My first Gakken kits were the Slow Clock (#8) and the DC Motor Car (#21), and they were both given to me as Christmas presents. This was just as the Hiraga Gennai Static Electricity kit (#22) came out on Dec. 20, 2008. At that point, the majority of the kits I bought were ones already on the market, and I would do the write-ups for the blog after I’d built them. After a few months, the Poulson Wire Recorder and the 4-Bit GMC-4 microcomputer had come out, and I got those as I was still playing catch-up with the remaining back issues. It was right around the release of the mini electric guitar (#26) that I started doing the write-ups a few days before the next kit would hit the market. Partly, this was because I really wanted to buy the kit right away, and partly because the Otona no Kagaku site would get updated with photos in advance and I’d be able to record my first impressions and the supporting science of the kit.
#33 presents a bit of a challenge in this sense, in that there’s no real science involved in making a vacuum cleaner. Most vacuums involve a fan or blower of some sort, with the mouth of the cleaner representing the intake of the fan air line, and a dirt collection bag that filters out the solids from the air line for easy disposal. In the case of the Dyson unit, the collection/filter bag is replaced by a kind of tray with the air coming in at an attack angle, maintaining better air suction than you get with filter bags because there’s nothing slowing down the airflow. The enhancements to the basic design will then be primarily mechanical, like shaped nozzle attachments, the hose attachment versus the rollers at the bottom of the unit, and brush height settings for wood floors and shag carpets. Ignoring the Dyson “cyclonic system” approach, the only really evolutionary leap was to make the vacuum autonomous by installing a computer ala the Roomba. To get to the Roomba, you need to add collision sensors at the front and sides, a drop sensor at the front to prevent it from falling down the stairs, and an algorithm for generating traversal patterns that can cover most, if not all, of the room. Not that difficult a challenge – until you try to pack it all into a package the size of a stack of 5 large dinner plates. But still, while there’s the technology, I’d argue that there’s very little science that needs explaining.
Kit #33: Desktop Vacuum Cleaning Robot. 2940 yen ($36 USD), Released Jan. 30, 2012
Where the Otona no Kagaku kit comes in, is when you try to take the Roomba approach and translate it to a table or desktop, at the low-end price-point, and with no electronics beyond the 2 AA batteries and a single DC motor. The collision and drop sensors consist of a lever mechanism that engages the worm screw on the drive shaft. The worm screw forces the drive shaft to shift sideways and change cogs on the left wheel. This causes the cleaner to immediately stop going forward, and instead rotate for about a second until the worm screw disengages and the drive shaft returns to its normal location. That’s it. It’s just that simple. From a conceptual viewpoint, anyway. The actual execution is much more interesting. The kit consists of about 20 pieces, not including the screws, tape and grease packet. Suggested assembly time is 60 minutes, and I came in just under that. It’s not really a tricky kit to build, but it will help a lot to have English instructions to follow from. In steps 11 to 16, you’re instructed to apply the grease with a toothpick at the ends of the various gear stems. In step 4, you assemble the 2 pieces of metal and a plastic lever to make the on/off switch, and you may have to bend one of the metal pieces to prevent the switch from remaining closed when in the OFF position. And in step 21, you have to take the cloth tape and fold it in thirds such that you create the scraper blade for the underside of the cleaner (see top photo). When I was done with the rest of the kit, I had 2 pan-head screws and one regular screw left over for fastening down the top cover. The book says to use 3 pan heads, which I think are too short to really grab the plastic of the cleaner body – they just keep spinning when I turn them. Having 3 regular screws for the cover would have been better.
The kit consists of a 3V motor that spins everything, including a small fan. The on switch has 2 positions – fan only, and fan plus gears. A small lever connected to the front spring-loaded plate allows the worm gear to engage over one wheel to make it turn backwards, and engages a timer lever that allows the robot to rotate at a fixed 123 (or so) degrees before kicking the worm gear back out of the way. You can adjust the sensitivity of the collision sensor by changing the position of the small lever within the unit. The vacuum part is created by a small fan blade that pulls air up into the collection chamber and through a filter. The collection chamber cover snaps into place over the AA batteries, so when you empty the robot, you can replace the filter and batteries at the same time. The scraper blade rubs along the floor or desktop and loosens some of the dirt so it can be vacuumed up. The number one problem will be that the robot senses false collisions and turns when you don’t want it to. You’ll have to open up the cover and adjust the small lever to fix this (it has a slotted hole). Next will be overheating at the gear contact points. The motor spins fast, and you’ll want enough grease at the spindles of all the gears. I’m getting a “hot plastic” smell, so I may need to disassemble everything and add more grease.
This kit is a bit noisy, and while the motor is running fast it’s so geared down that the robot itself moves maybe a foot in 2 seconds. It looks cute, especially with all of the brightly colored parts, so it really appeals to the Japanese people I’ve shown it to. I’ve got the bump sensor set to medium sensitivity, and it reacts to chair legs and trash bins with just a light touch. The intake slit is about 1/8″ x 1.5″, so it does have a limit to what it can vacuum. Still, the suction is good enough to pick up tiny pieces of thread, and dust. Of course, the most important part of the design is that it runs on a desktop, so it’s very light and compact, at a few ounces, and 4″ dia., 1.5″ high.
(When the front bumper hits something, or moves down because it’s at the edge of a table, the attached small yellow lever pulls forward to let the worm screw thread towards the left and causes the left wheel to turn in the reverse direction. At the same time, the worm screw engages the little yellow gear above it. This gear holds the lever in place until the robot has rotated 123 degrees. At the end, the drive shaft will try to snap back to the right, assuming that the collision has safely passed, and the left wheel will turn forward again.)
The mook starts out with a look at a machine shop that creates small plastic parts, then goes into a discussion of the operation of the kit. The author taped a pen on the back of the robot to show its travel pattern. The suggested mods are to add a cog to make a Pacman face, building a wood enclosure to hold a smart phone that displays ghost faces, and to wire in a string of LEDs and resistors and add a rotation sensor for causing the LEDs to change color as the kit moves. This is followed by an article from the Duskin cleaning company on how best to clean your PC and the rest of your room. Then there’s the look inside the Roomba, and inside its maker – iRobot. Next is a revisit of the Denshi mini Block kit, and an explanation of some of the easier circuits (a switch, parallel and series LEDs, and parallel and series resistors in the flasher circuit). The Japanino hack is to mount the Japanino on the vacuum robot, along with an LED and a servo. The Japanino sketch allows the cleaner to travel a short distance before rotating the servo arm to imitate a collision detect and making the cleaner change directions at random intervals. The LED turns on when the robot rotates. Then there are the pieces on a club that makes and launches large rockets, a guy that sculpts pencil leads and a hobbyist that made his own servo-driven humanoid robot. Lastly, there’s the photo display of old home appliances (sewing machine, washing machine, dial phone, etc.), a story on a scientist researching the Boson-Higgs particle, descriptions of animal and insect movement patterns and the manga on why freeway traffic behaves the way it does.
There’s no mention of the next Sound Gadget yet, and the next mook kit will be an unnumbered addition to the wind-up ornithopter line with the “Twister”. The Otona no Kagaku site doesn’t have the link for “Next Up” right now, though. From the photo at the back of the mook, the Twister looks fairly similar to the entomopter in kit #31
Summary: A challenging little gear-driven vacuum robot, and a mook with nice photos of the CERN accelerator. Recommended.