2026-03-18

Last modified: 2026-03-18 15:43:43

• Longitude by sundial
• Car engine mounts and gearbox mounts

Longitude by sundial

I tried to take a longitude observation using the sundial today.

I waited until the sundial read 12 noon, and compared it to the time on my watch. The watch is "MULTI BAND 6" so should be correct to well within 1 second.

I took the first reading when the trailing edge of the gnomon shadow lined up with the first bar at the top, the second one when it seemed to be in the middle, and the third one when the leading edge lined up with the second bar at the top.

1. 12:15:05
2. 12:15:33
3. 12:16:14

And then to convert from local solar time to local mean time we need to know the Equation of Time for today's date.

According to ChatGPT it is about -8m1s. So mean time is 8m1s ahead, this puts our observed solar noon at Greenwich solar times:

1. 12:07:04
2. 12:07:32
3. 12:08:13

Every 1 minute is 1/1440 of the way around the Earth, so every 4 minutes is 1°. West.

1. 1.76°
2. 1.89°
3. 2.05°

The true longitude at this spot is more like 2.5° West. We would have needed to record solar noon slightly later, so I think the sundial needs to be rotated by about 0.6° clockwise.

Car engine mounts and gearbox mounts

I've fully welded these now:

They would potentially benefit from some gussets, particularly the right-most gearbox mount as it only has a very small contact area with the chassis. I think cut out some steel triangles and weld them on the undersides, one at each end of the engine mounts, and one at the front edge of both gearbox mounts, so 6 triangles in total.