The Inventor's Notebook
By Karl Rabe
This issue of the Inventor's Notebook is a collection of notes and thoughts on mechanical music movements and their application in magic apparatus.
We are all familiar with a music box. You open the lid and music plays. Sometimes a tiny ballerina twirls as the music plays. Music box movements have been popular since the 1800s, some large and highly complex. After World War II, Sankyo in Japan used modern manufacturing methods to produce low cost movements we are most familiar with today.
Music boxes come in 72, 50, 36, 30, 18 note variations. I will be discussing the most common and inexpensive 18 note version. Interestingly, even music box music is subject to royalties, so movements that play royalty free music are typically a bit cheaper. For magic, since you will typically be disabling the playing of music, these are obviously the better choice.
Before we dig in, if you are interested in the basics and history of the music box movement and how it works in regards to producing music, I recommend this video by The Engineering Guy.
- Music boxes are typically wound using a key. Some however are wound by pulling a cord. These are typically used in mobiles that are hung over a baby's crib, or in stuffed animals. The advantage these offer, is the winding mechanism is typically a pulley with a cord wrapped around it instead of a key. If you want your music mechanism to pull a string to actuate something, this can be the ideal version to procure.
- The key can be replaced with a platform if you want a large turning disk. Disks come in a variety of sizes.. clear and opaque. These could be used in a cigar box flea circus for example by attaching a magnet to the platter. One disadvantage is that these need to be wound by turning the platter, which could be inconvenient depending on how you install it. Also, the platter will turn at the speed the key turns as the box is playing, which is fairly slow.
- Shafts can be inserted inside the barrel of the movement to drive something. These will turn at the speed of the barrel, which is faster than the speed of the key. Threaded shafts can have platters or pulleys attached to them.
- The part pictured below is the governor that prevents the spring from spinning the drum too fast. Without the governor the mechanism would unwind in about 3 seconds. The governor is essentially a paddle that works like a fan blade. Air resistance slows it down, but doesn't stop it. It is geared very high, so air resistance is sufficient to control the speed of the box. If you desire different speeds, you can very carefully trim the paddle. This requires experimentation and you can easily ruin it when you try to get the right speed.
- The "Comb" that plays the musical notes can be removed with two screws. This will make the mechanism silent but it will still turn at the same speed.
- For a push-button start/stop, the best way is to have a small piece of wire that interrupts the turning of the paddle on the governor. You can purchase these with springs already made and typically they fasten under one of the comb screws. You can see here, closing the lid pushes down the wire causing it to block the paddle from turning. This can easily be made yourself by the do-it-yourself-er.
- Remember these mechanisms are in "Boxes" because they require the amplification of the music that occurs when the mechanism is fastened to a hollow wood surface. This makes them louder. For magic, usually you want silence, so keep that in mind when mounting your mechanism. Isolate it with a little foam and don't fasten it to a large resonant surface.
- Timing - The mechanism can be used as a timing mechanism. A string wrapped around the drum slowly rolls up and then pulls some type of trigger release. The length of the string can determine the duration between activating and when the trigger releases.
- Circular movement - A platter can be attached to the key shaft (slow rotation) or to a shaft inserted in the drum (med rotation) -- this can be used for a flea circus to have them pull a chariot, drive a car or push a ball around the ring. A wire can be rigged as a hidden push button to activate the motion.
- Linear movement - A pulley wheel can be attached to the key shaft or a shaft inserted in the drum and a thread or line can be wrapped around either like a belt or as a take up reel. It could be rigged to move a high-wire in a flea circus, move a silk across a table top, etc.
- Rising card - A thread winds up on the music drum causing a card to rise out of a houlette with the typical routing of the thread.
Buying and Sources
- The most common variation I have seen in inexpensive 18 note movements is ones with all metal gears and those with plastic gears. You will find them with little plastic housings and without. The housings can easily be removed, so if the price is the same, get the housing just in case you have a use for it.
- Do not overpay. You can find 8 movements for $20 on ebay which is about $2.50 each. Stick with unpopular and royalty free tunes to keep the price down.
- I have always bought boxes, shafts and platters from here: https://www.musichouseshop.com/store/ . If you don't care what tune the music box plays (which magician's usually don't) give them a call at 1-888-88G-CLEF (884-2533) or 352-588-2800 and they probably will make you a deal. I picked up 10 music boxes recently for $15.