Orrery

DIY

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An orrery is defined as a clockwork mechanism of the solar system (or part of the solar system). The clockwork mechanism is of course the part that I find intriguing and I wanted to make a model that I can sell as a kit. Currently the kit is for sale (buy one here).

This is the result of several weeks of work:

 

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orrery

The assemble instructions are available for free download to anyone who are interested in how the mechanism is put together. The skill required to build this is advanced but very rewarding once done. It can be set for any year.

A video with some instructions to make assembly easier is available HERE:

A few interesting notes on this Orrery: 

The gear ratios for the orrery are very interesting. The bottom gear train (T39:T8:T39), rotates the Earth around its own axis once per year. The ratio is 1:1 and has the effect that the Earth is not tidally locked with the Sun (as the Moon is with the Earth). This simulates the seasons as the poles turns towards and away from the Sun at different stages of the year. The place where the tilt is at maximum, is indicated on the disk (these are the solstices in June and December). When the Sun is directly above the equator, is also indicated on the disk (the equinoxes in March and September). Note that the equinoxes and solstices are not on the exact same date each year and averages were calculated and used on this orrery. It is also interesting to note that the solstices and equinoxes are not equally far apart (i.e. the seasons are not equal in length). This is due to the slightly elliptical orbit of the Earth (definitely not simulated in this orrery).

There is a full Moon every 29.53 days (called the synodic month). Note that a full rotation of the Moon actually takes 27.322 (sidereal month – takes the rotation of the Earth into account) but for the orrery we are interested in predicting the Moon phases and this value is not used here. A full Moon every 29.53 days means there are 12.368 rotations of the Moon every year. This is the value that we need to simulate to predict the Moon phases. The following gear ratios were selected: 39:8 and 33:13. The combined gear ratio is 1:12.375. This means that one full rotation (i.e. one year) there will be 12.375 full Moon rotations. The simulated value is close to the real value and the error is less than 0.06% which means the accuracy is 99.94% over the course of one year.

The inclusion of the additional 13 teeth gear is also important. Having two 13 teeth gears in line does not affect the ratio but it does affect the direction of rotation. I called it the inverter gear (T13B) since it changes the Moon’s rotation from clockwise to counterclockwise when the Earth is moved in a counterclockwise direction (i.e. the direction the Earth rotates around the Sun when viewed from the North Pole).

The drive gears (T12RA and T48RA), does not affect the accuracy of the orrery. It is however interesting to note that the gear ratios for these gears are 1:4. This means with each full turn of the crank the orrery moves by 13 weeks. There are 13 radial lines on the shaft disk (BHS). There is also a line on the crank axel (D83). Turning the crank so that the line on the crank axel moves one segment on the shaft disk will thus advance the orrery by one week.

It is important to note that this orrery is made from wood with some limitations in accuracy. The “slop” between the gears means that the arrow can move 3-5 days without turning the gears (tighter gears will mean the mechanism will be hard to move). This means that the resolution is not accurate on a day basis but rather that is accurate within a 5 day interval. However, if the slop is taken into account and the midpoint of the arrow is taken, each time, when the Moon phase is set/read the accuracy is 99.94% per year (see below). I.e. the orrery will be within the correct 5 day interval for 64 years and start to deviate by one day after subsequent rotations.

In the future I want to make a much larger model with and include celestial items. I want to make it out of nice hardwood and and much much larger. But this is just one of the many things I want to make – if I do it it will definitely be documented!

R

Box and Hinge

DIY

I recently made Scrabble box and had several requests for the files (full post on how to make it here). I thus make them available for download here:

FILES

box.pdf

hinge.pdf

board.pdf (just a square board with 15×15 grid)

A few notes on the files.

  • The files are uncompressed PDF’s and it should be possible to import it into most drawing programs and get the vector lines.
  • The board has scoring lines in blue and I usually engrave these at 15% power on a 40 Watt laser.
  • The hinge parts fits onto a 4 mm dowel. The octagon parts will make the hinge a bit more stiff. I glue 3 octagon parts onto the dowel in place and use 2 round parts to pivot on for a loose hinge. For a stiffer hinge use 5 octagon parts with 3 glued to the dowel.
  • There is this awesome site to generate custom boxes: http://www.makercase.com/. The boxes I made here and here was made by editing designs from this site.
  • I do not share any games that might be copyrighted but check out Wikipedia for any rules that you may want to know and pieces that are required for any game. Some are just simple squares with some writing on.

Here is a few photos of the hinges and boxes I refer to (or you can watch the full build videos here  – I would love it if you subscribe to my you-tube channel 🙂  boxes (1)boxes (4)boxes (2)boxes (3)

More projects and maybe some other plans soon…

R

Wooden Chess Sets

Competitions, DIY, New Item, Shop Stuff

Using a laser to quickly make wooden items is easy. However, to make nicely finished items requires more than just a “cut-and-go” approach. I made some travel chess sets by cutting and engraving the board and pieces using a laser. But this was just a very small part of the project. Here is the finished project after many hours of designing, sanding, cutting, staining, more sanding, gluing, sanding and more sanding (available here).

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Finished chess set – Open, Closed and Ready for play.

