Small hammer-like actuator ideas

Hi,

I want to build a set of (tubular) chimes for the doorbell.

I *don't* want the "strikers" to be visible (makes it a cleaner presentation and more "magical"). This suggests the strikers must reside *inside* the tubes.

Apparently, designing these chimes is more art than science. Alternatively, *way* more science than most folks have the time for! (i.e., choice of material greatly influences sound)

But, from looking at other designs, it seems like the smallest tubes will be on the order of half an inch in diameter.

I can't imagine getting *anything* (electromechanical) to fit in there -- especially if it needs to have enough mass to sound the chime! (I think it also needs to strike the chime at a *point* and not at a "surface"/line)

Any suggestions as to other mechanisms I can look at for inspiration?

Thx,

--don

Reply to
Don Y
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Having stuff inside the tube, even stuff not touching the walls, will definitely affect the sound. Whether or not that's acceptable is obviously dependent on the application. And as you mention, you're probably going to end up with a bunch of trial and error.

You'd have to run the driver/solenoid vertically down the tube, and have it ram a hammer on a hinge, something like the hammer in a piano. Still, that's going to be a tight fit. I'd consider pneumatics.

Hide the hammers in the bell supports?

Hide the hammers in the backplane so they only pop out the instant they're about to hit the bell (perhaps a small spring loaded door over each hammer)?

Hide a speaker someplace and have it play chime/bell sounds, and make the exposed tubes purely decorative?

Hide *real* chime tubes/bars someplace and hit those, while leaving the exposed ones purely decorative? (This is probably the best idea of the lot).

Fire a steel ball (something along the lines of a large ball bearing) at the chimes from someplace easily hidden? Some care in mounting will be need to allow the balls to be captured after they bounce off the chimes. Something like:

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OK, that's obviously impossible, but it's a great piece, and does illustrate the idea - in reality you'd use far shorter paths, you'd just need a channel in the backplane with a curve pointing at the chime to drop the ball(s) down, and then a capture underneath it all.

There might be some piezoelectric hammers that (might) work for you.

Reply to
Robert Wessel

You will want to experiment I'm sure. I'd try supporting the chimes at a point 2/9ths their length from the top with a small hollow tube brazed (or -if available-a threaded hollow tube with hardware on the inside of the chime/w'ever) at a 90 dgree angle. That tube could then support the chime from a back piece. Then, a 'striker' could be a rod that pokes through the hollow tube and strikes the opposite inside surface of the chime. Check R/C plane hobby suppliers for components. Also, some model train layouts will have animated figures sawing wood or chopping logs. They often use motors with spiral shaped cams to lif

- then allow to drop - a hammer or ax. A custom jeweler may be of assistance too. I wouldn't be surprised that silver tubing is available for this project.

interesting project.

Reply to
1 Lucky Texan

Really? Why? (I abhor fyziks) I thought the trick was letting the tube itself vibrate as necessary (i.e., "point" supports placed at nulls on the surface).

And, that the actual *movement* involved is almost unnoticeable (i.e., any clearance around the actuator would effectively remain clear even while struck)

Yeah, I had begrudgingly resigned myself to that regarding selection of material and tuning of lengths. But, trial and error for a mechanism (esp one as critical to success as this) really increases the risk of successful completion.

Or, something that "twists" to deploy (with the actuator sharing its axis with that of the tube)

A friend suggested that. But, that adds "clutter" getting the air supply into the tubes. (you could conceivably run power to an actuator through the same "strings" that support the tube).

And, I am not sure how "crisp" a mechanism can be when you're moving air instead of electrons.

I had thought of that in an original design (where there was a wooden wall/surface along one side of the chimes). But, I decided that a better location for the assembly would place it free-hanging (sort of like a "room divider") so there would be no "back side" to hide things in (this is part of the appeal of this placement... it makes it more "magical")

Boooo...

See above. The appeal of the approach I'm proposing is that it presents a difficult bit of engineering: "How'd he *do* that?"

But then the focus would move to the balls instead of the chimes. It adds another aspect to the "piece" that detracts from the "performance" -- the sounds generated (it's a doorbell, not a piece of animated art)

Ah, that's an idea! Even short throw devices might work if the tubes truly *don't* "move" much. I think the problem is getting enough *mass* to create enough of an impact -- while still keeping small (OTOH, larger tubes are more likely to need more mass so this might be a solution that scales well)

I should also look into RC actuators to see what sorts of (small, lightweight) things they might have.

