How Your Hobby Started

Chapter XXX

Briggs and Stratton Engine

Courtesy of Carleton M. Mull, 3904-47th Avenue South, Seattle, Washington 98118

Carleton M. Mull

Content Tools

904 - 47th Avenue South, Seattle, Washington 98118

What happened to all of the pioneer gasoline manufacturers? This question is often asked by spectators at threshing and engine shows. Like many other industries, gas engine designs changed with the progress of our American life style.

The modern day compact light weight air-cooled portable engine is the culmination. It might be said of the old stationary water-cooled gasoline engine that took the drudgery out of the chores on the farm at the beginning of the century - that they performed so well and attracted so much attention that today's version not only makes modern farming possible with all the engine driven implements, but now have gone urban by doing the chores for city folk as well.

In accomplishing this progress many hundreds of gasoline engine manufacturers were either successful by emerging today into large producers of modern diesel engines, or to have gone out of business. Others developed the old slow-speed heavy duty engines of yesteryear into the automotive style for stationary and portable application.

A few builders improved the idea of the early air-cooled engine. In the process of elimination these remaining companies have developed an acceptable air-cooled engine that replaces the old 'Chore Boy' of bygone years for every kind of application for the urban and suburban user.

As in the automotive industry, the manufacturer of the present day air-cooled engines have taken over the market and have pyramided into about three or four dominating companies.

One of these is the Briggs and Stratton Corporation of Milwaukee, Wisconsin. This enterprising young company has produced engines since August 12, 1909.

Frederick P. Stratton, Jr. was kind enough to send me this information concerning the development of their company of which I am happy to submit for your pleasure.

I am sorry to say that due to a journey to the hospital and surgery, I will have to postpone my writing until I have fully recovered.

I also want to thank my many friends to whom I owe letters. You have sent me so many interesting catalogs and valuable information.

Briggs & Stratton was founded in 1908 as a rather casual partnership between Stephen F. Briggs, an electrical engineering graduate of South Dakota State College, and Harold M. Stratton, a Milwaukee grain merchant. The partnership undertook a number of projects, one of which was the production of an automobile called the 'Superior'. It was assembled from purchased components, including a four-cylinder Continental engine and a frame supplied by the A.O. Smith Company. Three Superiors were produced -- two touring cars and one roadster. Apparently this project convinced the young partners that automobile manufacturing was not for them.

The company was incorporated on August 12, 1909. The corporation's first product was an electric ignition system designed to replace the universally used magneto. This ignition system was displayed at the New York Automobile Show in 1910. This product line was sold to Atwater Kent, and Briggs & Stratton moved on to other automobile components -- mostly electrical. At various times the company made carburetors, air cleaners, door hardware, oil purifiers, fuse boxes, horns, and spring covers. It also supplied spark coils for the Model T Ford.

In 1910, Mr. Briggs brought Charles L. Coughlin, a fellow electrical engineering graduate and basketball star from South Dakota State College, to join the young corporation. Mr. Coughlin had earned 19 major letters in his four years at South Dakota State. His proficiency extended well beyond athletic competition. He guided the company from 1923 until his death in March of 1972.

Briggs and Stratton Engine Model FB produced from June 1923 to November 1924. Approximately 5000 produced.

During World War I, Briggs & Stratton turned to the production of war materials, making hand and rifle grenades and shrapnel case covers. After the war, the company tried manufacturing a number of products. It made the first electric refrigerator for a young inventor named Alfred Mellowes. Production of electric refrigerators lasted for only two years. Briggs & Stratton also made crystal radios and head sets and then a device called a battery eliminator, a plug-in power source which eliminated the need for A and B batteries in home radios. Unfortunately, radio manufacturers soon added power supplies to their radios, and that eliminated the need for the eliminator.

Not all the products the company tried during this period were unsuccessful. Window lifts, for example, which the company made for railroad cars, and eventually for the Model A Ford, were a viable product line. And two product lines, established during this period, eventually proved to be very successful.

When Charles Nash acquired the Jeffries Automobile Company in Kenosha, Briggs & Stratton became the supplier of a locking device known as the 'coincidental' system, which locked both the ignition and the transmission. The device incorporated a lock which was purchased by Briggs & Stratton from an outside supplier. It was an expensive lock, being made from solid brass on a screw machine. Mr. Briggs had become interested in the then new art of die-casting and had decided that he could make a die-cast lock cylinder at much lower cost.

