Just curious, I have not heard of anyone using a home-made buzz coil on a T. There are videos on Youtube showing how to make a buzz coil using a regular coil and a relay. Why not?
The problem is that relay contacts are not designed for that kind of service. The frequency of operation is too high for reliable and long life operation and the contact material is not hard enough. A capacitor across the contacts is not a complete solution to the problem either.
Yes, it will work to start with, but the contacts soon weld together.
Then to be pedantic, it would be difficult to adjust for equal dwell time, important for a smooth running engine.
If you were to substitute a master vibrator for the relay, then the scheme becomes more practical.
Man, it's your car. Do with it what you will. There's any number of ways you could make it crank up and run. Some easy. Some hard. Some cheap. Some expensive. Some will make it run like a scalded dog. Some? well, it would just be a dog. You want it to run well and operate like Henry intended? You done been told how to do that. You want something else? By all means, do what you want with the thing. You wanna jerry rig the thing? Like you say, "Why not?" So long as you don't start telling people how crappy a Model T runs with the original ignition system, I don't much care what you do to it. It's yours.
John is completely right. Yes a relay will work, but only for a little while. The contacts will eventually fail. The contacts in T coil points are made of Tungsten in order to withstand the abuse.
Keep in mind that the relay will be self-activating, that is, it has its own coil and will be buzzing itself, and simply turning the coil on and off in doing so. This won't provide an ideal dwell time. In a T coil, the coil itself opens the contacts when the iron core has built up a nice magnetic field and is ready to fire. That will give a better spark.
Now I make electronic coils which are similar to the relay and ignition coil concept. It uses an electronic circuit to fire the stock T coil windings. Because it's electronic and uses special transistors to fire the coil, it isn't prone to failure like a relay is, and you can control the dwell time very precisely. This makes a very hot spark, consistent firing times, and a smooth-running car.
I've been running my electronic coils for many years with no troubles. I'm using them because I currently don't have a working magneto (but will eventually).
Funny flashback for me because I brought up exactly the same topic here a few centuries ago. Before I knew better. It just doesn't pay. You'll end up, as Hal suggests, with a poor running car that will end up costing more $ to repair. Just not worth the effort.
What the others said. It can be done but will for some reason or another be a false economy.
Having said that, there are a couple of T parts I'd like to make just for the science experiment aspect of it. I know going into it I would see zero improvement but what I'd get out of it is a better understanding of how a particular system works, even more respect for the men who invented the proper version, and of course that "Look what I did!" factor. Personally, I'd like to try making a carb some day.
Sorry I asked. Charlie, I too asked because I didn't know.
Hal, I have bought original type coils for my T. I will not make my own for it.
Tim, I made a carb, actually just a mixer valve, for a small hit-n-miss motor years ago. I was amazed that it ran.
I have thought that, just for the heck of it, I could make a buzz coil for a hit-n-miss engine from an old car coil, a condenser and a horn relay. Never tried and now you guys have cleared it up for me. Thanks.
Tommy, a friend came into my shop and dropped a handful cast iron and brass scraps on the work bench. Told me it was the carburetor off his new (old) flywheel engine. It was a throttle-governed kerosene engine, so a little more complicated and the carb was really a mess. At a show I found a similar engine and took some measurements and made sketches. After a three months of spare time work I handed my friend a new carburetor which worked just fine. I walked a few inches above the ground for a few days.
I have 2 Witte flywheel engines. One is a 2 HP and the other is a 12 HP. The cast iron carbs have a reservoir that holds about a pint. If gasoline is put in the reservoir ,by the time the engine runs out the gas it will be hot enough to run on kerosene. The 2 HP was either a father's day or birthday gift , from me to my father. The 12 HP belonged to my grandfather, both since passed away, so the engines have sentimental value to us, and will be passed down to my son and his sons. He has 3 sons so I suppose one will inherit the 2 HP, one will get the 12 HP, and one will get a 1921 T Touring car.
I caretook a nice 6, 8 or 10 Witte at a show for awhile several years ago and its gas valve stuck open, just like I was warned it may do.
It took off after a couple hours. Doink, doink, doink, doink, doink, doink!!!
Shut the gas off and brought it back to Earth. Neat memory tommy! Thank you. Hadn't thought about that in a long while.