Thx!

--don

Reply to
Don Y

I had thought one could simply pierce the tube at this point (22.4%) and "hang from a string" (such that the string itself is at the sweet spot). Pursuing an electrical (actuator) solution, I would use fine wire in lieu of the string...

I'm confused. This tube *intersects* (pierces) the chime and acts as a guide for the hammer?

Yeah, I was looking at some tiny motorized actuators I had in my junque bin and figured something equally exotic might exist.

I don't think a simple gravity driven "fall" will impart enough energy. There's so little room *in* the tube...

For the chimes themselves, I had originally thought of *glass* but that just makes hiding the magic absolutely impossible! :<

A challenge. I don't need an immediate solution but have to decide what to do with this aspect of the house (and a set of "tubular bells" would be very interesting, there).

Thx,

--don

Reply to
Don Y

How about a speaker and a few recorded chime samples ?

*ducks*
Reply to
Arlet Ottens

You could experiment with a tubular solenoid, hanging in the pipe, and convert the axial plunger movement into a radial impulse to hit the inner wall of the pipe.

One way to convert the axial movement while minimizing moving parts is by using a two-headed Y-shaped hammer with resilient stems fitted to the plunger, something like (ASCII art alert):

| | | ### | | # # | | #|# | | #|# | | #|# | | | | | | | | / \ | | o o | | | ~ ~

Activating the solenoid pulls the hammer while inertia force bends its stems closer together. This will build up energy in both the stems and the heads (elastic potential in the stems and kinetic in the heads). The moment the plunger reaches the solenoid's stop position the accumulated energy will bend the stems outwards (and wider than their original position) which causes the heads to momentary hit the inner side of the pipe.

All calcu^W trial and error with respect to plunger speed, head mass, stem length, stem resilience is up to you....

--
Wil
Reply to
Wil Taphoorn

A big part of the sound is generated from the inside of the tube, and the stuff inside interferes with the sound waves in the air. You get extra reflections, damping, harmonic vibrations from the mechanism excited by the primary sound waves from the tube, etc. Again, whether or not that's acceptable is up to you. I'd cut some tubes and hang them with some stuff inside to see what the effect will be.

I was thinking a two stage hammer approach (again, think piano mechanism). Pneumatics could drive the "drive" hammer over a long linear distance fairly easily, with a nice narrow mechanism, allowing you to build up as much momentum as you need. At the end of the run, the drive hammer hits the strike hammer, and kicks it into the chime.

So the chimes will be suspended from only one end? I think this makes it harder - the chimes need to be "loose" in order to sound, but the hammer mechanism will generate some movement - unless it's completely loose (at which point you risk it banging around inside the tube after a strike), you're going to get damping as the inertia from the strike pushes the hammer against the mounts holding it away from the tube. Perhaps a symmetrical hammer design that generates no horizontal movement (for example, two hammers striking out in opposite directions at the same time) would be in order. That would change the sound, though.

Or go with much thicker tubes.

Or perhaps the tubes could be two part - with the upper section holding the mechanism, with the hammer extending into the lower sound tube (which would be suspended at a short distance from the upper tube. Perhaps you could use a nested design - the upper tube with the mechanism could be bigger, and could slightly overlap the sounds tube

- you could hide all sorts of sins in something like that. The upper (mechanism) tubes being smaller could work too.

Or extending the above idea - hid the *entire* "real" chime inside the fat decorative one.

Something like that would probably save you some expensive brass tubing.

I've always considered good engineering and cheating to be fairly synonymous. ;-)

Reply to
Robert Wessel

One more idea - arrange the chimes in a circle, like a wind chime, and have a striker plate in the center (just like a wind chime). Only make it spin and hit the tubes sequentially (instead of the tubes being swung into the striker by the wind). The actual hammer could pop out during the spin so you wouldn't normally see it.

That actually reminds me. I saw a great design for a wind chime skiing this year - someone did one out of bits of ski pole. I was going to do one for my deck, to complement the bench I built out of skies I have out there now (picture a park bench, but skies making up the horizontal slats). You probably have to be a skier* to appreciate either of those. ;-)

*I'm not so bad - a friend has an old ski lift chair for a porch swing, and he made the four posts of their bed out of skies. I just did a park bench. And a coat rack out of the handle ends of ski poles.

OK, one more idea - go pipe organ! All you need is tubing to move some air and some valves.

