The complete Orrery. (6/9/18)
What follows is a chronicle I made during the design and construction of the Orrery. It’s fairly long, but would be pretty helpful to anyone else who might like to make one.
A couple of months ago I bought a box of large brass gears on eBay. The box I received contains around 60 gears of various sizes. The picture below is just a portion of what I now have. The gears in the picture are all of the 32 DP variety.
Looking around for a new project I thought it would be fun to build an orrery. An orrery is a mechanical model of the solar system. Using gears it will rotate the planets through there orbits at the relative rates seen in astronomical observation. The image below is a picture of a typical orrey.
My plan is to use my box of gears to build the device. I will be building a Coppernican Orrey. This contains the six planets Mercury, Venus, Earth, Mars, Jupiter and Saturn. Uranus and Neptune as well as Pluto are left out. The Model will also include the Sun at the center and Earths moon. I am hoping to be able to use various combinations of the gears I have in order to get the orbital times correct.
So far I’ve looked at some of the things others have done in making Orreries, but my plan is to come up with my own design. I’ve done some research and have checked and verified some pertinent facts about the solar system.
I will use this chart not only to calculate the ratios of gears I will need to get the orbital times correct for each planet, but also the relative sizes and distances from the sun. There are two rotation ratios on my table. The first column is relative to Mercury the fastest moving planet. The second column is relative to the Earth. So when Mercury goes the sun once, one Mercurial year, the Earth will only move around the sun about a quarter of the way.
This week I’ve been working on the base design and figuring out what ratios of gears to use. The figure below is the basic concept.
There will be a series of brass tubes slid inside one another that can rotate independently around a central axis. There will be one tube for each planet. Two tubes for Earth more on that later. A solid rod will support the Sun. In this diagram I’ve simplified things to just Venus and Mercury but the rest of the planets will be similar. Mercury will be driven directly by turning Gear B. This will most likely be a worm gear driven by a motor, but I haven’t decided on a drive mechanism yet. By driving Mercury directly I eliminate the need to come up with gear combinations for this planet. When Gear B is turned it rotates Gear A which rotates the shaft attached to Mercury making it orbit the Sun. Gear B is mounted on the same shaft as Gear C so it will turn at the same rate. Gear C drives Gear D which is attached to the shaft for Venus. By choosing gears A, B, C, D at the correct ratios the relative rotation rates between the planets can be adjusted to the proper speeds. For Venus and Mercury the overall ratio in rotation is 2.55. That is for every one orbit of Venus, Mercury will orbit 2.55 times.
The pictures above are the brass tubes that will be used for each planet. There sizes are 1/8, 5/32, 3/16, 7/32, 1/4, 9/32 and 5/16 inches.
Not only can outer planets be driven by the inner Mercury tube, but as we go out the planets can be driven by the tube for any planet closer to the Sun than it is. So Saturn can have Gear A for it driven by any of the other planets shafts. This is handy because as we move outward more and more gear combinations will become available. This is important because I have a limited number of gears and I don’t want to make/buy more if I can help it.
With that in mind the table above was calculated showing the rotations of all the planets relative to one another. For example the first column, labelled “Mercury” are the rotations of the planets relative to Mercury. Each other column is similar.
So now to figure gear ratios for each of the planets. The first thing I did was count the number of teeth on each gear I have. This took a while. I have large sets of 15 tooth per inch (TPI) gears and 10TPI. The table below is the gears as I counted for each one (twice).
In order for the system to work properly the total number of teeth in Gears A plus B must be equal to the total number in Gears C plus D. This will ensure the planet tube will remain parallel to the outer shaft in the figure above. For each planet I can use either 10TPI or 15TPI gears for the four gears, but I cannot mix 10TPI with 15TPI or my teeth won’t mesh and my shafts will not remain parallel.
So I came up with an Excel spread sheet that will help me with these calculations. I use the “solver” function in Excel and enter gears A and B and Excel calculates gears C and D based on the required ratio and keeping the number of teeth in A+B equal to that in C+D. Even with Excel this is a tedious process. If I were a better programmer I could probably make a spread sheet to do the whole thing automatically, but alas I’m stuck doing things more slowly. The table below are the gear combinations I’ve come up with so far.
