Otona no Kagaku Flip Clock Review

If we look at all of the Gakken Otona no Kagaku kits as a whole, we can see that they start falling into specific categories. Optics and astronomy (Kaleidoscope, microscope, Galileo telescope, Newtonian telescope, planetarium), acoustics and music (Berliner and Edison gramophones, electric guitar, theremin, synthesizer), electricity and electronics (static generator, DC motor car, 4-bit microprocessor, 8-bit microcontroller), cameras (pinhole, stereo pinhole, dual reflex lens) and clocks (slow clock, Edo-era clock, flip clock). Notice how cleverly I snuck the latest kit, #38, into the list here.

The Flip Clock (3,500 yen) doesn’t really provide much in the way of new theory regarding how time pieces, or time itself, works. The kit consists of a pair of motors that slowly advance the minutes and hours sheet drums, and a circuit board that doubles as a motor driver/radio receiver. The receiver picks up a signal on a fixed frequency used for time synchronization, and uses that as a stable timing source for advancing the 2 motors. The motors are geared to the sheet drums to cause one minutes sheet to flip per minute, and one hours sheet to flip every 30 minutes (there are 2 sheets for each hour in order to make the hole spacing on the hours drum a little more like that of the minutes drum hole spacing). Two switches on the top of the case let you advance the minutes and hours to set the time (although, if you wait long enough, the clock will automatically go to the correct time for you). Power is supplied by 2 AA batteries. The fun part is watching the clock go into reset mode if the time isn’t at “00:00” when you put the batteries in. Additionally, the main motor gears have raised sections that open and close a pair of leaf switches to let the circuit board know what the drum orientations are (similar to that on the Edo-era clock).

(Notice how the one set of leaf switch wires runs under the plastic U holder, at the back of the circuit card. You can also see the DC motor connector color-coding alignment at the far end of the card.)

Gakken suggests 90 minutes for building the kit (finished size: roughly 15cm x 15cm x 10 cm), and I think I came in at about 100. You need a Philips head screwdriver, possibly one with a long shaft. Kit assembly is pretty straightforward, but there are a couple places that could be tricky. First, the “R” and “L” labeling on the gears that are used to make up the sheet drums are on the inside faces of the gears. So, when the drums are assembled, you can’t easily tell which is the left and which is the right drum. Just be sure to mark the outside face of the gear somehow before putting the drums together. Next, when you put the white side and bottom panels together, don’t tighten all the screws, and leave one corner screw off. The reason is that the drums need to be squeezed into place inside the case and you can’t do that if the case can’t flex. Also, there’s a plastic retaining “U” piece that holds the circuit board in place. One of the two pairs of motor wires is supposed to be routed under the “U” piece – you can see which wires in the assembly photos. (If you can’t read Japanese, the instructions for plugging the motors into the circuit board can be hard to figure out from the photo. Orient the two motors to match the photo, and make sure the wire colors are, from left to right, red-black, red-blue.)

(The antenna holder can rotate 360 degrees, letting you align it with the nearest radio tower to maximize signal reception.)

Most of the assembly time is taken up with punching out the number flip sheets and putting them into the retaining holes  in the drums. The sheets are made of soft vinyl and are easy to manipulate. They’re also easy to knock back out of the drum, so don’t push on them when trying to advance the drums forward. If you look at the assembly photo, you’ll see that there’s a small notch on the edge of the left and right drum gears. You need to start inserting the sheets at the first hole above the notch. Doing what I did, starting one hole below, means that you have to pull all the sheets out and start over again.

(Sheet drum mechanism close-up. The DC motor is at the bottom. It turns the next gear up, which uses a slotted rod to translate the motion up and down. The slotted rod advances the drum gear by one notch, and the stop-rod at the bottom of the drum gear  prevents the drum from rotating the wrong way when the slotted rod returns to the lower end of its stroke. You can see the raised piece on the sheet gear, which is holding the leaf switch closed.)

The radio time signal is probably on a different frequency in Japan than in the rest of the world (I haven’t checked yet), but I think the clock will work without it, just not as accurately. Be warned, though – the flipping of the clock is noisy, and you’ll either pull the batteries out at night, or move it to some other room where you’ll only see it during the day. Accuracy suffers anyway, if the batteries are not plugged in.

(Close up of the sheet drum mechanism showing the leaf switch in the open position. When the switch goes from closed to open, the circuit board knows that one of the two drums has reached the “00” point of the “00:00” reset display.)

As for the mook, the cover article features actress Maki Horikita posing with the clock. There’s 6 pages of “retro-futuristic” products like radios, clocks and telephones. This is followed by an 8-page photo manga describing how the clock works and how to align the antenna to your nearest radio tower. Tekken (who apparently goes by the name Leonardo da Tekken) is an artist working in Japan, and has created flipbooks the size of phonebooks. There’s 4 pages on him, 2 pages on augmented reality (i.e. – the Google glasses), 4 on futuristic watches and 6 pages on clock tower buildings, chronographs and old mainframe computers. Then we get 6 pages on the Doppler effect, and 2 on how GPS works. The suggestions for mods to the flip clock include giving it a lighted case; turning it into a smartphone-driven flipbook animation display; giving it a handmade bookstand; and giving it a striped plastic case.  The home hobbiest feature section introduces a woman that makes anime- and video game-inspired sculptures from used aluminum cans, and a group that has constructed a 1/50th scale model (41 feet tall) of the Tokyo Sky Tree out of bamboo poles. Then there’s an article entitled “60 years of radio hobby”, about a guy named Taro Oohashi; 8 pages on how Japanese astronomers are searching for another earth-sized planet; and, the instructions for making the kit. The mook ends with another of Yoshitoo Asari’s Manga Science manga, this one on the design principles behind knife and scissor edges.

