This Nixie clock was the result of a conversation about single tube clocks in the Facebook Nixie Clocks Fan Page.
Single tube clocks are not popular with some nixie lovers who prefers 4 or 6 digit tubed clocks for ease of reading. A single tube clock displays the time in sequence of H,H, M,M,,, and repeats but is very easy to get accustomed to the display format. They can be programmed to have a different RGB colour for each of the functions of the time as well as display temperature and humidity.
A lot of single tube clocks take on the basic format of being mounted in perspex, wood or metal cases with the tube sticking out the top of them. I wanted to make mine a bit different and got the idea of a 'Faberge' styled clock using an Ostrich egg shell for the casing.
Several problems presented themselves at the onset, the main one being trying to find a kit or circuit board that would fit inside the shell and leave sufficient space for the tube to be mounted. The SN18 clock kit from PV Electronics is ideal and would meet the requirement. It can be built with either an IN-18 tube or Dalibor Farny's R|Z568M tube
The next criteria was what tube? I have used a wide variety of Nixie tubes in my clocks from the small IN-17 to 30 mm digit ZM1040 and a good few in between including side view, top view and inverted display tubes. This clock needed a statement tube and I opted for an IN-18 which have a 40 mm digit size, 30 mm in diameter and are nearly 70 mm in height.
So that is the basis of the clock, now on with the construction!
My apologies if it seems long winded but I wanted to include the details of the steps for anyone to follow.
Step 1: Construction Materials
1 x Ostrich Egg Shell - Ebay
1 x SN18 Nixie Clock kit - PV Electronics
1 x IN-18 Nixie Tube - Ebay
3 x Single Pole Push to Make Switches (with nuts) - Farnell
1 x Orange 3 mm LED - Farnell
1 x Green 3 mm LED - Farnell
300 mm 12 way Ribbon Cable - Hobbytronics
150 mm x 3 mm Diameter Heat Shrink Tubing - Farnell
1 x USB B to USB A adaptor Cable - Any computer shop
1 x 3.5 mm Stereo Panel Mounting Socket - Farnell
1 off 1/2" x 3" Brass Repair Pipe - Plumbing stores
4 off 1/2" Brass Flange Nuts
1 off 3/4" Brass Tank Connector
1 off 3/4" Brass Flange Nut
1 off 50 mm x 6 mm Brass Disk - Metal Stockists
22 mm Round Brass Bar
14 mm Round Brass Bar
6 MM round Brass Bar
5 mm Flat brass bar
24 off 3 mm Short Dome Headed Brass Screws
3 off 3 x 30 mm Dome Headed Brass Screws - Ebay
Wood for the Base - What I had lying around
1 off 1 x 67 mm Diameter PET Circle - I had some from a previous project
3 x 35 mm Brass Pipe Olives - Plumbing store
35 mm Beech Dowel or similar - DIY or Timber Store
3 x 3 mm T Nuts - Hobby store or Ebay
3 x Small Wood Screws
500 mm Fine Brass Chain - Ebay
500 mm x 1/4" Brass Boiler Banding - Steam Modelling Suppliers
1 M x 3/16" Brass Boiler Banding
2 Part Epoxy Glue
1 can of Clear Acrylic Spray - Auto Accessory Shop
Thin Foam Sheeting - Craft Shop
Step 2: The Clock Casing
Faberge eggs are world renowned and extremely valuable with one fetching $18.5 million at auction in 2007. Mine is just a simple Ostrich egg that has been tarted up a bit to look expensive and I do not think it would be worth that much!
Ostrich eggs are approximately 150 mm x 110 mm (6" x 4.3") so there is a reasonable amount of space for my choice of the IN-18 Nixie tube inside it.
So, what to do with the egg shell? I have seen some very elaborate carvings and many have featured here in Instructables and decided to try and keep it simple in context as well as functional. Doors that open to view the Nixie tubes with a switch that cuts the tube supply when closed was the main idea I had with some decoration on them and the main shell part but hinging the doors would prove to be too difficult and would detract from the clean look that no doors gave.
When deciding how I was going to start the design of the egg I looked at a lot of work by others and was impressed as to the complexity that some of the designs exhibited. There was no way that my limited skills and lack of knowledge of engraving was going to emulate any of what I had seen so I opted for external decoration of the shell.
