The American Society ofMechanical Engineers

ROTARY DISTRIBUTORDIESEL FUEL INJECTION PUMPStanadyne, Inc.Diesel Systems DivisionWindsor, ConnecticutApril, 1988

National Historic Engineering Landmark

HISTORY

The year was 1947. The place was Hartford,Connecticut. Diesel power was about to make anhistoric move forward.

At that time, the world of high-speed dieselpower in the U.S. was very limited. Less than 5percent of all engines being built, even for non-automotive applications, were diesels.

Diesel power had proven to have realadvantages. But for many applications, the price

was prohibitive. A small ormedium-size high-speeddiesel engine simply cost toomuch compared to itsgasoline counterpart.

The high cost problemcentered around the dieselfuel injection systemsavailable at the time. Asimpler, less expensive formof fuel injection was neededbefore diesels could competeeffectively in the small ormedium-size high-speedengine field.

The answer came from aman who had learned aboutdiesel engines the hard way by installing and

Rotary Distribution Principle

maintaining diesel-electricgenerator sets in New York

City. His name was Vernon Roosa. And he broughthis answer to Stanadynes Hartford Division.

Roosa threw aside the traditional in-lineinjection pump with its pumping element foreach engine cylinder. Instead, he used a singlepumping unit to feed all the cylinders. Thus, thenew pump had the same number of partsregardless of the numberof cylinders.

Roosa then combined

this simple pumping system with the concept oninlet metering. This made the pump almost self-governing and meant that the actual governorcould be a simple, low cost mechanism, furtherreducing the cost and complexity of the pump.

The result was a revolutionary new design the first single cylinder, opposed plunger, inletmetering rotary distributor-type diesel fuelinjection pump.

It was the smallest, simplest fuel injectionpump the world had ever seen, at a much lowerprice than anything available before.

It opened up a new world for builders andusers of diesel engines a world that has beenexpanding ever since.

Simplicity Made It Practical Success did notcome overnight for the Roosa Master pump. Theindustry was full of skeptics who said it couldnever be produced commercially. Five years oftesting and development work were requiredbefore a single sale was made. Then, in March1952 came the first production order. HerculesMotors Corporation wanted pumps for OliverCletrac tractors.

Continental Motors followed Hercules as acustomer in 1953. Buda Engine Company, whichlater became part of Allis Chalmers, came next,and by 1956 Waukesha engines were utilizing therotary distributor pump.

Throughout this period, Roosa Masterengineers were busy working on making thepump even simpler, more versatile and lessexpensive.

Work began on the Roosa Master fuel injectionpump in May, 1947. From 1947 to 1952, activitieswere concentrated on laboratory developmentsand experimental installations. During 1952,

production of the Model A pump wasbegun. This model remained in

production through 1955.

The rotary distribution pump played a key role in the rapid growth of diesel usage in farm tractors.

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The period between 1955 and 1958 was adevelopment stage during which Model B andModel D pumps were introduced. Model B,with sand cast housing was the forerunner ofModel D of the die cast construction, and ModelD was replaced by the Model DB which beganproduction in 1958.

In general, the object of the Model DB wasstandardization. It incorporated all the basicfeatures of its forerunners, the Model A, ModelB, and Model D,into one standardhousing withbuilt-in pluses.Accessories suchas automatic

Size comparison of distribution type pump (left) totraditional in-line pump.

advance and electric shut-off could be built rightinto the DB housing. A single delivery valve waslocated in the center of the rotor, providingimproved part load regularity.

Due to the inherent design of the DB pump,cost-effective timing advance systems extended thediesels speed, and hence, power range to furtherencroach on gasoline engine use. In addition, thepump generally offered improved governorperformance, which was particularly attractive todiesel engine builders.

Most importantly, the Model DB pump couldbe mounted either horizontally or vertically.Because of the pumps lower driving torque, itcould be driven off smaller gears than other typesof fuel injection pumps. This meant that the pumpcould be mounted vertically in the location normallyused for the ignition distributor on a gasolineengine block.

This versatility was destined to save enginemanufacturers thousands of dollars by allowingthem to use the same basic block for both gasolineand diesel engines.

It paved the way for farm equipmentmanufacturers, who were already making their

own gasoline engines, to get into the production ofdiesel engines with a minimum of tooling costs.This move was to have a dramatic impact on thegrowth of high-speed diesels in the country.

