Build a Programmable Mechanical Music Box

If you've ever seen those little music boxes you wind up, or crank, and they play a little tune over and over from a little metal drum of notes, but wish they did more than play the same 10-second tune over and over for eternity?  If only you could change the song and write your own music for it... Now there's an idea.

After a year of design and work, I completed my Re-Programmable Music Box / Mechanical Synthesizer / Organ Grinder Thingy.  It has many names, and is 100% non-electric.  Just wood, metal, and good ol' people power.

I began this project as a sort of proof-of-concept, designing something from scratch without a lot to base it off of, and a whole lot of engineering problems to solve.  Also, I didn't really know what I was doing.  It was intended to be a learning and problem-solving experience.  And it was a lot of fun.

If you like my work, please vote for it in the Woodworking Competition beginning October 3rd.

Demonstration Video

Step 1 Design and Planning

Since this project was starting entirely from scratch, I needed to make a flawless design that could be easily worked with, and a good design always reduces waste.  I decided to use oak, and at $60 per 10ft plank I didn't want to waste any.  Also, its pretty complex and precision is extremely important for everything to work correctly.

I started with the idea: a large wood cylinder will hold metal pegs.  It will rotate and force the pegs to pluck metal tines, which are tuned to specific notes.

I selected 12 notes across, since it seemed like a very flexible number of notes and allowed me to fill it with a simple 8-note scale in the middle, with a few extra high and low notes.  I could also tune in flats or sharps if I wanted some specifically, or get almost all of a chromatic scale in.  I selected 32 notes "around" the cylinder, because that's what you need to play Pop Goes The Weasel, or any 8-bar song using quarter notes.

The cylinder is made of softwood, 8" in diameter, that I picked up from a nearby carpenter for free.  I found a belt that fit snugly around it to use along with a few gears and a belt for the cranking mechanism.

The tine material was cut from the prongs of a garden rake.  This works great because it is flexible but snaps right back into place.  The tine holder design was sort of up in the air until the rest of the machine was done, so that I could do testing.  Initial designs were too complex and tiny, but the final design (image 3 below) is about as simple as possible, I believe.

Originally I wanted to use almost all wood for this project, but it turned out wood wasn't going to offer the precision that I needed for the tines.  I ended up doing it with a CNC at my college.  In Step 7 I hypothesize how it could be accomplished without such expensive tools.

When designing the wooden frame, try to place the pieces to get as few exposed edges as possible.  The edges you do have, try to align them so that they create borders and still look appealing to the eye.

Comments

[drbill]

If you turn the cylinder on a lathe you will have exact centers so the cyl will be tracking perfect.

[mattthegamer463]

Yes I tried that a long time ago, the 3-sided chuck was making the wood split before it was holding it securely enough to be turned.

[sydkin2000]

Whoa.............................................OMG i could not do somthing like that if i had my whole life to work on it........*Bows down to you*

[NaturalCrafter]

I love mechanical devices so this one was way cool for me to read. Thanks for sharing.

[mattthegamer463]

Thanks very much.

[Harata]

Do you have a video of it working? It would help convincing us to do it!
Anyway, it's a great work and I'm thinking about doing one myself! Thank you, it gave me a lot of ideas!

[mattthegamer463]

It was on the first step, for some reason Youtube refuses to embed it properly.

http://www.youtube.com/watch?v=Mn7hVHlNN9s

[crash_gnome]

Can we see a video of it playing something please I think its really cool and would like to build one alike but would like to know how it sounds first. Thanks and keep up the good work

[mattthegamer463]

Video posted. The microphone is incredibly bad, and my tripod was giving me a hard time (its been modified specifically for my DSLR, so normal cameras don't fit right) so the camera angle was severely limited. The problem with some of the notes being too soft and some too hard is that the cylinder of wood was never perfectly round, its off by a few millimeters, and so that messes things up. If I don't hit some notes hard, it won't hit others at all. Crazy.

[eranox]

This is, to date, my favorite instructable! I'm planning to modify your design to make a musical jewelry box for my fiancee.

I understand your frustration in getting the cylinder precisely shaped.  I'm considering constructing mine out of more staves (maybe 24 instead of the 8) and possibly just forgetting about rounding it.  At those shallow angles, the pegs should have no difficulty plucking the tines.

