received by the International Bureau on 25 May 2018 (25.05.2018)

1. A system for the removal of heat generated by one or more electrical motors in a downhole tool comprising:

a hydraulic pump;

an output hydraulic passageway routed from the pump outlet that provides hydraulic fluid through a section of the downhole tool containing the one or more electrical motors;

a return hydraulic passageway routed from the pump inlet that receives hydraulic fluid through a section of the downhole tool containing the one or more electrical motors;

one or more heat exchanging areas of the downhole tool, arranged to receive hydraulic fluid from the hydraulic pump by way of the output hydraulic passageway, transfer heat to the outside wellbore environment, and deliver hydraulic fluid to the pump by of way of the return hydraulic passageway.

2. The system of claim 1 , wherein the output hydraulic passageway consists of multiple hydraulic channels.

3. The system of claim 1 , wherein the return hydraulic passageway consists of multiple hydraulic channels.

4. The system of claim 1 , wherein the return hydraulic passageway is the

hydraulic sump of the downhole tool.

5.

6.

7.

8.

9.

10. The system of claim 1 , wherein the electrical motor is mounted inside the wheel of downhole tractor.

11. The system of claim 1 , wherein the electrical motor is mounted inside the arm of a downhole tractor.

12. The system of claim 1 , wherein the return hydraulic passageway comprises a passageway through the rotor center axis of an electrical motor.

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13. The system of claim 1 , wherein the return hydraulic passageway comprises a passageway through the stator of an electrical motor.

14. The system of claim 1 , wherein the return hydraulic passageway comprises a passageway through the annular space exterior to the outer diameter of a rotor and inside the inner diameter of a stator of an electrical motor.

15. The system of claim 1 , wherein the return hydraulic passageway comprises a passageway passed the stator of an electrical motor.

16. The system of claim 1 , wherein the return hydraulic passageway comprises a helical passageway around stator of an electrical motor.

17.

18. The system of claim 1 , wherein the output hydraulic passageway comprises a passageway through the rotor center axis of an electrical motor.

19. The system of claim 1 , wherein the output hydraulic passageway comprises a passageway through the stator of an electrical motor.

20. The system of claim 1 , wherein the output hydraulic passageway comprises a passageway through the annular space exterior to the outer diameter of a rotor and inside the inner diameter of a stator of an electrical motor.

21. The system of claim 1 , wherein the output hydraulic passageway comprises a passageway passed the stator of an electrical motor.

22. The system of claim 1 , wherein the output hydraulic passageway comprises a helical passageway around stator of an electrical motor.

23.

24. A downhole tractor mechanism comprising:

an arm radially extendable from the tractor tool body;

a linkage pivotably mounted to the extendable end of the arm at a single pivot point;

a first drive wheel mounted to the linkage at a first position from the pivot point and a second drive wheel mounted to the linkage at a second and opposing position from the pivot point.

25. The mechanism of claim 24, wherein the drive wheels comprise electrical motors.

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27. The mechanism of claim 24, wherein the distance of the first drive wheel from the pivot point differs from the distance of the second drive wheel on an opposing side of the pivot point, to the pivot point.

28. The mechanism of claim 24, wherein the drive wheels comprise of motors.

29. The mechanism of claim 24, further comprising a gear train within radially extendable arm;

gear train within radially extendable arm arranged to transmit power to a gear train within the linkage;

gear train within the linkage arranged to transmit power to drive wheels.

30. The mechanism of claim 29, further comprising a gear differential within the linkage gear train.

31. The mechanism of claim 30, wherein the gear differential is a limited slip differential.

32. A downhole tool actuation system comprising:

first and second radially extendable arms on opposing sides of a downhole tool body;

the first radially extendable arm actuated by a first actuator, including a piston and actuation cylinder;

the second radially extendable arm actuated by a second actuator, including a piston and actuation cylinder;

a hydraulic passageway routed from a single pump, to each actuation cylinder;

a flow regulator on the inlet hydraulic passageway of each hydraulic actuation cylinder, disposed to regulate flow into the cylinder, such that the volume of fluid in the first actuation cylinder is within a desired range of the volume in the second actuation cylinder.

33. The system of claim 32 wherein the flow regulator comprises a variable

orifice which adjusts based on a pressure differential of its inlet and outlet ports.

34. The system of claim 32, wherein the radially extendable arms are arms of a downhole tractor.

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35. A method of centralizing an in-line arm downhole tractor in a wellbore, the inline arm downhole tractor including a first radially extendable arm disposed to actuate upon pressurization of a first actuation cylinder, a second radially extendable arm disposed to actuate upon pressurization of a second actuation cylinder, a first flow regulator disposed to regulate flow into the first actuation cylinder, a second flow regulator disposed to regulate flow into the second actuation cylinder and a pump, the method comprising:

providing an in-line arm downhole tractor in a wellbore;

powering the pump to provide fluid to the first and second actuation cylinders through the first and second flow regulators;

regulating the fluid flowrate to each actuation cylinder such that fluid volume in the first actuation cylinder is similar in volume to the fluid in the second actuation cylinder; and

positioning the in-line arm downhole tractor toward the wellbore central axis.

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