ROTOR END BAND

1 . An end band comprising:

a hollow cylindrical band wherein at least a portion of the band has a grain flow in a direction parallel to a hoop stress of the band and at least a portion of the band has a grain flow in a direction perpendicular to the hoop stress of the band.

2 . The end band according to claim 1 , wherein the hollow cylindrical band is made from a sheet of material having a uniform grain flow.

3 . The end band according to claim 1 , wherein the hollow cylindrical band is made from Inconel.

4 . The end band according to claim 2 , wherein the hollow cylindrical band has a grain size comparable or smaller than a grain size of an end band made from bar stock of the same material.

5 . The end band according to claim 4 , wherein the hollow cylindrical band has a grain size number of approximately 9.

6 . An rotor assembly comprising:

at least one lamination including a plurality of teeth;

at least one insulation ring having a plurality of teeth matching and aligned with the teeth of the lamination, wherein the at least one insulation ring is attached to the lamination;

slot insulation disposed between the teeth of the lamination and the teeth of the insulating ring;

a plurality of wire windings wrapped around the teeth of the lamination and insulation ring; and

at least one hollow cylindrical end band surrounding the rotor assembly, wherein at least one portion of the end band has a first grain flow in a direction parallel to a hoop stress of the end band and at least one portion of the end band has a second grain flow in a direction perpendicular to the hoop stress of the end band.

7 . The rotor assembly according to claim 6 , wherein the hollow cylindrical end band is made from a sheet of material having a uniform grain flow.

8 . The rotor assembly according to claim 6 , wherein the hollow cylindrical end band is made from Inconel.

9 . The rotor assembly according to claim 6 , wherein the hollow cylindrical end band has a grain size comparable or smaller than a grain size of an end band made from bar stock of the same material.

10 . The rotor assembly according to claim 6 , wherein the hollow cylindrical end band has a grain size number of approximately 9.

11 . A method for manufacturing an end band comprising:

hydroforming a hollow cylinder having an open end and a closed end;

stress-relieving the hollow cylinder;

aging the hollow cylinder; and

removing the closed end of the hollow cylinder to form an end band.

12 . The method for manufacturing an end band according to claim 11 , wherein a flat sheet of material is used to hydroform the hollow cylinder.

13 . The method for manufacturing an end band according to claim 12 , wherein the material is Inconel.

14 . The method for manufacturing an end band according to claim 11 , wherein a height of the hollow cylinder is substantially the same as a width of the end band.

15 . The method for manufacturing an end band according to claim 11 , wherein a height of the hollow cylinder is substantially the same as a width of a plurality of end bands.

16 . The method for manufacturing an end band according to claim 11 , wherein the closed end of the hollow cylinder is removed by machining.

17 . The method for manufacturing an end band according to claim 11 , wherein the hollow cylinder is aged to reduce internal stresses in the band.

18 . The method for manufacturing an end band according to claim 11 , wherein the hollow cylinder is stress-relieved to control the growth of the grain size.

19 . The method for manufacturing an end band according to claim 11 , wherein at least one portion of the end band has a first grain flow in a direction parallel to a hoop stress of the end band and at least one portion of the end band has a second grain flow in a direction perpendicular to the hoop stress of the end band.