What about a troup of trained hampsters. They could have little strings to pull, on cue, and wouldn't squeak too much ( unless they get under the bass pedals ). This would keep the costs down too, you would onlu have to get two of them, initially.
What about a troup of trained hampsters. They could have little strings to pull, on cue, and wouldn't squeak too much ( unless they get under the bass pedals ). This would keep the costs down too, you would onlu have to get two of them, initially.
I don't know about hamsters but mice sure love pipe organs with all the various places to hide. I keep that at bay by playing 3 blind mice.
Just be aware that the magnetic saturation of the material from which a permanent magnet is made might not be as high as, say, a low carbon steel. Whereas a low carbon steel might saturate at 2 to 2.3 Tesla, a NIB for example might be saturated at 1.6 Tesla, so you might lose something in the kick the solenoid can provide. Again, I'm stretching the limits of what I know about this, so there might be some clever workarounds or other magnetic materials that will hit the sweet spot and give you the best of both worlds. It's just something to keep in mind maybe.
Good point! Given, according K&J the magnetic forces are additive, in the manner in which I intend to use them I was looking for a relatively weak force from the coil ADDED to the strong force of the magnet would create enough force to open the valves.
I have ordered a few cylindrical magnets today for testing. Theory and real life sometimes throws you a curve.
I guess when you think about it Wicks never had the advantage of the modern magnets when they created their Direct Action.
Consider attaching a lightweight voice coil to the valve that would interact with a fixed magnet assembly. Very low mass and high speed. None of the problems of a steel core solenoid.
Consider attaching a lightweight voice coil to the valve that would interact with a fixed magnet assembly....
Rick,
that's an interesting idea. But can voice coils provide enough force to push a leather flapper around? I know they're good for moving air (in a speaker) and for precision position control (optics, hard drive readers, etc.) but can they pack enough punch for less dainty applications?
...in the manner in which I intend to use them I was looking for a relatively weak force from the coil ADDED to the strong force of the magnet would create enough force to open the valves.....
Keep in mind that what you're ultimately aiming for is a total deflection during actuation, a change in position of an object (your flapper actuator or whatever) which is held in place by a springy force of some kind. By starting out with a strong force (solenoid permanent magnet facing the flapper magnet), you are already "eating up" any room you have left for a smaller force (the electrified coil) to do any significant work.
Let me illustrate this way:
Let's say your valve is represented by the surface of a cushion on a couch. You bring in an elephant to sit on the couch. Wow man, you've really got some force acting on that couch now and the cushion surface is bowed under the weight of the elephant but, thanks to your design, it's not deflected all the way. But now you want to deflect that cushion surface the rest of the way and do so on command, so you have a chihuahua jumping onto or off of the elephant's lap as the dog responds to the shock collar it's wearing under the control of your radio-Wurlitzer keyboard. The chihuahua will cause the cushion to respond, but the deflection will be only a small fraction of what the elephant has already done, so your system might not behave the way you really want it to.
Am I making any sense? Or have I totally misunderstood what you're trying to do?
I have several complete voice coil motors that were used to move head assemblies in 14 in. disk drives. The ferrite magnets are about 2 1/2 in. in dia. and 7 in. long and voice coils about 2 3/4 in. x 4 in. They had to move head assy that may have weighed 6-8 oz. in 100 mS. They had enough power to break hand bones. I think, that with 1/2 to 1 in. voice coil, rare earth magnets and constant current drive, it could be done.
...They had enough power to break hand bones. I think, that with 1/2 to 1 in. voice coil, rare earth magnets and constant current drive, it could be done.
....
That's very interesting. So now I'm wondering why old-fashioned solenoids haven't been totally replaced by voice coils. And linear stepper actuators, too. Is it a cost issue, maybe? Any idea if voice coils can be easily made at home, or do they require some special manufacturing process? Wurlitzer sounds interested in making ~1000 of these.
bsnut: Don't know how much space he has for it. But it's worth an experiment.
ElectricAye: It probably boils down to amper/turns. Much more power in a smaller volume. Plus, a solenoid core can have sliding contact inside the coil while the voice coil needs to be rigidly supported to keep from contacting the magnet. A random external load would upset that alignment. Probably other reasons too.
The advantage that a voice coil has is that the movement is contained within the coil/magnetic flux, there is no remote iron work to try to get moving and then the need to stop the iron work from sticking together.
