National Historic The American Society of Mechanical Engineering Mechanical Engineers Landmark

Jacobs® Engine Brake Retarder Bloomfield, Connecticut October 17, 1985 would normally be the power stroke, no pressure remains in the cylinder to act on the piston. Thus, the energy transferred from the driving wheels into the compressed and highly heated air (through gravity or forward momen- tum of the vehicle) goes mostly out the exhaust pipe, with a portion en- tering the cooling water from heat transfer through the cylinder walls. This has two results: on long down- grades the engine cooling system re- mains at near normal operating temperatures, and in the case of tur- bocharged engines there is sufficient exhaust energy to allow the turbine of the turbocharger to power the companion compressor and main- tain a high enough degree of boost to increase the retarding effort. A diesel, being a free-breathing engine by virtue of having no valving or venturi restrictions (carburetor) offers inherently less braking effort than a gasoline (spark ignition) en- gine even though the diesel engine has about twice the compression Clessie L. Cummins at work in his Sau - A History of The Jacobs ® ratio of the spark ignition engine salito shop. Engine Brake (which obviously means that it re- By C. Lyle Cummins, Jr. quires more effort to force up the Long steep downhill grades not only piston on the compression stroke), provide anxious moments for truck that work is given almost entirely drivers, but they also add extra back (less friction and heat transfer hours behind the wheel. The advent losses) when the air is allowed to ex- of the Jake Brake® compression en- pand on the next outward stroke. gine retarder brought an oppor- Conversely, the spark ignition engine tunity to end this fear almost entirely becomes a vacuum pump when and at the same time to safely raise being motored with the throttle average speeds. closed. This is a basic reason why To a motorist or a bystander, the the spark ignition engine is so much Jacobs Engine Brake, commonly less efficient than the diesel or com- known as the “Jake Brake,” iS pression ignition engine when oper- sometimes associated with a char- ating at idle or light loading. Of acteristic “popping” exhaust noise course this assumes that the fuel is heard when a truck is decelerating essentially shut off and no combus- or descending a hill. To the truck tion can occur–which is true with driver, it is a device that turns his the diesel engine but not so with the engine into a retarder, giving him spark ignition engine. about the same braking effort at the Although the Jacobs Engine wheels as his engine puts out when Brake has been on the market since it is producing power. 1961, the need for it was terrifyingly How does this work? Quite sim- demonstrated to its inventor, Clessie ply, the Jake Brake retarder turns a L. Cummins, some thirty years ear- diesel engine into an air compressor. lier. In those times, Clessie was try- Rather than store the energy of the ing to prove the worth of the pressurized air in the cylinder, cre- automotive diesel engine as well as ated by the piston coming up on the to learn firsthand the kind of engine compression stroke, the Jake Brake the trucking industry most needed. retarder mechanism hydraulically In August of 1931, one of these com- opens the exhaust valve near the bination test and publicity stunts end of the upward piston stroke. The found him, Ford Moyer, and Dave stored energy in the cylinder iS re- Evans driving a Cummins Diesel- leased to the atmosphere so that powered Indiana truck from New when the piston descends on what York to Los Angeles in an attempt to set a new truck speed record across the continent. One of the first things proven was that the diesel engine does in- deed offer less braking than a gas- oline engine of equivalent size, placing a greater burden on the vehi- cle’s braking system. With the higher speeds being driven on this test run, plus the load on board that included the Cummins Diesel 1931 Indi- anapolis race car and extra equip- ment, the intrepid trio soon found it necessary to place more reliance on prayer than on brake linings. All went reasonably well until the descent of Cajon Pass, on old U.S. 66 leading into San Bernardino, Cal- ifornia. A long, winding and steep gravel road, criss-crossed by a busy mainline railroad, almost led to the demise of the truck, its driver Clessie L. Cummins (who was to become the “father of the U.S. automotive die- sel”), and a frantic crew who were tossed around their bunks in the cargo box behind the cab. In Clessie’s words: “About dusk on the fifth day, we caboose loomed out of the darkness. An American Automobile Association reached the top of Cajon Pass west of Its red lights cleared the highway just official (with flag at