Overhaul on the 0320 A1A Lycoming Engine - Research Paper Example

 Task: To disassemble a reciprocating engine using the applicable manufacturer’s maintenance manual, select the proper precision measuring equipment and dimensionally measure all parts using criteria found in the table of limits and recording all findings on the overhaul forms and determine if parts are serviceable or have to be replaced. Overhaul on the 0320 A1A Lycoming engine Lycoming O-320 refers to an extensive family of aspirated, air-cooled, 4-cylinder, direct-drive engines which are used in light aircrafts, for instance, Cessna 172 as well as Piper Cherokee. Its diverse variants are rated as either 150 or 160 horsepower which is equivalent to 112 or 119 kilowatts. As the name suggests, the engine’s cylinders are horizontally arranged in opposed configuration alongside a 320 cubic inches displacement. In this project, 0- 320 Lycoming engine was subjected to evaluation and inspection. To successfully accomplish this, a number of assumptions were raised in assessment of the machine’s actual serviceability as well as condition of the engine and its various components. Original condition of the engine before disassembly The process began with a short inspection prior to disassembly with major problems being recorded early enough. Such included inadequate safety wiring of the propeller bolts. Such problems are likely to cause unnecessary vibrations in instances where the propeller gets imbalanced. Additionally, various hardware such as spinner screws were found to be missing raising questions as to its ability to function as required. A number of critical engine components including magnetos, carburetor, operational fuel pump, vacuum pump and starter bolts were not appropriately installed. Additionally, there were no belts to drive the engine, the generator mounting was loose and disconnected from the spark plug leads. Additionally, the cost issue emerged as to whether it would be economical to service the engine or to simply purchase a rebuilt engine. In general, pre-inspection of the engine before being disassembled revealed a number of missing items. These included the following: Missing generator belt drive Poorly installed ignition harness Mission exhaust hardware Wire from starter was loose & disconnected including hardware All of the safety wire around the cylinder was missing On disconnection of the generator, carburetor was found missing, and so was the magnetos and magneto gasket. Similarly missing were starter bolts which were missing from sparkplugs. Additionally, the oil filter was missing. Additionally, the engine mount bushings were worn out. Engine strip down After pre-inspection, the engine was removed from the aircraft with aid of the IAW Piper Apache Service Manual. This then paved way for stripping down the engine. However, before stripping, the engine was cleaned wit help of degreaser, metal brush and wire brush. The engine was then stripped down with help of the O-0320 Overhaul Manual, alongside relevant Service Bulletins and Instructions for the O-320 Model engine. The engine was then stripped using the O-0320 Over-Haul Manual. The crank cases, conrod, and piston assemblies, among others were then removed. The same was done for the crankshaft, the gear shafts, and the gear clusters. The removed parts were all labeled to make sure that replacements will be done in the appropriate position. The most important parts that were designated for labeling included the smaller ones including the valve end caps, piston/conrods andmain bearing shells. In general, the entire stripping process was guided by the O-0320 Over-Haul Manual, as well as the Service Bulletins and Instructions for the O-320 Model engine. Tools and Equipment Applicable manufacturer's overhaul manual for selected engine. Overhaul forms for record keeping. Reciprocating engine. Engine overhaul stand. Parts storage racks and bins. Measurement tools. Parts cleaning facility. Student hand tools. Examination It had initially been anticipated that the problems encountered would be minimal in nature. It was expected that items such as piston rings will be the ones requiring replacement. However, on stripping the machines, more elaborate challenges were registered. It became apparent that the engine had problems way much more than we had anticipated. A closer look at the pistons revealed that most met the manual standards and were within the set standard tolerance limits. The cylinder bores within