After reading that the strength of magnet charging increases with the number of turns in the coil, and that having the coil around the magnet also boosts it, I decided to try combining the two.
The cores are a combination of junk Model T axle shaft and thin wall PVC. The completed coil has a little over 500 turns of wire. About three inches (67%) of the magnet's length is inside the coil.
I'm wondering about a power source. The usual thing is 36 volts from batteries in series. But I've read of some folks using higher voltage from a welder. I've never tried that, so I'm wondering if somebody who has done it can advise on how to set it up.
Steve, charging single magnets you only need 12 volts and a tiny amount of current. 36 volts is for charging the whole set.
OK, I'll see how that works out.
I was thinking it was a matter of "Amp-Turns", but I'm not positive. If so, you certainly have a some turns, but how many amps can you get through that wire?
Royce: How many turns and what gage wire do you use for single magnet charge with 12V? Thanks, jb
I did a thread a couple months ago where I inspected the transmission on my 1914's new engine, including recharging the individual magnets. I lost all my saved data on one of my computers so I don't have ready access to all the links I saved. Maybe someone here can find it.
A friend had an old starter switch and a solenoid on a board, with wires to a 6 volt battery and two coils to charge a magnet, but it no longer worked.
He asked me to fix it for him, which I did.
What I found wrong was that one coil was open. The wires were held in place with dried masking tape, which presented a problem to remove without damaging the wire insulation.
I finally put the removed wire in a large pail of boiling water and the tape just melted off. The clean wire sections measured 158 inches, so I did both coils.
I used plastic shrink wrap to coat the cleaned 3/4th inch magnet poles, wound a complete set of winding and covered them with shrink wrap, then did another set of wires the same way and I had enough wire for a partial third set of windings.
The whole thing was covered with another shrink wrap tube and the connection wires were covered with small red and black shrink wraps, to keep the polarities opposite and correct for the two coils, as the other one was done the same way.
I put the solenoid in a plastic box with an ammeter and push button switch for activation.
The two bolts that hold the solenoid in place also double as a storage point for the batter clips.
With the other coil added to the bar and 6 volts applied, the ammeter shows 60 amps with a good battery. Each coil was tested separately and both drew 30 amps each. The pole end measured 16000 Gauss on each pole when the button was pushed.
Three quick zaps with a magnet attached will let the magnet grab and hold hold my 3 pound test piston. The magnet ends measured around 500 Gauss after each test.
Several years ago, I saw the directions for building this charger, but have not been able to locate them.
The Magnet Bar with one coil attached.
The charging box.
This box was used to charge the 36 volt battery pack for golf carts and the carts used to clean floors in large stores.
It cost me $40 and looked bad before I cleaned it up.
There was a timer that let the batteries charge for 8 hours. That was broken and replaced with a push button switch.
The unit plugs in to regular 15 amp 115 volt service and delivers 40 volts at 40 amps DC.
It works well for laying a coil ring on a flywheel to charge all the magnets at once.
The magnets all have to be of equal height and making contact with the coil ring poles for maximum effectiveness, but it has also worked to charge the magnets in a complete engine, in place of the six 6-volt batteries.
I think Hal Davis is on the right track with "amp-turns". Here is a photo of the recharger I built a few years ago using information from the forum.
The details are no longer handy. but I seem to recall that relatively few turns of very heavy wire would enable enough amp-turns to do the trick. The wire is 10 or 12 ga solid copper as used in a kitchen stove or dryer circuit. North and South poles had to be wound in opposite directions as one can tell prom the photo.
I use 15 or 20 momentary flashes of power from my battery charger which is set for 12-volt 100 Amp boost. One needs to take a break every magnet or two to let the wire cool down so as to not melt the plastic insulation.
Results are impressive — second photo shows one of the recharged magnets lifting 2,563 gram/5.6 lb of piston and misc steel (scale 2,954 gram — 391 gram magnet weight). Of course, some/much of this magnetism likely fades over time but my magnetos have always maintained excellent voltage output.
This setup has recharged 4-5 sets of magnets with no apparent damage to the battery charger.
Thanks, Mark. In Royce's 2nd post you found--"I wound 13 turns of 12 gage stranded wire around each side, winding clockwise on one and counter clockwise on the other side" with single 12 V battery. Thanks, jb
This link should take you to a link of Ted's simple plans for winding the wire. Look for and open the PDF in the 4th post. This may the plans that are being referred to in the above posts.