Keyboard instrument

Discussion in 'The Projects Forum' started by thrashmetaljazz, Jun 17, 2013.

  1. thrashmetaljazz

    Thread Starter New Member

    Jun 17, 2013
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    I am working on a project to build a keyboard instrument. What I'm looking for is a mechanism that converts the motion of pressing a key down (onto a switch) into an alternating up and down strike of a strip of metal (the bit that will vibrate and make a sound), so that one press of the key causes an upward motion and the next causes a downward motion...

    I am aware that this can be done with a DC motor and a polarity reversing device to change the direction, but no idea what kind of motor or device can perform this up down movement...so I'm here!

    Thanks,
    Dan
     
  2. wayneh

    Expert

    Sep 9, 2010
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    If I understand your request, you want to use a keyboard such as you can buy off the shelf, and use it to thump some strings (or vibrating elements, if they are not actual strings)? And your question is how to build a thumper?

    I think a solenoid is worth looking at as the source of mechanical power for the thumper. You don't need variable force like a piano, right, just a consistent thump every time the key is pressed, like a harpsichord? One volume level?
     
  3. Metalmann

    Active Member

    Dec 8, 2012
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    Something you may look into is, buying old player piano parts. I tore one apart about ten years ago, and it had several mechanisms similar to what you describe.
    You could modify those already assembled pieces, to work with an elec. motor.

    I salvaged it for the lumber, mahogany, cedar, real ivory, and ebony.
    Extremely nice hardwoods, and old screws, felt...that looked like new, sweet hinges, hardwood bellows, and other small brass parts. I sold some of those mechanisms on Ebay cheap.

    They showed very little wear, but still worked great, even though they were over 125 years old.

    I bet the stuff that is made today, will never last 125+ years.;)
     
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  4. thrashmetaljazz

    Thread Starter New Member

    Jun 17, 2013
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    You're pretty much right with regards to my plan. I don't need variable force (it would be good in an ideal world but I'm happy to compromise).
    I have no knowledge of motors so 'solenoid' means nothing to me! I've googled it but I'd still have no idea of terminology or how to get the required movement if I had a motor...

    Thanks for your reply!
     
  5. wayneh

    Expert

    Sep 9, 2010
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    A solenoid produces a defined force along 1 axis. Push/pull, and the distance the solenoid plunger moves is also a specification. Think about a pinball machine - most everything that happens is controlled by solenoids.

    Translating the linear motion provided by a solenoid into the desired result is a mechanical challenge and I don't think we can help at arm's length without more information. If you post pictures or propose a design, you'll get feedback.
     
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  6. OoglieBooglie

    New Member

    Jun 3, 2013
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    If you simply use a normal rotating motor, the mechanism to move back and forth should be quite simple. Well, simple to understand, but perhaps not simple to make without the right materials or equipment unless you simply buy it ready made. I'll help with that after the idea part, though.

    Remember those old steam locomotives (I'm sure you've seen them on TV, the internet, or a picture in a book at least once, even if you were a kid)? Well, take a look at the drive mechanisms. The same principle is also used in modern car engines (but it may be easier to understand by examining the exposed wheel spinning rod things on the old steam locomotives. Basically, to get a back and forth motion, we can simply use the same principle but in reverse.

    The mechanism is more or less a straight rod attached to the face of a wheel (but not at the center, as that would defeat the purpose). As a piston/solenoid/(insert other linear motion source here) pushes, the wheel is forced to turn. A simple example of this principle can be done with a bike wheel. Place the bike so one of the wheels can spin freely. Now place your hand on a spoke. By moving your hand forwards or backwards, the wheel will spin, even though your hand is only moving in a linear motion. To allow a full range of motion, the rod is allowed to spin on the joint thing with the wheel, so it can still move in the same linear direction without having to rotate with the wheel. Voile! This converts between rotational motion and linear motion.

    Now, as to making it, there are several methods. Wood would be a fairly easy material to do it with, but wood would eventually wear down and each piece must be cut individually. Metal would be a much better choice, but it is much more difficult to work with. This may seem impossible, but it really isn't. You can actually make your own little blast furnace to melt aluminum with charcoal for like $30-50. Some finishing would still be required, though, as cast metals can have a rather rough texture (which is generally not desirable in a part that is designed to move easily). You would also have to make a pattern for the metal casting, but a wooden pattern (basically the same as the wooden method, but only done once instead of for each mechanism) can be reused to make multiple copies of the same item. The easiest method would be to simply order something like this online, though.

    After all this work, the solenoid method mentioned by the other guy would probably be a much simpler, cheaper, and quicker method, though. But hey, if you want to impress people with moving parts and machinery in your finished item, this is a relatively simple (but still more complex than simply using a solenoid) way to do it.
     
  7. Metalmann

    Active Member

    Dec 8, 2012
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    Check out this video describing mechanisms.:

    http://www.youtube.com/watch?v=Y5pen3QMgzQ



    My older books, have about every mechanism ever thought of by mankind.
     
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  8. thrashmetaljazz

    Thread Starter New Member

    Jun 17, 2013
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    Attached is an image of what I'm trying to do.
    Thanks for all the replies so far!
    Dan
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Extend the tine's rear end and attach the solenoid plunger there, perpendicular to the tine. You'll need to think about how far the plunger travel needs to be, and the force. Both will be affected by the leverage you give it.

    This solenoid has an integral spring to bring it back, so that may not be what you want, but the video there may help you.
     
  10. tubeguy

    Well-Known Member

    Nov 3, 2012
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    You could connect the button to a flip-flop, then to a solenoid driver. First push, lever down (solenoid activated) second push, lever up (solenoid released).

    EDIT: You would probably need to add spring tension of just a bit less than the solenoid can pull to get the released force somewhat equal to the pulling force.
     
    Last edited: Jun 24, 2013
  11. wayneh

    Expert

    Sep 9, 2010
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    Yeah, I don't know enough about available solenoids to fully sketch out the idea. I mean, I don't know if the solenoid can just be pulsed in either direction or whether it might need to be held by applying continuous current in one of its positions, or even whether two opposing solenoids might be needed (seems unlikely). I just know a solenoid is a "digital" device with two states and inherently easier than a motor for this particular application.

    I guess a half rotation of a cam on a stepper motor would be easy for somebody with experience.
     
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