document K.

Write the inputs beside the result. A review cannot check a tangent without the radius and the deflection.

Last checked 3 October 2026. The logic is the textbook relationship named above. It is not a code check. See standards these tools do not replace.