He sold Nash on the idea, and Briggs & Stratton was in the lock business. At first the die-castings were purchased, but in the early 1920's, the company installed its own die-casting equipment. Today all automotive locks, used in this country, are made in this way. Other automotive products eventually were phased out, so that today the company's only automotive product is locks, keys, and related equipment. Locks and keys are produced at 13th and Center. Early next year, production of locks and keys will be moved to the Good Hope Road Plant recently purchased from Square D. Automotive locks and keys account for about 8 % of the company's sales.

In 1919, Briggs & Stratton purchased the Smith Motor Wheel from A. O. Smith Company. The motor wheel was a 20' wheel mounted on the power take-off shaft of a small, single cylinder engine. It was rated at about one horsepower, and it was fitted with a fender upon which was mounted a fuel tank. Included in the purchase of the motor wheel was a buckboard, which consisted of wooden slats riding on two axles and four 20' bicycle wheels. It had two bucket seats, a steering wheel and a braking mechanism. Power was supplied by a motor wheel attached to the rear of the vehicle as a fifth wheel.

The motor wheel itself was not particularly successful. Soon after Briggs & Stratton acquired it, legislation was passed requiring the driver of a buckboard to have an automobile operator's license. Now the motor wheel sold for just under $100. Mounted on a $50 bicycle, it was a $150 product. Mounted on a buckboard, it was even more expensive. About that time, Ford was selling roadsters, without tops, for about $325, and used cars were available for less than that. So a combination of legislation and Henry Ford's concept of a mass-produced, low price car crippled the market for the motor wheel.

However, in 1923 there developed a need for a power unit for lawnmowers. So Briggs & Stratton modified the motor wheel engine for this purpose, and in 1924, 5,000 engines were sold. Today, we can assemble that many in an hour and a half.

In 1926, the company developed an entirely new design -- the Model F. This model had overhead valves, which subsequently proved to be a disadvantage because they increased the weight of the engine. The principal market for this engine turned out to be -- not lawn mowers -- but washing machines located in rural, non-electrified areas. Because of the height of this overhead valve engine, it usually was necessary to put the washing machine on stilts in order to get the engine under the tub. To reduce engine height, an L-head engine was mechanically operated valves was developed. This engine, the model Y, was very popular for almost 10 years.

In 1936, the model Y was succeeded by the model WM. The model WM was the first mass-produced small engine. Special automatic machinery was installed to produce these engines at a rate of 120 per hour. This was the basic design from which today's cast-iron engines were developed. Today, our cast-iron engines (8-16 H.P.) are produced at our plant at 32nd and Center.

Briggs and Stratton Engine Model FH produced from November 1925 to October 1933. Approximately 110,000 produced.

A little known part of our history is the fact that Briggs & Stratton acquired the Evinrude Motor Company in 1928. While the production of engines and outboard motors was similar, the marketing of these two products was not. Therefore, Briggs & Stratton decided to sell the outboard motor operation. Mr. Briggs had become intrigued by the potential for outboard motors, so he and Ole Evinrude formed Outboard Motors Corporation, which acquired Evinrude from Briggs & Stratton in 1929. Outboard Motors subsequently became Outboard Marine and Manufacturing, and eventually Outboard Marine Corporation. From about 1935 on, Mr. Briggs divided his time between the two companies. In 1948, he terminated his association with Briggs & Stratton to devote full time to Outboard Marine.

During World War II, Briggs & Strattor continued to make engines, and in addition manufactured a variety of bomb fuses for the Ordnance Department. The company also manufactured an aircraft engine magneto designed by GE and the Air Force.

Late in 1949, the need for a lightweight 4-cycle engine for rotary lawn mowers became more pressing, so Briggs & Stratton started to develop the best lightweight engine the company could design. There were other design. objectives: better performance, longer life, and lower cost for a broader market.

In 1954, after a very extensive test period, Briggs & Stratton introduced its new line of aluminum engines. This was a radical step. These engines were the first all aluminum cylinder engines mass-produced in the United States. The use of aluminum permitted about a 30% weight reduction and an equivalent cost reduction. The effect of the switch to aluminum can be seen from the average selling price per horsepower. This figure went from $15.35 in 1952 to $7.72 in 1962.