So I’ve got a bunch done, but many more to go. When this list is complete I will hopefully have enough gears to meet the requirements. If not I’ll have to make or find them somewhere else.
Well I have finally completed all the calculations for the gears I have in my collection. The two sets of gears I have are actually 48 DP (Diametral Pitch) for what I was calling the 15TPI and 32 DP for what I called the 10TPI. I know this now because the gears I am using are still made, even though they look old, by Boston Gear and use the same part numbers. So instead of counting all the gear teeth on each gear I could of just looked them up here.
Oh well live and learn, in this case I’m learning a lot about gears. Below is the list of all possible combinations of gears that I have that will work for each planet that I generating using Excel.
I then went through and selected a few promising combinations, one of which is below.
Each one selected uses just the gears I have enough for when I combine them. I also tried to keep the error level to less than 1%. In most cases I was able to have 0-0.5%. Good news is I won’t have to fabricate any gears. In case you cannot see it above, I’ve pretty much settled on the combination of gears below.
This portion of the project took quite a while. Things will get more interesting now even though the pace will be slow. I need to complete the design for the overall gear box and then start construction. All of the gears have different bore sizes so I’ll be making a lot of bushings in some cases and boring them out further in others.
When I went to collect the gears together for all of the planets as shown above I ran into a problem. The 60 tooth 32DP gears used as gear C for earth was not the proper size for making the four gears A, B, C, and D line up when Orrery was assembled. The rest of the gears I was going to use were all manufactured by Boston Gear. The 60 tooth was an odd gear I had found in the box of gears in my collection. The distance between centers when gears C and D were meshed together was about 1/64th of an inch shorter than the distance between centers for gears A and B. I went back into my list of gear combinations and came up with a new set of gears.
So this is my final set of gears. I’ve managed to keep all of the orbits within 1% of the actual values. This is when all gears are considered, remembering that some planets are running off of other planets with their own gears and errors.
Above are the gear sets for Venus.
Above are the gear sets for Earth
Above are the gear sets for Mars.
Above are the gear sets for Jupiter.
Above are the gear sets for Saturn.
Above are the gear sets for the Moon.
Just a note on how the moon is made to go around the Earth. The large gear above gets mounted onto a tube that is fixed and does not rotate. This tube is the one just outside the rotating shaft/tube for Earth. The stationary tube that is outside rotating tube for planet Earth is the same radius as the hub for large fixed gear (192 teeth 3 inch radius). A shaft with a small gear (16 teeth) is mounted vertically through the Earth so that the teeth will mesh with the large gear. This small gear will be rotated by the movement of the Earth around the Sun. If a moon is attached to an “L” shaped bracket attached to this gear it will rotate around the Earth 192/16=12 times for every time the Earth goes around the Sun. This is pretty close to the approximately 13 times the Moon actually orbits the Earth in a year.
This idea I found on Instructables.com here. MatthewS3 was making an Orrery from plywood gears and used this technique for the orbit of the moon.
The next step is to make some detailed measurements of each gear set and draft together a more detailed design for the Orrery than the one in my head. Once that is completed the hole in each gear will need to be adjusted the the diameter of the tube or shaft it will be mounted too. In some cases I will be making bushings, in others the holes will need to be made larger.
So I’ve been working on even more calculations and design. It seems like I’ll never get down into the work shop, but with all of the pieces that need to come together the design part was particularly important for this project.
Above are the measurements for all of the gears that I will be using. The gear diameters and radius are the most important information here and are highlighted in yellow. This information was used to design a layout for all of the gears. This allowed me to see how many individual sections/levels I would require for the complete gear train. The rod/tube diameters are the second most important information. These are the hole diameters that each gear will require in their hubs in order to mount to the tubes and rods required. The tubes are highlighted in green with the rods left white in the same column. The tubes will nest inside one another in one central shaft area. The rods will be placed parallel to the main shaft and will hold the gears A and C for each planet in the diagram above. Each planet will have it’s own outside rod.
