How to Make Your Own Sundial
Instructions for making an equatorial sundial
- 1. To make an Equatorial dial of 500mm diameter and set to your latitude you require a Polar ring and 2 half circumferences for Meridian and hour bands.
- 2. Buy 2 x 2m lengths of 25mm x 3mm aluminium, 1 x 4mm lengths of threaded rod and 1 x 6mm tube sleeve from a builders merchant.
- 3. To calculate the circumference of Polar ring – 500mm x 3.14 (pi) = 1,570mm.
- 4. Mark, cut and roll the Polar ring by finding a sturdy round object to wrap the metal round.
- 5. To establish length of Meridian and hour bands, the calculation is circumference plus twice the width of the Polar ring (25mm x 2 = 50 + 1570mm = 1620mm).
- 6. Cut 1620mm length in half to create the Meridian and hour bands, drill hole in centre of both and drill 2 5mm holes 12.5mm from each end 12.5mm.
- 7. To calculate hour increments, take 360˚ ÷ 24 hours = 15° per hour. Take circumference 1,570mm ÷ 360° = 4.36mm per degree x 15°= 65.4mm per hour.
- 8. Starting from the centre hole, create hour marks 6 each side at 65.4mm intervals and partially drill each.
- 9. The sundial's angle is set to your latitude and is the distance between hour band and Meridian's fixing point: circumference ÷ 360° x latitude. For my latitude, the calculation would be:
1,570mm ÷ 360° = 4.36mm x 51° = 222mm.
- 10. Drill base fixing of Meridian 222mm from centre hole.
- 11. Roll Meridian and hour bands into semi-circles and bolt together at 90°.
- 12. Place Polar ring on flat surface mark at 4 equal parts. Place bands over Polar so Meridian straddles the join. Drill and fix through existing holes.
- 13. To fit gnomon Drill hole in centre of Polar and Meridian inter-sections at top and bottom.
- 14. Cut tube into 2 x 250mm lengths.
- 15. Insert threaded rod through Polar hole, and through 250mm length of tube, place a penny washer on threaded rod and slide second tube through Meridian and Polar hole, tighten top and bottom with fixing.
- 16. Fix dial to base with screw and turn to face due South and check time, Noon is GMT.
- 17. Spray paint dial and partially re drill hour marks to remove paint.
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