Trying to understand how early cars worked ...

[Guest jonathon17]

I'm interested in the development of early cars, and I'm wondering if anyone can help me understand what it was about the de Dion Bouton 1895 ignition system that created the first high speed engine. Compared for instance to the Benz Tricycle of 1885 that also had electrical ignition. The books I have are all very vague on the details, and I don't know enough mechanics to make sense of them.

[Rusty_OToole]

The DeDion Bouton had a new type of ignition, at least new for that time. It would be familiar in later years as the typical coil ignition. If you have a car with points and coil ignition, it works on the same principle DeDion pioneered in the 1890s.

They used dry cell batteries (flashlight batteries) so they had to design an ignition that did not use much power. So the cam did not hold the points closed for long. The movable point did not have a pivot. It was made of a springy metal and was fastened solid at the end. You could adjust the tension of the spring, when it was set right the points would vibrate at low speeds giving a multiple spark for easier starting, when it sped up you got a single spark for longer battery life. When set right the spring made a distinct *twang* when plucked.

Previous engines had hot tube ignitions or electrical ignition made for low speeds. Typical engine speed, 600 RPM max. DeDion, 1800 RPM.

The secret of the DeDion motor was in its small size and light moving parts. The first one was made for driving machinery in the DeDion shops. They were surprised that it ran so fast and made so much power without flying apart. Only later did they think of putting it in a vehicle.

I'm not sure what the Benz had. It may have had a vibrator and timer like a Model T. But the Model T was good for 1800 RPM like the DeDion.

I think the DeDion ignition was designed because they needed something especially simple, light weight and of low current consumption for their tricycles.

There were other electric ignition systems such as the ones used on stationary engines that had a make and break set of points inside the cylinder.

Here is the DeDion timer. You can see the points cam, the round black thing at the bottom. Notice that as it turns the points close for a short time. The points are in the middle of the flat spring, and the spring is held fast at the far end.

As the cam turns the points close for a split second. This allows current to flow through the coil, saturating it with electricity. When the points open the current is cut off and the electrical field in the coil collapses. At this instant, the electricity from the coil grounds through the spark plug, creating a spark.

PS I use the word "points" in the modern sense. The timer shown does not actually have points. Just an adjustable screw that touches the spring when the timer is closed. "Points" were a later refinement to extend the life of timer.

This timer is arranged differently but works the same as that used on millions of small engines, motorcycles, cars, trucks etc from the 1890s to the 1970s.

Edited November 10, 2012 by Rusty_OToole (see edit history)

[Rusty_OToole]

I use the term timer rather than distributor. Being a single cylinder, it does not need to distribute sparks, just time them. But if you look inside a points distributor you will see the same kind of apparatus arranged a little differently.

[Owen_Dyneto]

I"m way out of my comfort zone on this but I believe another ignition feature that led directly to an extended engine speed range was automated spark advance. Here's a page from Packard's 1901 patent on that feature, maybe this will add something to the discussion.