I used the gear diameters in the table combined with the final gear combinations above (also in my post of 3/11/18) to design a 3D model of the gear train. I used Sketchup for the design. This took a while because I had to learn to use it first. I had drafting in high school, but we used drafting tables, triangles and pencils. At first I was going to us Sketchup as a 2D electronic drafting table. After working with it, however, it seemed that with the way it was designed it was easier to do the 3D model. I’m no expert yet, but I was able to get a pretty good 3D layout developed after working with Sketchup for a few hours. Below are some captured images of the 3D gear layout.
Angled view of all of the gears. A couple are hidden under other gears.
Another angled view where the gear designations are a bit more evident.
In this side view all of the gears can be seen. It looks like I will be using five levels. The first level will house all of the gears A, B, C and D for Venus and A and B for Jupiter. The second layer will hold gears A, B, C and D for earth and gears A and B for Mars. The top plate for this level will have the stationary tube attached to it that will support the 192 tooth gear used to rotate the Moon around the earth as described earlier. The Third layer will contain only gears C and D for Mars. The fourth, gears C and D for Jupiter. and The fifth level the A, B, C and D gears for Saturn. The sixth plate is the top plate holding the main shaft and the rods for Saturn in place. At least that’s the plan for now. As there are always problems in a first prototype like this I expect some tweaks along the way.
My next step will be boring out gears where the hub holes are too small, making sleeves for the holes that are too large, and adding set screws where needed. Some gears have no hubs so they will be fabricated from scratch.
Over the past week I spent a lot of time working on the gear hub hole sizes. Each gear needed a specific hole size to fit a specific shaft. Almost all of them needed set screws added to the hubs. I took a lot of pictures and had to adjust about 22 gears to the right size.
This gear had a hub that was too small so a new hub was created and the smaller one was removed. In this picture a brass rod is being bored to the same size hole currently in the gear.
After boring the brass was machined flat and then cut to length on the lathe.
The new hub is seen here sitting on top of the gear it will be added too.
Before attaching to the gear the hub was drilled and tapped so it would accept 6-40 set screws when done. I am making two set screws per hub. This will help keep the gear from shifting sideways when the set screw is tightened.
The the surface of the gear was lightly sanded. Flux was coated onto the mating surfaces of the hub and gear. The hub was centered onto the gear and held temporarily in place using a 1/4 inch screw with washers and a bolt. Finally the gear/hub combination was heated with the torch and solder was applied.
The gear with the new hub attached. The old hub remains in place at this point.
The gear was chucked up in the lathe and the old hub was machined off of the surface. The hole was then bored out to the proper diameter on the lathe.
The completed gear before boring the hole to the proper size.
After boring the “new” gear was temporarily attached to the shaft with the set screws in place in order to check the fit.
For this gear the hole was too large so a brass sleeve was turned on the lathe. First the outside dimension was turned to the correct diameter.
Then the center of the sleeve was bored to the proper size.
Then the sleeve was fit into the existing gear hole. Finally the hub would be drilled and tapped in order to accept set screws.
All an all I had to make adjustments to 22 gears. Four for each of the planets; Venus, Earth, Mars, Jupiter and Saturn, and then two for the Earth/Moon combination as described above.
Completed gears for Venus.
Completed gears for Earth.
Completed gears for Mars.
Completed gears for Jupiter.
Completed gears for Saturn.
Completed gears for the Moon.
After I had the hubs completed I had enough information to continue on with the design in more detail using SketchUp.
This is the 3D model with all of the gears adjusted to the correct thickness with hubs attached. The various shaft sizes are correct also.
This is a 2D version of the same design. Next I’ll need to start cutting each shaft to the correct length and from the correct tube or bar stock.
I was able to start working on the Orrery mechanism this week. The first step was to cut each of the brass tubes to the correct length based on the design above.
This picture shows all the tubes inserted into the respective gears and then slid into one another.
This close up shows how the tubes are nested inside one another.
Brass plates that were 6 x 12 inches originally were cut to the correct dimensions. The bottom two plates were cut to 6 x 7.5 inches. The top four are 6 x 5.875. Thicknesses varied from 0.0625″ to 0.03125″.
After cutting to size the corners of each plate were drilled 1/4 inch from each edge to create mounting holes. Here the smaller plates have been screwed together through the holes. This is for drilling the main gear shaft. By drilling all the plates at once it can be assured that the holes will line up from one layer to the next.