Today, over 90% of the farm and industrialtractors produced in this country are dieselpowered. But back in the mid 1950s, the reversewas true.

The switch to diesel power on the farm gainedmomentum in the late 1950s when farm equipmentmanufacturers began offering diesel tractors pricedcompetitively with their gasoline poweredequivalents. Farm equipment manufacturers wereable to do this because they had started producingtheir own high-speed diesel engines. They wereable to manufacture these engines for little morethan their gasoline counterparts, thanks in largemeasure to the savings achieved by using rotarydistributor fuel injection pumps.

Soon, Allis Chalmers, Ford, InternationalHarvester, John Deere, J.I. Case, and MinneapolisMoline became pump users. By 1961, practicallyevery diesel farm tractor built in this country wasequipped with a Roosa Master pump.

The first generation of diesel engines built bythese manufacturers were basically modifiedgasoline engine blocks to minimize the toolingcosts associated with entering a new field. Newgenerations of diesel engines were soon to follow.

Farmers were finally able to enjoy all theadvantages of diesel power for a very smallpremium. And take advantage they did! The high-speed diesel engine was on its way to becoming animportant factor in American life.

Diesel engine builders were not the onlycompanies interested in the new design. Theintroduction of the pump also had a major impacton manufacturers of traditional in-line fuel injectionequipment throughout the world. The prospect ofhaving a license for manufacture of the rotarydistributor pump was obviously very desirable ifthese manufacturers were to compete in thesmaller, high-speed engine field.

On May 1, 1953, an agreement was signedgranting CAV Ltd., of London, England the rights tomanufacture andmarket pumps ofthe Roosa Masterdesign for theUnited Kingdom,with furtherexpansion to otherparts of the worldin subsequentagreements.

Early RoosaMaster pump configuration

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TECHNICAL BACKGROUND

General Description An external view of atypical pump is shown in Fig. 1 and an internalsection in Fig. 2.

The main rotating components are the driveshaft (1), distributor rotor (2), transfer pumpblades (5), and governor components (11).

The drive shaft engages the distributor rotorin the hydraulic head. The drive end of therotor incorporates two pumping plungers.

The plungers are actuated toward eachother simultaneously by an internal cam ringthrough rollers and shoes which are carried inslots at the drive end of the rotor. The numberof cam lobes normally equals the number ofengine cylinders.

Fig. 1 Pump

Fig. 2 Sectional view

The transfer pump at the rear of the rotor isthe postive displacement vane-type and isenclosed in the end cap. The end cap alsohouses the fuel inlet strainer and transfer pumppressure regulator. Transfer pump pressure isautomatically compensated for viscosity effectsdue to both temperature changes and variousfuel grades.

The distributor rotor incorporates twocharging ports and a single axial bore with onedischarge port to serve all head outlets to theinjection tubings. The hydraulic head containsthe bore in which the rotor revolves, the meteringvalve bore, the charging ports and the headoutlet fittings. The high pressure injectiontubings leading to the nozzles are fastened tothese fittings.

Distributor pumps contain their ownmechanical governor capable of close speedregulation. Both all-speed and min-max typesare available. The centrifugal force of the weightsin their retainer is transmitted through a sleeveto the governor arm and through a linkage tothe metering valve. The metering valve can beclosed to shut off fuel through the linkage by anindependently operated shut-off lever.

Components:1. Drive Shaft2. Distributor Rotor3. Hydraulic Head4. Delivery Valve5. Transfer Pump6. Pressure Regulator7. Discharge Fitting8. Metering Valve9. Pumping Plungers

10. Internal Cam Ring11. Governor12. Governor Weights13. Advance14. Drive Shaft Bushing15. Housing16. Rollers

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Regulating pistonRegulating slotInlet side

Regulating springRegulator

Thin plate

Orifice

Spring Adjusting Plug

Discharge side

Fig. 3 Transfer pump regulatorShoe

The automatic speed advance is a hydraulicmechanism which advances or retards thebeginning of fuel delivery from the pump. Thiscan respond to speed alone, or to a combinationof speed and load changes. A more detaileddescription of each pump area will be coveredin the following pages.

