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Engine | R-2800 Overhaul Manual 

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Auxilliary Supercharger Section
Supercharger Section
Power Section
Front Section
Supercharge Inlet
R-2800 Overhaul Manual Illustrations

Power Section

Crankcase Sections | Rear Support Plate | Crankshaft | Masterods and LinkrodsCam Gear Trains | Valve Tappets and Tappet Guides | Cylinders | Pistons

Crankcase Sections:  The three crankcase sections are held together by studs and special bolts. Two rows of cylinder mounting pads are located around the outer circumference of the crankcase assembly. Steel backed, prefitted bearings with leaded bearing surfaces are shrunk into the bore of the crankcase front and rear sections to support the crankshaft front and rear sections. The crankshaft center section is supported by a two -piece bearing of the same type, which seats in a liner shrunk into the crankcase center section and is held in position by retaining plates. The front and rear main bearings are rolled over into the crankcase at the rear and front ends respectively and are held from turning by four loc tabs on the flanged end of each bearing. The cams and cam bearings re supported on integral, circular bosses on the crankcase front and rear sections. The rear ends of the front cam reduction gears and the front ends of the rear cam reduction gears are supported in the crankcase front and rear sections respectively. The valve tappet guides and tappets for each row of cylinders are supported in the crankcase front and rear sections. Four engine lifting links are secured to the crankcase, two in the front section and two in the rear section.

Rear Support Plate:  The rear support plate is secured to the crankcase rear section and supports the rear end of each rear cam reduction gear and the front end of the rear counterbalance intermediate drive gear shaft.

Crankshaft:  The crankshaft is machined from three steel forgings. The front and rear sections are held to the center section by bolts which pass through the crankpins. The end of each crankpin and its mating face on the crankshaft center section are serrated. Each crankpin has a special sludge retainer on is I.D. The crankshaft assembly is supported by the bearings in the crankcase sections. The crankshaft cheeks, which are integral with the front and rear section, support pendulum type counterweights. Each counterweight is supported on two large roller pins which pass through steel bushed holes in the counterweight and crankshaft cheek. The counterweights are designed to dampen the four and one-half and second order vibrations in the crankshaft cheek. The counter-weights are designed to dampen the four and one-half and second order vibrations in the crankshaft. The front counterweight dampens the second order vibrations and the rear counterweight dampens the four and one-half order vibrations. The pendulum travel of the counterweights is controlled by stops which are bolted to the crankshaft cheeks. In the R-2800-42W engine, the rear counterweight is supported on two large bushings which are secured in the crankshaft cheek through which two pins support a biflar damper encased within the counterweight halves. The pendulum travel of the biflar damper is controlled by the two pins.

A secondary counterweight is provided at each end of the crankshaft to dampen second-order vibrations caused by the eccentric masses of the masterod assemblies. The front counterweight turns on a leaded sleeve bearing splined to the crankshaft front section. A counterweight spring drive gear, splined to the reduction drive gear coupling, drives the counterweight intermediate drive gear. The rear counterweight turns on a leaded surface on the outside diameter of the crankshaft rear gear. A counterweight spring drive gear, splined to an adapter secured to the end of the crankshaft, drives the counterweight intermediate drive gear. Each intermediate drive gear drives its counterweight at twice crankshaft speed.

The hollow front section of the crankshaft contains two steel backed bronze bearings which support the rear of the propeller shaft. The reduction drive gear coupling, which supports the crankshaft oil transfer bearing and the front secondary counterweight spring drive gear, and the crankshaft front gear are splined to the front end of the crankshaft. The rear end of the crankshaft has internal splines to accommodate the accessory drive shaft adapter.

Masterods and Linkrods:  The one-piece masterods are located in cylinders No. 8 and 9. The masterod bearings are one-piece steel shells having a special leaded surface. Each bearing is held in place by two retaining plates which fit on the faces of the masterod. The retaining plates have fingers which fit over bosses at each end of the full-floating, silver plated link pins. Eight 1-section linkrods are attached to each masterod by link pins and a piston attached to each masterod and link rod by a piston pin. Each retaining plate on the model -18WA and on the model -42W engines has an extra finger which aligns with a drilled oil passage in the masterod.

Cam Gear Trains:  The double-track, four-lube cams, which actuate the ales in each row of cylinders, rotates on bronze bearings with leaded surfaces ad are mounted in the crankcase front and rear sections. The front cam is driven through a train of gears which starts with the crankshaft front gear and runs through two cam reduction gears which are supported by the front support plate and crankcase front section. The rear cam is driven through a similar train of gears, and both cams are driven opposite to crankshaft rotation at 1/8 crankshaft speed.

Valve Tappets and Tappet Guides:  The tappet guides are shrunk into the crankcase front and rear sections. The outer ends of the tappet guides are supported in the crankshaft wall, and the inner ends are anchored in bosses forged integral with the crankcase. Steel valve tappets with roller type cam followers are mounted in the tappet guides. These tappets actuate the valve operating mechanism in the cylinders through tubular pushrods which have ball ends.

Cylinders:  The cylinder barrels are machined from steel forgings, and forged aluminum sleeves, in which cooling fins have been machined, are shrunk over the central portion of the barrel. The heads are of forged aluminum with machined cooling fins and integral ale rocker boxes. The cylinder heads are screwed and shrunk onto the barrels. Each cylinder has one inlet and one exhaust valve and corresponding valve sears. The cylinder head also incorporates bronze inlet and exhaust vale guides, helical inserts for two sparkplugs, and two steel bushings to support each rocker shaft. The cylinder barrels are provided with mounting flanges and are secured by studs and nuts to the crankcase.

Pistons:  The aluminum pistons are the full=skirt type. Each piston has five ring grooves and is fitted with compression rings in the first three grooves, dual oil control rings in the fourth groove, and a rectangular sectioned compression ring in the fifth groove. The top compression right is chromium plated on the side which bears against the cylinder wall. Pistons in the model -18WA and in the model -42W engines have flat tops whereas the tops of pistons in the model -18W engines are dome shaped.

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Last modified: September 18, 2012

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