The gears were placed on top of the plates in order to determine exactly where to drill each side gear shaft.
Here the plates were set over the first layer gear to check fit. The height of the support rods for this layer could also be verified/adjusted. I wound up adjusting the support rod length of this layer to 1.75 inches. These are 1/4 inch brass rods cut to length and then threaded on each end to accept 6-32 screws.
Here the two plates are screwed together.
Another view. This layer contains the tubes for Mercury and Venus. The side shaft for the Venus drive gears C and D are visible in the front right. The long shaft rising up the the rear right is the drive shaft for Jupiter. This runs off of the Venus shaft, so gears A and B for Jupiter are also found in this first layer.
In this view the gears for Earth and Mars have been set in place in preparation for drilling the plate that are part of the first layer. The next plate will also require drilling for all these tubes and rods.
Today I made quite a bit of progress with the remaining gear levels.
First I had to drill holes for the gears on the next level that contains all the gears for Earth as well as gears A and B for Mars. This is a picture of the gears in the bottom level with the top plate removed.
After drilling the gear holes the next plate was set in place to make sure everything lines up. Of course it did.. Thanks Sketchup.
Next I made the support posts for the Earth/Mars level top plate.
This level is now complete. Gears C and D for Mars could also be attached.
A side view better showing the internal gears.
The Top plate for the Mars level was completed and gears C and D for Jupiter could be attached.
The base plate for the next level is set in place for measuring the post height for this plate.
The Saturn Gears are seen here temporarily set in place.
This is where I am as of today. The top plate has been set in place. I still need to make the support posts for this level and drill the holes for the Saturn A and C gears. The Shaft for these gears also needs to be made. When that is done the drive mechanism for the Orrery will be complete. Then I’ll move on to cleaning things up and making a base. The planets will need to be made as well as the rods that support them.
During the week I finished attaching the top plate to the Orrery. Here are some pictures of the unit at that point.
This weekend I worked on cleaning up the mechanism and adding spacers and washers to the shafts that needed them. I also adjusted the lengths of the tubes that weren’t quite the correct length. I then spent some time motorizing the unit.
I went through my box of old motors (yes I have a box of old motors) and found this 120VAC clock motor. I like the idea of using a clock motor as they are fairly quiet and turns at a very low speed with a lot of strength. They are also designed to be run continuously if I were to want to just leave the Orrery running.
This is the location where I decided to add the motor. In this location I can add a shaft to the motor with a gear and drive Mercury directly by impinging my drive gear onto Venus gear A.
A 1/4 inch hole was drilled into the top and bottom plate so the shaft would be supported by the plates.
A 1/4 inch shaft was cut that could be slid through the holes and hold the gear in place. The gear also has a 1/4 inch hole.
A hole was bored down the center of the shaft and set screws were also added. Set screws were also added to the hub of the drive gear.
The motor and shaft in there final location. All that is left is to drill some holes for the mounting screws. These will go through the holes seen on the mounting brackets that are part of the motor.
Before I put everything back together I started on the wood base. I needed the bottom brass plate to get the correct hole locations so I thought I would do that while the Orrery was disassembled.
A close up of the wood base temporarily attached. You can also see one of the screws holding the motor in place by the mounting bracket.
The whole Orrery has been put back together in this picture. You can see that the brass has all been cleaned up and I’ve added a cord to the motor for testing. Below is a video of the test run. Tape is attached to each planet tube in lieu of the rods that will hold planets eventually. The Moon gear is not mounted on it’s tube. The Moon tube still needs to be soldered to the plate that supports Mars gears C and D.
The motor turns at about 8 rpm. This is attached to a 48 tooth drive gear that impinges on Venus gear A which is 128 teeth, which is attached to Venus gear B which is 80. Venus gear B is attached to the tube for Mercury. So the orbit for Mercury takes about 12 seconds. This would be one Mercury year. Venus has a orbit that takes about 31 seconds. Earths year is about 50 seconds, with Mars being about 94 seconds. The years for Jupiter and Saturn are quite a bit longer. Jupiter is about 9.9 minutes and Saturn 24.5 minutes.
The last few days I worked mostly on some fine tuning of the drive mechanism. I put spacers and tubes on the shafts holding gears to better hold them in place. I also filed slight flat spots on each planet tube where set screws impinge. This will help them stay in place better. Here are some close ups of each gear layer.
