Nicholas Fluhart

Another actuator post….This Morin unit is a typical double-acting rack and pinion type that I rebuild. It came in with an internal leak-through problem. Although each brand of actuator has its own unique characteristics and components, most of the basic principles are the same. In this post, I’ll outline what it took to rebuild this particular unit.

In for Rebuild

I applied air to it and determined a piston o-ring must be damaged. I begin disassembly by removing the end caps and then the pistons. The end caps are held on by four bolts and come off easily. To remove the pistons I unscrew each stop screw and rotate the pinion a full rotation which pushes the pistons out to the end of the cylinder. If needed, I carefully apply compressed air to push the pistons the rest of the way out.

End Cap Removed

Piston Removed

When I pulled the first piston I immediately saw a broken piston ring. I continued dismantling the unit further by removing the pinion. I begin by removing the pinion retainer, then the pinion can be pulled out directly. Note that I marked the orientation of the components with a white liquid paper pen. This will make it easier to time the unit upon assembly.

Removing Pinion Retainer

Disassembled

Now it is time to clean and inspect the hard parts. I look for any type of damage or excessive wear while cleaning the old grease, o-ring, and bearing material from the components and the bore.

Pinion Inspection

Inspecting the Bore

Once everything is cleaned and inspected I begin installing the soft parts, such as the new bearings, seals, and o-rings. This also includes guide bands on the piston.

Soft Parts Installed

Once the soft parts are fitted to their appropriate parts, I begin the unit assembly by first installing the pinion and then I apply  grease liberally to the gears and the bore of the cylinder.

Now it’s time to install the pistons and time the actuator. The unit must be timed properly or the pistons may not stroke equally resulting the inability of the pinion to make a complete revolution, which in this case is 90° so I’m not sure “revolution” is the correct word. It’s also imperative to install the piston gears on the correct side of the pinion to ensure the pinion rotates in the right direction, which in this case the functional direction is counter clockwise making the return direction clockwise.

Piston Installation

Once the pistons are installed I replace the end caps and begin testing the unit. First I pressurize the actuator and begin testing for leaks by spraying soapy water on the sealing components. Then I stroke the actuator at the appropriate air pressures and set the stop screws.

Leak Testing

I finish up by cleaning the exterior to the desired cosmetic status, insert any needed cap plugs in the air ports, and it’s ready to ship.

Finished Product!

Until next time…