How Radial Piston Motors Leads to Damaged Final Drives?

The main power source in the final drive is the radial piston motor. When it fails to operate, then you will not be able to run your excavator’s final drive. Knowing the preventive measures to make your radial piston motor perform efficiently is crucial.

This article will cover various damages to various radial piston motor components. How can you avoid such damage to your radial piston motors? If this sounds exciting to you. Let’s move on to find out!

Introduction: Radial Piston Motors

A radial piston motor is a hydraulic motor. This motor utilizes hydraulic power to pressure the pistons using hydraulic fluid to generate turning movement. The final drive receives this turning movement to power gear assembly, which ultimately runs the track drive.

Several components make up a radial piston motor. Different kinds of damages associated with different types of components. Let’s discuss the damage on or because of each component in radial piston motors.

Rotator Assembly

The rotator assembly houses radial piston motors, which house rollers, cam rings, cylinder blocks, and pistons. Without the rotator assembly, the radial piston motors are nothing.

The rotator assembly is the main place to find the damage (if it exists in radial piston motors). You can observe all the components in one place. In the image shown below, you can observe various components facing damage. The damage they are as follows:

  • Cam rings have a lot of scars on their surface
  • Rollers are missing on pistons
  • You can witness rollers have trapped the cylinder blocks

All these signs represent a bad radial piston motor contributing to a bad excavator final drive. This image could be a good source of detailed damage depiction of radial piston hydraulic motors.

1.   Cylinder Block

A cylinder block refers to the engine component that houses cylinders. It functions as a central frame providing connections between several components of an engine.

You can see in the image that a piston sticks into the cylinder block without indicating a roller. This represents a damaged cylinder block. Without a roller, you will experience even greater damage. You cannot repair this type of cylinder block. The only thing you can do is the replacement.

In the depiction below, you will see the roller in the cylinder block. In this case, the roller has taken a turn. This turning resulted in severe damage, especially on the edges. It reflects a bad sign.

Moving on further while discussing cylinder block different kinds of damages. Here comes another one. In the image below, you can see this type of damage mainly because of excessive contamination in hydraulic oil. You also cannot repair this type of damage. Even after experiencing this kind of damage, you will observe severe contamination that is unacceptable.

You should consider this point that traditional motors can cope with contamination. But then, modern hydraulic motors are unable to do so.

As in detail, scratches in the figure below determine how severe contamination it has faced. It reminds us that you cannot ignore the importance of eradicating contamination, especially when it comes to radial piston hydraulic motors.

2.   Cam Rings

Cam ring refers to the outermost ring of a camshaft. It utilizes a place on ground lobes for effective installation. Unequal lobe separation allows for a more efficient valve lift curve. This results in improved intake and exhaust flow.

As shown in the figure below, the cam ring suffered from pitting damage. It may lead to the loss of efficiency and performance within your radial piston hydraulic motor.

Another damage you can see on the same cam ring is the raised section. This represents wear and tear. A new cam ring from a factory features a wavy appearance rather than the shape of an hourglass. The image below will clear your concept in this regard.

Rollers and Pistons

The roller is the rolling element of a radial piston motor. You can use it to transfer the motion of the piston into rotation. The roller itself can be thought of as a rolling bearing. It sits between two shafts or plates, separated by an annular groove.

The piston is a cylinder or cylindrical chamber with a piston rod in the center of the piston. The piston is a mechanism that utilizes a pull or pushes by high-pressure liquid or gas. This, in turn, rotates the main shaft using this mechanical power.

You can see three different types of the piston in the figure below. The one that is on the left side, you can repair. The second that is in the middle, you can also repair it, but it needs extensive working. The third that is on the right side, you cannot make it repair.

In the image below, you can see the trapped piston inside the roller. It has completely rolled over on the sides. It represents a worse situation with your piston and rollers.

How to Prevent Damage in Radial Piston Motors?

As mentioned above, contamination causes severe damage to your radial piston motors. You can follow these measures to prevent damage to your radial piston motors.

1.   Changing Oil Filter Regularly

The hydraulic filter is a small filter that filters the hydraulic fluid in the excavator. It filters dust, debris, sand, foreign particles, and dirt from the hydraulic fluid before going to the engine. It reduces different types of wear because of the foreign particles. The filter also extends the life of the hydraulic system.

With time it gets too clogged that it cannot filter out more foreign particles. This can result in severe damage to different components. When this time comes, the only solution is the replacement of your old filter with a new one.

2.   Utilize Right Hydraulic Fluid

Always use the right type of hydraulic fluid in your hydraulic motor. Using the wrong oil will also lead to wear and tear and contamination. The fluid with the right viscosity levels may play the role. Please refer to the manufacturer or supplier while choosing your hydraulic fluid.

3.   Do Not Open Hydraulic Motor Cover in Dirt

When you repair your final drive motor, you should do so after cleaning it. If the dirt is present in its surroundings and you open it. Then the dirt will get into the motor. This will lead to extra contamination.

While repairing your final drive motor, ensure the surroundings are free from dirt, dust, or debris. This will also affect motor longevity.

4.   Avoid Leakage and Damage Seals

It is not acceptable to use worn-out seals. Keep an eye on your seals and replace them if they show any damage. If they leak, then you cannot bear the consequences. They may lead to component damage resulting in expenses on components.


We have discussed each kind of damage in your radial piston motors resulting in final drive damage. Now you are also familiar with the preventive measures you can follow to avoid these damages. We hope you find this information very useful.

Xugong has a team specializing in overhauling and repairing Final Drive Radial Piston Motor Systems. We offer our customers guaranteed peace of mind, up-to-date equipment, and a reputation for the highest level of quality workmanship.

Choose Xugong to do the repair work on your Final Drive Radial Piston Motor System right away! Feel free to reach out anytime.


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