When I was a school kid ('70s) I used a wrecked loudspeaker to move a pen on and off of a rotating water pipe (advancing on a thread ) as a sort of fax machine it even had tone recording onto cassette.
The piezo benders would be interesting with their resonances and all those sound vibrations.
ElectricAye, are you calling me an Elephant? {;^p)
Once the leather surface has lifted off the pipe bottom board, the air pressure forces quickly start to equalize and then the major force to overcome is the lightweight spring which sole purpose in life is to keep the valve closed when the organ is turned off and to aid in closing the pneumatic that was originally used. A coil/magnet assembly designed so that at its weakest point in operation is sufficient to overcome this spring will be sufficient as long as when the coil/magnet assembly is strong enough when the valve is close to overcome the air pressure differential will be the balance I am attempting to achieve.
I know the pressure will be .3lb per sq inch so I can create a VB application which will calculate the force required for each of the many different sized valves.
The current secondary pneumatic (the one actually connected to the leather pipe valve has a total travel of 1/2 to 3/4 of an inch for the smallest to largest valves respectively so the travel is not huge.
So to sum up, I need > .3lb per sq inch of valve surface area to lift the valve off, after that both the required force and the available force will start to decline rapidly. So the fully closed OR the fully open force will dictate the bare minimum I can use. Knowing how little force is required once the valve has started to lift I am sure it will be the closed force will be the design limit.
Consider attaching a lightweight voice coil to the valve that would interact with a fixed magnet assembly. Very low mass and high speed. None of the problems of a steel core solenoid.
Rick
That is an interesting idea as the response certainly would be a slam dunk provided the initial force is sufficient. The force must be > .3lb per sq inch of valve surface are and the valves are many different sizes. IIRC, I would be looking at a 1.5 sq inch min to a 9 sq inch maximum.
On a similar approach, if I could get my hand on 1000 old hard drives....well that might be stupid.
Awesome. I admire the sheer purity of your obsession. Well then, if you're going to roll your own, then it will be important to learn about magnetic materials.
I have already rolled my own coils ~~200 to convert every key and pedal to an analog input and using the Propeller to determine the position of each key as I need to use 2 trip points for first and second touch. (2nd touch allows for some louder pipes to play if additional force is applied to the keys and the key travels further down.
Each key has a small steel threaded shaft hanging below and that shaft enters my home brewed coils to vary the inductance and then the counters in the prop tell me how far the key is pressed. Once again the Prop shines.
Wurlitzer,
Great project! I have seen voicecoil motors used in many different applications and think the concept may just be a sound idea. Just for grins, I googled voice coil motors and found that there are manufactures out there that make them with 1" stroke and 1.9 pound force capability, so the concept is sound ( they want big bucks for that kind of capability). The speed capability should be well within your requirements. Have fun and keep us posted!
RS_Jim
Find a cheap/damaged woofer and stack some coins on it. Vary the current through the coil to get a rough idea of how much weight it can lift. Wire in a series resistor to set the holding current and momentarily short the resistor to simulate the initial kick to start the movement.
Rick
P.S. Another idea. Substitute a shorted turn for the voice coil such as a small slice of aluminum tubing. Fit it on a ferrous core extending out of multilayer winding. Apply pulse of enough ac to bring the core nearly to saturation and watch the shorted turn go into orbit. This might work with a short pulse of dc, but haven't tried it
Find a cheap/damaged woofer and stack some coins on it. Vary the current through the coil to get a rough idea of how much weight it can lift. Wire in a series resistor to set the holding current and momentarily short the resistor to simulate the initial kick to start the movement.
Rick
P.S. Another idea. Substitute a shorted turn for the voice coil such as a small slice of aluminum tubing. Fit it on a ferrous core extending out of multilayer winding. Apply pulse of enough ac to bring the core nearly to saturation and watch the shorted turn go into orbit. This might work with a short pulse of dc, but haven't tried it
Strange you should bring up the aluminum shorted turn concept. When I first started the venture to improve the pipe valving, I was going to use aluminum to be repelled in the manner you described. I believe it has some merit with the only downside, assuming I can get enough force, is switching AC vs DC but as we all know there are many devices available to us for that purpose.
....Substitute a shorted turn for the voice coil such as a small slice of aluminum tubing....Apply pulse of enough ac to bring the core nearly to saturation and watch the shorted turn go into orbit. ....
