Autolite: (2) Prologue
An internal combustion engine would be worthless unless explosive gases inside a cylinder could be ignited with and electric spark. The pioneer engine makers had to be concerned with how this could be done.
In 1860, a patented gas engine by a man named Lenoir was probably the first to utilize a spark plug similar to those used today. However, many early engines did not employ this device, but rather a pair of metal contact points located inside the combustion chamber. These were opened and closed mechanically, and the spark was created when the contacts opened.
This systen had many limitations, and a version of today’s spark plug soon was adopted.
Most early spark plug were bulky and formed with large flanges, and were held against the cylinder head with stud and nuts
Around 1900, the threaded spark plug mounting appeared, some using a pipe thread, as in the old Ford Model “T”,and others using standard threads, sealed with gaskets against the engine head. As the engine became more pretentious, the techniques for doing this became more and more demanding. someone figured out that wire should pass into the engine cylinder through an insulating medium, such as a ceramic tube, and the spark could then “jump” from the wire to the cylinder head or “ground.”
The early spark plug insulators were made from low grade ceramic (probably a porcelain from which dishes were made at that time), even though this material had a relative low melting point, low mechanical strength, and an inability to be a good electrical insulator at high temperatures. Also, these early plugs were very susceptible to thermal shock, and often would break or shatter inside the cylinder with very disastrous results.
Other materials, including wood, rubber, glass, quartz, and mica, were used as insulators. Mica had a distinct advantage over the early ceramic material because it had a higher mechanical strength, better heat conductivity, and better insulating qualities at temperatures and pressures at which the engine operated at that time, but a disadvantage was that mica would dehydrate and disintegrate when operated at a high temperature. The mica plug was made by punching out mica washers and compressing them on a metal rod. Then these were shaped as desired on a lathe.
A great deal of effort was made to improve the life of spark plugs by having them made of pyrex glass and other insulating materials; allowing them to be dismantled for cleaning and replacement of various parts in the plug; developing many configurations; arranging for adjustable electrodes; and using all sorts of materials for electrodes; to give the latter more useful life.
Ingenious designs developed from these efforts such as: multiple electrode shells, ball-shaped center electrodes, disc-center electrodes,adjustable electrodes, and a (Cont.) fan-cooled center electrode, which was designed to turn and cool the insulator as the piston would operate up and down in the cylinder. A great deal of research was done on the nickel alloy electrode materials, and the use of platinum and its alloys. The wire had to be able to withstand electrical, and chemical erosion, as well as be a good heat and electrical conductor. Suppplies had to be plentiful and costs relatively low.It seemed that the engine development and the development of the spark plug had to go hand-in hand, as one would deter the progress of the other. This was brought to the attention of the spark plug industry very forcibly at a meeting called in Dayton, Ohio, by the United States Air Force at the beginning of World War II. At that time, most of the U.S. military aircraft were equipped with mica plugs, made by the BG Corporation of New York. The United States Air Force had engines that could not be run, due to the lack of a satisfactory spark plug. The Air Force pointed out the fact that our fleet of planes was practically grounded, and showed examples of good ceramic insulated plugs that were captured from “downed” German Planes during the Battle of Britain.
Our United States Military Air Corp “limped along” with ceramic plugs (which were made in lilmited supply in England) and the BG Corporation obtained a license from England to manufacture the “Lodge Ceramic Aircraft” plug to keep our Air Corp going. The other major spark plug companmies, such as chjampion, AC, and Electric Autolite, were requested to intensify their research and development, in order to produce a satisfactory plug for planes in the war effort, since a greater supply was needed from more than one source. Needless to say, the spark plug makers came through, and the planes were equipped with satisfactory plugs made in the United States.
Just before World War II, another major development in fuel required a change in the ceramic member of the spark plug. The introduction of “tetraethyl lead” into gasoline to improve its octane (anti-knock) properties, provided the industries with additional problems, because of the detrimental effects of the leaded gasoline on the insulator and the electrodes of the spark plug, so that much research was required on ceramic and electrode materials. The solution for the problem of the insulator was to make it out of high percentage aluminum oxide mixes which were resistant to lead attack, and had other satisfactory qualities.
The first manufacturer of spark plugs in the United States was the Champion Ignition Company (“Champion”), Boston Maassachusetts. This company was then the sole supplier of plugs to virtually all engine manufacturers in this country.