There were some problems at first; some old mechanics didn't believe that a cylinder made of a soft material, like aluminum, would wear less than cast-iron, or that bolts could be torqued into aluminum without stripping the aluminum threads. (At one time we didn't believe it either, but our tests had proved it to be true.) These problems were minimal, and demand for aluminum engines was so strong that the company could barely keep up with it. Additional manufacturing facilities were needed, and thus began the company's association with the City of Wauwatosa. The company had acquired an 85 acre site at the corner of 124th and Burleigh Street, and construction of a 450,000 square-foot plant, to be used for service department operations and warehousing was added in 1958. A 675,000 square-foot addition to the plant was completed in 1967. Earlier this year, another 340,000 square-foot addition was announced. This addition now is under construction. It extends to the south of the present building. It is a two-story structure, and it will make the view from Burleigh Street much more attractive. This probably will be our last major addition at this site; there just isn't room for another. All Briggs & Stratton aluminum engines (2 to 10 horsepower) are manufactured at the Wauwatosa plant. Except for crankshaft and camshaft castings, some flywheel castings, and electrical components, which are trucked from our West Allis facilities, and a few odds and ends that we buy from outside suppliers, all aluminum engine components are produced at that site. During the busiest times of the year, production exceeds 30,000 engines per day. The Wauwatosa plant employs approximately 5,400 people, half of them women. It uses 200 tons of aluminum every day. In addition to aluminum engine production facilities, the company's executive offices, service parts distribution center, and test facilities are located at the Wauwatosa site.


Our discussion will be limited to the development of small, four cycle, single cylinder, air-cooled, gasoline engines. By small engines we mean engines that develop 3 brake horsepower or less.

Many of you are very familiar with our early days - for some of you younger folks, I hope a little history will be of interest.

In 1919, Briggs & Stratton Corp. of Milwaukee started in the engine business by purchasing the then famous 'Smith Motorwheel'. This was a gasoline powered unit for propelling a bicycle, a British patent that had been brought to this country a few years previously by the A. O. Smith Corp. The engine in this unit was 2-1/2' bore by 2-1/2' stroke and the cam shaft, the driving member, was forged of special chrome nickel steel. The connecting rod was also forged of steel with bronze bushings at both ends. The Motorwheel was capable of pushing a bicycle at speeds of from 4 to 25 miles per hour and sold retail for $115.00 in 1920. A few of these units are still in use today and we are still servicing the parts of these engines built almost 40 years ago. A week or so ago a letter arrived from Holland asking for an Instruction Book on one of these engines and commenting that the engine was still in fine condition.

Harold and his 1917 Moline Universal tractor.

A short time later the Briggs & Stratton 'Flyer' was built. This snappy little flyer had a buckboard type body and was driven by the Motorwheel, which could be lifted from the ground when starting and stopping the Flyer.

In 1923 there developed a need for a power unit for lawnmowers. For this purpose the Model PB was developed, essentially by removing the outriggers of the Motorwheel engine crankcase and by installing a belt driven axial flow fan. On this engine as on the Motorwheel, the intake valve was opened by the suction created by the piston on the down stroke.

In 1926 we developed an entirely new design of engine, our Model 'F', equipped with dual blowers and with flywheels providing a blast of cooling air on both sides of the cylinder. This model had overhead valves, which later proved to be disadvantageous because they increased the overall height of the engine. The chief application at that time turned out to be, not lawnmowers, but rural washing machines and it was usually necessary to put the machine on stilts in order to get the engine under the tub of the washing machine. To reduce the engine height, an 'L' head engine with mechanically operated valves was developed and this engine, known as our Model 'Y' was very popular for almost 10 years.

In 1936 the Model 'Y' engine was superseded by the Model 'WM' engine, which had a 2' bore and 1-1/2' stroke. This model was the beginning of the 'Mass Production' of small engines.

Special automatic machinery was installed to make these engines at a rate of 120 per hour. From this basic design a large variety of models were developed, including our Models '6' and '8' cast iron engines.

In the latter part of 1949 the need for a light weight engine became more pressing, mainly because of rotary lawnmower applications. The majority of rotary mowers were not self-propelled and, therefore, light weight became quite an advantage as far as handling the mower was concerned. We, therefore, started to develop the best light weight engine we knew how to design. Don't forget -there were also other objectives, namely, we were also designing for better performance, better life, and also lower costs to broaden our markets.

