TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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castings as outlined in Specifications QQ-A-601 and MIL-W-8604. Preheat slowly in an oven or by other suitable method for two hours to ap- proximately 350 degrees ± 35 degrees F. Control preheat process to avoid incipient melting, excessive grain growth or other un- desirable structural changes which might reduce the mechanical properties. Caution: Do not attempt to preheat by using welding torch. (7) Welding. (a) Cracks. The inert gas shielded arc welding process shall be used when making repairs on aluminum alloy. After casting has reached the prescribed preheat temperature, position the casting into the most advantageous welding position. Cover casting with asbestos blankets, except for area to be welded. Weld the outside milled groove with a good root weld. Apply fillet welds until groove is closed. Rotate casting and weld inside groove in the same manner if double “V” is used. Remove asbestos blankets and allow castings to cool progressively to room Temperature. (b) Fracture and missing metal. Following the procedure outlined in (a), above, place insert piece in opening, aline and secure with clamps or tack weld in three or four places with one inch welds. Place a good root weld in groove and apply fillet welds until groove is closed. Rotate casting and weld inside groove in the same manner. Note. The temperature of the casting surrounding the welded area should not exceed 395 degrees. If necessary, stop welding, cover casting with asbestos blanket and allow to cool to a satisfactory temperature then resume welding. (8) Final inspection and clean up. Repaired cracks and areas where metal has been replaced must be radiographically inspected and be equal to or better than reference standard 3, TACOM STD 113, Apr 69 (available from USTACOM AMSTA-R). All other areas shall be inspected by dye penetrant. Defects must be re-welded in accordance with above methods. Measure casting and compare dimensions taken before repair. Dimensional change will not exceed that as specified on applicable engineering drawing, except as noted. Check machined surfaces for warpage or other dimensional changes. Clean seams with a wire brush and remove weld beads and all sharp edges. X-ray entire repaired area. Remove excess flux with suitable material, rinse with clean water, dry and alodize. Pressure test oil passages that have been repaired to 90 psi hydrostatic pressure using engine oil (OE). d. Ball and Needle Bearings. (1) Replace all galled, pitted, or damaged bearings. (2) Replace all bearings which do not conform to tolerances specified in the ap- propriate repair and rebuild standards table. (3) Refer to TM 9-214 for information on inspection, care, and maintenance of anti-friction bearings. e. Studs. Replace all bent or loose studs or studs showing evidence of stretching. Repair minor damage with a thread chaser. Replace all studs having stripped or damaged threads. Remove and replace studs as outlined in (1) and (2), below. (1) Stud identification. Stud identification tables appear in the overhaul sections of this chapter. Each table contains the appropriate inform ation regarding stud setting heights, oversize studs, number required and reference figures of stud identification and location. (2) Removal. Using stud extractor, back studs out slowly to avoid heating and possible seizure. When studs are broken off too short to use stud extractor, drill stud and extract with a suitable remover. Short studs may also be removed by welding a piece of bar stock or a nut to stud and removing with a wrench. 6-6