left) begins count- Barstow, California. Before retiring to down for a December, 1931 endurance as we reached the tracks We had run at Indianapolis Speedway. The Cum- the sleeping compartment, Dave had escaped certain death by Inches.” mins Diesel-powered Indiana truck had warned me against this thirty-five- The memory of the dark night been used in an August, 1931 cross- mile stretch of mountainous down- was never forgotten. The venerable country trip which demonstrated the grade. ‘Wake up Ford and me when diesel-powered lndiana did set a new need for an engine brake. Clessie L. Cummins, Ford Moyer, Dave Evans and you get to Kayhone Pass,’ I had un- coast-to-coast truck speed record of T. E. Myers (Speedway Vice President) derstood him to say, ‘I don’t want to 97 hours, 20 minutes running time are poised in readiness for the run. be in this box when you start down for the 3,214 miles, and one of its that twister with the kind of brakes drivers vowed someday to make his we’ve got.’ I had heard but not seen, engine work when going downhill just my Spanish being nonexistent, the as well as going uphill. word Cajon failed to register when the Twenty-four years later, in 1955, sign appeared. Soon, however, I real- Clessie Cummins’ inventive genius ized my error. The brakes wouldn’t again addressed the engine retarding hold. Now running in third gear, I tried question. In retirement in Sausalito, desperately to get into a lower speed. California, he began studying what Nothing doing. I saw I would just have might be done to turn his engine into to ride it out. an effective “brake.” Well down the long grade by now, It was also in 1955 that Clessie I suddenly saw something moving enticed his youngest son Lyle, a across the road ahead. There was a graduate mechanical engineer, to long dark shadow and then a red join forces and form the large con- glow flared in the sky. I realized with cern which he named Centco (short new alarm that a freight train was for Cummins Enterprises Company), cutting across our path. The truck a name chosen to keep the house- roared on. Dave and Ford screamed hold accounts separate from bloody murder in the compartment Clessie’s ventures in the basement. behind me. And I clung to that steer- The basement was actually an area ring wheel like a madman. Had Mack that included an office with a view, a Sennett been on hand with a movie soon to be equipped machine shop camera, he would have gotten with the usual lathes, milling ma- enough footage for one of his famous chine, etc. and a four-car garage. An- Keystone Kops features. other member of the Centco team, As we raced inexorably toward added in 1957, was Ray Hansen. the crossing and doom, the train’s Hansen was an able machinist, The Engine without a Jake Brake welder, and sheet metal bender scratch pad and was telephoned During the piston’s normal compression whose hobby was building and rac- back to son Lyle in Sausalito early the stroke (2), air compressed in the cylin- next morning. By the time the vaca- ders raises internal heat to almost ing sports cars. 1,000°F. At this point, fuel is injected Lyle’s initial effort was expended tioning Stella and Clessie Cummins and combustion occurs, raising temper- on thermodynamic analyses to prove returned home, layouts of possible ature even further. Pressure from this the Clessie’s idea of turning the en- design solutions were waiting, albeit expanded gas forces the piston down gine into a compressor really would in retrospect, they were more compli- (3). The engine has thus produced the positive power necessary to turn the provide sufficient retarding potential. cated than proved to be necessary. crankshaft. The answer was an unqualified An important subtlety of the in- “yes,” but how to do it? One scheme vention made it novel enough that a was to clutch-in a high pressure very broad patent was ultimately pump and a timed distributor to granted, affording strong patent pro- carry hydraulic force to a slave tection dating from the time of its piston, which in turn would act on the application. The application was in exhaust valve to open it at the proper the U.S. Patent Office for seven years point on the compression stroke. A due to new pertinent additions being second method considered was to twice added after the original filing in use a multi-plunger pump 1957. hydraulically timed to act on the A very thorough patent search slave piston. While both of these made prior to filing Clessie’s patent methods could be made to work, nei- showed that the idea of opening a ther was considered a best solution. valve, exhaust or otherwise, at or An idea for a practical method, near the end of the compression emphasizing the heat of the inven- stroke was not a new one, some re- tion, came to Clessie in 1957 during lated patents dated back to 1918. a