the engine were found to be in a perfect condition with criss-cross honing marks fromprevious reconstruction being clearly visible. There were no observations of bores scoring and no discernible lip was found at the cylinder’s top. The main bearings and the crank journals were also checked and found to be in substantially good condition. The little end bearings were also found to be in perfect condition and within the tolerance limits. Also examined was the clutch assembly which was in good condition. The same can be said of the pressure plates which did not show any signs of ‘blueing’ or even warping. The clutch basket was also found to be in perfect condition. The friction plates were also found to be in good condition and with acceptable tolerance limits. However, all was not as perfect as it may seem, a number of items were found to be missing including the following: Missing Parts and Service Replacement Sets Seal and Gasket set Part No Description Qty Per engine 72053 Gasket, Governor drive 2 8313 Gasket, Vacuum pump 2 62922 Seal Shroud tube 8 60096 Gasket, fuel Pump 1 71973 Gasket, Intake flange 4 60592 Gasket, Intake flange 4 LW-11997 Seal, Crankshaft oil 1 60820 Gasket, Oil suction tube flange 1 74068 Ring, Oil level gage seal 1 61165 Seal, Tachometer shaft 1 61173 Gasket, Oil pressure housing 1 61183 Gasket, Accessory adapter 1 68972 Gasket, Oil Sump 1 61531 Gasket, Hydraulic valve 1 62224 Gasket, Magneto adapter 4 65321 Gasket, Exhaust Flange 4 66224 Gasket, carburetor 1 71481 Seal, Oil 4 68315 Gasket,Accessory drive adapter 1 70310 Seal , Shroud Tube 8 STD-208 Seal, oil 1 STD-294 Gasket, Annular 2 72075 Seal, Oil 6 72091 Ring, Oil Seal 2 STD-1045 Seal, Oil 6 61523 Container 1 69551 Gasket, Accessory pad cover 1 69720 Gasket, DalaAccessory drive cover 1 69827 Gasket, Governor spacer 1 STD-548 Seal, Oil 1 66224 Gasket, Carburetor 1 74065 Ring, Oil level Gage Seal 1 61156 Lock plate, Crankshaft gear 1 76501 Gasket 1 72059 Gasket 1 69345 Spacer 4 LW-12273 Spring 4 72078 Lock plate, Camshaft gear 2 73817 Lock plate, Crankshaft idler gear shaft LW-12272 Lock plate, Shroud Tube 4 LW-12795 Gasket 1 STD-111 Gasket 1 STD-213 Seal 1 1691-c Gasket 1 69164 Gasket 1 71646 Seal 1 72312 Ring oil-Seal 2 73383 Lock plate 1 72312 Ring, Oil Seal 2 73383 Lock plate 2 74524 Ring, Oil Seal 1 LW-12681 Magneto Gasket 2 78728 Carburetor/ Model MA-42pa 1 It is however pitiful than no information on previous rebuild had been availed. The supplied information did not cover any of that and circumstances which the engine had failed had not been included in the availed information. Measurements Most, if not all the componentswere measured with the help of appropriate measuring instruments. The measurements were recorded in the table as shown in the table below: REF# NOMENCLATURE DIMENSIONS   CLEAREANCES         Min/Max Ser. Max Actual Dimensions Min/Max Ser. Lim Actual Clearance Comment 511 O.D. of Tappet 0.7169 0.7166             0.7177             #1 Int Tappet 0.718             #1 Exh " 0.719             #2 Int " 0.717             #2 Exh " 0.717             #3 Int " 0.7175             #3 Exh " 0.7171             #4 Int " 0.7173             #4 Exh " 0.7173                             511 I.D. Tappet Bore in 0.7187 0.7203             Crankcase 0.72               #1 Int " 0.718   0.71825             0.7185               #1 Exh " 0.719   0.71925             0.7195               #2 Int " 0.717   0.7183             0.7196               #2 Exh " 0.717   0.71725             0.7175               #3 Int " 0.7175   0.7173             0.7171               #3 Exh " 0.7175   0.7178             0.7181               #4 Int " 0.7171   0.7172             0.7173               #4 Exh " 0.7173   0.71675             0.7162             513 Tappet Socket and       .002L         Body       .005L .007L       #1 Int 0.5947   0.5938           Socket OD 0.5929               #1 Exh " 0.5943   0.5935           Socket OD 0.5927               #2 Int 0.5947   0.5943           Socket OD 0.5939               #2 Exh 0.593   0.59285           Socket OD 0.5927               #3 Int 0.593   0.5929           Socket OD 0.5928               #3Exh 0.5947   0.593           Socket OD 0.5913               #4 Int " 0.5927   59205           Socket OD 0.5914               #4 Exh 0.5919   0.5929           Socket OD 0.5939             514 Camshaft and       .002L .006L       Crankcase       .004L         Front       1.031                 1.028         Center       1.032                 1.029         Rear       