Saturn layer is on top.
The center here is the Jupiter drive gears.
The center is the Mars drive gears. The lower level are the Earth gears as well as the A B gears for Mars.
Better view of the Earth layer of gears.
This is the Venus layer, but also contains gears for other levels.
I soldered the tube for the Moon to the Mars plate. This will hold the gear in place while the Earth orbits the Sun. A gear mounted to the Earth axis will rotate around this stationary gear causing the moon to orbit the Earth.
This is the top level of the oak base.
The router was used to round the edges of the base.
I routered the edge of an oak strip that will be made into the lower part of the base.
The strip was cut at 45’s and made into a frame for the lower base. Here they are just set in place.
The frame was glued and clamped while the glue dried.
The lower frame was then glued and screwed to the top plate.
The completed base ready for sanding.
The completed base after staining. At this point I had a major problem. When I went to varnish the base I noticed that the top plate was turned on the frame slightly. I was out about an eighth inch from one side to the other. It was glued and screwed into place. So….. I wound up making the whole base a second time. That was not one of my better moves.
The one on the left is the good one.
I didn’t do too much on the Orrery over the last week as I was on vacation. I did do a bit of work last weekend before I left and then again today after I returned home.
This is a picture of the first two plates mounted to the finished base. I assembled it this far because I needed to measure the area for the power supply that will illuminate the sun. It will be mounted to the second plate in this picture in the open region on the lower left of the plate as seen here.
I will be using this 5 volt wall mount power supply.
I removed the cover and pulled out the PC board. I then soldered new AC power in and DC power out wires into place.
The wall plug plates were removed and the new power in wires threaded through the holes.
The completed power supply will be hidden inside a more Steampunk looking box. The box will have a connection inside the box for the power cord and motor wires.
Speaking of the motor I taped it off and spray painted it with a gloss black.
The motor after removing the masking tape.
The motor will be mounted to this location when completed.
This is the final 3D Sketchup drawing for the Orrery.
One final note. I wasn’t happy with the finish on the second base. I rushed the staining and varnishing a bit and wound up with small inclusions in the varnish surface. I assume these were from not wiping down the surface properly after staining and small bits of cloth and saw dust must have been on the surface. Sooo…. today I used paint stripper and removed the varnish and stain. I then re-sanded the piece and applied fresh stain. I will be much more careful on the surface prep before varnishing this time.
This week I worked on making a electrical box to house the Sun power supply and the electrical connections for the cord and motor.
A strip of brass was used to make the box.
The brass was cut to the correct width and notched where bends would be made.
Holes were pre-drilled for mounting screws and openings for wires.Then the box was shaped by bending right angles at the notch sections. Flaps on the top and bottom were also bent at right angles.
The final box shape is shown above resting where it will be mounted on the Orrery.
The box was screwed to the surface and an electrical connector mounted in one end.
The motor was then mounted and wired into the electrical box. A cloth sleeve was put over the white motor wires to cover them .
The power supply was mounted and then wired in.
A copper cover was was fabricated that is held in place by 4 chrome acorn nuts.
I had some vintage reproduction wire from another project that I used for the power cable.
The 5 volt line from the power supply runs out of the box on the left and through the base to the under side.
The Orrery was then put back together.
On the under side an aluminum piece was fabricated to hold the 3/16 inch tube for the sun in place.
Adhesive felt was added to the bottom and the Sun power wires threaded up though the Sun rod.
I wasn’t happy with the motor strength the way it was set up. The motor is designed to reverse direction when it binds tight and the motor was doing that periodically. I had two options. Use a bigger motor or switch to a smaller drive gear. Since I did not have another motor of this type I decided to switch out the drive gear.
The current drive gear is a 48 tooth as shown above.
My plan was to switch the current 48 tooth for this 30 tooth gear. This would decrease the speed by 60%, but also increase the torque by the same amount.
Above is the 30 tooth gear mounted in place. All in all it took about 3 hours to make this switch out. I had to take everything apart and re drill the drive shaft and motor mounting holes on the bottom two plates. I am pleased with the result and it was well worth the time spent.