In 1909. General Motors acquired the assets, except for the trade name “Champion”, leaving the latter still in the manufacturing field. The principal owner of the Champion Ignition Company was Albert Champion and General Motors saw fit to use the initials of Albert Champion as its name--AC Spark Plug. The Stranahans bought the rights to make spark plugs from Champion Ignition Company and manufactured plugs under the “ Champion” label.
From 1909 - 1936, General Motors and Champion were the only significant spark plug producers in the United States, and they accounted for all spark plugs installed as original equipment in vehicles, and for more than 90 per cent of all plugs made and sold in the United States.
During this period, there were many small companies which entered the field to produce brand spark plugs. They would purchase their insulators from Frenchtown Porcelain Products, Frenchtown, New Jersey, the shells and wires from other suppliers, and would assemble them in small “garage or basement” plants. Their merchandising was done from the backs of autos or trucks.
Every supplier of parts for the automotive industry felt its name would carry enough prestige to enable its plugs to be sold in the after-market. Some even started plants and assembled plugs with their trade names.Such giants as Firestone, Goodyear, Edison Battery, Sears Roebuck, Montgomery Ward, J.C. Penney, Western Auto Supply, Bill’s Auto Stores, W.T. Grant, and Standard Oil, to name a few, few are still merchandising plugs with their own trade names, but long ago stopped putting them together. At the time Electric Autolite Company entered the spark plug manufacturing business, there were over 140 producers of plugs in the United States. The principal supplier of trade name brand plugs is now Prestolite, with Autolite, Champion, and AC still manufacturing some. Electric Autolite bought the assets of Firesstone Spark Plug Division and, for a period of time, made plugs with the Firestone name and Firestone color,”pink”.
The design of a spark plugis not an exact science. There is no particular formula that fits this product, to decide which plug will perform satisfactorily in any given engine. Constant increase in horxsepower, compression raatios, location of the spark pllut within the cylinder, fuel inprovements, changes in economy, characteristics of the driver (fast or slow), distances traveled, climate--all have a bearing on which plug is used in any given engine. Hence, a spark plug furnished to the motor manufacturers is the one determined to be closest to meeting all of the above requirements. The “Big Three” spark plug manufacturers, as Champion, AC, and Electric Autolite are refered to, must work closely with the engine producers to determine the proper plug with the correct heat range. This term “heat range” refers to a spark plug’s thermal characteristics in its ability to transfer heat from the firing end to the engine cooling system. Heat range is detirmined by the length of the plug’s insulator tip, wire stick-out, diameters of the insulator tip and wire, the internal chamber of the spark plug shell, thermo conductivity of the ceramic body, and the seal between the wire and the insulator, among others. “Hot” plugs are usally manufactured with long insulator tips, and “cold” plugs with short ones.
The “Big Three” manufacturers have large investments in equipment to enable them to test their plugs under most driving conditions, and comparisons are made with the findings of the engine manufacturers and verified by actual ”fleet” testing (a number of cars equipped with recommended plugs and driven under field conditions). It is obvious that the spark plug supplier who furnishes his product for the new engine has the advantage of the testing knowledge of the proper plug to use before it goes on the market. In order to be able to sell plugs for all engines, it is mandatory to be able to test one’s brand plug against another’s brand, so as to enable the supplier to cover all of the applications in the after-market. It is usually the wish of the independents to carry the top 10 percent of the current volume plugs, so that they would not need to handle plugs that are slow movers in the market place.
A “rule of thumb” indicates in volume that 90 percent of the total plugs made are usually in about 10 percent of the numbers of types, and 90 percent of the types produced are only approximately 10 percent of the production volume of the maker. An independent spark plug seller without ties to an engine manufacturer only wishes to make spark plugs which are considered high volume for the current market, Plugs for engines no longer made, but which are still in use, are being produced and sold in the market place by the “Big Three”.
Just the problems of the automotive industry have been covered, but when these are multiplied by the perplexities that are incountered by furnishing plugs for applications for marine usage, farming, recreation vehicles, outboardmotors,snowmobiles, stationary engines, household tools (such as lawnmowers, weed cutters, etc,) all types of aircraft with internal combustion engines, construction machinery, etc., one can realize the magnitude of this type of business. The selection of the proper design for all these applications requires a company with diversified skills to satisfy these need and to compete in the market place.