Okay, I'm clueless about this. Why would you replace the voice coil with an aluminum ring instead of replacing the permanent magnet attached to the actuator with an aluminum ring?
And even more confusing to me: Can somebody explain to me why you would need AC to do this instead of a DC pulse?
EDIT: Wait a second - I don't think a shorted ring could work for anything other than transient actuations. You might kick open the valve but it can't stay open. And if you use AC to continuously keep changing the magnetic field to effectively keep kicking the ring, I suspect you'll end up with a buzzing effect, not to mention lots of heat being generated in the aluminum ring. I can't see how this would be a good idea for a valve that you have to keep open for more than a fraction of a second.
Okay, I'm clueless about this. Why would you replace the voice coil with an aluminum ring instead of replacing the permanent magnet attached to the actuator with an aluminum ring?
And even more confusing to me: Can somebody explain to me why you would need AC to do this instead of a DC pulse?
EDIT: Wait a second - I don't think a shorted ring could work for anything other than transient actuations. You might kick open the valve but it can't stay open. And if you use AC to continuously keep changing the magnetic field to effectively keep kicking the ring, I suspect you'll end up with a buzzing effect, not to mention lots of heat being generated in the aluminum ring. I can't see how this would be a good idea for a valve that you have to keep open for more than a fraction of a second.
I had seen numerous demonstrations of AC being used to repel aluminum disks/slugs/rail gun etc. so as I was working on the premise that repelling forces might work better for this application I entertained it for awhile.
In all honesty I think the solenoid using a cylindrical magnet will be superior for this application.
Thanks to all for the active and informative support for this project.
I will be out of computer contact until after the first of the year and by that time some of the magnet samples I ordered will have been delivered and I will evaluate them for the smallest and the largest valves to determine if the concept has merit and what the coil current/turn and magnet strength requirements will be.
I'll post as soon as I return.
Thanks again to all for the ideas, it has been very helpful.
Comments
I don't know about hamsters but mice sure love pipe organs with all the various places to hide. I keep that at bay by playing 3 blind mice.
Good point! Given, according K&J the magnetic forces are additive, in the manner in which I intend to use them I was looking for a relatively weak force from the coil ADDED to the strong force of the magnet would create enough force to open the valves.
I have ordered a few cylindrical magnets today for testing. Theory and real life sometimes throws you a curve.
I guess when you think about it Wicks never had the advantage of the modern magnets when they created their Direct Action.
Rick
-Phil
Rick,
that's an interesting idea. But can voice coils provide enough force to push a leather flapper around? I know they're good for moving air (in a speaker) and for precision position control (optics, hard drive readers, etc.) but can they pack enough punch for less dainty applications?
Keep in mind that what you're ultimately aiming for is a total deflection during actuation, a change in position of an object (your flapper actuator or whatever) which is held in place by a springy force of some kind. By starting out with a strong force (solenoid permanent magnet facing the flapper magnet), you are already "eating up" any room you have left for a smaller force (the electrified coil) to do any significant work.
Let me illustrate this way:
Let's say your valve is represented by the surface of a cushion on a couch. You bring in an elephant to sit on the couch. Wow man, you've really got some force acting on that couch now and the cushion surface is bowed under the weight of the elephant but, thanks to your design, it's not deflected all the way. But now you want to deflect that cushion surface the rest of the way and do so on command, so you have a chihuahua jumping onto or off of the elephant's lap as the dog responds to the shock collar it's wearing under the control of your radio-Wurlitzer keyboard. The chihuahua will cause the cushion to respond, but the deflection will be only a small fraction of what the elephant has already done, so your system might not behave the way you really want it to.
Am I making any sense? Or have I totally misunderstood what you're trying to do?
Rick
That's very interesting. So now I'm wondering why old-fashioned solenoids haven't been totally replaced by voice coils. And linear stepper actuators, too. Is it a cost issue, maybe? Any idea if voice coils can be easily made at home, or do they require some special manufacturing process? Wurlitzer sounds interested in making ~1000 of these.
ElectricAye: It probably boils down to amper/turns. Much more power in a smaller volume. Plus, a solenoid core can have sliding contact inside the coil while the voice coil needs to be rigidly supported to keep from contacting the magnet. A random external load would upset that alignment. Probably other reasons too.
When I was a school kid ('70s) I used a wrecked loudspeaker to move a pen on and off of a rotating water pipe (advancing on a thread ) as a sort of fax machine it even had tone recording onto cassette.
