I thought I would share my design of an out-of-car magnet charger, based on ideas from this forum and elsewhere:
The charger is mounted on a board sitting on top of a 12 car battery. The power is supplied through a starter solarnoid activated by an ignition switch. The charger consists of 60 turns of 14 gauge solid wire (total 40 ft) around 2 short pieces of plastic pipe, paying attention to the polarity desired. These are slipped over the magnet and a keeper is placed on the ends. The magnet is given 3 quick shots of current. I measured the voltage during a discharge and it was found to drop to 10.8V. According to my calculations, this gives a little more then 100 amps of charging current. The coils would get somewhat warm after 3 shots.
I wanted to measure the magnetism of the magnets before and after charging using something better then a piston or a bucket of metal parts. And I didn't have a gausemeter. So I made a design using a metal yard stick beam mounted in a pivot on one end:
The magnet straddles the beam around 8" from the end, and a metal keeper bar is placed under the beam, which holds it up a bit. A weight on a slider is slid away from the magnet increasing the force on the keeper until it breaks away. The distance is noted and the breakaway force is calculated.
The results turned out pretty good. The average breakaway force before charging was around 3.5 lbs and after charging brought it up to an average of 10.5 lbs. The keeper holding force is very dependent on the quality of the contact surface. The Ford magnets have rough ends that don't provide a good contact surface, which gave a range of results.
The standard magnet test is to see if the magnet can hold a cast iron T piston, which weighs about 2 pounds. So either all my magnets (except for a broken one I found) were "good enough" before charging, or the piston contact surface is even worse.
I ordered a couple of magnets from a popular vender and I asked them to charge them up before sending them to me. I measured them on my device and found they had a breakaway force of 6.0 and 6.8 lbs. After charging they had a force of 7.9 and 9.2 lbs.
I also experimented with the charging procedure. I found that the first quick shot gave most of the improvement. A second shot would give an additional 20% or so. A third shot rarely showed any improvement. I also tapped a magnet with a small hammer during a sustained forth shot and saw no improvement.
It got too cold before I had a chance to install the engine and test the magneto but I did turn it over by hand and it easily fired a coil hooked up to it.
If you easily fired a coil, then you will probably be able to start the car on the mag. Good post. I like that magnet checker.
Robert thanks for sharing your project, how many turns and what gage wire did you use on your charger.....Model T's are great for gear heads like me, I love people sharing their home spun tools and methods for repair......Bob
"...The charger consists of 60 turns of 14 gauge solid wire (total 40 ft) around 2 short pieces of plastic pipe, paying attention to the polarity desired...."
Robert you said the ends of the magnets are rough would it help or hurt to maybe run a 2nd mill cut file across the ends to smooth them out and give a better contact surface love the tester but I am afraid If I got one of my wife's metal yard sticks from her sewing room I would end up in the dog house
A great result with inexpensive materials and a lot of ingenuity
Looks like a good setup for magnets that are off the flywheel. I didn't have any loose pistons handy for testing my magnets so I used a spindle, which weighs a little more.
My theory on smoothing the ends of the magnets is that it's best to leave them alone. If the magnet is strong enough to hold the weight despite the less than ideal surface, you have a good charge.
During charging I placed a keeper on the ends of the magnets in order to complete the "magnetic circuit". Smoothing the magnet ends would give a much better contact of the keeper, producing less "resistance" during the shot. That should increase the performance of the charger, but I think the performance is already more then good enough, so the effort in smoothing the ends would have diminishing returns in this case. I suspect the magnets are close to thier saturation limit anyway.
It would also change the testing results considerably. The max pull I measured after charging was 14 lbs. A smooth contact would have produced a higher value, but its all relative. A gauss meter would be the best tool to use. And besides, the condition of the ends will have no effect on the performance of the magneto.