Since you're having difficulty getting your cylinder to shape, perhaps you could mount it on a mandrel and use an electric drill as a makeshift lathe.  You could cap each end of the cylinder with a large metal disc with a hole in the center (basically a very large fender washer) so the pressure would be exerted evenly, and then run a length of threaded rod through the center and clamp the piece in place with a couple of nuts.  I use a similar method when building handles for my fishing rods, and the cylinder is big enough in diameter that I think you would get an acceptable speed of rotation on the outside face to effectively shape it.

Regardless, it's a really great project, and I'd be thrilled if mine turned out as well as yours did as-is.  I'd like to find a wind-up mechanism similar to what you see in commercially available music boxes, so that the cylinder doesn't need to be manually cranked, and the music would start and stop when the box was opened.  I'd just hack an old music box, but I doubt the mechanism would be strong enough for a cylinder this size.  Any ideas?

[mattthegamer463]

Thanks, yes it is quite difficult to get the precision required. I have an idea I will try, eventually, to plug the bottom of some of the holes with some sort of non-magnetic substance that will elevate the shorter pins to the height of the longer pins, that way they will all be the same height and will strike properly, and the fix won't depend on different size pins.

The mechanisms inside a music box are incredibly weak. They are a coiled piece of metal which when cranked, is tightened up, and when let go, it expands back to its original size, rotating a center shaft. The scale you would need to go with for that kind of mechanism, for this size of application, would need to be huge.

I would recommend electric drive, its the only way to get the torque required. Using a drill motor, a worm gear, and a large gear on the cylinder would give you slow speeds and no slippage (worms can't slip backwards.) I would say this is the only practical way to do it. You're saying you want this for a music box, but unfortunately its hard to miniaturize this design any further. I would recommend you take a old music box and maybe try to make a new drum cylinder to play a different tune, a favourite song or something, using the existing notes. I don't know how you would machine something that small and precise, though.

Its a major challenge. There are a lot of difficult mechanical and practicality issues here.

[eranox]

My plan is to use a modification of your design in roughly the same dimensions as you built it, with a large box below to store the jewelry. I looked at some of the windup mechnanisms after I posted, and it's clear that you're right. No practical way to do it for something of this size.

The electric motor solution would work, but I feel that it would detract from the handiwork appearance of the music box, and I don't want her to have to hassle with batteries or an adapter. She won't mind the hand-crank mechanism, I think, so I'll probably just save myself the extra frustration and leave that as-is.

I tried my hand at a simpler project (basically a mitered box) to give myself a refresher before I ruin anything of this scale. I'm having a difficult time getting my cheap Skil table saw to cut miters accurately enough to make a box, let alone a cylinder. I think my best bet will be to only use 8 staves in my cylinder, as you have. Any advice on getting the cutting angle just right?

[mattthegamer463]

I didn't make the cylinder myself, it was an end piece from a non-load-bearing architectural column. I got it from a local carpenter. I imagine that the staves could be done without too much concern, and that the last one could be hand-shaped to complete the fit. You'll still have to turn it smooth though.

I haven't got much for suggestions for that, I'm afraid.

[jjgodinho]

if your drum is off by milimeters, why dont you use a lathe to round it off? as for the project it is very well made, ease on the eye and with a professional apearence.

[mattthegamer463]

I tried that, but the lathe that it was made on must have been massive. The chuck on the one I have couldn't open wide enough to grab it from the outside, and grabbing it from the inside made a cracking sound. I couldn't grab it tight enough without splitting the wood, and it would never turn true. Nothing I could do.

Thanks very much for the kind words. Its the community here that helps keep me going.

[realalchemy]

hello matthegamer
out of respect for the be nice policy i will be nice
i worked for over 5 years to come up with the idea of the mechanical kalimba
look at my blog timmymontanaautomata
its is an original idea of mine
it is wrong to enter a contest with a strict alchemist idea

[mattthegamer463]

Hello,

Thanks for posting. I have never seen your work, and I do see how it is very similar in concept to what I built. However, I'm sure you're aware that organ grinders have been using "barrel organs" for well over 100 years; now we can agree neither of us invented those.

This is merely my take on what I did, building a unit that can be re-programmed at will. This is something that the original organ grinders did not allow.

Also, Instructables isn't about original ideas, its about writing guides to build things so that other people can do so, too. I could write "How to take apart a car" and nobody can say "you didn't invent cars" or "you didn't invent taking things apart" because I didn't claim to. This doesn't need further discussion.

