Pre-stretched tie-bolt for use in a gas turbine engine and method

A tie-bolt for use in a gas turbine engine having a main shaft, the tie-bolt comprising:

• a rotor having a central bore;
• an elongated tubular portion having a first and a second end and configured to pass through the central bore;
• an apparatus for connecting the first end of the tubular portion to the main shaft;
• a retaining portion having a first and a second end, the first end of the retaining portion being unitary with the second end of the tubular portion, the retaining portion having a diameter larger than that of the tubular portion;
• an apparatus on the retaining portion for connection to a device pulling the tie-bolt;
• and
• an annular spacer removably provided between the retaining portion and the rotor, the tie-bolt having a pretension to retain the spacer against the rotor, the annular spacer having a thickness corresponding to a required elongation of the tie-bolt to achieve a desired value for said tie-bolt pre-tension.

A method of mounting a tie-bolt to a main shaft in a gas turbine engine, the tie-bolt having opposite first and second ends, the method comprising:

• threading a first end of the tie-bolt on the main shaft until the tie-bolt abuts a component to be retained;
• exerting an axial pulling force at the second end of the tie-bolt for stretching the tie-bolt with reference to the first end thereof, thereby creating an axial spacing between the tie-bolt and the component to be retained;
• inserting a spacer in the axial spacing;
• and then
• releasing the axial pulling force.

A rotor assembly comprising:

• an engine main shaft having an axis, the axis defining an axial direction;
• a turbine rotor mounted about the main shaft, the main shaft passing through a central bore of the rotor, the rotor having an aft face;
• a tie-bolt having a forward end coaxially mounted to an aft end of the main shaft, the tie-bolt extending co-axially through the rotor central bore to an aft end of the tie-bolt, the tie-bolt having a face adjacent the tie-bolt aft end which face opposes the rotor aft face, the tie-bolt having a portion configured to be engaged by an axial pretensioning apparatus, the tie-bolt being in an axial pre-stretched state when initially mounted to the rotor assembly;
• and
• a spacer disposed between the rotor aft face portion and the tie-bolt face and there maintained at least partially by compression between the rotor aft face and the tie-bolt face, wherein the spacer has a thickness configured to maintain a desired axial pre-stretching on the tie-bolt when a load of the axial pretensioning apparatus is released.