The piezo benders would be interesting with their resonances and all those sound vibrations.
Once the leather surface has lifted off the pipe bottom board, the air pressure forces quickly start to equalize and then the major force to overcome is the lightweight spring which sole purpose in life is to keep the valve closed when the organ is turned off and to aid in closing the pneumatic that was originally used. A coil/magnet assembly designed so that at its weakest point in operation is sufficient to overcome this spring will be sufficient as long as when the coil/magnet assembly is strong enough when the valve is close to overcome the air pressure differential will be the balance I am attempting to achieve.
I know the pressure will be .3lb per sq inch so I can create a VB application which will calculate the force required for each of the many different sized valves.
The current secondary pneumatic (the one actually connected to the leather pipe valve has a total travel of 1/2 to 3/4 of an inch for the smallest to largest valves respectively so the travel is not huge.
So to sum up, I need > .3lb per sq inch of valve surface area to lift the valve off, after that both the required force and the available force will start to decline rapidly. So the fully closed OR the fully open force will dictate the bare minimum I can use. Knowing how little force is required once the valve has started to lift I am sure it will be the closed force will be the design limit.
On a similar approach, if I could get my hand on 1000 old hard drives....well that might be stupid.
Space is not a huge issue as even if I used a brute force method of just a huge solenoid for the largest pipes, there would be sufficient space.
The constraint in this project is simply the force required with a closed valve and a fairly reasonable response time (< ~~60ms)
I have already rolled my own coils ~~200 to convert every key and pedal to an analog input and using the Propeller to determine the position of each key as I need to use 2 trip points for first and second touch. (2nd touch allows for some louder pipes to play if additional force is applied to the keys and the key travels further down.
Each key has a small steel threaded shaft hanging below and that shaft enters my home brewed coils to vary the inductance and then the counters in the prop tell me how far the key is pressed. Once again the Prop shines.
Great project! I have seen voicecoil motors used in many different applications and think the concept may just be a sound idea. Just for grins, I googled voice coil motors and found that there are manufactures out there that make them with 1" stroke and 1.9 pound force capability, so the concept is sound ( they want big bucks for that kind of capability). The speed capability should be well within your requirements. Have fun and keep us posted!
RS_Jim
Find a cheap/damaged woofer and stack some coins on it. Vary the current through the coil to get a rough idea of how much weight it can lift. Wire in a series resistor to set the holding current and momentarily short the resistor to simulate the initial kick to start the movement.
Rick
P.S. Another idea. Substitute a shorted turn for the voice coil such as a small slice of aluminum tubing. Fit it on a ferrous core extending out of multilayer winding. Apply pulse of enough ac to bring the core nearly to saturation and watch the shorted turn go into orbit. This might work with a short pulse of dc, but haven't tried it
Strange you should bring up the aluminum shorted turn concept. When I first started the venture to improve the pipe valving, I was going to use aluminum to be repelled in the manner you described. I believe it has some merit with the only downside, assuming I can get enough force, is switching AC vs DC but as we all know there are many devices available to us for that purpose.
Okay, I'm clueless about this. Why would you replace the voice coil with an aluminum ring instead of replacing the permanent magnet attached to the actuator with an aluminum ring?
And even more confusing to me: Can somebody explain to me why you would need AC to do this instead of a DC pulse?
EDIT: Wait a second - I don't think a shorted ring could work for anything other than transient actuations. You might kick open the valve but it can't stay open. And if you use AC to continuously keep changing the magnetic field to effectively keep kicking the ring, I suspect you'll end up with a buzzing effect, not to mention lots of heat being generated in the aluminum ring. I can't see how this would be a good idea for a valve that you have to keep open for more than a fraction of a second.
I had seen numerous demonstrations of AC being used to repel aluminum disks/slugs/rail gun etc. so as I was working on the premise that repelling forces might work better for this application I entertained it for awhile.
In all honesty I think the solenoid using a cylindrical magnet will be superior for this application.
I will be out of computer contact until after the first of the year and by that time some of the magnet samples I ordered will have been delivered and I will evaluate them for the smallest and the largest valves to determine if the concept has merit and what the coil current/turn and magnet strength requirements will be.
I'll post as soon as I return.
Thanks again to all for the ideas, it has been very helpful.
To all have a very safe and happy New Year.
Jim