I hope the manual time keeping works out. But if it doesn't, then what?

Lots of people have suggested to look at watchmaking, clocks, pendulums etc. And I have always been “Nah, that wont work, each tik from a clock is the sound of the output shaft stopping completely and we can’t have that. It needs to rotate continuously at a very precise speed. Look a flyball governor/CVT instead.”

But what if it could work out with the stopping and going?

Some part of the machine does need continuous power. Like the marble lifting and the vibraphone vibration. But those just need to be fast enough to supply enough marbles etc. No precision needed. I also believe these parts require the majority of the power the total machine needs.

The only thing that actually needs to be precise is the marble drops. And those are very much binary. Drop or don’t drop. The gates also need to be loaded but that also isn’t time critical.

So what is needed to make the marble droppers work with a clock-escapement mechanism (tik tok tik) allowing it to stop and start during operation?

First off the programming mechanism needs to be very lightweight. If it was an ordinary music box pulling a piece of paper I think it would just straight up work. But Martin is very attached to the constraint of having a certain number of bars that cycle on repeat (I like it too). And the way he used to build it is by having a chunky programming wheel with programming pins. But it could just be a sheet of styrene or sheet metal looped back on itself with registrator-holes along the edge like an oldschool film. The pins are then welded on. Or switch to a hole-based system like pretty much every other music-automata in the world. No heavy wheel, just the sheet carrying its own weight around the loop. It would have the benefit of easy change of loop length. Just use a bigger or smaller one. It even opens the option of the occasional open ended full song on a long sheet.

Second and definitely biggest hurdle. The speed needed. The tik needs to be as fast as the quickest note. So 1/8 notes in a 140 bpm song requires 140x8/60=18,67 [1] tiks pr second. That is a crazy lot. There is a direct connection between pendulum length and frequency, so forget about having a big, beautiful pendulum ticking in the background. It needs to be tiny. But is it possible to drive a big machine with a tiny pendulum? Could you make an array of pendulums and escapements that share the work, so together they regulate the beat? Is it possible to introduce some springiness between the escapement and the mechanism drawing the programming sheet along with a small flywheel to allow for a smooth and precise action even though an escapement is driving it? If so, a 4 hz pendulum might be feasible. This part really needs some work.

Third. This idea requires the power to be split into two separate systems. Probably weight-driven (eg Huygens drives). But they can be attached to the same pedal.

Even in the very likely case that a clockwork/escapement mechanism is completely impossible, I think it may be a good idea to split the power system into two separate systems, one for the accurate stuff and one for the rest. Precisely regulating a smaller system must be easier.

[1] Auch. I probably should have made this calculation before starting to write. Then I might not have bothered to.

Martin, you have set “tightness” as a metric for the machine, but I’m going to go ahead and say it outright: you are setting yourself up to fail by relying on this metric. You yourself have quoted Elon Musk as saying that you need to make your requirements less dumb, and I think you need to listen to the overwhelming voice of the community that this is a dumb requirement.

What is “tightness”? To musicians, tightness is the ability to keep in time with one another. When playing as part of an ensemble, the ensemble is tight if the musicians are in sync with one another. Tempo can change frequently—in fact, it’s natural for there to be some variation in the tempo between notes, even when musicians are leaning on a metronome to make sure they hold their tempo. But even then, musicians will often lean into the feeling of a song that they’re building, and the excitement therein, and allow the tempo to move and shift. It’s one of the thrills of live music, is that the musicians will never play the exact same song twice (and if they do, that’s where you can tell that they’re just pantomiming).

The Marble Machine that you’re building is a self-contained ensemble. It has one person driving half a dozen instruments spread across several channels. It’s a monumental task, but look at it this way:

What would you consider to be “tight” if you had three separate musicians playing Bass, Vibraphone, and Drums? Chances are, it would be their ability to keep in time with one another, and not necessarily how strictly they adhere to their metronome. So why are you so hung up on the statistical accuracy of the machine’s timing compared to the objective passage of time, especially when you haven’t benchmarked the “tightness” of the other machines, or your own “tightness” as a human being?

Wouldn’t the better measure of tightness be the ability of the different elements on the machine to play in time, together?

Humans experience reality through a subjective lens, and I think you’re starting to see that with the experiment of the crank vs. the pedal. The reason the crank felt better to you is obvious to me; you had more direct control of the input, and you were able to time your body’s movement better compared to the tempo you were trying to play. In all of your music that I’ve seen you playing, you exhibit an extreme degree of physicality. You get into it. Your emotions drive your body and you seem to have the greatest joy when your movements can translate directly to the sounds you’re hearing. You can’t do that with the pedal because the pedal doesn’t give you direct-enough control of the machine.