We were well aware of the potentials of aluminum as an engine material. We had proven that our alloy aluminum die cast pistons, although light in weight, could well withstand the explosion temperatures and pressures encountered in our engines. For many years we had used aluminum die cast bearings and these were largely used against hardened steel crankshaft journals. We had noticed that when wear was experienced, the wear was usually on the hardened steel journal, and the aluminum bearing very seldom, if ever, wore any appreciable amount. From this fact it was reasonable to assume that if the piston rings were operated on an aluminum bore, and if the aluminum piston were equipped with slider rings or with a steel skirt, that the cylinder bore would not wear rapidly. To test this theory we built an engine.

The engine used for this test was our Model 'N' engine and into this cast iron cylinder we installed an aluminum sleeve. Instead of operating the piston with a steel skirt or on slider rings, we chose to chromium plate the piston because it appeared to be easier to manufacture a chrome plated piston than it would to manufacture one with a steel skirt. We know at that time that aluminum pistons were operating satisfactorily against chrome plated aluminum bores. This was the construction used on the famous Porsche engine noted for its high performance, racing characteristics, etc. Therefore, we could see no reason why a chrome plated piston would not operate satisfactorily on an aluminum bore. We assembled the above engine August 4, 1950 and operated this engine for a total of 1436 hours. At the end of this time the bore was in good condition and had worn only .0003. This test gave us considerable encouragement so we built another engine to further test the operation of the chrome plated piston on the aluminum cylinder bore and to try to determine whether the valves would operate satisfactorily in aluminum guides or whether we would need to put special guides into the cylinder. A test was arranged. Again our Model 'N' engine was used and we placed an aluminum sleeve into the cylinder and put aluminum valve guides into this engine for test. We tested this engine for over 1500 hours and at the end of this time the size of the cylinder bore at right angles to the crankshaft increased only .0009. We found no appreciable wear on the valve guides during this test. We also found that the length of guide should be approximately 6 times the diameter of the valve stem. One of the foremost valve makers in the country tells us that their experience shows that this holds true regardless of the material of the guide. If the guide is considerably less than 6 times the diameter of the stem, difficulties can be expected.

At approximately the same time we decided to make some cylinders similar to our Model 'N' cylinders, but with the sand castings made of aluminum alloy similar to our die cast aluminum using the same patterns we normally use for the cast iron cylinder. We had considerable difficulty getting sound castings in this manner, but we finally did get some castings and had them machined, and in October of 1950 we started a test of one of these engines. After about three days of operation, this engine failed by cracking at a point in the cylinder barrel directly below the top fin. Therefore, we re-enforced the castings at this point and started another test. These engines ran so well that we then wondered whether chrome plating was necessary on the piston, and, therefore decided to test other coatings to see whether some less expensive coating on the piston was entirely satisfactory. The first coating we tried was an anodized coating and an engine of this type was started on test in November, 1950. Some of these engines ran as high as 900 hours with less than .001 wear on the cylinder bore, but we also had other engines where the bore increased or wore as much as .0025 in 150 hours. Also some of the cylinder bores with the anodized pistons were deeply scratched. At approximately the same time we also tested some engines with the tin coated pistons of the type normally used in cast iron engines. These results also were not as satisfactory as on the engine equipped with chrome plated pistons. By this time we had run one of the aluminum cast cylinders with a chrome plated piston for over 5000 hours and the wear on the cylinder bore was .0037 in one direction and .0042 in the other direction on this particular cylinder.

In our previous development work we had run across cases where sand cast aluminum parts made from the same aluminum alloy used in our die casting process, were not comparable in respect to wear with the actual die cast part. Hand poured experimental samples appeared to be better from a wear resistance standpoint than castings which were cast under pressure in the die cast machines. Therefore, to be sure that our idea of running an aluninum chrome plated piston on an aluminum unplated cylinder bore was feasible, we made die cast sleeves in our die cast molds and then inserted these sleeves into the sand cast aluminum cylinder and ran additional tests. These all proved to be very satisfactory. Some of the above cylinder bores were finished by boring with a fine finish and with carboloy tools and others were finished by honing. Later on in production we chose to hone the cylinders because we could control the finish on the cylinders more easily with the hone finish than we could with a bored finish. Also, we could hold size more accurately automatically with a honed finish than we could with a bored finish.

