Heliochronometer Clock Hybrid Sundial - with Reading Accuracy Optimization

Introduction

This design is loosely based on the Scottish Ilay Glynne sundial, a mechanical standing equinoctial ring dial which utilizes an integrated clock face with hour & minute hands. The Ilay Glynne dial was made around 1715 by Richard Glynne, a successful and well-regarded maker of mathematical instruments and is the most important surviving example of his work.  It was used to measure local time from the Sun, providing the most accurate means of setting clocks available at the time.  It was commissioned by and belonged to Archibald Campbell, Earl of Ilay and later 3rd Duke of Argyll (1682-1761) who was a hugely influential figure in post-Union Scotland.

How Does it Work?

In a typical sundial, the time reading accuracy is is a function of sundial type, design, size, construction, assembly inaccuracies, etc.  This sundial compensates for most errors by utilizing a planetary gear system which is coupled to the Alidade, Nodus & Analemma components of this uniquely styled heliochronometer sundial design.  The sun's shadow is aligned onto the Analemma plate by rotating a knob located under the main hour dial plate. Once aligned, the minutes are easily displayed on a secondary dial.  This is achieved using gears of an appropriate ratio such that 1 hour movement on the main dial equates to 1 full rotation of the secondary minute dial, or 60 minutes. The Alidade, Nodus & Analemma assembly rotates around the main hour dial as the minute dial rotates independently displaying the minutes of the hour.  The minute dial rotates a total of 24 times in 24 hours, or for every complete rotation of the Alidade assembly around the main dial plate.  The design results in a hour-by-hour,  minute-by-minute movement synchronized to the sun's position.  No complicated tick mark arithmetic required anymore to tell the time to within a 1 minute accuracy!

Please note that this design is meant to be used in the northern-hemisphere.  If you are interested in a southern-hemisphere design, please refer to this Printable to download the additional parts:  Heliochronometer Clock Hybrid Sundial for Southern Hemisphere by 3DMason | Download free STL model | Printables.com

Main Features

• Planetary Geared 0 to 60 Minute Secondary Time Scale Dial with a 1 minute reading resolution, consisting of a sun gear & two planetary gears traveling around an outer ring gear located under the main dial plate; 

• A Tilt Adjustable Nodus within a curved vertical arm for Sun Elevation Compensation throughout the year. This feature enables a sharper shadow to be cast against the Analemma plate, especially at the elevation extremes;

• A 25% Larger Curved Analemma Plate for improved reading accuracy;

• A Simplified Design of the Primary Time Scale Dial with a 1 hour reading resolution;

• Time readings are accurate to < 1 minute throughout the entire solar year from any location in the northern hemisphere. In practical terms, however, the accuracy will always be determined by the quality of it’s construction, assembly and precision of its final alignment;

• Displays Local Mean solar time directly by computing corrections to the true, or apparent solar time.  It achieves this by utilizing a visual-mechanical computer, also known as an Analemma plate;
• Converts Local Mean Time to Standard Local Time via meridian offset dial adjustments of ± 1-¾ hours, with 5 minute reading resolution;

• Also Compensates for Daylight Savings Time using the same meridian offset dial;
• The time is “tuned-in” by turning a knob located under the main hour dial.  Rotating the knob moves the entire Alidade, Nodus & Analemma assembly and enables the precise positioning of the sun's shadow against the Analemma vertical plate.  The time is then read from the main hour & minute dials;
• Adjustable Latitude Scale Dial with 1 degree reading resolution;

• 4 base options are available; 3 with integrated magnetic compass and levels, and 1 without.  For compass/level options, refer to these printable links:
  • Tri-leg:  Improved Heliochronometer Sundial Base Design with Integrated Bubble Levels and Magnetic Compass by yba2cuo3 | Download free STL model | Printables.com
  • Leveling base & tripod head:  Heliochronometer Sundial Mount for Head Leveling Base or Tripod Ball by yba2cuo3 | Download free STL model | Printables.com
• Assembly measures 180x200x200mm (W x L x H).

This heliochronometer was constructed out of ABS plastic filament.  

How was it Designed?

A:  Sundial Specifics:

For definitions on the various parts that make up a heliochronometer sundial, see my other Printable at:  Heliochronometer - World's Most Accurate Sundial by yba2cuo3 | Download free STL model | Printables.com

The spacing between the Nodus & Analemma vertical arms was increased to 100mm; or 20mm greater than my original 80mm design.  This spacing increase results in a 25% dimensional increase of the Analemma Curve, therefore increasing the overall reading resolution by an equal amount.  

The larger Analemma curve was calculated & designed using the instructions from one of my Printables which utilizes several Python scripts within Blender.  Check out How a Curved Analemma Plate was Designed into this Heliochronometer from:  Curved Analemma Plate for a Heliochronometer Sundial by yba2cuo3 | Download free STL model | Printables.com

The Nodus was modified to add a tilt feature & the original flat vertical arm was converted to a curved design.  Therefore, the Nodus elevation can now be adjusted to match the sun's height above the horizon during the course of the year.  This results in a sharper sun spot casted against the Analemma plate which also helps with the reading resolution.

The mounting locations for the vertical arms on the original Alidade remains unchanged from my original heliochronometer designs which means that the larger curved plate Nodus & Analemma designs presented here can be used on my other heliochronometer designs without any additional modifications i.e. 

