Complete Specification
Of
Repair Scheme for Gearbox Magnesium alloy housings bores wear out through
Steel liners.

1. Title of the invention
Repair Scheme for Gearbox Magnesium Housings wear out bores througn Steel Liners.

2. Field of invention

This invention is related to Gearbox Magnesium Housings wear out bores through Steel Liners of Helicopters.

2. Use of invention

This invention is used to repair the Gearbox Magnesium Housings wear out bores of Helicopters.

3. Prior art

This method was unique. There was no previous scheme was available.

4. Draw backs of prior art

Not applicable, as this Scheme is a newly developed for the first time on Magnesium alloy material for Housings of Helicopter.

5. Comparison between prior art and present invention

Not applicable, as this Scheme is a newly developed for the first time for Helicopter.

6. Aim of the invention

Aim of the invention is to Repair of Gearbox Magnesium Housings wear out Bores through Steel Liners of Helicopters.

Summary of the present invention

This repair scheme is used for repair of Gearbox Magnesium Housings, where bores worn-out during flying due to dynamic loads. These wear outs will happen due to inadvertent loads being transferred from main rotor rotation after flying few hundreds of hours.

Brief description

The Repair Scheme of Gearbox Magnesium Housings liner compliance having operations in brief: Pre-machining of Housing Bores, Selenic acid touch-up at machined bores locally, Installation of Steel liners by applying anti corrosive paste in the Housing bores, Installation of Dowel pins by drilling of Housings/ Liner interfaces with applying Loctite, Post machining of Housing bores as per drawing,CD checks by FDP Method, Magic blue touch-up at Liner inner diameters, Final Inspection.

Statement of invention

This Repair Scheme has helped to Repair Gearbox Magnesium Housings bores by reworking of bores & using steel liners with anti-rotation locking pins and re-utilization of same housings. After flying two or three Overhauls, again same repair can be carried out.

Detailed description of invention

Function: The Gearbox magnesium housings being used for giving power from Engines to Main rotor blades by reducing speeds with different gear & pinion arrangements in the Housings. Also power will be transferred Tail rotor Blades.
Realization of Housings during Manufacturing period: Gearbox Magnesium Housings are critical in nature in terms of Raw materials, forging the required shape, Critical machining operations during manufacturing and also various processes involved before utilization on Helicopters. Being Housing is critical in nature in terms of Raw material forgings manufacturing, machining, Time involved is explicitly more Frequency of Housing Bores wear-out: Bores wear-out will happen where Bearings beings used for installation of Gears & Pinions in Housings. Wear-out will be happen after completing one over-haul or two over-haul stage. It is mainly due to dynamic loads of Main rotor or Tail rotor blades and also flying with different envelops.

Procedure for Repair of wear out Bores on Gearbox Housings:

1. Initial Measurement of Bores: Gearbox Bores to be measured locally for wear out and also with respect to the geometrical tolerances of other bores & Faces surfaces Housings and recording as reference purpose. Use CMM machines for geometrical tolerances purpose.

2. Pre-machining of Bores: Open the existing bores for installing the steel liners by loading on jig boring machines with rotary tables/ Fixture plates. Carry-out through dialing of liner or radial surfaces of bores with respect to Housings main reference surfaces before machining.

3. CD Check & Selenic Acid touch-up: Carry-out CD check by FDP method locally on machined bores. Carry-out Selenic acid touch-up in the machined bores locally.

4. Preparation of Steel liners: Manufacture the Steel liners by considering fit & keeping the stock inner bore for finishing in assembled stage. Carryout surface protection with Phosphate or Cadmium plating method.

5. Installation of Steel liners in to gearbox housings:

Heat the gearbox housing to a temperature of 60 to 75deg centigrade in oven. Apply anticorrosive paste into the gearbox housing bores uniformly.

Claims

1. Method for Pre machining and post machining of housings.

2. Method for Installation of Steel liners and Dowel pins in to Housings

3. Method for controlling of geometrical tolerances ensuring with respect to requirements.