Prototype with infinite pivot lenght

Well, my xKey Air 37 already uses that principle!

I saw this other video

And I am reading now the corresponding thread on PW which I missed at the time….

I just wanted to stir PC with some pivot length discussion. Besides the weird change in shape of the keys this guy proposes (if we should change the shape I'd vote for Janko, by I digress), my intention was to say Yamaha could make a keyboard with this "leverless" design and call it infinite-pivot-length and close the "battle" with Kawai on that argument 🤣

CyberGene Well, my xKey Air 37 already uses that principle!

But the travel of the keys with that is very short, whereas with this the travel is normal for a piano.

Just say no! This keyboard action does away with our precious discussions of pivot length! 🙂

MacMacMac This keyboard action does away with our precious discussions of pivot length!

This IS our precious discussion of pivot length! It would go it away if everybody did it this way, but I don't see that happening for real 🤣

Oh no, not again!

Count me as a skeptic. I predict this thing will never work, particularly for any valuable length of time.

Wherever one places the finger to play a key, the downward force of the finger is converted to torque exerted on the vertical guide at the point where the guide is connected to the key. The guide will always operate at varying amounts of dis-alignment with its travel channel. And, since the guide-to-channel interface is a friction surface, there will be constant wear and deterioration. I think this will always be a source of unpredictable friction, rendering each keystroke a unique experience, instead of the consistent experience presented by a key on a pivot.

This dog won't hunt.

Ralphiano I think this will always be a source of unpredictable friction, rendering each keystroke a unique experience, instead of the consistent experience presented by a key on a pivot.

Excellent criticism, thanks.

How about a parallelogram approach instead?

Like this (keys are light blues, the rectangle/parallelogram is the hidden part of the action, not to scale). Of course the limitation of this design is that the keys go "inward" besides that down, but that can be probably made negligible?

Do you see any other flaws here?

I like finite length pivot, because by playing closer to the fallboard you can make the sound more soft (being slightly harder to press). I think there is a video (posted somewhere in this forum) of a pianist that did fast repetitions moving continuosly the fingers closer and farther from the fallboard to make variations in the sound timbre.

magicpiano I like finite length pivot, because by playing closer to the fallboard you can make the sound more soft (being slightly harder to press)

That's a good point even if arguably a good pianist should be in control regardless of playing point. And it goes contrary to PW wisdom of "mine is longer than yours" 🤣 so perhaps on PC as we age which should aim for a shorter or perhaps "optimal" length? But I digress…

Let's instead go back to my technical question about the parallelogram design. Do folks think it will work as expected for piano? Any obvious-to-you flaw like @Ralphiano did on the other one I posted earlier?

RIP

That is an interesting approach. It is similar to the parallelogram already in widespread use in bicycle rear derailleurs. But, they differ in that the derailleur receives force applied directly to one of the three moving sides of the parallelogram (one side is fixed to the bike frame). So, the derailleur force is applied very close to the critical pivot connecting one of the moving sides to the fixed side. On the other hand, when used as a piano key, the force would be applied to the key at a great distance from that critical pivot point. What effect these differences would have is another discussion.

I would anticipate that a main weakness would be the necessity for four pivots, one at each corner of the parallelogram. These corner pivots are the main point of destructive wear in a bicycle derailleur. As they wear, the parallelogram can begin to operate out-of-plane as the forces applied to the initial side can move the next, subsequent side in a twisting or direction different from its originally intendeded direction.

Though pivot wear is similarly a factor in plastic piano actions, it is not a factor in an acoustic piano that uses a balance rail instead of a pivot.

Another weakness of the parallelogram would be the necessity for a spring or other unnatural force to return the key after is it released.

If available space was not an issue, this could perhaps be mitigated by connecting the parallelogram to the piano at the midpoints of the horizontal sides of the parallelogram, and then adding appropriate counterweight to the side of the parallelogram that is exactly opposite the side to which the key is attached. It seems like this could introduce a more 'natural' feeling resistance force to the key stroke.

I'm out of time and have to run.

