The Luthi spark plug

As mentioned earlier, Rudolf Egg was the inventor of the very successful spark plug with the bell-shaped electrode. But why is the brand name of this spark plug “Luthi” and not “Egg”?

Let us start with the very first Luthi spark plug (see part 2 – -Bougie Luthi type 1a) that was an instant success when the first high voltage magneto ignition systems appeared, since the nickel electrodes of this new type of spark plugs could withstand the higher temperatures and would therefore not melt.

This spark plug was invented by Rudolf Egg. He sold his invention to Hermann Lüthi who in turn granted a license to produce and sell this spark plug to a French company in Paris. I would think that the first “Bougie Luthi” must have been quite a good spark plug, judging from the ads published by the company in the leading French newspapers bragging about the fact that the motorcycles and cars that won certain famous races in France were equipped with Luthi spark plugs. But maybe not good enough for prolonged use, because Rudolf Egg soon further developed the initial concept and patented on Christmas day in 1902 the “Bougie Luthi” with a bell-shaped electrode in France and sold the license to produce this type of plug to the same Paris based factory that produced the first Luthi spark plug.

During the “Salon de l’Automobile” in France of Christmas 1903 “Bougie Luthi” advertisements announced that they had already sold 120’000 spark plugs – 8 years later the sales figures amounted to 1’500’000. The “Bougie Luthi” was very successful, even the Paris Police Department and the French Navy equipped their vehicles exclusively with this type of spark plug. The success story of this spark plug must have been very impressive in those days. Apart from the many testimonials by racing drivers, famous people and known automobilists who confirmed the high quality of this bell-shaped spark plug, a multitude of automobile , motorcycle and boat races were won by vehicles equipped with “Bougie Luthi” spark plugs; often the “Bougie Luthi” would win  “Medals of Honour” in famous European exhibitions, for example in Milan in 1905 and Turin in 1907. Still, the success and fame were not limited to France, the bell-shaped “Bougie Luthi” was exported to most European countries, the USA and Australia. This very illustrious spark plug was sold in a wooden box sealed with a ribbon mentioning the name “Bougie Luthi”

The French “Bougie Luthi” company was very active and creative in marketing as well as in the development of the spark plug design and technical components thereof. As described in part 2, the “Bougie Luthi” underwent a steady development from 1902 to 1907, making it quite easy to determine the production year of every French made bell-shaped Luthi spark plug.  Another interesting and well-known marketing principle used by the company is “Win on Sunday and sell on Monday”. I have found innumerable newspaper ads by the “Bougie Luthi” company with references to races, stating that the winning vehicle was equipped with “Bougie Luthi” spark plugs.

However great the race victories were, sometime around 1908 the production of the French made “Bougie Luthi” bell shaped spark plugs stopped, the factory ceased its production and the remaining spark plug stock was sold to a dealer located in the outskirts of Paris. The last ad for “Bougie Luthi” I could find is from 1909. Why the production stopped is unclear, I can only presume that the design could not be further developed to meet the requirements of the new engines with higher compression ratios.

Unfortunately, I have so far been unable to find a copy of the magnificent 16-page catalogue of the “Bougie Luthi” that is mentioned so often in the French ads. If you have one of these catalogues or know somebody who does, please contact me hermann@zedel.com).