After hearing all about problems with weak magnetos and trying to recharge the magnets, it occurred to me. How about using a transformer to boost the voltage coming out of the mag?
The mag can put out much more current than the coils need, so I think that using a transformer that doubles the voltage would not put too much of a strain on the mag. So instead of getting just 3-4 volts when trying to hand crank it, you could get 6-8! Plus the coils will get healthier voltages at speed.
This transformer would probably have to be custom-wound (which is easy enough) and would probably be an autoformer, which is convenient due to its small size and one winding.
Still, this would be a band-aid for a deeper problem, but would be a very easy and effective solution.
What do you all think?
The voltage is one thing, but you need current to fire the coils. When we measure voltage at the mag post we do so with an 1156 lamp wired in series to represent the minimum load necessary to fire a coil which is about 1.3 AMPS.
I suspect that changing the voltage on a weak mag by using a step up transformer would still result in low current, and thus be a fruitless endeavor. There's no free lunch.
What comes out of a transformer largely depends on what you put in. Then there's always a trade-off. If you want more of one (amps, watts, volts), you'll get less of the others. Royce is right on this one: there's no free lunch.
I appreciate your thoughts. The coils can still receive their required 1.3 amps using a step-up transformer at the cost of drawing more current out of the mag. In a 2:1 ratio, that would be 2.6 amps. But as the mag can easily supply about 9 amps, that extra draw shouldn't be an issue.
I may throw a transformer together and see how it works. A few of the T's at the museum do have weak mags and are good test subjects. If the transformer works well, this might be something to pursue. If not, then oh well!
Cameron, did you try to recharge the magnets in the vehicle first? That would seem to be the logical way to go.
You need direct current to charge the magneto. You would need a rectifier in the output from the transformer. I have heard of others using a battery charger, which has a built in rectifier, but I would be very reluctant to do so. You can control exactly how much voltage you apply to the coil with batteries, but every charger is different.
The reason the magneto puts out alternating current is because the positive and negative poles are passing the coils when the engine is running, but when we charge the magneto, it is not moving. We line up the poles with the coils and it is stationary, so we use the correct polarity of direct current to charge the magnets. And with the batteries, we "flash" the contacts. It is true, that the magnets are charged when the current increases and decreases quickly during a flash, but the current moves in one direction when using a battery. The "flash" is what is called, "pulsating direct current".
I will, but the way I'm going to go about this is to try the transformer without recharging the magnets to see if it works, and if so, then how well. This will be the most definitive test, so that is why I'm going to start with this first. If it can bring the magneto back up to snuff to the point that I can crank start the car with the mag, then I might be onto something!
Then I'll recharge the magnets and try the same test again. Charging the magnets is an easy enough job.
Cam, Always fun to experiment! Let us know what you find out.
I drove my TT for a long time on batt only because the mag never worked.Or so I thought.
1 day it dawned on me I was riding a 36 volt golf cart and it takes 36 volts dc to charge the magnets. I went thru the procedure and I can drive on mag now with a smoother running engine.
I know for a fact some spots on the mag ring have Indian head gasket cement over defects in the cloth insolation but it still works fine.I cant remember exactly how to do it now,but it involves a compass and 36 volts of dc power and turning the hand crank a 1/4 turn before bumping the cable to the terminal.
I would suggjest not bumping current to the mag terminal but clamping to it firmly and do the bumping with the ground connection so as not to burn the threads on the mag terminal with the arcing.
Sounds like a good "science project", However the inductive losses introduced by a transformer will probably negate any advantage. Darned Physics!
You'll find the current output varies directly with the voltage. Weak magnets mean weak output.
Too bad Henry built such an awful to maintain device. He should have continued with the K magneto.
Go for it Cameron, it's worth a try. Nothing ventured, nothing gained.
You could try a doorbell transformer. Its about a 4:1 stepdown, in reverse a step up. Should be pretty inexpensive.
How about a Variac (variable auto transformer) connected backwards.
Awful to maintain, indeed! Every damned hundred years you gotta recharge the magnets and rewind the coil ring. Why can't they build stuff to last anymore?
Mine didn't last 100 years! Maybe 'cause some fool tried to remove the starter before taking off the bendix.
I say "go for it, Mr. Edison" and let us know the results.
Royce is on the right track. Let's start with the basics.
1. The ignition coil is a current operated device. Within reason, it does not care what the Mag voltage is as long as the Mag can produce the 1.3 Amps of current needed to operate the coil.
2. We generally measure the open circuit voltage output of the Magneto - this is a meaningless number.
3. The correct way to measure the output capacity of a Magneto is connect an 1156 lamp to Mag Post and see if it illuminated properly at a low engine RPM.
3. The Magneto will output a fixed amount of power at any given RPM – measured in Volt-Amps or VA.
4. If the voltage is doubled by a 2:1 transformer the available current at the transformer output will be half of the input current.
5. The Power Output (VA) will be the same minus about 5% in transformer losses. Most likely the coil will fire poorly - if at all.
It's a simple deal to try, why pour cold water on it? I say give it a whirl and see what happens. It's certainly not going to destroy anything or cause a fire.