While the above information was being accumulated, we, of course, were very busy designing the best die castable aluminum engine we knew how to make. Also, at the same time the above tests were being made, much data was being accumulated in our laboratory such as the amount of cooling air and the amount of fin area required for the cylinder, vibration characteristics of long stroke versus short stroke engines, the proper material to be used for valve seat inserts, the proper method of assembling these inserts, etc. Time will not permit a full resume of all these activities, but we would like to give you some of the highlights of the results.

A Best Tractor which I have restored is pictured above -I don't know the year it was built. The patent date is December 1907 through October 22,1918. Serial number is 5-3322. I have spent two years work on restoring it and hunting for parts.

In the next minute or so I will mention 'Degrees' and 'So many thousands of an inch'. These data may not be of particular interest to all of you.

To check the comparison of temperatures on an aluminum cylinder engine to the temperatures on a cast iron cylinder engine, we built two engines which were identical with the exception that the cylinder and crankcase casting on one engine was made of cast iron and the cylinder and crankcase casting on the other engine was made of aluminum alloy. The temperature at the top of the cylinder barrel on the power take- off side of the cast iron cylinder checked with thermocouples with the engine at wide open throttle and at 3600 R.P.M. is approximately 480 degrees F. In other words, with the identical amount of cooling fins on the cylinder and with the same amount of cooling air, the aluminum alloy engine was approximately 85 degrees cooler at the hot side of the cylinder barrel than the cast iron engine. Also the variation in temperature between the blower side or cool side of the cylinder, and the power take-off or hot side of the cylinder on the aluminum alloy engine was only 65 degrees compared to a variation of temperature on the cast iron engine of 110 degrees. These figures give you a good idea of the tremendous advantage of using aluminum alloy from a heat conductivity standpoint.

I have mentioned 'Aluminum Alloy' many times. This is a very broad term. We have learned much about alloying in these last several years and the future holds perhaps even more.

To test the vibration characteristics of a long stroke versus a short stroke engine, we built a 2-1/2 bore x 1-1/2 stroke engine to compare it with a 2' bore x 2' stroke engine. We checked the vibration by means of an MB vibration meter, with the engine mounted on a springboard so that it would vibrate in the free condition. From this arrangement we came to the conclusion that the short stroke engine should be easier to balance than the long stroke engine. The above held true in practice and on the final engine we developed, which was our Model 6B engine with 2-5/16 bore and 1-1/2 stroke, the vertical vibration velocity in inches per second was 1.31 compared to 2.05 on our Model 6 engine, which had a 2' bore and 2' stroke. The horizontal vibration velocity at the base of the engine on the 2-5/16 bore x 1-1/2' stroke was .8 inches per second compared to 1.0 inch per second on an engine of 2' bore and 2' stroke. The displacement of both of the above engines is 6 cu. inches. On a single cylinder engine, of course, vibration is a matter of compromise insofar as the more you reduce the amount of vertical vibration the more you increase the horizontal vibration and vice versa.

Regarding the valve seat inserts, we tested a wide variety of materials, including materials similar to those used in our cast iron engines, materials of bronze composition with a co-efficient of expansion similar to aluminum and also Ni-resist inserts. The Ni-resist inserts showed a remarkable resistance to corrosion and also to burning and guttering. We finally chose the Ni-resist inserts because of the above facts and because the co-efficient of expansion of the Ni-resist was very close to the coefficient of expansion of aluminum and none of these inserts showed any tendency to come loose or our tests even though they were not rolled or staked into place. In production to preclude any possibility of the seat coming loose, we do roll a shoulder of aluminum over the top of the insert similar to what has been standard practice in the aircraft industry. After determining the material for the valve seat inserts, the next problem was to determine a method for installing these inserts. The amount of press fit was important as well as finish on the aluminum counterbore in order to prevent the insert from shearing the counterbore at the time it was assembled. We could have die cast the inserts in place, but we thought they would not be as easily replaceable in the field if this should be necessary. We tried many methods of inserting the seats, including heating the aluminum cylinders, cooling the inserts by means of dry ice or liquid nitrogen, and also by pressing the inserts in place. We devised a test whereby we could grip the insert and check the rotational torque on the insert to see how tight the insert was assembled into the cylinder. We also checked the direct pull-out load to see the variations in different methods of assemblies. The method we finally chose to assemble the inserts into the cylinder proved to be one of the simplest, namely, to use a vibrating press fit. By this method we were able to assemble the inserts without shearing the aluminum even under the maximum conditions or press fit, and we were able to insure that the bottom of the insert was always down tight against the bottom of the counterbore. This construction turned out to be extremely trouble-free. Of course, many of you know all about most of the things I speak of.