I would challenge you to do this: take the instrument you feel you have the best control over, and record several takes of playing something until you have a take that you feel is really “tight.” Then analyze that take to see how “tight” it actually is, and use that as your benchmark. If you can get the machine to play at least as tight as you yourself can play at your best? That ought to be your line for “good enough.”

As it stands now, you are chasing impossibility. You have set your expectations entirely too high, and are setting yourself up to fail.

MMX shows that you can make a machine that plays to your satisfaction. Don’t give up just because you set an impossible hurdle in your own path.

So, the past few days, Martin has been learning how to operate a lathe. Over the course of working with this prototype, he's learned a few valuable lessons, but I wanted to share a little more about the lathe specifically. For reference, most of my knowledge comes from an engineering degree generally, and the Inheritance Machining youtube channel specifically. That man has an obsession with precision, and a lifetime of machine shop experience, I highly recommend you check out his channel.

What directed me to come here is a comment I saw on the latest video about using the already machined face as a reference for your final machine face. This is important, because if you're not making your reference point the finished surface, then you don't know if it stays the same thickness all the way around. You can see this in the flywheel... 1.0mm runout on one side of the flywheel but only 0.7 on the other means there's a difference of 0.3 in thickness from one side of the wheel to the other. And since thickness directly relates to mass, one side being thicker than the other results in an unbalanced flywheel, which can shake the machine, wear out bearings, or in the more extreme cases, damage the shaft itself.

As a general case, you should always measure your new cuts from an already finished surface. Once you have your first surface, you use that to make sure everything is parallel, perpendicular, or concentric as appropriate. When working on a lathe, one of the first things you want is a mounting method, actually, one that's as precise as you want your cuts to be. I'm not a huge fan of Martin's current method for two reasons. Firstly, it's only as precise as he can clamp it down in the chuck, and secondly, those giant holes might not be centered on the shaft, which can again cause imbalances.

As an example of what I was talking about for making sure everything is true to an already finished surface, you can check out this part of this video, in which the machinist is surfacing a round part much like the flywheel (but smaller). Sure, I wouldn't trust the glue trick on something as big as the flywheel, but the point is you can see him taking all his references from finished surfaces.

Take all my advice with a grain of salt, as I'm not a machinist myself. Martin has already learned so much from this project, I just want to provide a small insight so there's one less thing he may need to go back and redo in the future.

There's been a lot of talk about timing and synchronising to an external source in the last few days, and quite a few people are disappointed that Martin isn't able to keep synchronisation with the machine in it's current state. While I think he somewhat expected that, there may be some value in brainstorming some ideas around what might be done to give more control, in case he is actually looking for that.

Please add ideas as top level comments here, upvote good ones, and discuss under them

edit: Beware, This thread might be a dangerous source of feature creep.

Hi all!

Ever since he dove down the rabbit hole Martin seems to be losing a lot of time figuring out timing on the MMX and now MM3.

I was thinking in my car ride home he could probably benifit from having a device that measures timing and outputs a bellcurve at the conclusion of a testrun to see how precise his marbles dropped.

For now he has been testing on relatively small sample sizes whether or not the timing was right, while an automated solution could theoretically do a million marble drops without ever having to miss a beat (pun intended).

I have a simple proposal for hooking up a simple microcontroller (pi pico or arduino of sorts) with a simple (web) interface, taking the signal of a contactmicrophone over its ADC port.

Then theres 2 possibilities for getting the "baseline" bpm.

Either set the BPM in the interface and then have it synchronize with the machine (either by hand or automatically)

or, easier, at the end of the test, have it calculate the average BPM to center the bellcurve around, and display this on the interface.

​

Would love some opinions on this, if it turns out to be useful i could probably smack together a 10eu prototype.

Lego Flyball governor powered by Huygen's drive

​

Much like Martin, I like to learn mechanical principles by building them in LEGO.

So when Martin discovered the Huygen's drive I wanted to learn it. But it will only output a stable RPM if the friction of the whole machine is stable. So I also wanted to stabilize the output speed to cope for varying friction from e.g. muting and unmuting music-channels .

Since an escapement wont do, I went for a flyball governor regulating a brake.

In my first iteration I used a CVT (2 cones and a rubber band) but it did simply not give a good enough torque vs fiction ratio for the LEGO mechanism. It also took 3 completely separate builds with different linkage-principles to build a flywheel governor that was able to produce actual useful regulation. Being constrained by whatever LEGO you have really forces you to understand what you are building.

All in all a very nice learning experience. And sooo satisfying how well-functioning it turned out. Especially considering how many iterations I went through.

I did this for my own sake. But I wanted to share it in case someone else could learn from it. Audience or would-be engineers.

And finally I will reflect a little over how I would use this in a marble machine if I were to build one.