Reply to
Robert Wessel

Hmmm... from :

'In instruments such as an organ pipe, the pitch is determined primarily by the length of the air column, It is the air that vibrates. The pipe material helps determine the "timbre" or "voice" of the pipe, but the air column determines the pitch. In a wind chime, the pipe itself is being struck and the air column has little to do with the sound produced.'

(As I'm 107% clueless on this subject, I rely on others -- yourself included to make sense of all this stuff :> )

However, it should be easy to take an existing wind chime (save myself the trouble of fabricating something) and putting some material (wooden dowel?) up inside a tube (without touching the walls) to see if the sound changes noticeably...

(I'll wait until my neighbors fall asleep and then borrow theirs! ;> )

Seems like even more "mechanism" to cram into a tiny space (?)

And, still leaves me with the issue of hiding the (air) tubes feeding the mechanism.

[Hmmm... as an afterthought... I wonder if I could put "something" inside the chime *across* the opening. Then, *fire* a projectile (or an actuator) up *into* the tube and strike that "thing"?

I.e., move the actuator mechanism outside the tube and just leave the "hammer head" inside. This would be a real chore for the longer chimes, though...

And, much more visible than the other schemes mentioned]

Yes. Imagine building an "office partition" out of pipes hung from above.

I was thinking that it's "strike axis" could be in line with the "wires" that are passing through the chime to support the chime (and the actuator as well as supplying power). So, there isn't as much give/swing tolerated by the supports...

Or, tune the mechanism so the mass of the mechanism counteracts that of the flying hammer (?)

That drives everything down in frequency. I'd like to be able to hang ~30 chimes and cover a couple of octaves. "Make music" instead of just "tinkling noises".

So, the "extension" would act much the same as a sound box on a guitar, etc. (?) I'm not sure how that affects the overall design of the actual chime...

In some cases, the "trick" is the whole point. In other cases, you want to display just "craftsmanship" ("Wow, I can't believe someone spent all that time and effort for something as 'unimportant' as this...")

For example, my thoughts regarding making the chimes out of glass is far more *technically* challenging! But, aside from the Wow-factor ("Wow, they're *clear*!"), the issues involved in their making would be lost on 99.99732% of the folks who see them as they would be unaware of the difficulty of machining the glass. Of the remaining

0.00268% of observers qualified to realize the difficulty of machining the glass, none would be aware of the critical locations of the "suspension point" nor the extent of the machining effort required to tune the chimes' lengths.

OTOH, hiding a clapper is obvious: "What is causing it to sound? Ah, *I* see! Wow, how did you fit that in such a tiny space??"

(you want people to *think* about things, not just *observe* them)

Reply to
Don Y

But then you can't play arbitrary music (?). Well, I guess the hammer could *selectively* pop out! But, you would be limited to a small number of chimes (or, a really large diameter arrangement?)

Aren't ski poles made out of aluminum? I wouldn't think that would be a very melodious material (?)

You could have the "tips" of the skis arranged vertically (flaring to the rear soas not to stab a person in the back) to form the back of the bench!

Now *that* sounds cool!

... and *that* sounds "disturbing"! Gives a whole new meaning to the word "shushing" :>

That was my fallback idea. Almost.

Imagine glass tubes supported from below. Blow air across the tops of the tubes (like blowing across a soda bottle).

*But*, programmatically control the filling/emptying of the individual tubes with to change the dimensions of the air column (and, thus, pitch of the note). So, you fabricate some number of these (each designed for a range of pitches) and shuffle the liquid around dynamically to "play" the melody.

The interesting aspect then becomes how rapidly you are able to change the column volumes -- as most folks can easily relate to the "soda bottle" analogy.

[and, of course, the insanity factor: "Why the hell would someone go to this much trouble for a doorbell?"]
Reply to
Don Y

Ah, that's clever! Instead of *direct* action (i.e., through a linkage). It also wins because the two stems offset each other (I wonder how different the chime strike would sound, though)

I think you'd have to be careful to ensure the system is damped properly (to eliminate double-strikes).

And, I suspect each individual hammer would have to be tuned. I can't see how you could come up with one implementation that would scale to the various diameter chimes involved.

Reply to
Don Y

Steel, aluminum, titanium, carbon fiber... (in order of increasing cost.) And no, the sound quality isn't stellar, but that's not the point. Just like comfort isn't the main point when building furniture out of skies.