In the meantime, we completed the design of our engine, and decided to build about two dozen experimental samples so that we could adequately test the new design. In parts of the Model 6B-H vertical crankshaft engine, we believe that this design has a great number of advantages. With a minimum amount of changing of parts we can make a wide variety of models. For instance the main cylinder crankcase casting is designed as one casting with only one main opening on the power take-off side of the engine. By means of a slight change in the mold insert we can use the same mold to cast either vertical cylinders or horizontal cylinders. The cylinder used for the vertical engine has mounting feet at the bottom of the crankcase casting where the feet are normally omitted on the horizontal cylinder. With these exceptions the same casting can be used for any of the models. By having one side of the crankcase open and only this side open, it is very easy to assemble the crankshaft and cam gear assembly into the engine.

A crankcase cover, which in this case serves as an oil sump, completely encloses the crankcase of the engine. This means that we have only one gasket face on the crankcase of the engine to contend with whereas on all previous engines we had made, we had at least two gasket faces. By replacing the sump with covers of various designs, we can get a wide variety of models demanded by our customers without affecting the main cylinder crankcase casting. For instance, some covers have flange mounting holes for mounting a water pump or a generator onto the crankcase cover of the engine. Other covers are arranged for ball bearing, while still other covers are arranged for plain bearing. Some covers are arranged for use with mechanical governors, other covers are plain and on these engines we use a pneumatic or air vane governor. We have some covers where it is necessary to fill the engine with oil on one side of the engine and other covers where it is necessary to fill the engine with oil on the opposite side of the engine. By having practically all of the variations in the crankcase covers, we greatly simplify our servicing problems in the field on the expensive parts, such as the cylinder crankcase casting.

On the vertical shaft horizontal cylinder design of engine, the lubrication is by means of a nylon gear, which is driven by the cam gear of the engine. The nylon gear has paddles which throw the oil to the upper bearing and the remainder of the engine is also lubricated by splash. On the horizontal shaft vertical cylinder engine the necessity for the nylon gear is eliminated and lubrication is by means of splash created by a dipper attached to the connecting rod working in the oil reservoir.

The cam gear is shell molded and the cam gear bearings are directly in the aluminum. This is a further simplification over our previous engines where the cam gear casting pivoted on a shaft which was supported on either side of the crankcase. On vertical shaft models this construction also allows us to extend the lower end of the cam gear through the sump so that we can secure a half-crankshaft-speed power take-off from the end of the cam gear.

The cylinder casting is designed with a die cast wall on the side of the casting which serves a triple function. In addition to acting as a cooling fin to dissipate heat from the casting, this fin or wall acts as a convenient place to gate the die casting. In addition, this wall, serves as a cylinder shield to confine the air which is directed around the cooling fins of the cylinder.

On engines to be used on rotary mowers where the blade is attached directly to the lower end of the crankshaft, we use a light weight flywheel on the engine. This flywheel is made of aluminum and carries the Alnico magnets for the ignition system and the blower vanes for blowing the cooling air to the cylinder. On other applications we install a heavy flywheel on the magneto side of the engine. This flywheel is made of zinc with a steel magnet ring insert cast into the zinc die casting and also has a sintered hub.

All models are available with either rope starter or with a recoil starter or 110 volt electric starting.