If you would like to comment more send me a private message. Thanks.

PS. What is a "strict alchemist idea"?

[Taranach]

You could try getting a very large hose clamp to hold the outer diameter steady while clamping to the inside.

[paleotool]

Wow! This is great. I want to build one very soon.

[mattthegamer463]

Thanks very much. Hope you vote for me!

[paqrat]

Very very good instructable. It reminds me of an antique one we had at the store where I work. The major difference was size, it was a bit larger, mounted on its own wheels and that it had no tines but used piano (or guitar?) strings. As I recall the pegs on the wheel, which in the antique's case were nails positioned to play just one song, pushed spring loaded hammers like the ones in a piano. After the peg pushed the hammer forward enough to slip past the end of the hammer the springs would then cause the hammers to strike the strings. It had a pretty good sound. I think combining your idea of the cylinder with adjustable pegs with the hammers and strings would eliminate the need for the magnets and the resulting work in setting them. It seems to me that once working with the hammers was worked out it would be possible (using different sort of head on the hammers) to use something like a zylophone or marimba (sp?) or, on a smaller scale, bells.

The antique one had a cylinder that appeared to be a section of limb or tree trunk. It didn't appear to be that rounded but I imagine that, if only one song is to be played, the position could be tweaked as needed. One tweaking of each peg would be enough.

[mattthegamer463]

You're right, antique organ grinders used a similar method to activate valves attached to different pitch whistles.

[jelleAtProtospace]

Cool project! But why did you opt for the massive oak drum? If you use a cnc mill anyway, an easier solution would be to cut some endcaps from ply that accept strips of wood that form the surface of the drum. If you make each strip per count of your melody, all the holes would be oriented the same way, and still be easily cuttable with a 2.5d cnc router.
If you put a strip of iron at the back of your holes, you could glue the magnets to your pegs, and need much less magnets.
Another idea that springs to mind is to put a tuned resonating chamber under each tine (or per two, to halve the number of chambers needed). That might give it some more volume.
And a last thing: did you choose your gearing such that each forth (or second or third)count coincides with a downstroke of the crank?

[mattthegamer463]

The CNC was used as a last resort, because I couldn't get the precision I wanted any other way, or do the design easily any other way. Easier solutions are always more visible after-the-fact.

The gearing is not tuned to anything specific. I couldn't tell you the gear ratio, but its probably something like 20:1

[Madrigorne]

for the parts of the cylinder that are not close enough to your comb - make the peg a bit longer - yes I know uniformity is awesome, but for the sake of mechanical usability - sometimes ya just gotta do it the way it works. I love this - will make one as soon as I finish my kabillion other projects...

[mattthegamer463]

If I put a piece of paper or something in the bottom of the hole it will extend the equivalent length of the rod, and the magnet will still be able to hold it through that slight gap. I'll do this sometime.

[Madrigorne]

or another little piece of metal - the magnetism should translate through and hold the whole stack together, like when you can pick up an whole pile of paperclips with one magnet...

[Dagless]

This is very well done. Thanks for sharing.

Can you tell us more about the pegs used – how did you get/make them, are they easy to move, are the magnets really necessary?

I think your tine and bridge design are excellent. I wonder if a larger body/thinner wood might give you better resonance though.

In the case of Pop Goes The Weasel, you'd be better off with 48 holes around the circumference (12 per bar for 4 bars) since it's really in 3|4 or 6/8 time. That wouldn't be useful for tunes in 4/4 though. 96 holes would be versatile. 4 bars at 24 notes per bar would give you the option of 1, 2, 3, 4, 6, 8, 12 or 24 evenly spaced notes per bar. It goes without saying you'd need a pretty big cylinder though.

I have theorised about a similar (much more crude) design. I was thinking of a large diameter PVC pipe for the cylinder, driven directly with a crank handle (without the gearing you have used). Each peg could be a nut and bolt - with the a nut glued to each hole in the PVC (effectively making each hole threaded) and bolts screwed in to strike the notes. Perhaps varying the height to which each bolt protrudes could affect the dynamics (loudness and softness) of the notes, or perhaps that would adversely affect pitch. However, you'd probably want an easier way of recomposing the pegs – e.g. some sort of springy push-pull pegs. The key thing would be to make it easy to create new tunes.