I've seen that done, but then to need to do something to seal the base of the ski, after stripping some of the base/wax off it. The top side is usually a nice plastic finish already, and the bottoms are usually less attractive anyway. Or you have a tall chair back, (think Adirondack chair) where the bend "out" is over your head.

On my bench the tops are the sitting surface, but the tips are way off on the sides.

That's *always* justification. ;-)

Reply to
Robert Wessel

Imagine two cylindrical magnets, say 1/4 inch diameter, magnetised along their length, that is, north one end and south the other. These magnets are arranged so as to be attracted to each other and touching. Each magnet has a 'string' at the other end. The magnets are positioned half way along the inside of the tube, with the taut strings extending to the tube ends and centred with some sort of cap or bung. In this way, the magnets are suspended in the centre of the tube, not touching the sides.

The tubes are non-magnetic and vertical.

Now imagine a spring joining the magnets together on one side only, say about half way up each side. The spring is arranged such that it's relaxed when the magnets are clamped together by their attraction.

If you then pull one of the strings, the magnets will part suddenly when the string tension overcomes the magnetic attraction. The 'off centre' spring will cause the magnets to rotate sideways to strike the wall of the tube.

When the string is released, the magnets assume their original position.

Maybe the 'strings' could be Nitinol which contracts on heating (with a current).

I'll try and ascii it, imagine it's vertical...

======================================================== ~~~~~~~~~~~

----------------NNNNNSSSSS|NNNNNSSSSS-------------------

========================================================

=========================================================

----------------NN ~~~~~~~~~~~~~~ SS---------------------- NNNSS SSNNN =======================SSS||SSS===========================

The diagram is crude in the extreme.

In the top one, the spring ~~~~~~~~~~ is relaxed, the magnets are touching and the string ---------- is taut.

In the bottom diagram, the string is pulled, the magnets have parted and the spring is stretched a little. The magnets have hit the tube =================. Dong!

Cheers

--
Syd
Reply to
Syd Rumpo

A magnet and ferrous plate could capture the striker(s) on the rebound. Naturally, increased force would be required to 'fire' the mechanism.

Also, I think tubes can be suspended from the top. Rods or plates may need the

2/9ths suspension.

Will you also need dampers?

see;

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Reply to
1 Lucky Texan

I'd consider looking at the _mounting_ as opposed to the tubes themselves. It occurs to me that you don't really need to do anything particular to the tubes, just disturb them and let them collide with another object. The traditional wind chime doesn't have any control - it's essentially chaotic.

Since the tubes are presumably going to be mounted via string or wire can one end of the wire be discreetly attached to e.g. a solenoid? You may be able to use muscle wire for much the same effect and an even more discreet mechanism, but I have to admit I don't really know anything about the stuff.

A simple wind chime style device would be very simple to operate in this way (disturbing all the tubes at once), but since you apparently want to play tunes you'll presumably need multiple separate strings with an actuator for each one.

--
Andrew Smallshaw
andrews@sdf.lonestar.org
Reply to
Andrew Smallshaw

Would it be possible to have a piezo mounted inside the chime, tuned to vibrate the air at the resonate frequency of the chime?

Alternately, attach the piezo to the inside of the chime and vibrate it directly.

Mike

Reply to
Mike Paff

Good luck. I could use a set of 25 for my Cyclonophone, made from Cyclone wire fence posts I scavenged:

Unfortunately, despite the wonderful sound, it's too heavy for a musician to want to lug it to gigs :(.

Clifford Heath.

Reply to
Clifford Heath

Ah. No idea -- the idea of paying (lift ticket) for the privilege of breaking some of my bones never appealed to me! :>

[And the amounts of money my friends would go through during the season made me wonder if they weren't, secretly, supporting a DRUG HABIT! :-/ ]

Good point. Of course, you could always start with NEW skis! :>

Understood.

Could you have arranged for the tips to curl up *under* the arm rests?

I see we suffer from the same (mental) illness...

Reply to
Don Y

Or, an *electro*-magnet so it's only active when needed.

There is supposedly some difference if you hang from the top edge.

No, I figure it's a chime, not a "musical instrument" (even though it is "played")

Cool! Of course, having the tubes ready made/tuned sure makes life easier :>

IMO, this design hides the "impressiveness" of the chimes/tubes. I.e., like a church organ where all the pipes are hidden behind a wall :-/

Part of my reason for doing this is to create a wall/screen/divider instead of erecting a (boring) traditional wall/screen/divider. So, hanging the series of tubes next to each other *makes* that "wall".

Reply to
Don Y

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