When I was looking a egg shell carving I saw that a lot of the people doing it had a jig to hold the shell and they were able to rotate the shell as they worked. I decided I would make a simple wooden frame that would hold the egg in place with suction cups at either end with one end having a spring to apply some pressure to hold the shell in place. Suction cups are available in packs of mixed sizes and I got a few 30 mm and 40 mm cups. Making the frame was straight forwards, a base plate, 2 uprights and 2 wooden disks. The fixed disk had a flat bottomed hole in it where a wood screw held it to one of the uprights and the suction cup fitted into this hole as well. To get some pressure on the shell the other disk was attached to a piece of dowel and a spring slipped over the dowel before it passed through a hole in the other upright. The larger suction cup was fitted to this and it was just a case of pulling against the spring to insert the shell. This would have been great if not for the tendency of the egg shell to slip when rotated, so Plan II had to be devised!
The second jig was actually so simple I could not have believed that I hadn't thought of it at the start!
It consists of a base plate, a single upright that has a 20 mm dowel sticking out at the centre line of the egg shell. The shell is just slipped onto the dowel and a block whose height is just below the mid point of the egg to allow for a pencil to be moved along it and mark the shell. I had measured the circumference of the shell at 444.00 mm and set the dowel at a 67.20 mm centre (C = 2 * π * r - transposed to - r = C / (2 * π) (yes, I paid attention in maths class!) and made a pencil line around this by rotating the shell. I just measured 74 mm along the line and marked out the start point of the divisions, measure and rotate it again the same distance and mark again until I had 6 equally spaced marks on the circumference, To get the segments I just moved the pencil along the block from the mark until I reached the 'crown' of the egg shell and repeated for the rest of the marks. Sounds complicated but if you look at the photographs of the technique you will see how simple it actually is. All you need to do is hold the shell steady as you mark it.
I later found this which is in development at present. Would probably be beyond my means!
The next step was to cut the shell to get the parts free. Dremel make ultra thin cut off disks and I have a good few of them along with the mandrels needed to hold them, I also have diamond cutting wheels so it was a case of which would work best.
A dust mask is essential for this task along with some form of extraction near the cutting area, I used my shop vac for this after making a wide nozzle from cardboard that could fit near the cutting area. I tried out both cutting disks on a spare piece of shell I had asked the supplier for and the cut off disks proved to be the best solution to make the cuts in the shell. They wear down quite quickly but are effective.
Now the shell was cut and ready for the next step, mounting it to the base. With the shell having a 20 mm hole where it was 'blown' this is ideal for the connection to the base. Some foam rings and then the lock nut to hold it in place. Do not over tighten this, allow some slight movement or there is a risk of damaging the shell.
The inside of the shell has a membrane attached to it that had to be carefully removed from the visible areas as I sprayed the interior with clear acrylic to make it partly reflective, I didn't do the bottom half of the shell (out of sight, out of mind!) I removed this membrane with coarse steel wool and by holding the shell up against a light source to see if there were any areas that still had bits of membrane attached. Wear a dust mask whilst doing this part as well. You can see the membrane in the photo where the main shell is on the pedestal.
Step 3: Scrap Wood Comes in Handy!
Woodwork for base.
I had a lot of cut offs (or is it off cuts?) from hardwood that I have accumulated from making other clock bases so I made them into a chequered block by planing them square and gluing together in two alternating layers to get a chequer board effect on the ends of the block. I drew as large a circle as I could on the block and roughly cut it out with a jig saw. I marked the centre and drilled a 10 mm hole for mounting it in the chuck of my lathe with a piece of screwed rod and a flanged nut, an ordinary nut and washer does this job too. One thing I had forgotten to take into consideration was the clearance to the bed of the lathe, luckily I got away with it as the widest part of the rough circle missed it by 1 mm!
I had to mount a tool so it stuck out quite a bit from the tool post and then start to remove the waste from the circle. I had to take extremely thin cuts until I got it nearing a circular shape and then cut it to the diameter I wanted,
Next was to round off the outer edges with a router and a round over bit. I don't have a router table so I mounted my router underneath the table that my mitre saw sits on after cutting a hole that would allow the bit to be raised above the surface. I screwed a scrap length of wood set at the radius of the now round base section to make rounding it off easier. I cautiously eased the base along the wood until it made contact with the round over bit and then turned it anticlockwise against the bit feeding it round carefully. Once this was done I flipped it over and did the other side to match. The base was remounted in the lathe for sanding the surfaces and edge to get a smooth finish for the later application of clear acrylic.
