Introduction: Hand in Hand Clock



I recently moved (and out of my parents home) and among the huge amount of stuff missing, is a clock. Now I like quirky stuff, so a bought normal clock simply won't do. There are already a ton of DIY led clocks out there, but I wanted something mechanical.

The thing I wanted is a hand in hand clock. This clock type has the minute hand attached to the end of the hour hand (and optionally, the second hand to the end of the minute hand). It is a fairly unknown clock type, but I was introduced with it 5 years ago by an old classmate and have been thinking about building one for 3 years now. Finally, with a clock missing, it was time to build one. The clock is 3D printable and requires no support. It does require a printer 200x200mm for the minute hand, but otherwise, 150x150 will also work.

This clock is (or will be) entered in the 3D Printing Contest, Move It Contest and Mind For Design contest. A vote would be great, but only if you think this clock has deserved it. Thanks in advance.

Step 1: Parts and Tools

To make this clock you will need several things.For some of the screws, amounts may vary by a bit.

Stuff:

  • 200-300g of 3D printing filament in a colour of your choice.
  • 2x 608 bearing
  • 3x 624 bearing
  • 3x 683 bearing
  • 3x 684 bearing
  • 6x M3 washer
  • 3x M3 nut
  • 3x M3 screw, 6mm
  • 6x M3 screw, 10mm
  • 6x M3 washer, drilled to 4mm
  • 7x M4 washer
  • 7x M4 nut
  • 2x M4 screw, 20mm
  • 2x M4 screw, 40mm
  • 1x M4 thread, 75mm
  • 1x M8 nut
  • 1x M8 thread, 25mm
  • 1x Nema17 short stepper motor
  • Any arduino compatibel microcontroller with at least 5 I/O's
  • Stepper motor driver
  • 9V or 12V power supply, 250mA+
  • 16V 100uF electrolytic capacitor
  • 2x switches
  • 3x 10k resistor
  • Piece of prototype board
  • Thin cable or white wire

Tools:

  • A 3D printer
  • A drill with 2mm, 2.5, 3mm, 4mm and 4.5mm metal drill bits
  • Super glue
  • Locktite
  • Basic screwdivers, pliers and wrenches
  • files

Step 2: 3D Printing

The most laborious tast of the clock is 3D printing it. It is one of my smaller projects, but it will still take around 10 hours to print, depending on your printer and settings. I printed it at 40% infill, at 0.4mm layer thickness. I don´t want to hide the fact that it is 3D printed.

Download files here: http://ytec3d.com/hand-in-hand-clock/

A full list of the 3D printed parts:

  • HIHC face minute bracket 1
  • HIHC face minute bracket 2
  • HIHC face plate
  • HIHC hour hand holder
  • HIHC hour hand
  • HIHC HTM1 z48 m1.25
  • HIHC HTM2 z45-12 m1.25
  • HIHC HTM3 z48-15 m1.25
  • HIHC minute bearing holder
  • HIHC Minute end gear z12 M1.5 a25
  • HIHC minute hand
  • HIHC minute inbetween gear 1 z13 M1.5 a25
  • HIHC minute inbetween gear 2 z15 M1.5 a25
  • HIHC minute inbetween gear 3 z25 M1.5 a25
  • HIHC minute Receiver gear z12 M1.5 a25
  • HIHC motor gear z12 m1.25

Step 3: Hand Assembly

When the printing is finally done, you can start assembly. The starting point is the hands.

  1. Press fit an M4 nut in the minute hand. When you are statisfied it is perpendicular, use super glue to secure it. Also get as much weight as possible in the back of the minute hand, to balance it out. (this step can also be used for the hour hand)
  2. The Hour hand requires some work before it can be used. Drill the 6 holes with a 2.5mm drill, so the M3 screws will thread themselves in. Also carefully file the 2 bearing holes so the bearings will not destroy the hour hand.
  3. Press fit 2 684 bearing in the hour hand. Also press fit the 3 M3 nuts in the hour hand. The small holder needs a 684 bearing, the large holder a 624 bearing and the 3 gears need 683 bearings. The remaining 2 gears need M4 nuts, which need to be glued in place.
  4. Mount the 3 idling gears in the hour hand. The bearing needs to be down, and the 25 tooth gear (the largest gear) need to be placed first. After that, there is only one way it will fit properly.
  5. Mount the minute hand to the hour hand with the assembly of nuts and washers shown in the pictures. Use locktite on the minute hand when it fits right.
  6. Drill a hole through the 25mm M8 thread. Start of small (2mm) and work your way up to at least 4.5mm. Try to stay as much in the center as possible.
  7. Tap an M8 thread in the hour hand holder. Then, screw the hollow M8 thread in the hour hand holder, and when it is in the middle, glue it in place.
  8. Attach the M4 thread to the receiver gear. Use good thread locking glue on this, to secure it. It will receive the most strain of any part in the clock.
  9. Mount the hour hand holder assembly on the end, using the pictures as guide. Try and spin the minute hand to see how smooth it goes. If needed, you can sand some of the gears to make them run smoother.
  10. When you are satisfied that the hand assembly is running well, disassemble and use thread locking glue and super glue to properly secure everything in place.