Transfer pump pressure regulation Refer toFig. 3 for the following description. Filtered, lowpressure fuel from an overhead tank or a liftpump passes through the transfer pump inletscreen. This vane-type pump consists of astationary liner and four spring loaded blades,which are carried in the rotor slots. Excess fuelis recirculated to the transfer pump inlet bymeans of the pressure regulator piston, spring,and ported sleeve. Fuel pressure from thetransfer pump forces the piston in the regulatorsleeve against the spring. The pressure curve iscontrolled by the pump displacement, springrate and preload, and regulating slotconfiguration. Therefore, pressure increaseswith speed.

The transfer pump operates consistentlyover a wide viscosity range determined bydifferent grades of diesel fuels and also whenaffected by varying temperatures. A thin plateincorporating a sharp-edged orifice is located inthe spring adjusting plug. Flow through anorifice of this type is virtually unaffected byviscosity changes. An additional biasing pressureis exerted against the spring side of the pistonand is determined by the linear flow aroundthe regulating piston and the flow through theorifice. With cold or viscous fuels a reducedflow occurs through the piston and sleeve

Plunger

Rotor

Leaf spring

clearance, and the additional biasing pressure isslight. With hot or low viscosity fuels theclearance flow increases and the pressure withinthe spring chamber increases. The regulatingspring and higher biasing pressure forcescombine to control the slot area. This controlmaintains a nearly constant transfer pumppressure over a broad range of fuel viscositiesand thus maintains stable automatic advanceoperation over various fuel types andtemperatures.

Hydraulic head and rotor Fig. 4 shows anexploded view of the rotor and the pumpingplungers. The cam rollers contact the innersurface of the cam ring form and push theplungers toward each other for injection. Theshoes act as tappets betweenthe rollers and plungers.

Cam roller

Leaf spring screw

Fig. 4 Rotor and plunger

Refer to Fig. 5. As the rotor revolves, its twoinlet passages register with the charging annulusports in the hydraulic head. Transfer pump fuelcontrolled by the metering valve opening, flowsinto the pumping chamber forcing the plungersapart. The plungers move outward for a distanceproportional to the amount of fuel required forthe next injection stroke. If only a small amountis admitted, as at idling, the plungers move outa short distance. If half-load is required,approximately half the pumping chamber isfilled. This process is known as inlet metering.

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Full-load delivery is controlled by themaximum plunger travel. This plunger travel islimited by the leaf spring as it is contacted bythe edge of the shoes.

Roller betweencam lobes

Plunger Meteringvalve Circular

fuel passage

Rotor

Leafspring

Cam

Shoe Inletpassages Charging

passageIransterpump

cam lobe RotorCamOutlet fitting

Delivery

Roller contacts

valve Discharge port

Pumpingchamber

Fig. 5 Plunger charging

Refer to Fig. 6. The leaf spring contacts twopoints near the outer ends of the rotor. As theadjusting screw is turned inward, the center ofthe leaf spring moves in and its ends extendoutward. This increases the maximum plungertravel. Turning the adjusting screw out has thereverse effect. The adjustment set point isretained by the screw head-to-leaf spring

Cam ring

Leaf springPlungers

Fig. 6 Cam, plungers and leaf spring

friction and the coating material on the screwthreads.

As the rotor continues to revolve (Fig. 7),the inlet ports move out of registry and therotor discharge port indexes with one of thehead outlets. The rollers then contact opposingcam lobes which force the shoes inward againstthe plungers. At this point high pressure pumpingbegins. Further rotation of the rotor moves the

Fig. 7 Plunger discharging

rollers along the cam ramps forcing the plungerstogether. During the discharge stroke the fuelbetween the plungers is displaced into the axialpassage of the rotor through the delivery valveto the discharge port. The pressurized fuel thenpasses through the outlet fitting, enters theinjection tubing and opens the nozzle. Deliverycontinues until the rollers travel over the camnoses and begin to move outwardly. The pressurein the axial passage is then reduced, allowingthe nozzle to close.

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VERNON D. ROOSA

Vernon D. Roosa

Born on a farm in New York state, VernonRoosa came naturally to his inventive turn ofmind. His father, who raised Holstein cattle,devised a hydraulic dam to raise the water level,constructed a windmill and had one of the firstmilking machines.

Fascinated by mechanics as a youngster,Roosa had to leave school at age 15 because ofthe familys financialreverses. His first job asa gas attendant led to hisbecoming the stationmanager within a year.He left to attend anaviation engineeringschool. During theDepression, as amechanic with a large buscompany, he first becameinterested in dieselengines and finallylanded a job installingand maintaining a dieselpower plant.