Experimentation is a great endeavor. I have learned many a lesson by experimentation. Look back on the forum and read my attempt to make a DC Magneto. I failed completely but had fun doing it.
Physics is Physics, Science is Science and Math is Math – we can’t change that.
But … Experimentation is fun !!!
I understand physics, I don't know how much power the mag can produce. I imagine a sick mag will produce less power than a strong mag. Edison made dc magnetos years ago , they were called dynamos. Tesla and Westinghouse with their AC magnetos and transformers forced Edison to play catch up.
Cameron wants to build his own transformer and must have some knowledge of physics, I think he should proceed with his experiment.
No harm in experimenting, but experimentation is usually preceded by a hypothesis. My hypothesis is that since the coils are require a certain current to operate and since there is already a problem with their operation, that the current is already lacking. Raising the voltage will reduce the current (Ohm's law, not hypothesis) even more, and the coils will be even less likely to fire correctly.
Not pouring cold water on anything. Just making a hypothesis. The experiment should not hurt anything, so give it a try. Let us know how it goes.
May be I missed the memo - what is the lowermost voltage and amperage, AC and DC, will will a coil operate? At what voltage and amperage, AC and DC, will a coil fail? As the magneto was designed to produce maximum voltage and amperage at a designated powerband (20 hp), is it a possibility that the introduction of the transformer may cause the coils to fail?
Yes we all experiment with our vehicles, but if all things are in good working order - coils and wiring - isn't recharging the magnets an easier solution than reinventing the car's power grid?
Another missed memo - would the transformer introduce a constant load on the magneto coils. As the magneto originally was engineered to provide power to the ignition coils. The ignition coils operated intermediately on and off, and not providing a constant load to the magneto?
The transformer can not introduce a constant load, the load is determined by the voltage and amperage used, not the the voltage and amperage changed.
Here are some thoughts on your questions :
“May be I missed the memo - what is the lowermost voltage and amperage, AC and DC, will will a coil operate?”
For DC Voltage :
Ohms law will determine the voltage at which 1.3 Amps will occur. The value of the voltage will be a function of the DC resistance of the circuit (measured in Ohms) – coil primary winding resistance, circuit wiring, etc. This will vary slightly from coil to coil.
For AC Voltage :
An AC Voltage varies from positive to negative. At any given moment the instantaneous value can be positive or negative. It is measured as an RMS (Root Mean Square) value. In an AC circuit, the frequency of the AC voltage will determine the resistance (called Inductive Reactance) of the circuit which is also measured in Ohms. In the Model T, Frequency of the Magneto Voltage is determined by the engine RPM. The higher the frequency (RPM) – the higher the Inductive Reactance of the coil. The voltage at which 1.3 Amps occurs will be a function of the circuit Impedance (the mathematical sum of the DC resistance and AC reactance) of the circuit.
“At what voltage and amperage, AC and DC, will a coil fail?”
By “fail” I assume that you mean cease to operate. A properly set up coil will open the points and produce a spark when 1.3 Amps (DC or RMS) flows through the primary winding. Less current will not cause the points to operate properly. At some point there will not be enough current in the primary coil to open the points. Because the points are a mechanical device, the exact point at which this occurs will be different for each coil.
“As the magneto was designed to produce maximum voltage and amperage at a designated powerband (20 hp), is it a possibility that the introduction of the transformer may cause the coils to fail?”
I must reemphasize that the Magneto is designed to provide a current, not a voltage. The worst that can happen if a transformer is placed in the circuit is that the coils will be under powered. That should not cause and failures with the coils themselves.
“Yes we all experiment with our vehicles, but if all things are in good working order - coils and wiring - isn't recharging the magnets an easier solution than reinventing the car's power grid?”
I absolutely – 100% - Totally & Completely Agree.
“Another missed memo - would the transformer introduce a constant load on the magneto coils. As the magneto originally was engineered to provide power to the ignition coils. The ignition coils operated intermediately on and off, and not providing a constant load to the magneto?”
During the periods when no ignition coil is operating, the load seen by the Magneto will be the amount of energy needed to cover the transformer internal losses.
Actually you don't need a transformer in the circuit between the magneto and the coils. The coils themselves act as a transformer changing the low voltage input to the high voltage spark. The current to operate the points is 1.3 amps. It is the spark which ignites the fuel/air mixture. The spark occurs at the spark plug when the primary reaches 1.3 amps. Only difference between lower and higher voltage in the primary circuit is that the current reaches 1.3 amps faster as the voltage increases, therefore acting as an automatic spark advance as the engine speed increases. That is the primary reason the engine runs better on magneto than on battery.
This thread started as a new way to charge the magnets and has drifted to the coils. It is still the easiest way to charge the magnets with direct current produced by a series of batteries.
"This thread started as a new way to charge the magnets.."
No, it didn't.
Here is the original premise: "How about using a transformer to boost the voltage coming out of the mag?"
The OP just wanted to step up the voltage coming out of the mag with a transformer. For reasons explained very well, that most likely will not work.
That's what it says, but he started the first sentence about trying to recharge the magnets. I thought he was talking about using a transformer to charge the magnets. I guess my brain has a hard time with a change of thought when I start on a certain track.