Electronics > Projects, Designs, and Technical Stuff
High force solenoid
i_am_fubar:
I want to try and compress a syringe plunger to give a jet of air by gluing a neodymium magnet to the plunger and discharging a cap bank through a coreless coil. Basically, a speaker coil. But on a higher energy scale. Does anyone know of a 'thing' that already uses this mechanism to produce an air jet that I can get and take apart?
Ta
SeanB:
Not going to work too well, you will degauss the magnet well before you make the air jet. how about using a motor and a gearbox to drive the syringe via a crank, or just use a peristaltic pump like inkjets use. Depends on how much air you need volume wise, how much pressure and what flow rate you want, but you are better off using a lower loss thing like a diaphragm or a collapsible bellows instead of a high friction rubber bung.
T3sl4co1l:
I mean, without pole pieces, it's just disgusting. But even with, you're limited to a pressure of the Maxwell Stress, B^2 / (2 mu_0). A 1T magnet is equivalent to about 4 atm, if the field is entirely on one face and zero on the other.
Much better off using a servo, gearing and crank. Needs far less magnet (low torque motor), the magnet goes through many cycles as the plunger is pushed, you get all the mechanical advantage of the gear train and (about) as much power as the motor is capable of, without quirky or custom magnetic designs.
(Even if direct drive is stipulated, it's still better to use a transverse-field linear motor over a copper rod: the entire surface area of the rod can produce a shear pressure, rather than just the cross-sectional area of a magnet the same size. Well, fine, it works the same with a stack of properly magnetized ring magnets on a steel shaft, doesn't need to be an induction machine. But yeah, area or speed is the key to power.)
Tim
Zero999:
A syringe will have a lot of friction.
How often is the air jet needed and at what pressure?
You might be better off using a small compressor, a reservoir and solenoid valve.
i_am_fubar:
It's for a BB gun mechanism. I know, I know, they use a rack and pinion. Have designed a few of the conventional ones. This is just a 'I wonder...'
Diagram is definitely a better idea.
Will look into the magnet physics. Degaussing is a concept I knew about, but now I actually understand why it's the limiting factor in magnet Vs electromagnet.
Am I right in thinking that electromagnet to electromagnet has no theoretical upper limit? They just need to be big and powerful enough?
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