I have asked a member of our local club who charges magnets how they run in a car. So far he has found nobody who knows. He is currently restoring his own car, so maybe we will find out soon. My question would be: If a magnet which can lift 2 lbs is sufficient to run a T magneto, what would be the effect of charging to 10 or 14? Would the charge quickly dissipate to 2 lbs? Or would the extra magnetic force tend to slow down the engine? Certainly the drag of all those magnets against the poles would slow it down. I would like to find out the result in practical usage, before I would over charge my magnets. As I understand it, the coils perform at 1.3 amps when correctly tuned up. So what happens to the extra electricity generated by the over charged magnets? It would seem to me that it would be wasted.
I has to do with the conservation of energy, energy can be neither created nor destroyed. The coils only use what energy they need and the magneto only puts out what the coils use. If the coils do not use any (battery operation), then there is no load on the motor. If the coils use some and there is another load like a magneto battery charger or lights, there is more load on the motor.
Gee Robert, you could have at least used a straight 2x4 for the test base!
Would a (49 FORD) starter push button work better for the on switch? (Of course, it could be almost any push button, the relay takes all the electrical load--just trying to keep it "vintage" )
Very clever you are--the (magnetic) force is strong in you, BTW!!
Regarding magnet keepers - is any old piece of steel cut to fit ok, or do they need to be made of something special?
Any material that is attracted to a magnet should work fine in this low tech application. This would include most steels and irons but not stainless steel.
Clever setup Robert and what I like most is the ability to make a good comparison test. I have not re-magnetized a lot of magnets personally so have no exact point of reference but when I did do it with a friend one time he stated that repeating the exact same magnet strength test after a few weeks or so of sitting around results in the magnet having weakened somewhat. His test was simply the ability of the magneto to pick up a block of steel he had laying around that was kept for magnet testing. I wonder if you have the time to repeat your test of a few magnets that you have already recorded the data on after waiting a bit of time just to see if your tester confirms my friends findings. Your tester method seems to have the ability and accuracy to be able to confirm this time lapse weakening and by how much if at all. Thanks for sharing your idea.
Here is my solution to Shunt Bars. i used some metal banding material. It can usually be found just about anywhere in an industrial area .
Robert, I'm taking it for granted that the lead going to the battery cut-out is the positive side of the battery. Would this be a correct assumption? Also might it not be a good idea to have a little more separation between the battery and any possible sparks from the charging operation. Battery explosions are not good. Jim
John, I was wondering the same thing about recharged magnets degrading over time. The 2 recharged magnets that I got from a major T vendor showed significantly less strength then mine did right after charging. As much as I would like to, I cannot believe my charger could be any better then thiers! I measured mine right after I charged them, but it had been at least several days since the vendors magnets were recharged. I think maybe magnets "relax" a bit right after recharging, and settle down into a strength level which will then last for many years.
Unfortunately shortly after I recharged my magnets I installed them on my flywheel. I wish I would have checked them several days later. I do have one magnet left from the vender that I recharged; it looks like it will get above freezing soon so I'll go out to the garage and test it.
Sparks around a battery are a hazard usually when the battery is being charged. I used the enclosed solenoid and switch to eliminate the sparking that would occur using a knife switch or just touching 2 wires together that I saw in other designs.
The green cut out is connected to the positive terminal, but the important thing to watch is what direction the current flows around the magnet.
So far, so good, bit of a nice way for folks to do something D-I-Y including your arc-less start Yet I too think going forward with further testing will yield further results that will not be bad…will just be reality.
If you are not in the middle of a rebuild and need them like ‘tomorrow’ maybe set aside a few for a month without the keeper and set aside a few with the keeper left in place until just before the test. Then run your yardstick weight test again and table against the original readings for the given magnet?
I'd expect that they would lose 'some' because a steel core can only retain a certain amount of atomic adjustment. Yet to my knowledge no one has ever answered what the ‘some’ may be! One old rule of thumb was 4500 amp-turns were usually good enough for a magnet without cracks…you went to 6000 amp-turns (60 wraps @ 100 amps) so the magnets have had their caffeine jolt…
Hey guys,(I don't mean to be sexist),
I am always impressed with all the knowledge among this group! Good ingenuity and critical thinking.