So this week I started making the mounting brackets for the planet rods. I want to make the whole set up as light as possible so I will use aluminum that will be painted black after fabrication is complete.
These are some 3/8ths and 1/4 inch aluminum I will be using.
These are the rough cut outs for the Mars, Jupiter and Saturn brackets.
These are the Saturn and Jupiter plates after drilling the main holes for the horizontal rod and vertical planet tubes on the Orrery. Holes were drilled and tapped for the set screws that will hold the brackets in place. A slot was cut into the hole for the vertical tubes so that the set screw could be used to pinch the bracket tight.
These are the Jupiter and Saturn brackets mounted on there respective vertical tubes. For the rods extending vertically I am using 1/4 inch brass tubes to keep the weight low.
Similar picture with the Mars bracket also mounted.
The Mars, Jupiter and Saturn brackets were removed sanded and painted. While waiting for the paint to dry I started work on the Earth bracket and mount. This one is a bit more complicated as the Moon gear is mounted below it and the moon rotates via a smaller gear on the planet mounting end of the rod. Here is the Earth mounting bracket completed and a 3/16ths inch rod slid in place.
The Earth end of the bracket. The rod in between is not cut to the correct length in this picture.
A close up view of the Earth brackets prior to painting. The one on the left will have a bearing inside the larger hole that will allow the Moon and Earth to rotate while the Earth orbits the Sun. The bracket on the left holds the Earth rod to the vertical Earth tube of the Orrery.
I had a busy week and was able to complete a lot of work on the Orrery. I did some finish work on the Mars, Jupiter and Saturn brackets. I did a bit of a redesign of the Earth/Moon bracket/bearing.
In this picture the Mars, Jupiter and Saturn Brackets have been primed, painted and mounted to the proper planet tubes.
The outside end of the Earth bracket was painted and the Moon bearing was inserted. The bearing is held in place with set screws.
This is the modification I made to the Earth bracket. I made it longer so the brass mounting rod would be deeper into the bracket. It is held in place with two set screws.
This is the moon bearing and gear. To the right is the brass rod that will be used to fabricate a shaft that will insert into the bearing. The shaft was to the proper dimensions. The one end is wide enough to stop against the inside of the bearing. The other end slides through and is threaded for the mounting bolt.
This is the completed Earth/Moon assembly.
These are a couple of pictures of the completed Earth bracket.
A larger piece of brass was used to make a bushing that will have the Earth and moon vertical mounting rods attached to it.
This is the Earth bracket with the bushing attached. As the horizontal Earth rod rotates around the Sun the small gear spins on the large stationary gear. The gears are set so for every time the Earth goes around the Sun once this bushing will rotate 12 times. Not exactly right, but still the equivalent of about once per month.
I added a rod sticking out of the Earth bushing. This will have the Moon mounted to it eventually.
The Venus and Mercury brackets were then fabricated.
This is the Venus bracket in process.
This is the Orrery with all of the brackets attached except the one for Mercury. Paints still drying on that one.
Set screws for Mars, Jupiter and Saturn were made by soldering brass screw pieces into standard brass knurled nuts.
These are the set screws inserted into the brackets. Mars, Jupiter and Saturn will have brass tubes inserted into these brackets that will extend outwards horizontally. The one for Saturn will be about 29 inches long. I still need to make some elbow pieces for these tubes. These will have vertical tubes sticking up from them that the axis for each planet.
The table above has the dimensions I will be using for the orbital radii and planet diameters. (second and third columns on the left). The relationship between planet diameters will be consistent with the size ratios in the solar system. The orbital radii and rotation speeds will also match the ratios seen in real life. Two things will be different however. First, I will be making the Sun 2 inches in diameter which is much smaller than it would be given the diameter of the planets I am using. Second, the planet diameters with respect to there orbital radii will not be consistent with reality. Given the orbits I am using I would have to make the planets very tiny to match this ratio.
Today I worked on the “elbows” that will be on the ends the horizontal planet rods. The planets Mars, Jupiter and Saturn will be mounted this way. Vertical 1/8 inch planet axis will extend out of the elbows. I am making these out of aluminum stock for light weight. These will be painted black.
Each of the three elbows was cut from this 3/8 inch aluminum piece.
