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"If a solenoid core is iron, or any ferromagnetic metal, then this can increase the solenoid’s regular magnetic power substantially. Air core units are usually made from glass and do not increase magnetic strength, but they do work better at high frequencies. While a core is common in a solenoid, it can be removed and the solenoid can still work. A solenoid core also helps protect the solenoid coil’s shape and prevents major denting to the coil.
The most common type of solenoid core is an iron or ferromagnetic core. This type of core reacts strongly with magnetic forces and boosts the solenoid’s normal magnetic force. Some metals can boost the strength slightly, while others can increase the solenoid’s strength by 100 times."
The above is talking about solenoids, however the same rules should apply, If an Iron core can magnify the effectiveness up to 100 times then shouldn't coil guns use barrels made from Iron tube, steel or stainless steel instead of glass, plastic etc ?
anyone experimented with a ferromagnetic barrel material?
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
the problem you tend to get is the high frequency; a 1cm long projectile moving at 10m/s needs a 1kHz signal to drive it.
Incidentally, the 100x magnification is mostly a fantasy; it's more like a factor of 2-4, you're scooping the flux that leaks out the side and bunging it back into the bore; but the air gap dominates particularly at the front and back of the projectile.
the problem you tend to get is the high frequency; a 1cm long projectile moving at 10m/s needs a 1kHz signal to drive it.
Incidentally, the 100x magnification is mostly a fantasy; it's more like a factor of 2-4, you're scooping the flux that leaks out the side and bunging it back into the bore; but the air gap dominates particularly at the front and back of the projectile.
I don't understand, the charging circuit operates at a few khz to drive the high voltage transformer but its charging a capacitor bank, when that bank discharges it is producing a massive pulse of high voltage DC to the driving coil.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
Yes, the pulse has a whole mess of frequencies in it, but the key frequency is at about speed/projectile length.
For added excitement it turns out that for good performance the projectile should be about the same diameter and length (ish), and the pole length should be similar too.
Registered Member #1451
Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661
A ferromagnetic barrel will focus almost all of the flux of the coil through the barrel. No flux will be left over to magnetize the projectile and therefor there will be no force imparted on it.
It's been tried before, usually by first time builders, and it doesn't work.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
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I haven't tried it, but I would think it works better if you make the projectile U-shaped around the outside of a phased series of coils i.e. set the coil(s) on edge through the slot in the projectile.
That way the projectile closes the magnetic circuit, and it sees a DC-ish field, so you don't need to laminate.
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Ferromagnetic barrel material for extra power?