Hopefully that's a quality solenoid and not a cheapie - they can stick when actuated causing the circuit to stay powered ... not good ...
Thats amazing, Congrats.
What's the best way to store spare magnets?
What I do is charge them w/a rig similar to Robert Anderson's and then glom 2 together. N-S, S-N and stack them up. I've been told that this is not a good thing to do, and that they should be stored w/keepers on them.
In the flat box that Ford shipped magnet sets in there was no keepers.
I am going to do a study to see how effective keepers are. See my thread:
I ran some tests about 4 years ago. This test was about magnetic field dissipation over time only and not about initial state versus recharged state.
I recharged Model T magnets (checked for cracks) on my recharger and watched over time the initial dissipation measuring with a Gaussmeter making sure each check was the same position/distance. I did not use "keepers" and the magnets were left sitting on the shelf.
This recharger produces 8800 AT on the right winding and 11130 AT on the left winding. Very similar in size that ford used in the Factory for recharging magnets.
N Pole-B4-472 Gauss, After recharge-545 Gauss, 3 months later 484 Gauss, today no change four years later.
S Pole-B4-492 Gauss, After recharge 594 Gauss, 3 months later 517 Gauss, today no change four years later.
The results were similar for several magnets.
I came to the conclusion there is a small dissipation over a the short term and little more over the long term assuming no disrupting influence.
Exactly what one would normally expect of a hysteresis curve for saturation charged forged iron.
Ron the Coilman
Here is the photo.
Has anyone tried using a old starter/generator armature tester(growler) hooked up to a battery or other DC voltage source to recharge a magnet? It would likely require making some pole piece extensions but I would think it would work.
I'm curious to know why there is an unequal number of turns on one spool as opposed to the other. Also if you reversed the the polarity of the DC source (and flipped the magnet to match) would the difference in charge follow? Another way to put it, do you think the difference is based on the winding count or is it just undefined variances?
Also would like to learn, is it known what DC source Ford used and how many hits of what duration did they used.
Love this thread, to anyone with intimate knowledge of magnets please jump in.
I'm also wondering if it makes any difference if an entirely separate magnet is used for charging like Ron's, or if windings that are right on the magnet like mine and others are used. The coil diameter is also much larger on the separate magnet.
Would love to know what Ron's power supply is for that awesome beastie!
Here are some links to previous discussions on using a growler to charge magnets.
Every magnet recharger I have ever seen has two non concentrically wound iron poles, appropriate DC power supply and switch. Set the magnet poles on the cores and momentarily apply proper polarity power. One short closure of the switch is all that is needed, but if it make you feel better do a few more. If the number of winding is sufficient and the amount of current flowing to create sufficient AT's you saturate charge the magnet. As I discussed above the magnet charge will dissipate very slightly in a short time after charging, but not materially over the long run.
In answer to Roberts question; the "beast" is powered by one 12 volt battery and connect my DC battery charger in the "start" mode in parallel. There is a bit of ripple on the charger output, but the batteries act as a filter. I measured the current flowing to be 30 amps.
Ron the Coilman
Will a metal shelf act the same as the individual metal keepers if the magnets are placed open ends downward and contacting the metal?
If all the magnets are left on one shelf, will their fields tend to weaken other nearby magnets?
I think that would work, Eric. For the last 15 years or so, I've stored my welding angles either attached to a metal cabinet or a gantry post. They don't seem to have lost any magnetism.
Ken, pardon my ignorance. What's a welding angle?
Those are magnetic angles/clamps that hold steel in place while you weld parts together. I have about six shaped like an arrowhead and a couple that are adjustable.
I also have many magnets I use to hold paper patterns down on sheet metal while marking. These are stored on the side of a cabinet also.
Magnets to hold the parts at the correct angle while they're being welded, how cool is that? Obviously I don't weld but if I did I would sure have some of those!
Always learning stuff here. Thanks!