1.035                 1.028                         515 Camshaft End     0.003 .002L .015L 0.003     Clearance       .009L                         516 Camshaft Run-out       0 .006L 0.001     Center Bear. Jour       .0010L   0   Engine components analyzed Valve Operating Mechanism: this is a typical type of camshaft located above and lies in parallel to crankshaft. This system was found to function appropriately with all components matching the set system standards as per the product manual. Crankcase: the assembly of the crankcase has two reinforced aluminum alloy castings, which are fastened together using studs, bolts and nuts. The crankcase was found to be okay with most components matching the required standards. Nonetheless, some bolts and nuts fail to meet the prescribed limits. The tolerances are a little way off the desired limits. Crankshaft: we found the crankshaft to be made of chrome nickel molybdenum steel forging with all the surfaces nitrided. These were found to be fine. Connecting Rods: these rods are made using "H" sections from alloy steel forgings. The rods are replaceable and bear inserts in crankshaft ends as well as bronze bushings found at the piston ends. In this section some bolts and nuts were found to be missing. These were bolts intended to pass through each of the caps. Pistons: the pistons were made from aluminum alloy. Some pistons were found to be missing and requiring replacement. Accessory Housing: as stipulated in the manual, the accessory housing is made using aluminum casting and is fastened to the crankcase’s rear and to the sump’s top. This was found to be perfectly operational. Cooling System: These engines are designed to be cooled by air pressure. Baffles were provided to build up a pressure and force the air to flow through the cylinder fins. One of the fins was found to have worn out and non-effective. Torque values for the parts Connecting Rod Nuts = 480 in .lbs Magneto Numb (to attach drive member to magneto) Bendix sintered Bushing gray 120-150 in .lbs Magneto NO (To attach drive member to magneto) Bendix Steel Bushing 170- 300 in. lbs Magneto Nut (To attach drive member to magneto) slick 120-300 in. lbs Magneto Nut (To attach drive member to magneto) 15in .lbs Rocker Box Screws 50 in.lbs Exhaust Port Studs 40 in.lbs min Spark Plugs 420 in .lbs Fuel Pump vent fitting (approximately two turns beyond finger tight) = 96 in. lbs Alternator Pulley Nut 450 in. lbs Alternator Output Terminal Nut = 85 in lbs Starter Terminal Nut: = 24 in. lbs Piston Cooling Nozzle in Crankcase = 100 in lbs Oil filter bolt (Ac Can and element type) =300 in.lbs Oil Filter (throw Away Type) 240 in lbs Converter Stud 720 in. lbs Carburetor Drain Plug 144 in lbs Oil cooler by pass Valve =300 in. lbs Oil Pressure Relief Valve == 300 in lbs Hose clamps (Worm type) 20 in lbs Hose Clams (Worm type) 45 in lbs Cylinder Head Drain Back Hose clamp’s = 10 in. lbs Alternator Auxiliary Terminal Nut = 30 in. lbs Crankshaft gear bolt=660 in lbs Cylinder hold down stud= 100 in lbs Cylinder hold down nut = 300 in Lbs Cylinder hold down nut=420 in lbs Allen head screw (Diaphragm fuel Pump) 225-250 in. lbs Oil cooler bypass valve Com Load Min= 6.50 Max 7.25lb Serve Max 6.41lb min Oil pressure relief valve = 300 in lbs Hose clamps ¼ Hex Head and below= 20 in lbs Hose clamps5/16/ Hex Head and above = 45 in lbs Head drain back hose clamp= 10 in lbs Crankshaft gear bolts ½-20 = 660 in lbs Exhaust Transition studs. 5/16 if 5/16/(Driving Torque)-18= 100 in lbs Exhaust Transitions _Studs (Driving torque)= 200 in lbs Accessory plate bolts Magneto Nuts =120-150 in lbs Rocker box screw = 50 in lbs Exhaust port studs =40 in lbs Fuel Pump net fittings = 96 in lbs Alternator pulley nuts= 450 in lbs Alternator output terminal Nut =85 in lbs Parts replaced VISUAL INSPECTION AND ANNOTATE CONDITIONS: 1. Crankcase Finished Surfaces: one of the sides of the crankcase had a worn out finished surface with minor signs of corrosion. Additionally, there was a bent edge which was out of round and hence required replacement. Some metal particles were also noted with a few score marks and scratches. This required minor polishing. Studs: while most of the studs were okay, two were found to be damaged and required rep Oil Passages: The oil passages were okay except for a few clogs which only required cleaning. Flanges: excellent condition Thrust Bearings: worn out and requiring replacement Bearings (main): Fully functional Cam Bearings: Damaged with signs of corrosion and hence required replacement Remarks: The crankcase had some work to be done. The journal surface required replacement due to one side being out of shape. Further, the key was noted to have been exposed to some kind of damage warranting a replacement. 