He subsequentlywent to work for a LongIsland firm making dieselelectric generator setsfor New York apartments.

His inventions have ranged far beyonddiesel engine pumps. He holds 350 patents,both United States and foreign, which fill threethick volumes. Among them are a stapler, abutane lighter for outdoor fireplaces, a noveltoilet flush system, a nail polish remover bottlewith a brush, a gas tank filler and numerouselectrical switching devices.

The inventor has akeen interest in highereducation. He donated achair in applied scienceto Trinity College, wherehe once taught as anadjunct professor, and in1984, pledged funds fora chair in manufacturingengineering at theUniversity of HartfordsCollege of Engineering.In addition, to help traindisabled workers, heinvented a hands freehead lantern for theHartford Easter SealRehabilitation Center.The Center makes andsells the product to thegovernment, forest fire

Vernon D. Roosa

In the fall of 1939, to fill fighters, and on thecommercial market. He also developed anddonated the equipment for manufacturing thehead lamp.

the need for a variable speed and output generator,he concentrated on making a fuel injection pumpthat would meet the stringent requirements ofthis application and a year later had one inoperation. About this time, the armed serviceswere seeking a new method for close speedregulation of generator sets. Roosa produced asecond design, simpler and extremely small insize compared to other makes, with a self-contained plunger completely sealed against dirt,water and oil leakage.

This is the model that caught the eye ofStanadynes Hartford Division, in 1947. Roosacame to Hartford that year and embarked on afive year program to perfect his miraculous pump,and later a fuel injection nozzle and filter designwhich became widely used. He also designed anautomatic drill machine, required for thenozzle assembly.

Vernon worked closely and was respected byall major engine manufacturers worldwide. In1986 he received the SAE Edward N. Coleengineering award.

After 22 years at Stanadyne nurturing hisbrainchild through numerous improvements anddeveloping accessories, Roosa retired as vice-president of research and development to devotehis time to independent inventing, although heremained a consultant to the company.

At 77, he is still active in the design of newproducts from a fully equipped laboratory in WestHartford, Connecticut.

NATIONAL HISTORIC MECHANICALENGINEERING LANDMARK

DISTRIBUTOR-TYPE DIESEL FUEL INJECTION PUMPHartford, Connecticut

1952

Vernon D. Roosa invented the rotary distributor-type fuel injection pump in 1941. It

provided a compact, low-cost fuel injection system for diesel engines up to 200 HP.The first production order for 500 Roosa Master Model A pumps was received in

1952, and approximately 23 million distributor pumps have been manufactured by

Sranadyne and its licensees worldwide.

Vernon D. Roosa Inventor

Ernest J. Willson Development Engineer

Leonard N. Baxter assisted in developmentAmerican Society of Mechanical Engineers

1988

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ACKNOWLEDGEMENTS

The Hartford Section of the American Societyof Mechanical Engineers gratefully acknowledgesthe efforts of all who cooperated in thededication of the Distributor-Type Diesel FuelInjection Pump as a National HistoricMechanical Engineering Landmark.

The American Society of Mechanical EngineersRichard Rosenberg, PresidentDr. Wellen G. Davison, Vice President, Region IDonald W. Kitchin, Jr., History and Heritage,

Region I

ASME Hartford SectionRay Schneider, Chairman

The ASME National Historyand Heritage CommitteeDr. Euan F.C. Somerscales, ChairmanRobert M. Vogel, Smithsonian InstitutionDr. Robert B. GaitherDr. Richard S. HartenbergDr. J. Paul HartmanJoseph P. Van OverveenDr. R. Carson Dalzell, Chairman EmeritusCarron Garvin-Donohue, Staff Liaison

Stanadyne, Inc.Many dedicated Stanadyne employees

played a key role in the development of therotary distributor pump and its subsequentplace in diesel engine history. Stanadyne thanksthem all and would especially acknowledge thefollowing people.

George J. Michel, Jr.Gerald R. BouwkampJames A. Taylor (deceased)Michael J. Perrin (deceased)Augustus D. RoseC. Eugene BradyPaul H. WabrekJames J. FordThomas D. HessVernon D. RoosaErnest J. Willson (deceased)Leonard N. BaxterFrank Link

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