sleepless night in a Phoenix, Ari- These were either for the purpose of zona hotel room. The idea that hit easing the cranking load during start- Clessie revolved around taking ad- ing or for actual engine retarding. vantage of perfectly timed motion al- A vital point had always been ready built into Cummins and Detroit overlooked, however; this prevented Diesel engines; these engines have a any of the old braking patents from third cam on the main camshaft that becoming commercially feasible activates the fuel injector of each cyl- products. None of the prior art made inder. A simple retrofit mechanism the conversion to the braking mode should be able to transfer this motion without altering in some way the ex- to open the exhaust valve. The idea isting valve train, i.e., cam, pushrod, was jotted down on a bed-side rocker lever, etc. Clessie’s idea was to The Engine with the Jake Brake The key to the Jake Brake’s perfor- mance is the slave piston. Hydraulically actuated, the slave piston opens the en- gine’s exhaust valve (2A) near the end of the compression stroke. The com- pressed air, which normally forces the piston down even though no fuel is added, is vented through the exhaust system (2A). By releasing this energy, the Jake prevents any positive power being exerted on the piston. The vehi- cle’s forward momentum provides the energy needed to return the piston to its bottom position (3A), thus complet- ing the process of generating maximum retarding power with a Jake Brake.

superimpose onto the existing ex- ated piston to hold the injector handling was far from that of a sports haust valve motion an already avail- plunger seated whenever the locking car! able and correctly timed motion (the pin was engaged. This piston had a Downhill braking performance of injector cam, for example, but not wedge-shaped outer end acting the 6,500-pound test wagon with its limited to this cam) without prevent- against an extension to the injector cylinders acting in the mode of air ing the exhaust cam from acting to plunger spring retainer and bridging compressors was most encouraging. open and close the exhaust valve as it around the injector rocker level. Second gear allowed the diesel en- normally would during non-braking The vehicle selected for first field gine to slow down from governed times. tests of the completed device was a speed to an idle in less than 200 How best to transfer the injector 1955 GMC “Suburban” station yards on a thirty percent grade. Con- cam motion was developed during wagon repowered with a Cummins siderable retardation was also easily the next two years. The simplest JN-6 diesel engine. The purchase obtained on direct drive on six per- method was to tie together mechan- and conversion were made in early cent hills. After recovering from their ically the injector and exhaust rocker 1956 when the vehicle was used for fright at the way the vehicle began its levers with a one-way locking con- some investigative work prior to the downhill test runs in San Francisco, nection so that the injector cam final “assault” with the engine brake riders witnessing the operation of the could open the exhaust valve, but the prototype. The Cummins JN-6 diesel invention as invited guests came exhaust cam could not actuate the engine had a displacement of 401 away pale but visibly impressed. injector plunger. The experimental cubic inches and was rated at 125 Since the major market potential construction consisted of blocks BHP at 2,500 rpm. Because of addi- was in the Cummins NH series die- welded to standard rocker levers tional engine weight and length, as sels at that time, the engine brake over the rocker shaft bosses. The in- well as accessibility reasons, heavier mechanism was scaled up and jector rocker block had a deep springs were added in the front and adapted to a Cummins NHRS super- curved slot open to the rear. Engine the Suburban’s frame, fenders, and charged model of 300 BHP at 2,100 oil pressure, controlled by a three- hood were lengthened by some rpm. The chief reason for selecting way solenoid valve and acting eleven inches. The sheet metal work this model was simply because a pair through a hydraulic piston, forced and modifications were done in the of these diesel engines were installed the pin into the exhaust rocker lever body shop of British Motors, the in Clessie’s 96-foot yacht Canim slot. Engagement occurred during Rolls Royce dealer in San Francisco. based at the Sausalito harbor! the exhaust, intake, and part of the Clessie’s friend Kjell Qvale, who Clessie saw no reason to invest large compression strokes on a catch-as- owned the dealership, suggested sums of money in a test facility with a catch-can basis. that the shop would be a good place motoring dynamometer when one of Because the Cummins fuel sys- to perform the “surgery.” Needless his boat engines could tell almost as tem at the time tended to inject some to say the work was beautiful, but much! By powering the front four cyl- fuel into the cylinder, even during expensive! The longer wheelbase inders to drive the rear two, continu- coasting conditions, it was necessary and additional weight helped the ous downhill braking conditions were to add another hydraulically-oper- suburban’s riding characteristics, yet simulated on the two acting as com- were barely warm to the touch. Bill said he never wanted to drive a truck again unless it was equipped with Clessie Cummins’ new invention! Marketing of the engine brake began while the design and patent processes were still being com- pleted. As a result of a prior contrac- tual arrangement, Clessie was obli- gated to show his ideas first to Cum- mins Engine Company. This was done three times during the engine brake development because of the patent refilings. The novelty of the idea, which broke into untried mechanical areas, plus the uncertainty of its commercial merit caused it to be re- jected by Cummins Engine Company. Lest incorrect surmises drawn, all of the other major manufacturers contacted, who either built or used “three cam” diesel engines in their trucks, also turned down the oppor- tunity to license or buy the idea. Nonetheless, Clessie was not dis- couraged, because he also was thinking about starting a small com- pany to manufacture the brake him- The Jake Brake today. pressors, without the boat (truck!) self. At seventy years of age, he was even leaving the dock. (In the Cum- just getting his second (or tenth) mins NH series six-cylinder engine, wind! each head covers two cylinders.) The story of how Clessie Cum- Although the principles were mins’ engine brake became the Jac- proved by mechanically transferring obs Brake retarder is the tracing of an the injector motion, a more practical improbable and complicated set of method was to use a fully hydraulic circumstances. Follow this through if motion and force transfer. A test was you will: Clessie’s brother Deloss next made with the rudiments of a Cummins, once service manager of final hydraulic design that later be- Cummins Engine Company, lived in came the production prototype. The Phoenix, where he and a partner ran first retarder housings of the proto- a successful Cummins engine dis- type design were installed on a Cum- tributorship. He visited Clessie oc- mins diesel engine in a truck owned cassionally in Sausalito and knew of and operated by the Sheldon Oil the ongoing “basement” activities. Company. The work was done at Deloss’ son Don was serving in the Sheldon’s shop in Suisun, California U.S. Coast Guard, with one of his last during August 1959. Sheldon Oil stations being in New London, Con- Company trucks were then hauling necticut. The Cummins Engine Com- 400°F asphaltic oil to “batch plants” pany distributor in nearby Hartford making highway paving material. was a good friend of Deloss and had The initial run with the engine known Don Cummins for years. This brake was to one of these plants just resulted in an invitation to Don to at the eastern base of the grade, come to Hartford; naturally the visit down the Sierras on U.S. Highway 50 would be more pleasant if Don could near Lake Tahoe. Bill Hill, an eigh- also spend some time there with a teen-year veteran driver for Sheldon, person more his age (especially a said he normally was forced to pass person of the opposite sex). Thus a the turnoff onto the job site because blind date was arranged with the of faded brakes; he would come back daughter of a good friend. The girl’s when he could slow down enough to father, Bob Englund, also happened turn around! With the engine brake to be a Vice President of Jacobs Man- he needed to use his wheel brakes ufacturing Company, the world’s briefly only two times on the descent leading manufacturer of drill chucks. from the summit. The turnoff was There was a mutual attraction be- easily made, and the brake drums tween Don Cummins and Roberta Englund, and in due course wedding bells were heard. Don knew through his dad that Uncle Clessie was working on some kind of engine brake as one of his retirement projects, and the word eventually reached the ears of Jacobs Manufacturing Company’s President Louis Stoner and his brother Arthur, then head of engineering at Jacobs (The description of what was going on in California by this time was rather remote from any relationship to the actual device!) Since Jacobs was actively seeking new projects in order to diversify its operations, the “air compressor” brake that Bob En- glund’s son-in-law’s uncle was work- ing on might be worth looking into! Just weeks before the Sheldon Oil Company test began, a letter was received in Sausalito asking if the Stoner brothers and