The holes for the push buttons and the LED housings were marked out and drilled. Usually with a solid wood base I would create a cavity that would house the circuit board but in this clock I made a smallish one and channels out to the holes for each function. I cut a recess for the base plate that would cover everything on the bottom and leave it looking neat. The base cover is made from clear 1 mm sheet PET and one side sprayed with black acrylic paint. There are no screw holes for this as it is held in place by the 3 bun feet that are screwed to the base.
Another task that needed to be done was the outlet for the supply cable and for the GPS socket. A simple recess was milled across the back edge of the clock base with a tool I made specifically to do this and a shaped brass plate screwed onto the flat surface with the shroud I always tend to fit to the outlet plates on my clocks. I drilled a hole through the recess into the cavity for the cables.
To mount the clock board in the shell I needed to make a disk that would fit snugly inside the shell that would not need fixings to hold it in place. As I had no suitable plywood to hand but had some 3 mm modelling ply I cut 4 disks and glued them together after drilling a central 10 mm hole that would be used for machining it later. Modelling ply is very light as it is intended for use in model aircraft and is quite flexible. When gluing the disks together I alternated the lay of the ply to give it more strength. I found that ostrich egg shells are not exactly round after machining the disk to the diameter required and had to shave a bit of areas to get a good fit inside the shell. I also had to make a slight taper to compensate for the internal curve of the shell. Once it was machined to the correct diameter I needed to cut the centre out to fit the tube plate and mark the fixing holes that would retain the board to the underside.
I used a modified tank cutter to make the two major diameters, one on either side of the disk, before mounting it in the lathe to remove the excess which allowed the disk to break free from the centre portion. I positioned the circuit board in the underside hole and marked out the screw holes for mounting it to the disk.
Step 4: A Little Bit of Brass Work
From my previous Instructables you would pick up on the fact that I like brass and wood in Nixie Clock construction. For this clock there are quite a few brass parts used on it. A support column for the shell, boiler banding 'waistband' and vertical ribs, push buttons and the socket panel at the back of the clock.
I use a lot of brass plumbing fittings in my clocks as well as stock brass, modifying the fittings to become decorative and functional parts. It is a cheap way of doing things compared to buying large section round brass bar and having to machine most of it away to get the same result.
The column is made from a pipe repair tube and is clamped to the wooden base and the base of the egg shell.
I used a brass flanged tank connector and nuts for this that were soldered to the brass pipe repair section. The one on the bottom of the shell was dished slightly to meet the curve of the shell. Between the flange nut and shell is foam sheeting that takes up any variation and allows some pressure to be applied to hold the shell firmly without damaging it with direct contact. I had to step the contours between the fittings as when I was trying to get a smooth finish to the sweep from the pipe to the top fitting the threads of the lock nut and tank fitting broke away, I just cut a straight recess to make them disappear and smoothed it out with emery paper. The other end of the brass tube had a 40 mm brass disk that was clamped between two smaller flange tank nuts. The underside of this disk has 3 x 3 mm tapped holes for screws that pass through the wooden section to fix it firmly. I smoothed out the top flange nut to make then look less industrial by putting a radius between the hex and the face of it..
. I also added some narrower boiler banding (3/16") from the 'egg cup' below the egg to the 'waistband' around the circumference. To get a consistent hole in them I made a little jig that I slipped the banding into for drilling 3 mm holes in each end. I rounded the ends off by pinning them by the holes and turning against a milling cutter. I made 2.4 mm holes in the 'egg cup' at 60 degree intervals, tapped to 3 mm and screwed the narrower banding into them. That sounds easier than it seems as they had to be drilled at an angle and I managed to break 2 drills doing it. To fit the vertical banding to the waistband I fitted it and set every thing square before marking the positions of the ribs on the 'waistband'. I drilled 2.4 mm holes through both and tapped them to 3 mm. I fitted some dome headed screws to the joint and soldered them into position for added security. The joints were then sanded smooth on the inside. I had soldered two little blocks of brass to the ends of the waistband, one with a 3 mm clearance hole and the other tapped for a 3 mm brass screw that would tighten the band to the shell.