This parallelogram thing is interesting.

Make the mechanism from nylon. Then lube it with teflon. That'll take care of things.

Or … you could always resort to bacon grease. It slickens the path, and it smells like Sunday breakfast. 😆

Ok, so I'm thinking of this approach for a (slightly) different kind of application (still hybrid piano action). Sounds promising. I'll leave that story for another day, so let me get back to the common one.

Yes, in this case too, one side of the parallelogram is fixed somewhere on the structure of the instrument (and can be of different proportions compared to how I quickly drew it). The out-of-plane movements should be easy to take under control with the front rail key pin (like in a regular acoustic action), of which there could be even a second one in the back of the key. The wearing of the pivot points should not be a big concern, since there are similar ones on each flange for whippen and for hammer shank, and wear is not a huge problem. However there are two of them in an acoustic piano and they are considered an important source of friction which may become too much. So having four might be a problem. Using nylon and/or teflon (rather than wood/cloth) as @MacMacMac suggested could help a lot, and it's certainly something to explore, but that may require very tight tolerance to get it right or at least that is my understanding from the reading the technician's literature on the topic (mostly but not only regarding WNG).

Regarding the weight in the back, if there is lots of room one could just do the regular seesaw balance rail. The purpose of this is to make it less deep. You can still add a counterweight in the back with a very short leverage, but that will need each weight to be quite heavy, which is also not desirable. Alternatively, one could design a simple seesaw mechanism (or similar other folded action thing) and put it under the key. That way, there is plenty of design freedom to make it of the right touchweight without actually being very heavy (basically the only constrain is that it needs to be "out of the way" and not interfere with the parallelogram or the key itself.

I will start by saying that I could not follow all the mechanical details (and the engineering/physics principles...) of the proposed designs (I am too obtuse to understand the paralelogram), but I would like to raise a question. The piano key (flawed as it may be...) acts as a lever, and in that sense the force required to lift the whippen is smaller at the key tip than at the fallboard. By getting rid of the lever, will you transform the key in a long tip or in a long fallboard? My bet is that infinite length key will require fallboard force throughout the key. If so, what is the advantage?

vagfilm I will start by saying that I could not follow all the mechanical details

I'll see if I can build it with LEGO and post a video about it [1]. That'll make it obvious.

vagfilm By getting rid of the lever, will you transform the key in a long tip or in a long fallboard?

Well, I am not sure I understand your question, so let me rephrase it. Pardon me if I am answering something else, let me know if that is the case. You are asking "how heavy" this approach will make the touchweight: like it commonly is at the tip of the key, or like it commonly is at the fallboard?

The answer to the rephrased question is: it depends on how you build it. If you are using this thing as a digital piano key, you can either use a spring (and so it will be as heavy as the spring you put in) or you can use a seesaw below it (similar to a regular piano key) and have the actual key push the seesaw, but touching it in one point only. You can adjust the touchweight by choosing the place where it touches and the actual counterweight. Of course if you'd be using this in a regular piano (why? I don't know, you asked 😁) you can't change the "counterweight" (since there is none, and the whippen+hammer act as one), but you can still change the place of contact. I might need to add also this to the LEGO model or drawings.

🎶

[1] Does it need to be in youtube or could be an attachment here?

RIP I'll see if I can build it with LEGO and post a video about it

Hi. No need to patronize me. I was honest when I said that the details on the parallelogram approach and how it is similar to "bicycle rear derailleurs", is beyond me. I simply stated that I could not understand it, and since I did not ask for a clarification nor an explanation, no lego explanation is necessary for me. Keep up your adventure.

vagfilm

I think delvento probably mentioned the LEGO with the real intent of showing how it works, I doubt he meant being dismissive/patronizing, at least that’s how I interpreted from aside. Peace ✌🏻

Don't worry CG: all is well (but I cannot do the peace emoji... I don't understand derailleurs and I go as far as a few face emojis... 😁 )

CyberGene Peace

Is there a "Live long, and prosper!" emoji as well? 😁

So long as it's technical lego, it qualifies as a technical explanation.