Step 4: House Assembly

The housing holds all the gears and the motor.

  1. Press fit the bearings into the right components. The Housing needs 2x 608 bearing, on top of each other. The 2 brackets both need a 624 bearing. The HTM1 gear needs an M8 nut glued in place, and the smaller, HTM3 gear needs an M4 nut, but that does not have to be glued in place.
  2. if possible, try to use a 3.5mm drill to drill the 4 holes in the housing to make the M4 screws catch the plastic. Also use a 4mm drill on the HTM2 gear to get a clean 4mm hole.
  3. mount hand assembly in the housing, and secure it in place with the HTM1 gear.
  4. Mount the first bracket over the hands M4 thread. Do not yet secure it, but do align it.
  5. Mount the HTM2 gear, with a 20mm M4 screw. Do not over tighten it, or it will cause friction.
  6. mount the HTM3 gear over the M4 thread. Rotate it in place. At some point, it will engage in the gears of the hour hand, but this is no problem. Keep going until you reach the bearing.
  7. Set the clock to 12:00 by rotating the gears.
  8. secure the third gear with an M4 nut. Test the rotation to check if everything is running smooth.
  9. Press fit fourth gear to motor. You may need to file the gears and hole a bit first, then using a vice, press the gear over the shaft. You do need to have something on the other end of the shaft, so you are not breaking the bearings.
  10. Mount the motor, test rotation again.
  11. If everything is running smooth, Disassemble, then reassemble the entire housing with locktite and glue.

Step 5: Electronics

For the clock's microcontroller you will need something that has 5 I/O's and a built in power regulator. I used a trinket, which I stole from my bicycle rim lights (no front wheel anymore :( ) It has 5 I/O's, but does require some careful planning, because not all I/O's respond the same. 3 and 4 cannot be safely used as inputs. To run the stepper motor, I use a stepstick A4988 stepper motor driver. There are 2 buttons on the clock to make the time go up and down.

I made my circuit on a piece of prototype board. I do not plan on making more of them, and it is quicker than making a PCB. I cannot really share a design, because there wasn't one, but if you follow the schematic, it should be fairly easy to replicate. The input voltage (9-12V) needs to go to the Vin or VBat pin of you microcontroller. The 5V comes from the microcontroller.

To get the power to the clock, you can pick one of two approaches. First, you can try to hide the fact that there are wires running to the clock, secondly, you can make it pretty. I tried to hide the wires by using very thin white wires to feed the clock. The current to these wires on average will be only around 50mA, so there will be no problems.

Step 6: Firmware

The code will run this clock. It does not actually keep track of the time, it simply triggers a step on a constant interval. The length of the interval will depend on the electronics. I have a 1:4 reduction to the minute hand, and 200 steps per rotation. I also have 1/4 microstepping on the motor driver (the smallest amount before the steps will skip). Totaling this, I needed 3200 steps per hour. This means that the clock will step once every 1.125 seconds. This is odd, a clock that doesn't step every second, but it works.

The 2 switches on the back will make the time go up and down. holding both at the same time for 3-5 seconds will toggle the mode between normal running mode and fast running mode. Under normal circumstances, you should not need the fast mode, but I did need it, and it isn't in the way.

If the clock is running the wrong way, disconnect the power and rotate the stepper motor cable 180 degrees. Now the motor should be running the right way around.

The code is universal enough that it should run on any Arduino compatible microcontroller by simply changing the pin numbers.

Step 7: Final Thoughts

Before I end of this instructable, there are always improvements, and this clock is no exception.