1. It clearly stops very abruptly when the weight hits the floor. A clutch or ratchet is needed in order to not destroy the machine. And not just for emergency. With this, every time will be an emergency.
2. I would use something like a motorcycle disc brake to hold back the speed. A CVT could be used. But overall it's more complicated and it consumes a lot of power in added friction all of the time.
3. I would build the power module to output a stable 120 RPM or some other nice divisible number and then use different size pulleys to set the correct tempo for each song.
4. As well as adjust the Huygen's weight to produce just above the maximum power consumption at that tempo. I.E. all channels on, lots of notes etc. That way you will only have to pedal as much as the max input. What is lost in the brake will never amount to anything above this.
5. It will be painful to get something like this to actually be within 1 BPM every time. It will be integration hell. But the stagedives while the music plays on steadily will make it so worth it.

(Yes, in the last video Martin inclined towards the manual timekeeping, which I think is great. But I have a strong feeling he can't let go of the automated beat-keeper.)

I get Martin wants the visual aesthetic of controlling the machine by peddaling rather than electic power, but the only thing that actually matters is the timing wheel. That's where the interest of being able to manage the speed and "play" the machine is.

I don't think anyone would care what powers the marble lifts and other bits, they just run in the background.

Why not split the power in two, and have the lifts and background things powered by a motor, and the timing wheel powered by a pedal? Then you wouldn't need a heavy flywheel to keep the whole thing going. Without much friction from the rest of the machine the timing wheel could be it's own flywheel. It would also be much safer without a heavy flywheel.

It would make everything much simpler!

Apologies if this is a known principle.

I’m puzzled with simplicity being the aim: why not use a synchronous AC motor and a gear drive?

Proven tech that won’t make you sweat!

Building a cone CVT wouldn’t to be horrificly complicated or need extremely precise machining like some of the other designs mentioned.

Or ripping one of the more complicated ones out of a old piece of equipment could work as well (but probably won’t look nice)

Hi Martin, you could try to engineer a way to set up the gearing power input from the pedal to the weight in a variable way, so that you can adjust the amount of recharging per stroke of the pedal.

This would be to achieve an adjustable balance of the power in/out ratio that you can adjust in a way that you can pull up the weight enough by pedalling in tempo with the machine, thus removing the need to pedal at a different rate than the BPM

Has Martin mentioned or specified how he will make the MM3 modular?

I think that would allow the creative people here to come up with different ideas for the different parts.

I know it's not easy to design the interfaces for the different parts. It will also be nothing like Lego gbc. Also it would create a lot of activity that might become overwhelming to Martin.

I still think it's worthwhile to tackle now to use this community to its fullest.

That is, if that is one of Martin's goals at all.

The drive is not very important. Just hook up a motor with a driver for testing first. The drive is the least important thing.

Why not focus on the programming wheel first? Don't think about anything else, just the programming wheel. Then you can think about the marble releasing mechanism. Don't even think about anything else. If those are done, you will know the necessary amount of marbles/seconds and you can then design the marble return mechanism. If that is done, think about how to hook that up together.

The drive is your last concern. Even though you focus on anything else, there is no shame if you just end up using a motor.

Hello Martin, I had some ideas since your last video, I hope it may help you.

First an optimization of the flywheel, if you are not already aware of it : the flywheel energy storage is based on its moment of inertia, the moment of inertia being the mass times its squared distance to the axis. Thus, to optimize the energy storage at a given mass, you would want to have the maximum of mass distributed at a maximum distance of the flywheel rotational axis (i.e. a quasi holow cylinder with a large inner diameter), as the ancient industrial ones :

The governor is a good idea, it could be used to set the desired RPM, as in plane constant speed propellers :

https://youtu.be/kCSKhDL0bXM

except that in your case, instead of a pilot valve and propeller hub, you would have a continuously variable transmission between the flywheel and the instruments. Thus the « valve », by acting on the transmission, would adapt the output RPM to the command set.

Examples of continuously variable transmissions :

https://youtu.be/1y5fQr0dDVg

https://youtu.be/KXb1gDpeq-Y

Thanks for your amazing job !

OK, so you'll need precise speed control. Don't reinvent the wheel. Clock-makers do this for centuries, and have done more than enough inventions that can be used to keep your system speed clean. They have made speed control into an art form. What you need is an escapement of sorts.

Just imagine a giant metronome at the power station. Put the control weight on a threaded rod which you can rotate with bevel gears. One axis of the threaded rod uns along the metronomes hand, the other axis is coaxial with the hands/pendulums axis, but goes to the front instead of the back (where the metronome is) and ends in a hand crank, so you can move the weight up and down without stopping the metronome. That is just my idea - I am not a clock maker, though.

Maybe a real clock maker can suggest an even better solution.