Shaft assembly
A shaft assembly may include two or more Poka-Yoke bearing caps, each Poka-Yoke bearing cap having a pair of reference bores offset from a central axis of the bearing cap by differing offset distances, and each bearing cap defining a semi-circular recess that is positioned so as to align in use a central axis of the semi-cylindrical recess in the bearing cap with an axis of rotation of a shaft rotatably supported by the bearing cap. The differing offsets of the reference bores prevent the bearing cap from being assembled in a reversed orientation. To ensure that each bearing cap can only be fitted in one position, a center spacing between the first and second reference bores of each bearing cap is different to the center spacing used for other bearing caps used to support a single shaft.
1. A method of producing a shaft assembly, comprising:
manufacturing a shaft;
manufacturing a component having at least two bearing support structures each of which has a semi-cylindrical recess, first and second reference bores, and two or more threaded bores;
manufacturing a like number of bearing caps as there are bearing support structures, each of the bearing caps having a semi-cylindrical recess, first and second reference bores, and two or more bolt clearance holes,
wherein the method further comprises machining the two reference bores in each bearing cap so that the first reference bore is offset from a central axis of the respective semi-cylindrical recess by a first distance and the second reference bore is offset from the central axis of the respective semi-cylindrical recess by a second distance that is different than the first distance, machining the two reference bores in each bearing support structure to match the spacing of the first and second reference bores in the respective bearing cap to which it is secured in use, fitting dowels in the first and second reference bores in the bearing support structures and the bearing caps, aligning and bringing into mating contact each bearing cap with the respective bearing support structure so as to produce full engagement of the dowels with the first and second reference bores in the bearing caps and bearing support structures, securing the bearing caps to the bearing support structures, and simultaneously line boring the semi-cylindrical recesses in the bearing support structures and bearing caps to produce a bore of a required diameter.
2. The method as claimed in claim 1 , wherein the method further comprises removing the bearing caps from the bearing support structures after the line boring is complete, placing the shaft and associated bearings in position, replacing the bearing caps on the matching bearing support structures, and bolting the bearing caps to the bearing support structures.
3. The method as claimed in claim 1 , wherein before the line boring, the semi-cylindrical recesses of the bearing support structures and bearing caps each have a first diameter, and wherein after the line boring, the semi-cylindrical recesses of the bearing support structures and the bearing caps each have a second diameter larger than the first diameter.
4. The method as claimed in claim 1 , wherein machining each reference bore of the bearing support structures comprises machining a chamfered lead-in at a mounting face end thereof, wherein machining each reference bore of the bearing caps comprises machining a chamfered lead-in at a mounting face end thereof, and wherein the dowels comprise chamfers.
5. The method as claimed in claim 1 , wherein each bearing cap comprises first and second bolt clearance holes in a first foot thereof and third and fourth bolt clearance holes in a second foot thereof, and wherein machining the first and second reference bores in each bearing cap further comprises machining the first reference bore at an offset from each of the first and second bolt clearance holes and machining the second reference bore at an offset from each of the third and fourth bolt clearance holes.