I am also very interested in rford's comments about punch cards. I would very much like to see this idea expanded upon. There is a simple music box available using this idea here: http://www.grand-illusions.com/acatalog/Large_Music_Box_Set.html
The potential is quite exciting, but I have no ideas how to implement this. :(

[mattthegamer463]

Hi, answering each of your paragraphs with a paragraph, in order.

I bought the pegs from a local store, they're 1" x 1/8" length. Using 1" holes on the drum with a 1/8" long magnet at the bottom makes them protrude 1/8".

A thinner body would definitely give more resonance. Something thin and reinforced like an acoustic guitar would be good.

The thing about this is that if you know the song, you can add rests by just strategically stopping the rotation. About additional holes, it becomes a massive undertaking to build. It took 4 hours to drill and 2 hours to glue all the magnets into the holes. The magnets alone cost $42 for 400.

Screws was an idea at the beginning of my project, but I determined the wood would deteriorate from being screwed into so many times with self-tapping screws, and the amount of screwing required to program would make changing the song very unappealing. Also, simplicity is important when theres so many pins.

At this scale, paper punch strips may be too fragile for direct interaction with the pegs and tines.

[Dagless]

I was thinking perhaps the magnets could be done away with by drilling the holes 7/8" deep on a slight angle so the angle upwards towards the tines as they rotate around, but of course if they weren't snug they'd just fall out as they rotated toward the bottom.

I agree that self-tapping screws in to wood would have a limited lifespan. And that simplicity and ease of re-programming tunes is key to functionality. Your magnet solution is the best so far I think.

Just thinking out loud: I wonder if my nut and bolt idea would be more feasible if the screw thread was much steeper, so that it only took, say, half a turn to set or remove the pegs? I don't know if such a thing exists though.

Another option might be to have all the holes filled with pegs/bolts screwed down flush with the cylinder and just unscrew those you want to protrude on any given tune. If the cylinder was wood, perhaps you could use internally threaded anchors set into the cylinder. Something like this:
http://www.kevinbrassind.com/images/brass-%20pool%20-cover-%20anchor.jpg

Anyway, once again, very nicely done and thanks for sharing.

[mattthegamer463]

Nice idea. It certainly could be possible.

[rford]

Good work. It is going into my "must have" list.

What do you think of the idea of making it run on punch cards.

If the pegs were spring loaded, and only extruded where there was a hole in the card. It would remove the limit on the length of the song.

An extra row of pegs on the out side edges, with no notes. Just to register the card and feed it in properly.

Now if I could just think of some way to have it re-tune itself from the punch cards.

[Dagless]

Hi rford,

Can you elaborate on your punch card idea? I have found this existing product:
http://www.grand-illusions.com/acatalog/Large_Music_Box_Set.html

... but I can't get my head around how this works. The springs would have to be sensitive enough that the card prevents them from protruding but strong enough to pluck the tines without retracting.

Have you seen any Instructable on this, or similar products?

[rford]

My idea was too make the springs sensitive so they are easily retracted by the card.

The idea was to have the tines would first impart a perpendicular force that would lock them into place and keep them from being pushed in as they pluck the tines.

I know it can be done some how, there are a lot of examples of card controlled music boxes.

Maybe we need a "destructables" where people take things apart to see how they work.

[mattthegamer463]

I would imagine this would be a difficult task, since the springs would need to be soft enough that the force of hundreds of them doesn't push through the paper. Also, the current tines have bent ends to make plucking easier and prevent jamming; this causes what would normally be a 100% lateral force to now have compression force included. The pins would simply recess back into the drum when the tine touches them.

[jimwi]

You don't need a lathe to make the drum parallel, just set up a sander or an angle grinder with a sanding disk on it to a fixed place, a strait edge and just move the drum in front of the sander. Rotate handle to take off high spots as you slide music box along strait edge. Hope this helps, good job.

[Wildrat]

When we get the major CME, I will have this PDF printed and ready to build, so I can supply Mechanical music boxes to everyone with a digital music device. I'll be selling the boxes for one ounce of gold, pre-orders can be made now since it won't be long now before the big CME.
Nice box man, I thought we were going to here some Scorpions though. Good Work!

[mattthegamer463]

What are you talking about?

[Wildrat]

Coronal Mass Ejection
End of civilization as we know it scenario
Gold will be a currency
All the dweebs will want music
sell it to them for 1 ounce of gold
Scorpions- a rock band

[courtervideo]

WOW!! This is a FANTASTIC project!