1. Heliochronometer - World's Most Accurate Sundial by yba2cuo3 | Download free STL model | Printables.com
2. Heliochronometer (version 2) - World's Most Accurate Sundial by yba2cuo3 | Download free STL model | Printables.com
3. Gard Heliochronometer Sundial Derivative by yba2cuo3 | Download free STL model | Printables.com
4. Curved Analemma Plate for a Heliochronometer Sundial by yba2cuo3 | Download free STL model | Printables.com

Both hour & minute dials where generated using an online template design tool; i.e.  Clock Face Templates - Metric + Inch  The SVG drawing was then imported into Inkscape & then modified/enhanced for Blender.  Once imported into Blender, a thickness was assigned to each dial & then saved as an STL. 

B:  Planetary Gear Design Specifications:

• Common:
  • Pressure Angle:  20 degrees;
  • Module:  1;
  • Backlash: 0mm;
  • Root Filet Radius:  0.5mm.
• 2 Planet Gears with Carrier:  
  • 69 teeth;
  • 69m Pitch Dia.
• Sun Gear: 
  • 6 teeth;
  • 6mm Pitch Dia.
• Outer Ring:  
  • 144 inner teeth;
  • 144mm Pitch Dia.

Print Settings

• Printer brand:  Prusa
• Model:  MK4S
• Supports:  Yes, on some of the parts which flagged in your slicer app
• Resolution:  0.15mm & 0.2mm on the larger parts
• Infill:  20%
• Brim: Yes, on some of the larger parts if you use ABS
• Filament brand:  Doesn't matter
• Filament material:  ABS
• Filament color:  Doesn't matter
• Special Notes:  
  • Print in an enclosure for best results. 

Multi Color Faceplate Options

There are a number of approaches to highlighting text on printed surfaces.  Two print options are presented in this design:  (A) Debossed Single Part Object;  (B) Separate 2 Part Object (no deboss).

(A) Deboss Single Part Object:

1. The traditional method is to deboss or engrave the text & numbers into a single part and then use a slicer program to change the filament color at a specific deboss height below the main surface .  Pros: simple & durable with no post-processing.  Cons: Any (lighter color) main surfaces may darken due to (darker) deboss colors “bleeding” through to the main surface;
2. Another option is to print the main surface in one color then fill in the debossed area using an engraver filler like Markal B Paintstik Paint Pencil, followed by wiping off the excess with a dry cloth then with a bit of Isopropyl Alcohol to remove any “staining” from the main surface.  Pros:  Simple & Effective. Cons: Messy & not as durable outdoors. See this article for explanation on the procedure: Labeling Your Parts with Engraver Filler
3. Paint the deboss area then sand off the excess paint from the main surface. Pros: Durable. Cons: Messy & labor intensive. It may also remove some finer detail from mechanical abrasion.

(B) Separate 2 Part Object (no deboss):

The best approach is to have letters and numbers as separate objects and at equal heights which can then be printed in different colors. Separate objects create cleaner & clearer boundaries. Two part dial & scale designs for this Printable are provided in the folder section below: i.e. 2 Part Dials & Scales (non debossed parts).  If you are looking for more details, the technique is clearly explained here:   http://3dfaq.net/03_designing_for_3d_printing/01_multi_colour 

There is also a faceplate design example using Fusion 360 which further illustrates the principle:  https://www.printables.com/model/1040553-sundial-faceplate 

2 Part Object Import using PrusaSlicer 

If you use PrusaSlicer, there is no need to align or center the parts after importing.  They will come in at the correct superimposed positions.  Here is the procedure:

1. Import Part A (main body) 1st.  The part will center on the bed;
2. Under Editing, left click the icon next to Part A, then add part & load then choose Part B (text & numbers). Re-center Part B overtop Part A.  Both parts will now be aligned in the 3D viewer.

You can then use Multi-Material Painting feature following this guide:  Multi material painting | Prusa Knowledge Base

Required Assembly Hardware & Instructions

The construction of this sundial is relatively simple, making use of M2 & M4 Stainless Steel Button or Cap Head Screws and Nuts. A list of assembly material is provided along with where it's used. All parts can be easily disassembled and reassembled to facilitate transportation. See the file section for Planetary Geared Sundial-Clock Hybrid Assembly Instructions.

Tools For Sundial Alignment 

1. Magnetic Compass
2. Circular Bubble Level
3. Alternatives:   Smart phone with:  1) Compass or GPS app, 2) level app.

How to Use

Before using, make sure that:

1. your sundial is perfectly level;
2. your latitude is set on the latitude scale;
3. your sundial is pointing to true north.

Update (01-04-25): For alignment procedures, adjustments for time zone meridian offsets & daylight savings time, etc. refer to the attached file named:  How_to_Setup_your_Heliochronometer_Clock_Hybrid_Sundial-Detailed-Instructions-v1

Simply turn the dial knob located at the bottom of the main sundial plate to rotate the Alidade until the light through the Nodus hole is aligned onto the dark curve on the vertical Analemma plate.  Ensure that you are on the correct portion of the Analemma curve which corresponding to the current month of the year.  Do not try to move the Alidade from the Nodus or Analemma vertical arms or you may end up damaging the gear system.  Only use the knob to move the alidade.  The hour will be displayed on the main hour dial & the minutes on the secondary minute dial.  That simple!

If you think this is a cool design, don't forget to hit the like button. I hope you enjoy building this design & thanks for your support!

 References:  

1. Heliochronometer - World's Most Accurate Sundial by yba2cuo3 | Download free STL model | Printables.com
2. Gard Heliochronometer Sundial Derivative by yba2cuo3 | Download free STL model | Printables.com
3. Curved Analemma Plate for a Heliochronometer Sundial by yba2cuo3 | Download free STL model | Printables.com
4. Sundials - Their Construction & Use, R. Newton Mayall & Margaret Mayall, Dover Publications Inc., 1994
5. The Equation of Time:  The Equation of Time