Downhole mud motor with adjustable bend angle

1. A downhole motor, comprising:

a first housing;

a second housing coupled to the first housing at a movable joint;

a turbine within the first housing in selective fluid communication with a bore of the first housing;

a biasing mechanism coupled to the turbine and to the movable joint, wherein the biasing mechanism comprises a rotatable cam with an eccentric inner bore and a profile on an exterior surface of the rotatable cam; and

a locking mechanism positioned at least partially around the rotatable cam, wherein the locking mechanism comprises a locking ratchet engagable with the profile.

2. The downhole motor of claim 1 , further comprising a bit shaft at least partially within the second housing.

3. The downhole motor of claim 2 , further comprising a fluid-driven rotor coupled to a drive shaft, the drive shaft at least partially within the first housing and coupled to the bit shaft.

4. The downhole motor of claim 3 , further comprising a valve positioned between a bore of the first housing and the turbine.

5. The downhole motor of claim 1 , wherein

the movable joint comprises a constant-velocity joint assembly with a shaft; and

the shaft is at least partially within the eccentric inner bore.

6. A method for drilling using a downhole motor, comprising:

rotating a drill bit in a borehole using a downhole motor with a first bend angle, wherein the first bend angle comprises a first angle between a first longitudinal axis of a first housing and a second longitudinal axis of a second housing of the downhole motor;

changing the first bend angle to a second bend angle while the downhole motor is within the borehole by rotating a biasing mechanism coupled to a movable joint, wherein

the biasing mechanism comprises a rotatable cam with an eccentric inner bore and a profile on an exterior surface of the rotatable cam;

the movable joint couples the second housing to the first housing; and

rotating the biasing mechanism comprises exposing a turbine coupled to the biasing mechanism to a flow of drilling fluid through the downhole motor;

rotating the drill bit in the borehole using the downhole motor with the second bend angler; and

selectively locking a locking mechanism positioned at least partially around the rotatable cam by engaging a locking ratchet of the locking mechanism with the profile.

7. The method of claim 6 , wherein

rotating the drill bit in the borehole using the downhole motor with the first bend angle comprises rotating the drill bit with a drive shaft at least partially disposed within a first housing of the downhole motor.

8. The method of claim 7 , wherein

the second bend angle comprises a second angle between the first longitudinal axis and the second longitudinal axis.

9. The method of claim 6 , wherein the movable joint comprises a constant-velocity joint assembly with a shaft that is at least partially within the eccentric inner bore.

10. The method of claim 6 , further comprising selectively locking the downhole motor to maintain the second bend angle.

11. A downhole motor, comprising:

a first housing;

a constant-velocity (CV) joint assembly at least partially within the first housing;

a second housing coupled to the CV joint assembly;

a fluid-driven rotor coupled to a drive shaft, the drive shaft at least partially within the first housing; and

a rotatable cam with an eccentric inner bore within the first housing, a shaft of the CV joint assembly at least partially within the eccentric inner bore;

a turbine coupled to the rotatable cam; and

a valve that provides selective fluid communication between a bore of the first housing and the turbine.

12. The downhole motor of claim 11 , wherein the rotatable cam comprises at least one profile on an outer surface.

13. The downhole motor of claim 12 , further comprising a locking mechanism positioned at least partially around the rotatable cam.

14. The downhole motor of claim 13 , wherein the locking mechanism comprises a locking ratchet engagable with the profile.