2. Oil Sump Screen: a closer look as the screen revealed presence of debris in the oil sump. Plugs: The plugs were fully okay with no significant signs of wearing out. Studs: The studs were in excellent condition Finished Surfaces: Some particles and a few scratches were recorded in the finished. Remarks: The oil sump did not require a total overhaul. It simply required a little cleaning and surface cleaning taking care not to exceed the specified limits. 3. Top Cover Plate Finished Surfaces: save for a few small scratches, the top cover plate had nothing serious to warrant overhaul. It required small cleaning and surface polishing. Remarks: The surface required polishing and cleaning. 4. Cam Follower Cam Follower Body: The bush roller was recorded to have moved. This resulted into contact marks which in turn caused some minor damages to the fuel cam follower. Hydraulic Unit: fully functional Finished Surfaces: the measured clearance fell out of the conventional range of 0.5 - 0.8 mm to stand at 0.9mm. Remarks: The cam follower required some considerable work starting with realignment of the bush roller and repairing of the finished surface to within the prescribed clearance. 5. Crankshaft Thrust Bearing Journals:signs of metal particles, and score marks/deep scratches were registered Main Bearing Journals: signs of metal particles, and score marks/deep scratches were registered Rod Bearing Journals signs of metal particles, and score marks/deep scratches were registered Oil Tubes: The oil tubes showed signs of wearing out Finished Surfaces: signs of cracking, bending, and physical damage were recorded Spline: excellent Threads: Signs of damage Counterweights: Fine Rollers Damaged Plugs: damaged Sludge Chambers: Showed only a few signs of damage Remarks Crank shaft requires considerable work 6. Accessory Housing Finished Surfaces: there were considerable signs of metal particles, deep scratches Studs: Excellent Oil Passage: Clogged Remarks: The housing for accessories required a replacement 7. Oil Relief Valves Spring: Reduced elasticity Seats: Excellent usage conditions Plungers: Excellent usage conditions Body: Excellent usage conditions Remarks The old relief valves were in good condition and functioned as expected 8. Starter Drive Gear: Worn out teeth Seals: Some seals were loosely fitting Mounting: Quite easy Remarks Gears need 9. Crankshaft Gear Remarks: In excellent condition 10. Thrust Seal Remarks: Excellently functions 13. Fuel Pump Drive Bearings and Shaft: one bearing had a problem and required replacement. Seals: Perfectly fitting Mounting: easy to mount Remarks: Required cleaning replacement of the damaged. 14. Hydraulic Pump Drive Bearings and Shaft: Two bearing had a problem and required replacement. Also worn out was a shaft Seals: Perfectly fitting Mounting: easy to mount Remarks: Required cleaning replacement of the damaged. 20. Shroud Tubes Remarks: Fully operational and required no adjustments or replacements except for some clogging which required cleaning to solve 21. Baffles Remarks: Fully operational and required no adjustments or replacements 22. Tachometer Remarks: Fully operational and required no adjustments or replacements 23. Gear and Shaft Remarks: The gears and shafts had worn out due to usage with some teeth exceeding the acceptable clearance limits. These were earmarked for replacement. 23. Intake Pipes Finished Surfaces: The surfaces were fine except for a single point which had worn out due to wrong placement. This called for replacement of an entire section. Connections: The connections had been laid pretty well in case for a single joint which seeming leaked a little. Remarks:The worn out section were identify for replacement replaced and loose connections for tightening. 24. Rocker Box Covers Remarks: The Rocker Box Covers were in excellent condition and required no engineering modifications except for cleaning. 25. Ignition Harness Cable: a few cables were worn out, with some having been corroded Fittings: Corrosion effect from the cables seem to have spread to the fitting Shielding: Loosely attached Remarks: The corroded cables required replacement and so were the fitting. The shielding required tightening to make it more effective. Read More