  • Normal clocks can run of a battery for years, this one needs a power supply. It will cut of power to the steppers after each step, but it still uses orders of magnitude more power than a conventional clock. I do not know if it is possible to make a clock like this, that can run for at least a month on some sort of battery, but it would require more efficient electronics and lighter motors.
  • There is no second hand. This had to be, and it wasn't a wrong choice, but somewhere, it would have been nice. The problem is that the clock becomes more than twice as complicated with an added second hand. Maybe the next one?
  • Noise. While it is not the end of the world noisy (it is about as noisy as most battery powered mechanical clocks) it still make a noticeable noise. Since my living room is my bedroom, I might look for a better alternative at some point. maybe something DC gearmotor with encoders. For living rooms it is fine, but for my bedroom, I might revisit.
  • The hand are not balanced. This is not the end of the world, but for any future version that runs smoother and lighter, this will need to be fixed.
  • The 3D printed gears are far from optimal. Sometimes they have friction, sometimes backlash, and sometimes both at the same time. Using a better printer would already help, but using cast gears would improve this clock immensely (but reduce the maker friendliness).

Comments

author
nsarzyns (author)2016-07-14

Where does the cap go? It's not in the schematic lol. I'm designing this on a pcb and I'm adding a few other things to it

author
dragonator (author)nsarzyns2016-07-14

The cap goes from 5V to ground and cancels the noise of the stepper motor. Closer to the stepper motor driver is better.

author
jjcasalo (author)2015-12-14

Very nice watch !

author
aad345 (author)2015-06-30

Did you use M8 Washers for the minute hand? If so then you missed it in the list of items.

author
AndreasH7 (author)2015-06-21

Hi! Great Design! Well done instructable :)

One question:

Is this one

http://www.exp-tech.de/stepper-motor-nema-17-200-s...

the right stepper?

author
dragonator (author)AndreasH72015-06-22

Looks like a pretty thin stack stepper.

The stack (the motor part) is around 1mm thicker than mine, but that should not be a massive problem.

author
AndreasH7 (author)dragonator2015-06-23

Ok, thx for the quick reply :)

author
moshe.boruhin (author)2015-06-04

cool design! I did a variation on this once:

http://www.coroflot.com/moses/Halo-Clock

author
AhmedA27 (author)2015-06-01

can I use a smaller stepper motor

author
Ricardo Furioso (author)2015-05-30

I love this project.
I love the description (although parts sources for bearings and motors would be great additions).
I love that people are suggesting interesting improvements.
And I love that people disagree here with so much respect and kindness.

This is my second favorite site, after Wikipedia.
Thank you for your contribution.

author

I have a small issue with adding parts sources. Most of the people here are from the US, I am from the Netherlands. Sadly for the internet, almost all of my sources are useless to anyone not from or around the Netherlands, not to mention the sites are in Dutch, so no one can read it.

I try to give full parts names so people can still find it, but I am not going to add part sources I didn't use, because that would just be pasting in google search results.

author
bpark1000 (author)2015-05-28

To solve the gear problem, why not make magnetic gears? Buy tiny rare-earth magnets, and embed these in the edge of your printed "gears", with alternate poles pointing outward (you must use "gears" with only even numbers of "teeth"). (You will need tiny magnets, on the order of 1mm cubes or cylinders. They are inexpensive.) The "gears" will arrange themselves with attracting "teeth" opposite. Unlike mechanical gears, you can "cheat" and have the pitches of mating "gears" not exactly the same. Keep the "gear" clearance about 1mm so they don't pull together too hard. This low-torque, low speed application is a perfect one for magnetic gears.

You should be able to drive this with a conventional battery-powered clock mechanism, available inexpensively. Mount your hour hand on the hour shaft. Use a friction mount to allow for setting. First magnetic "gear" will be mounted on the minute hand shaft of the battery clock. You can synchronize the minute hand by "slipping" the magnetic "gears".

skepticaljay made a comment that the speed relation between the hour and minute hand didn't seem right. I checked the gear ratios, and they seem right. (The gear train in the housing is 12:1 (15:45 and 12:48), and the gear set to the minute hand is 1:1, correct?) I can not exactly figure out the gear arrangement in the motor housing. Motor is 12:48, to minute hand 12T gear/train, correct? Then 12:48 and 15:45 to the hour hand? What I do note is that in the video, when the minute hand rotates 3 times (from 12:00 to 3:00) the hour hand appears to have turned more than a quarter turn. (To really tell, I need a video of a complete hour hand turn).

author
dragonator (author)bpark10002015-05-29

I will see if I can make a simple video of the clock making a full 12 hours, but give me a few days, I am busy right now.

