Hi guys,

I thought you might be interested in an experiment I ran to determine if I could make a cheap case neck induction annealer.  The experiment was not a success but you may learn something from the article which is posted at the following link.

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Wayne

marlinguy wrote on Dec 8^th, 2018 at 12:11am:


I "played" with the setup for some time with it running and nothing in the coil.  It warmed up but did not get overly hot even without coolent through the coil.  If left on for some time I have no doubt the coil would heat up but that could easily be mitigated by turning on the cooling system.  By the way, when a metal rod is inserted in the coil, the radiant heat transfer from the rod to the coil was much more than any heat created by the coil itself.

Selenoids & elect. starter coils are a different design & typically are designed to work with DC.  I haven't tried pulling the core out of a selenoid to see if it gets hot but inductors (coils) are used in all kinds of electronics without getting hot.  Some have metal cores and others don't.  BTW, the coil in the annealer circuit is oscillating at high frequency.

Based on a suggestion on another forum I plan to try another modification to the setup & will post the results here if successful.

Wayne

Wayne,
Thanks for posting this, I researched these components only with hopes of going the other direction, heating larger parts.  Never gave it a thought for annealing cases.  It will be interesting to see what you come up for cases.   
Greg

I think capacitors discharge too quickly to anneal brass. And since they discharge so quickly, the largest capacitors can create damage to anything connected to them at discharge. And if not firmly connected they will create huge arc that will damage the brass.

marlinguy wrote on Dec 10^th, 2018 at 10:55am:


Capacitor discharge time = rc, seconds, ohms,farads. A resistor in series with the case neck slows things down.


Huge arc? Depends on e, 37 microvolts don't make much of an arc. 


Unless electricity has changed since tech school, (1957), probably an rc circuit will anneal case necks. 
 

Another alternative is an scr or Zener diode ? controlled lv ac circuit, turn the ac off at ? 2 volts above 0 on the + side; get a max 2 volts with 0 for half the cycle. Avg I is small with avg e ? 30% of 2 = .6 volts.


Some hobbiest electronics guy could design this/make this work.


Is AM if still 455 kc?

texasmac wrote on Dec 7^th, 2018 at 11:44pm:


About 1965 I was at a copper tube redraw company in NY, (Reader's Digest town). where the tube was annealed as it was drawn to smaller and smaller sizes, with induction coils. The redrawn tube was automatically inspected with eddy current detectors.   

Annealing coils of tubing is one thing, a small case neck is a whole 'nother ball game    The biggest issue will be Ohm's Law working against you using a relatively heavy material over a short distance. You will have no literally no resistance and no way to generate impedance in the material; therefore, when the power from the capacitor or a circuit enters the case mouth on opposite sides you have a dead short.  It will be very difficult to find any happy medium between meltdown and exhausting your power supply without making any noticeable heat.  

Probably the easiest way to make the device in question work would be to make a induction coil around a piece of ferrous metal tubing that fits the case mouth relatively closely.  Design it with maybe 400 hz or higher frequency.  That will put some heat on it     


On passing around your garbage can lid capacitor parts, everything is a matter of references in electrical power.  As long as they are isolated, the charge will remain.  We used to work 480 volts hot all the time early in my career.   After a few people publicized their research on 480 volts ionizing the atmosphere in short circuit situations, everyone decided that might not be such a good idea anymore  . Working 120/208/240 volt circuits hot isn't a big deal unless you get grounded. If you are nervous and your hands get wet and sweaty, the risk goes up exponentially    There are people who work in 110,000 volt transmission lines hot.  It is just a matter of isolating the high voltage potential and not making a circuit to another phase or ground.