The controls for the clock being remote from the board meant that I had to make buttons for them. The drawing shows how they were designed. These just fit into holes in the base and are epoxied in place with wiring going back to the board through the support column. The same applied for the indicator LEDs for the DST and GPS SYNC functions, a couple of 10 mm brass rod pieces with holes for the LEDs. The 'lens' is epoxy infill stirred to get small air bubbles which diffuses the light from the LEDs. Here is an Instructable I made on how to do it.
The feet for the base are made from pipe olives, a piece of beech dowel and T Nuts in the same way as the Tantalus Clock but a bit smaller. Instead of gluing the olives to the dowel I tapped them onto the dowel with a mallet and I drilled small holes through the olive and hammered some cut down panel pins into it until they were flush to the surface. These are kept to the back when fitting the feet so they are not seen.
3 mm T Nuts are available from most R/C hobby stores and modelling shops.
When fitting the clock board to the support disk I noticed that there was a gap between the tube plate and the tube board. To hide this I made a ring from the 1/4" banding to fit over this. Bending the banding to the size of the tube plate was made easy as the diameter of a can of WD40 was the exact same as the diameter of the tube plate. I put a copper loop around the banding and drew it closed by twisting the wire together then it was just a case of soldering the butt join. This would be at the back of the tube plate and would not be seen.
I hid the facing cut edge of the shell with some 3 mm brass tubing bent into the shape and filed the back off the tubing to leave it as a channel section. I dressed it up with a 2 mm diamond cutter so that it would be a neat fit onto the shell edge.
I dropped the level of the wooden tube plate and added an internal brass band made from the 1/4" boiler strapping that gave a better look to the inside of the shell. The join is hidden behind the 3 mm tubing for the RGB LED on top of the shell..
The additional RGB LED that adorns the top of the shell was made in a similar fashion to the temperature sensors cover made for the Victorian Tantalus clock and I made a small adaptor to mount it onto the shell with a 3 mm hole drilled in the stub that was on the inside of the shell for the pipe with the wiring for the RGB LED. The wiring is fed through a piece of 3 mm brass tube that is curved to match the inside of the shell. The tube is just pushed into the stub of the RGB housing to help support it along with epoxy to hold it to the shell.
The rear panel was made from 15 mm brass flat bar and I added a shroud for the supply cable entry as the plug to the board has to pass through this, the GPS socket is sunk into the surface and the wiring soldered to the back of it.
Step 5: The Electronics Side of Things.
The electronics in this clock is the SN class kit from PV Electronics which uses a single IN-18 Nixie tube to tell the time in this format - H,H,,M,M,, repeat. It displays the tens of hour digit then the units hour digit and does the same for the minutes. Once you get the hang of the way it works then it becomes instinctive to know the time.
I am not going into details about the kit as you can check it out at the link above.
So how do you mount the controls in an egg shell?
Short answer, you don't!
You remote them to the base of the clock to minimise damage. Brand new clock kit for me and already hacking it to suit my needs! The push buttons are housed in brass enclosures on the base with the wiring going up the column to the original positions on the board, the same goes for the LEDs and the PSU and GPS sockets which are brought out to the back of the base.
Another addition to the board was adding a second RGB LED to the circuit and fitting this to the top of the egg shell in the same style as my SARA and Tantalus clocks. I added 3 extra 270 Ohm resistors and took the feed from the input side of the existing RGB LED resistors that come from the PIC chip with the 4 wires fed up through a curved 3 mm OD brass tube to the housing on top of the egg..
It would have been nice to have an LED that pulsed the seconds in this design but there is no facility to add one to the circuit. This is something I hope that future iterations of the kit might have. (Just found out that the kit can be programmed to do this for a little extra on the price.)
Step 6: All Together Now!
Here is the 'Faberge' clock fully built and 'ticking' away merrily.
The last picture is testing the clock before adding the RGB LED housing, the rear plate and polishing the brass up.
The overall look of the clock is quite good and the additional RGB LED gives it a nice touch.
I am thinking of doing a two tube version of this clock that will have time, temperature and humidity capabilities. As I am hopeless at electronics I will have to enlisted the help of another enthusiast to do the electronic side of things. It will be in the same lines as this and hopefully I have enough scrap wood to make another base for it!
During the build process and compiling of the Instructable I kept all of the photographs and sketches in a folder marked 'Humpty Dumpty' and hoping that the egg shell would not have a great fall before I completed it.
I am entering this Instructable into the Big and Small Contest as it is the biggest egg you can get!
If you think it worthy of a vote then please do so.