As for the magnetic gears. There is one assumption that is wrong here. They are low speed, yes, but not that low torque, this design actually has more torque than a normal clock, dut to weight and it being out of balance. Also, magnetic gears have an uneven force throughout the rotation, which would be noticable in the clocks motion. Therefore I would not use magnetic gears for this purpose myself, but please prove me wrong if you think it is possible, I do find the idea interesting.

author
bpark1000 (author)dragonator2015-05-29

The torque is higher then an ordinary clock, but way lower than for most other geared applications. You have wisely used ball bearings, so static friction torque should be low. You can better balance it to lower torque further.
Magnetic gears do not have "uneven force". There is an attraction force that will be dealt easily by your ball bearings. In fact, I would wager that magnetic gears will have smoother force then 3D printed gears, because the magnetic force is "blurred" by its spreading out with space. You have 1.5 module gears, right? That means the circular pitch is about 4.5mm. I would propose 1mm magnets, spaced 1mm apart, and double the number of teeth (module 0.75), and space the gears about 1mm apart. (You may need to reduce tooth counts on the large intervening gear to accommodate this spacing). If you use a battery-powered mechanism, all gears will be eliminated except the "coupling" gears to the minute hand.

author
jdftoo (author)2015-05-29

is there any way to make this without a 3D printer? I don't have one but I was wondering if I could go to the hardware store and buy the same pieces but just not 3d printed ones. Thanks

author
Laral (author)2015-05-28

That is very nice. I've never seen this type of clock before. The only thing similar is the 60s clock with the glass disk face that rotates with hands that are geared.

author
bpark1000 (author)Laral2015-05-28

I have a working pair of those!

author
Laral (author)bpark10002015-05-29

Nice. Maybe you could make one.

author
0zzy (author)2015-05-29

Love it i really wish i had a 3D printer now

author
loki2012 (author)2015-05-28

That ... is really cool!

and jumbuck68 has a point, make it a skeleton clock!

author
dragonator (author)loki20122015-05-29

I actually really like the idea of a skeleton clock myself too. Maybe I will give it a go at some point.

author
DoItOrDie (author)2015-05-28

A brilliant and quirky idea. Love it. An alternate way to do it would be to use two synchronous or stepper motors,with the motor/stepper for the minute hand mounted on the hour hand. Naturally you would want the minute motor/stepper as small as possible, perhaps mounted to the back of the hour hand and connecting to the minute hand through a hole in the hour hand.

I wonder if it might be better if the hour hand were longer making it more of a pointer in it's own right? I guess if it were only a little longer then the clock markings could be concentric rings of tick points, with the hours being inside the tick marks for the minutes. Still, I'm having a hard time visualizing how the minute tick marks would be done. A spiral of repeating numbers? Or maybe a moving disk of numbers and marks attached to the hour hand that go around with it. The disk would also have to rotate in a synchronous manner to remain upright as the hour hand moves around. Gravity could do that if it sort of had an oval in the middle of the disk so that it just laid on the minute hand shaft, slipping on it as the hands went around. Perhaps a weight on the bottom of the back of the disk to insure it stayed upright. Or maybe with the disk mounted on a bearing that allowed the disk to rotate freely on the minute hand shaft, gravity and the weight still keeping it upright, like the seats on a ferris wheel.

The hour numbers and tick marks would be around the circumference of the clock just like normal but the hour hand would need to be long enough to show up outside the sweep of the minute disk (the minute hand mounted at the same place from the center as it is now). Making the minute hand shorter could help to keep the disk size down diameter-wise. Though a narrower minute hand would allow it to sweep the disk in such a way that the minute hand can extend way beyond the disk yet still show up such that it can be easily seen and understood. Come to think of it, if the disk were transparent such that the hours could be seen through it, the hour numbers could be inside the sweep of the disk and the hour hand need not be so long. Another variation would be to just put a view hole in the disk such that the hour numbers show up in the hole as the disk goes around. Some interesting possibilities and variations in any event.

author
BitisG (author)2015-05-23

Anyway of making this without a 3d printer?

author
bpark1000 (author)BitisG2015-05-28

Do you have a circuit board machine? You could make it (with modifications) with that. Otherwise, you could use old-fashioned hand tools, especially if you used the magnetic "gears" I propose trying.

