Electromagnet Vibration unit using a Neodymium cylinder.
I have a project creating an epoxy based granite material.
The sphere packing density is quite high with aggregate sizes from 2 to 600 microns.
So that means I'm left with a very thick mix.
Plus the added complication of doing this in a vacuum.
Requirements:
I need to make a shaker/vibration unit (freq from 10 to 2000 Hz).
Using a motor to vibrate has been tried and it overheats... go figure :)!
Materials:
1 inch diam x 2 inch long Neodymium magnet.
Lots of magnet wire and even a coil winder.
Supposition:
It
seems to me that I could mount magnet to base to vibrate, then create a
coil around the magnet (with suitable separation) and drive that? I can
dissipate the heat with a simple water jacket created from aluminum
tubing and encapsulate that with an epoxy mixture designed to conduct
heat which would be mounted to the rack in the chamber.
Question:
Is it possible to create a simple voice coil using a cylindrical magnet?
If so given almost 13000 Gauss, how do I calculate the coil parameters (windings,gauge,amps,voltage).
Or do I need to resort to using Axially magnetized magnet setup found in speakers?
You leave off a few things.
What deflection do you require?
What is/are the weight(s) of the objects you wish to vibrate?
You
are not likely to needs lots of magnet wire as the frequencies you want
to operate at and the small permanent magnet will limit your motor.
Have you considered devices that will work near their natural frequency?
Ah yes I did leave that out and one of the things I wanted to get clarified.
Weight can range from 10 lbs to 150 lbs (perhaps 300 depending on density).
Deflection should be in a range of .05 to .25 inches (this is what I was doing with the motor driven version).
I
can also supply any power requirements to drive this... if we make it a
4 ohm coil, I could hook it up my 500 watt amp and play AC/DC... err...
drive it with a signal generator.
I guess it would be helpful to know what the limits are given a reasonable amount if heat dissipation.
Essentially
the mass (epoxy with quartz and ceramics in a mold mounted to a spring
loaded table in a vacuum chamber) needs to be vibrated to assist in
deairing the mix which then fills in the corners, edges, and sets the
final packing density (and all the while maintaining the right vacuum to
keep the epoxy from boiling).
Some experimenting is obviously
needed to obtain empirical data for just how much we should shake this
stuff. In doing so I find the required range of frequency and velocity.
Then I can spend the money (or not) to purchase off the shelf vibration units.
.25" at 2000Hz, lets use a middling mass of oh 100 _lbs.
Note: I'm not particularly good at this, I just happen to run a shaker motor for certian types of testing.
1/2000s
is the total time to complete one cycle. (you dont say wether you need
+/-0.25" so we'll go with total travel of .25" so +/-.125")
Dist= .021ft
TSD calcs: Time=.0005sec Speed(Avg)=41.7Ft/sec Dist=.021ft
using some basic guesses WTR max velocity and the shape of a sine wave we can say that max velocity is ~1.414*Avg Velocity....
So the mass must acclerate to 60ft/sec in .00025sec.
giving Acceleration as: 235855ft/sec^2 (or approximately 7000*G)
Requiring
aproximately 2.35x10^7lbf*Ft/sec^2 or 5896ft-lb/sec or approximately
8000watts. If you can get better than 50% efficiency out of a voice coil
I'd be reallly suprised. About a 120Hp or bigger motor should do the
trick.
Now lets do the same math for 2Hz.
Time=0.5sec Speed(Avg)=0.042ft/sec Dist=0.021ft
Vmax=0.060ft/sec/Filter
Acceleration=.237552ft/sec^2
23.8lbf*ft/sec^2 or 5.938ft-lbf/sec or only around 8watts.
At 20 Hz (the official lowest threshold of heard sound) we should see around 80watts required.
Note:
I dont really think that I am right with these calculations, however
you can see what happens when you increase the frequency by steps of
ten. The power required also goes up as quickly.
(I'm also an
audio engineer, my biggest system has a power output btw 200-2000hz of
~1200watts, the speaker cones dont move anywhere near 0.25", Heck I dont
think the 1500watts btw 60-200Hz even get that much movement, the
1400watts at 35-80Hz just might, but they're not horn loaded so they
arn't pushing 100lbm back and forth.)
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