This chess set is based on another set that I have, but people dislike the pixelated pieces (see/get the pixelated set here). Using the same layout  as with the pixeladed set I redraw the pieces, first in Corel Draw. I then added the shade in Photoshop and ported it back to Corel to finalize it before sending it to the laser.

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“Classic” piece design.

(In previous projects I started with drawing the images first using Photoshop and saving them as .jpg. I then generated the vectors and exported them as .ia files from Photoshop. I imported the .jpg into Corel and overlay the .ai vectors. This allows me to make the cuts after the images have been engraved, exactly where the outline paths are generated (I used it in several other projects). HOWEVER, the paths that are generated from a bitmap type image are not exact. This means when a circle is converted from a bitmap to a vector, it is not completely round as the path is followed where the pixels are located. These which are never at a high enough resolution to be perfectly round (for the pixelated chess set I fixed ALL the lines in Corel since the lines are supposed to be straight but the path generated is often not). The inaccuracies creates a small problem as pieces are not 100% symmetrical. It cannot be seen by eye but since the front and back pieces in this chess set is the same it is possible to place the piece backwards when storing. This asymmetry can make the piece get stuck when placed in backwards. – Starting with the vectors, as I done in this project is much thus much faster and mode accurate.)

In addition to the wooden parts I also design the leather hinges, feet, latches, and cardboard sleeve. The design of the board and pieces, and other parts (including some test cuts), takes the second place for most time spent on this project.

I use a custom jig to hold the plywood flat when cutting. This is probably the best jig that I have ever made since plywood is never completely flat and the focus of a laser is always exact (this is one of the main reasons why I was considering the Glowforge laser, which has auto-focus).

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My favorite jig.

The boards and pieces are engraved and cut at an angle (4 degrees), relative to laser bed layout and wood grain (see below). There are several reasons why I do this. The first is that it ensures that the pieces are less likely to break. Since I engrave on both sides there is a chance that the wood in the middle sheet (there is only 3 sheets in this plywood) would need to carry most of the strain. If the grain in this sheet is in the wrong direction the pieces would could break more easily. However, when engraved at an angle the grain cannot be parallel to the weakest point and the pieces are stronger. I also found that engraving at an angle makes the horizontal lines slightly lighter and the vertical lines slightly darker (this is due to the laser only flashing quickly when engraving thin vertical lines part while being continuously on while engraving thin horizontal lines – when engraving lines at 90 degree angles). The engraving is thus much more even. A larger angle would probably be better but 4 degrees is the maximum I can turn the parts and get the same number of boards cut.

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Engraving the pieces at a 4 degree angle.

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Engraving the boards – also at an angle.

After the pieces are engraved and cut, I engrave them on the other side.

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The engraving of the back.

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Pieces engraved and cut. Top – front engraving, slightly more stained because this is also the cutting side. Bottom – back engraving.

I remove the pieces and make a deep engraving to create recesses for the leather hinges and feet. This allows the leather parts to sit in the wood. It also ensure that the parts are glued much more securely. I add masking tape at this stage to reduce the amount of sanding needed to clean the part later.

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Masking to reduce stain before deep engraving.

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Recesses for hinges and feet.

Next the feet and hinges are cut.

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Leather feet and hinges.

Once all the parts are cut, the biggest part of any woodwork project begins – sanding. First I remove the burrs on the bottom of the pieces where they were attached to the wood. This means they will slide more easily into and out of the recesses when the board is assembled (I also sand the burr in the recess).

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Removing the small burr where the piece was attached.

I sand everything with 400 grit sandpaper to remove all the laser burns and stains, being careful not to sand to deep and remove any of the engraving.

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The start of the sanding process.

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Top – not sanded. Bottom – sanded. Both pieces were wiped with ethanol to remove some of the stains.

I stain the dark pieces with light walnut (this gives a similar color to the dark squares on the board).

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Test staining to get the color correct.

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Staining.

After drying each piece is sanded again, very gently with 800 grit sandpaper. The light pieces is also sanded at 800 grit to give a silky smooth feeling to every piece.

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More sanding – up to 800 grit.

During this time the board is assembled. The front and back parts are glued together.

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Never enough clamps.

After gluing the edges are given a final sanding and the corners slightly softened.

The leather feet and hinges are glued in place. Small screws are added to the hinges, more for aesthetics than anything else. Everything is clamped overnight.

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Adding the leather hinges.

The last part to make is a sleeve for each set. This is also done on the laser. Although it may not seem to be very exciting (and no one really cares to hear about this part) it is very nice, just insert cardboard or paper into the machine and get perfectly fitting boxes and sleeves (or circular labels). I of course spent a bit of time designing these but now I can make many without too much trouble.

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Cardboard sleeves.

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Perfect cut labels.

The final step is to check that each piece fits into their respective slots and into the board. I fix any minor problems with more gentle sanding, and touching up with stain if required.

With the pieces stored the board can be closed with the custom leather lathes. These are now ready to be sold (buy it here), used, or given away (see the video to see when I give them away).

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Custom latches to keep set closed – see video for how they work.

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Cat tax – photo of the Kwagga taste testing the camera tripod.

I think I am now done with the flat-pack type travel chess sets. I like this set more than the pixelated set. I may make another chess set in the future but the next project I am working on is more mechanical with several gears and other moving bits, stay tuned to see how it turns out…

R