Overall the kit is fun to make, but I live in a small apartment and the flipping sound can be heard in the bathroom with the door closed. It’s not something I want running when trying to sleep at night. I’m not sure if there are any mods I want to try making at this point. You do get about 5 blank sheets with the kit, but it’s going to be a pain having to cut out 100+ pieces from card stock by hand to make a flipbook, if you don’t want to mark up the regular number sheets. The mook’s worth getting for the retro photos, and the spotlights on the aluminum can sculptures and bamboo sky tree.

Next up: Kit #39 – An updated version of the Kit #9 pinhole planetarium.
Tentatively scheduled for late July. No price set.

[Edit: I just finished taking the kit apart and putting it back together again because the plus connector had been pushed out of the battery holder as I was removing and replacing the top battery. So, I suggest two things – first, melt the plastic of the battery connector slots to keep the connectors from accidentally sliding out. Second, before you put the kit together, drill a hole in the back of the case for a toggle switch and splice it in series with the red battery wire to give you an on-off switch when you need it.]

Leave a comment


  1. Anonymous

     /  May 10, 2013

    Any ideas on making the clock operate much quieter?

    • Not off hand, beyond putting it in a solid plastic case. The primary noise source is the gear-lever combination visible in the above side panel photos. When the push lever advances the drum gear, the locking lever snaps into place to keep the drum from reversing direction. That “snap” plus the sound of the flipping number card is what’s so noisy. Either make the pieces from hardened rubber, or remove them entirely.

  2. Anonymous

     /  May 10, 2013

    I read your excellent review before purchasing it, but didn’t realise it was that loud! I also live in a small apartment, and don’t have a clock so would love to use this flip clock.

    • Loosening the springs might reduce the clicking somewhat. I put in the power toggle switch, and I just turn the clock off before going to bed. If you want this to be your primary clock, and to use it at night, then be sure to look at the mods suggested in the mook. One mod is to make a case, put a push-bar on top for pressing down on the hour and minutes switches, and to add LEDs for illumination. You can then select the case based on how well it absorbs sound.

  3. Anonymous

     /  May 13, 2013

    Thank you for the tips. I had a closer look at the clock and it doesn’t seem like there is an easy solution to really quieten down the clock. I’ll keep thinking and tinkering.

  4. Bob

     /  October 5, 2014

    Does the circuit board in this radio-controlled flip clock work with the time signal broadcast in the United States, that is WWV, WWVB? Is there a non-Japanese version (circuit board) for the non-Japanese market?

    • Hi Bob, thanks for dropping by. I don’t know if the board works with the US signals. Since I’m in Japan, I have no way of checking. No one else has commented on getting the kit themselves, so I can’t ask anyone. But, no, there’s no American version of the kit that I know of. Gakken does have a number of the construction pdfs translated into English, so they do recognize that they have users from outside Japan, but so far I don’t think they’ve come out with multinational kits.

    • As a follow-up comment, though – you could replace the driver board with an Arduino or similar controller. Don’t know how easy it is to get a WWV shield for the Arduino, but you could use a wireless interface from your PC to the Arduino to drive the clock motors, and that gives you options for doing a gag clock if you want.

  5. Troy

     /  December 11, 2014

    I am in the usa and this clock works great. It syncs up fine. But this thing is loud about like a 8 track player when it changed tracks Since there is not time zone setting you might have to set the hour but mine is working fine in cst. Also at 01:11 this thing syncs up and my god it is loud since it resets the minute side to keep it in time. It also does it at about 02:02.

    If you get this in the usa you might have to wait tell 1 am for it to set itself. I am not sure what time they send the code but for me about that time was when it got it.

    In Germany, the time signal DCF77 is transmitted on the frequency 77.5 kHz. MSF is the signal from Great Britain and WWVB is the signal in the USA – both are transmitted with a frequency of 60 kHz. The two Japanese signals JJY are transmitted with a frequency of 40 kHz and 60 kHz. The Chinese signal BPC is sent on a frequency of 68 kHz. The radio-controlled watch decodes the relevant signal and displays the exact local time.

    • Troy

       /  December 11, 2014

      A tip if you buy one for putting cards in. When you get to the hour cards do like this. Put batteries in clock and let it rest to 00:00. At this point remove the batteries and lets start adding hour cards like this. Put the top 00: card behind the holder at the top so it stays in place by itself.

      On the hour cards were going to skip the order one time only. Look at the cards that are 23: on the back of then find the only one that has the other part of the 00 this is the bottom of the 00. Lets add it at this point to make the hour read 00.

      Now make sure you got the 00 in the right spot or manual set will not work right. Put the batteries back in clock and watch it reset. You should now see the time as 00:00 if not move the 00 hour card and try aging. Once you have this part done then put the cars in the order like it said 02 03 etc

      I had to remove the hour cars once and it is no fun to put them back in to get the clock right.

  6. Hi, Troy. Thanks for the tips and info on time signals!


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