Page Wodel, a capable young Jacobs salesman, could come to California to see what invention Clessie had under develop- ment. A demonstration of the brake on the boat engine, plus the infec- tiousness of Clessie Cummins’ deter- (now named Vehicle Equipment Divi- An early Jake Brake. mination and foresight experienced sion) for manufacture of the engine during a yacht ride on San Francisco brake. Bay, excited the visitors to the point Although there was never any that agreement was soon reached to doubt on Clessie’s part as to the build brake assemblies for ten en- quality of the product that Jacobs gines as quickly as possible from would build, he did have reservations drawings that Lyle provided. that they could succeed in a new An option agreement between market totally foreign to their pre- Clessie Cummins and Jacobs Man- vious experience. Thus, while he was ufacturing Company was entered selling Jacobs on the value of his en- into in December of 1959. Based on gine retarder, they in turn were the results of Centco-conducted wooing him on their ability to make it tests with trucks using the Jacobs- a commercial success. made units, along with market sur- The “Clessie L. Cummins Divi- veys and independent tests, Jacobs sion” title was chosen to show that it would then be allowed to make their had a tie to the man whose name was decision as to whether or not they on the diesel engines for which the would exercise the option. Consoli- product made by that division was to dated Freightways, Pacific Inter- be used. The final contract between mountain Express, Willig, Sheldon, Clessie and Jacobs Mfg. Company O-N-C, and other trucking firms specified that he would also be will- kindly furnished test trucks. While ing to act in an advisory capacity several minor problems appeared, when either party felt the need. This the tests demonstrated conclusively clause was actively exercised during the engine brake’s improved, safer the first few years. Others in the operation, as well as a large potential Cummins family also participated. cost savings in brake linings and Deloss Cummins assisted Page drums. Wodell in establishing a dealer net- Increased engine life, due to the work. (For a number of years, all fact that the engine remained hot on sales were on an aftermarket basis.) long downhill runs, was an advantage Don Cummins, now a mechanical en- proven later, though assumed by gineer, went to work for Jacobs, and, Clessie from the very beginning. In in addition to his official title of sales April of 1960, Jacobs Mfg. Company and service engineer, provided prac- made the decisions to establish its tical know-how for many years in new Clessie L. Cummins Division more areas than his title indicated Lyle Cummins was also involved with Jacobs Mfg. Company, first while on loan from Centco, and later in the Jacob engineering department work- ing in product design. Methods used by Lyle and Don were sometimes un- orthodox, but sudden situations aris- ing with a new product, in a company unfamiliar with the market where the product was used, often called for direct and “interesting” approaches to problem solving! Nevertheless, the Jacobs organi- zation, particularly under the direc- tion and dedication of Page Wodell in sales and Gerry Haviland (Chief Engi- neer after Arthur Stoner’s retire- ment), rose to the occasion and a competent team was the result. The first production units for the Cummins NH series engines left the factory in 1961, followed shortly by a brake for the Detroit 71 series. Today Jake Brake retarders are available for the major U.S. heavy duty diesel truck engines; Caterpillar, Cummins, Detroit Diesel and Mack. Military ap- plications have also become signifi- cant with Jacobs retarders, being standard on several U.S. military vehicles. Clessie Cummins’ idea for mak- ing a diesel engine work downhill as well as uphill has thus been imple- mented. The Jake Brake retarder has become a major contributor to greater control and safer operation of heavy trucks worldwide.

The text of this brochure is based on an article by C. Lyle Cummins, Jr., from Diesel Car Digest, Vol. 6, No. 4, Winter, 1981, reprinted here with the kind permission of its editor, Robert E. Flock, Diesel Car Journals, P.O. Box 160253, Sacramento, CA 95816.

The Jacobs Engine Brake is the 81st National Historic Mechan- ical Engineering Landmark des- ignated since the program be- gan in 1973. In addition 18 International and 9 Regional Landmarks have been recog- nized by the Society. Each rep- resents a progressive step in the evolution of mechanical en- gineering, and each reflects an influence on society. Forfurther information contact ASME, Public Information Dept., 345 The American Society ofMechanical Engineers East 47th St., New York, N.Y. 345 East 47th Street NewYork NewYork 10017 H108