To completely test the durability of this design, we accumulated over 140,000 engine test hours before deciding that the engine was satisfactory for production. During this time we ran every imaginable sort of test we could think of -- for instance, the cylinder casting was stressed coated and loaded to simulate the loads imposed onto the casting by the engine. By means of this method testing, we found that the cylinder crankcase casting had a weak point at the area where the crankcase barrel joins the crankcase of the engine and the casting was re-enforced at this point by putting in a suitable type of re-enforcing rib onto the casting. We, of course, thoroughly checked the temperatures all around the cylinder barrel and our preliminary work had been sufficiently accurate that it was not necessary to modify the finning to any great extent. We even blocked all of the fins on the cylinder with asbestos and ran the engine at full load on the dynamometer. Because of the tremendous heat conductivity of aluminum, this engine continued to run satisfactorily at wide open throttle with the cylinder cooling fins completely clogged. Although we do not recommend running the engine in this fashion, it is a fact that the engine will continue to run for a reasonable period under these conditions. This is quite important from the standpoint of operation in the field on rotary mowers. Even with the rotating screen protecting the cooling air intake, it is difficult to always keep the cooling fins from becoming completely clogged where the mowers are used for commercial grass cutting. For instance, one of the engines in Milwaukee County Parks which ran for a total of 568 hours last year was completely clogged at the end of the test. We found that even though the fins were completely clogged, the engine was completely satisfactory at the end of the test.

Fred Schneider has just accepted the trophies he earned at the Pontiac, Illinois Steam, Gas and Antique auto show in 1973. One of the high-lights at the Pontiac show is the brother team of Fred and John Schneider. They never fail to put on a good exhibit. Shown above is the 1904 Apperson they had at this show. Their equipment always runs and they tell me it is all their old family possessions of many years use.

We also ran dust tests to compare the wear of a cast iron engine with an aluminum bore engine of our final design to be. sure that under very dirty conditions of operation that our aluminum engine would operate satisfactorily.

The engines are mounted on rotary mowers and the mowers are fastened to a rotating merry-go-round. Under this condition all of the engines in one test are bound to get the same amount of dust, so that the results can be readily compared to see which unit is relatively the best from the standpoint of wear. Under this accelerated type of dust test we found that the aluminum engine in this test was slightly better in wear, than the cast iron engine. For instance, this test which is typical, showed the increase in gap on the top compression ring was .091 on the aluminum engine compared to .147 on the cast iron engine and the increase in oil ring gap was . 148 on the aluminum engine compared to .165 on the cast iron engine.

We also put test units out into the field, operating pumps, generators, blowers, etc. and our men checked the operation of these units regularly for reports of difficulties. One engine on a water pump accumulated 3100 hours, another on a concrete vibrator accumulated over 1800 hours, another on a blower accumulated over 1800 hours. All of these engines were in good running condition at the end of these tests. After making all of the above tests we made a few changes, one of them being to increase the size of the crankpin on the crankshaft. Our life tests in our plant indicated a weak spot at this point. We then built a substantial quantity of prototype engines made of sand castings and immediately started tooling for the new design.

After production engines had been in service for some time, we received a few complaints of rapid wear of both new and old models from some of the dusty localities, notably the drought areas of Texas and Oklahoma. We ran further dust tests and found that by fully venting the breather into the carburetor so that all air taken into the crankcase of the engine would be air which had passed through the oil bath air cleaner, that we could make a tremendous difference in the amount of engine wear. For instance, on an accelerated dust test, and we made many of such tests, we found that without a vented breather we could wear .019 off the crankpin compared to .0002 off the crankpin of an engine with the breather fully vented into the carburetor. We also found that by putting only a breather vent tube onto the breather that we could, without fully venting the breather, reduce the wear to approximately .0005 on the crankpin compared to .019 on the engine with the unvented breather. Needless to say we installed vent tubes on all engines. We also carried out an extensive program of getting the breather vent tubes installed on engines which had already been sent into the field, especially in parts of the country where dust was a big factor.

We then ran tests to determine whether this breather problem was any different on an aluminum engine than on a cast iron engine and we found that we had the same problem on the cast iron engine as on the aluminum engine and the difficulty had been brought to our attention because the Southwest had a prolonged period without rain so that grass cutting was an extremely dirty operation in these areas. These aluminum alloy engines have enjoyed tremendous success. We have produced over 7 million of these engines with chrome plated pistons. They are proving their superiority on a wide variety of installations, such as water pumps, generators, garden tractors, tillers, lawnmowers, blowers, grain elevators, concrete finishers and many other applications.

In June of 1957 the production of the older models of less than 3 H.P. with cast iron cylinders was discontinued because of the tremendous customer acceptance of, and preference for, the aluminum alloy engines.