These are two of the three roughly cut to shape.
Each was machined, drilled and tapped to accept 6-40 allen set screws.
This is the Jupiter elbow attached to the horizontal rod temporarily. It still needs to be painted.
In this picture the elbow and rod for Mars has been attached. This one is painted.
Here the Jupiter rod is attached.
The whole thing as of today. Next I’ll be working on the vertical axis for each planet. Then it will be time to create the planets and Sun.
Finally a video of the Orrery working as completed so far.
This week was all about the Sun, in my model version.
I found a company (KitKraft.com) the distributes clear acrylic hemispheres of various sizes. These are the two inch diameter hemispheres I will be using as the outside shell of my sun.
I first needed to accurately drill 3/16 inch holes in the center of each hemisphere so they could be slid onto the tube for the Sun. I used my mill for this as I could find center to 1/1000th of an inch.
The hemisphere slides onto the Sun tube. I small brass ring with a set screw was fabricated for around the tube that the bottom. The hemisphere rests on ring.
The top piece was similarly drilled and another brass ring with set screws fabricated for the top. A brass plug was made for inserting into the 3/16 Sun tube. It is held in place by the top ring also. A slot was cut down the side of the tube where the positive lead from the power supply could come out into the inside of the Sun. The brass rod itself will serve as the negative/ground for the lights.
Next I drilled and tapped the ends of a 1/2 inch piece of square quarter inch brass rod. These were tapped for 6-40 set screws. This piece will serve as a mounting block for the Sun light bulbs and will be held in place in the center of the sun by the 6-40 set screws.
The center of the rod was drilled with a 3/16 inch hole for sliding onto the Sun tube. Two pin type electrical connectors were soldered on the the brass. One of the leads for each bulb will be inserted into these connectors and provide the negative side of the voltage.
This picture shows the two bulbs inserted into the ground pin connectors. The positive terminal use the same pin connectors only soldered to wire and covered with black shrink tubing in order to prevent shorts. There is also a pin connector that allows the wire harness to be unplugged from the positive lead. This way the wire can be pulled back through the Sun tube if it needs to be repaired without cutting or de-soldering. The bulbs I used are two “Mini Maglite” 2 cell bulbs designed to work at three volts.
The ground line was attached directly from the negative power supply line, through a 1.2 ohm 5W power resistor. This cuts the voltage from the 5V power supply to the Maglite bulbs down to more or less the required 3 volts.
This is the completed mounting and wiring of the sun. A added a coil spring between the top hemisphere and ring. This does a better job of holding the top piece in place.
The assembly from farther out.
And of coarse “let there be light”. I still need to paint the Sun sphere with yellow and orange translucent paints. That way we’ll see the Sun glow, but not the inner workings.
I also purchased acrylic hemispheres for Jupiter and Saturn. I am making Jupiter 1-1/2 inches in diameter. Saturn will be 1-1/4 inches. The inner planets and the Moon will be made using Fimo clay. Just a note on planet diameters. When making an Orrery I have found one main issue. The solar system is so vast when compared to planet diameters that unless you make a huge Orrery the planets will be very tiny. What I have opted to do is make the planets large enough to see. The ratios between Jupiter and Saturn will be close to reality. The ratios of the inner planets will also be close to the ratios found in the solar system, that is, the diameter ratios between Mercury, Venus, Earth, the Moon and Mars will be fairly accurate. These inner planets will be much bigger in comparison to Jupiter and Saturn than found in nature. The Sun diameter will be much smaller than real life in relation to all the planets.
It’s getting very close now. I have finished painting the Sun and completed the inner planets and Moon, mounting them on there axes.
It’s hard to see in this picture but the Hemisphere on the left was spot painted on the inside surface with an Orange. The one on the left has been dappled with a bright yellow on the outside surface.
Both hemispheres complete.
The painted sun pieces mounted on the Orrery. I added a felt pad between the mounting spring and the Sun to protect the painted surface.
Axes were cut from 1/8 inch brass tubing. Because the diameter of Mars and Mercury are so small I soldered on a 3/32 inch tube to go through these two planets.
This is the mounted axis for the moon attached to the Earth. It is a 1/16 brass rod soldered to a small mounting ring.