author
dragonator (author)BitisG2015-05-24

Depends on how hand you are with a fretsaw or laser cutter. I personally wouldn't try it because I lack the tools, but in theory it should be possible. It all depends on what tools you can use and how much time you have.

author
DoItOrDie (author)2015-05-28

Another possibility for making this would be to use two stepper or synchronous motors with the minute motor mounted in the hour hand itself. Of course, the minute hand motor would need to be as small as possible. Perhaps mounted on the back of the hour hand, connecting through a small hole in the hand. If the disk thing were done, that would cover the minute motor/stepper regardless.

author
ZaneEricB (author)2015-05-28

How Large do you think this could be Made?

I want one!!

author
pcarew (author)2015-05-28

Very nice,

What are the gear ratios?

author
NitroRustlerDriver (author)2015-05-28

If you sourced generic gears from somewhere and then designed the clock around the gears, you could eliminate some of your binding/backlash problems. You could even design it to use a standard gear motor instead of a stepper. You would just have to calculate the gear set based on the gear motor's RPM. Might be a good idea to add some kind of speed adjustment though in order to calibrate the clock.

author
gcai_fwb (author)2015-05-28

super design - got my vote - now I have to make :)

author
Justjager (author)2015-05-28

Very cool and one I've never seen. At least 5 yrs and no one has put it out yet? I'd buy it if I couldn't make it myself... You get my vote... :)

author
spylock (author)2015-05-28

I really like this one,steampunk it up,a little copper,and a little brass with gears exposed,and who knows how bitchin it would be.Of course as is it is pretty awesome as is,great job!

author
bterry01 (author)2015-05-27

Very cool. I'm a clock nut and this takes the cake!

author
jumbuck68 (author)2015-05-25

Wonderful concept

Having had to calculate all that gearing, it seems a shame to hide it. This would look wicked as a skeleton clock in siome kind of metallic finish

author
aimzzz (author)2015-05-24

This is awesome, great job. I'm even having all the needed parts here, but a microcontroller. Can you tell me the name of the one you used?

author
silentbogo (author)aimzzz2015-05-24

That looks like a Trinket - excessively/obsessively fancy breakout board for ATTiny85. Since this clock only uses 5 pins - you can use pretty much any controller (Tiny13A, Tiny2313A, Tiny85 etc.)

author
dragonator (author)silentbogo2015-05-24

You are absolutely correct, but I didn't have anything else, plus I do not have the programming tools to program bare ATTinys. Also, the fancy breakouts do have power regulation. Not impossible to add, but nice that it is already there.

Anyone else can indeed do it with those.

author
silentbogo (author)dragonator2015-05-25

>> I do not have the programming tools to program bare ATTinys

There is an easy way of doing that even in Arduino IDE: all you need is to download board modules for ATTiny, set up an environment and start coding the way you are used to with Arduino.

http://highlowtech.org/?p=1695

Initially I was using my old Nano as an AVR ISP, but few weeks of jumper/breadboard nightmare forced me to obtain used USBASP 2 clone - best $3 I've ever spent.

author
Dani78 (author)2015-05-24

Love your design, it is awesome.

Thanks for sharing.

author
skepticaljay (author)2015-05-24

The video looks like the hour hand was over rotating. Counting from 12 o'clock at the top, by the time it it made for revolution it was almost all the way at the bottom. Is there a video of it rotating 12 times and going back to top dead center? I think this is an excellent clock and I really want to make one.

author
dragonator (author)skepticaljay2015-05-24

I probably could, but I can guarantee you, I checked and double checked when designing, and when it was printed, I check it some more. It was the intricate gearbox that also made me worry. If you are really that worried of it not making the right movement, give me a few days.

author
PuechP (author)2015-05-24

Très bonne idée. Bravo !

author
silentbogo (author)2015-05-24

That's very creative!

I've always wanted to make a cool-looking clock, so now I'll jst have to make this one =)

Thx, dragonator

author
Digital Flame (author)2015-05-24

This is insane. I would vote without hesitation! But I can't as the contests must have ended, which is a shame! I'm sure you will do well!

author
bravoechonovember1 (author)2015-05-23

wow! thats one of the best clocks i have ever seen!

author
Crybaby84 (author)2015-05-23

verry nice idea! i like it a lot. good instructable, my compliments .

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