Method of assembling a shaft and apertured member

The method of joining a plurality of axially spaced members with at least one tubular element comprising the steps of:

• forming in each member an aperture with a lobular cross section having an odd number of lobes;
• forming at least one hollow tubular element having at least one body portion, and joining portions sized to snugly fit within the respective apertures of the members, the joining portions each having an inner diameter smaller than that of the body portions;
• aligning the members with their respective apertures on a common axis;
• inserting the joining portions into the apertures;
• restraining each tubular element against elongation by application of longitudinal clamping force to both ends of the element;
• forcing through each joining portion at least one hardened ball having a diameter larger than the joining portion inner diameter and smaller than the body portion inner diameter and passing the ball from one joining portion to another for successively expanding the joining portions into tight conformity with the respective apertures.

The method of assembling a crankshaft from separate hollow tubular crank pins, main journals and counterweights, each counterweight having a center aperture on the axis of rotation for receiving a main journal and an off-axis aperture for receiving a crank pin;

• including the steps of:
• forming in each counterweight an off-axis aperture with a lobular cross section having an odd number of lobes;
• forming on each crank pin a crank pin body portion, and end portions sized to snugly fit within the off-axis apertures of the counterweight, the crank pin end portions having an inner diameter smaller than that of the crank pin body portions;
• inserting the crank pin end portions into the off-axis apertures;
• restraining the crank pins against elongation by application of longitudinal clamping force to both ends of each such crank pin;
• expanding the crank pin end portions into tight conformity with the off-axis apertures by forcing through the crank pin end portions at least one hardened ball having a diameter larger than the crank pin end portion inner diameter and smaller than the crank pin body portion inner diameter, whereby the crank pin end portions are selectively expanded;
• and
• assembling the main journals with the center apertures of the counterweights.

The method of assembling a shaft in an aperture comprising the steps of:

• forming in a first member an aperture with a lobular cross section having an odd number of lobes;
• forming a hollow tubular shaft having a body portion, and a joining portion sized to snugly fit within the aperture of the first member, the joining portion having an inner diameter smaller than that of the body portion;
• inserting the shaft joining portion into the aperture;
• restraining the shaft against elongation by application of longitudinal clamping force to both ends of the shaft;
• and
• expanding the joining portion into tight conformity with the aperture by forcing through the joining portion at least one hardened ball having a diameter larger than the joining portion inner diameter and smaller than the body portion inner diameter.

The method of assembling a crankshaft from separate crank pins, counterweights and hollow tubular main journals, each counterweight having a center aperture on the axis of rotation for receiving a main journal and an off-axis aperture for receiving a crank pin;

• including the steps of:
• assembling the crank pins with the off-axis apertures of the counterweights;
• forming in each counterweight a center aperture with a lobular cross section having an odd number of lobes;
• forming on each main journal a main journal body portion, and end portions sized to snugly fit within the center apertures of the counterweights, the main journal end portions having an inner diameter smaller than that of the main journal body portion;
• inserting the main journal end portions into the center apertures;
• restraining the main journals against elongation by application of longitudinal clamping force to both ends of each such main journal;
• and
• expanding the main journal end portions into tight conformity with the center apertures by forcing through the main journal end portions at least one hardened ball having a diameter larger than the main journal end portion inner diameter and smaller than the main journal body portion inner diameter, whereby the main journal end portions are selectively expanded.