These are the axes for the four inner planets attached to the elbows made earlier.
At my wife Kathleen’s suggestion I decided to make the inner planets out of FIMO clay. These are the completed FIMO clay planets before painting. The top left is Mercury. The one in the middle is Venus. The bottom left is Earth, the top right is Mars and the bottom right is the Moon. After baking the planets had the following final average diameters:
Mercury = 23/64 inch
Venus = 33/64 inch
Earth = 37/64 inch
Moon = 15/64 inch
Mars = 23/64 inch
Each planet was centered using the mill and then drilled to the correct diameter.
This is a close up of the Earth/Moon after mounting and painting. Model glue was used to bond all of the planets to there axes.
A close up of all the planets mounted and the Orrery plugged in.
Finally, this is a video of the Orrery working with all four inner planets and the Moon completed.
All that is left is to complete the planets Jupiter and Saturn along with there axes and get them mounted.
I’ve got just a few updates today. I have been working on Jupiter and Saturn along with there axes.
Here I drilled and glued the 1 1/2 inch hemispheres for Jupiter.
The holes are 1/8th inch. The surface of the now sphere was then sanded.
This is the mounting axis for Jupiter. It is cut from 1/8th inch tubing.
Brass retaining rings were cut from 1/4 inch brass rod, bored out the 1/8th inch. Each was drilled and tapped to accept a 6-40 set screw. One one these goes on the bottom and one on the top for both Jupiter and Saturn. These hold the planet onto the brass tube that serves as an axis for each planet.
Jupiter test mounted before painting. The top retaining ring is visible. One is also on the bottom of the planet.
This picture shows both Jupiter (left) and Saturn (right). The Saturn hemispheres have just been cut and not glued together. I still need to paint Jupiter. Saturn has to be glued painted and have the rings added.
This picture is not to clear, but it shows Jupiter after painting.
This is another of Jupiter painted. Saturn’s 1 1/4 inch diameter sphere is mounted on the right.
This is a fresh closeup of the Earth/Moon. When I was done making the inner planets and Moon from FIMO clay I was taking the tray of FIMO into my basement workshop. Passing through a dark area I noticed I had a glow in the dark piece of FIMO. I remade the Moon from a glow in the dark piece.
I haven’t had a lot of time lately to work on the Orrery lately, but I have been working on making the final planet Saturn.
The Saturn hemispheres are 1.25 inches in diameter and are on the right. Similar to Jupiter these were pre-drilled, glued sanded and painted.
In addition to the axis holes on the top and bottom 1/16th inch holes were drilled at the equator and brass rods were inserted. These will serve to support Saturn’s rings. They are set at and angle to provide an axial tilt to Saturn of about 27 degrees. I chose to spray paint Saturn with a light yellow base coat.
The surface was then painted with yellow, orange and brown stripes.
The brass rods were taped off and Saturn was sprayed with several layers of clear coat.
I used this circle cutter and colored card board stock supplied by my lovely wife Kathleen to fashion the rings.
These are the size of the two rings I will be adding. The one on the left is more orange than seen in this picture and the one on the right more brown.
Here the rings are laid onto the brass support rods and the colors can be seen more clearly.
A thick piece of card board was sectioned into quarters so the rods could fit through the ring. A second layer of colored rings was laid on top.
The hole ring structure was then glued and clamped.
These are the rings after gluing. The edges of the rings were coated with colored markers to match the tops.
A set of inner rings were glued to the surface of the wider brown ring.
So here is Saturn so far. I need to do some light sanding on the rings and then I will put a few layers of clear coat on the surface. After that I just mount it and the Orrery will be complete.
The clear was added to Saturn. I used two layers.
Today I also added a brace for the 39 inch Saturn support rod.
I quarter inch by 1/16th inch strip was made to strap to the bottom of the rod.
The support helps keep the bar from bouncing and warping due to gravity.
Finally, here are the pictures of the completed Orrery for your perusal.
Mars and inner planets.
Earth and Moon
Venus and Sun
Signature close up.
So that is the completion of my latest project.
Just in case anyone wants to use this blog to make their own Orrery I have included the parts numbers for the Boston Gears I used. I realized I hadn’t listed these before.
Below are some of the spreadsheets I used for my calculations: