The thrust block bearing change out is fairly straight forward. All you need is a press, short piece of pipe and a 1/2" deep socket. Remove the rubber end dust cap. Place block over the pipe section which will allow the bearing to pass completely out of the block.
The picture shows the setup. Put the deep socket squarely over the bearing. Start applying pressure. You will hear a "snap" sound as the bearing breaks free. It will then smooth push through and pop out. If there seems to be excess pressure, stop and relieve the pressure. Check alignment and if everything is good continue.
Clean the bearing cavity. Remove any burrs lightly Scotch-Brite. Place on the press face up as in the picture to the left. Place the new bearing, numbers out, over the cavity. Carefully lower press ram into contact with the bearing. Verify that the bearing is aligned and vertical. Slowly apply pressure, again verify that the bearing is being pushed evenly into the cavity. Press until flush as pictured.
I recommend that you don't grease the bearing until you are ready to immediately hang the blades. The reason is that this helps prevent contamination from dirt and shop debris. It is also a good practice to clean the recess for the elastomeric bearing including the Teflon/Delrin strip. Blades should be removed, as a minimum, once a year for the condition inspection. At this time check condition of the block bearings (re-lubricate) and the elastomeric bearings.
This is a common condition after trying to remove a blade with frozen aligner bearings. The internal race and pins pull out with the blades. Clean out any remaining roller pins and as much grease as possible before inserting puller mandrel
. In this case the larger mandrel was required to pull the bearing. Insert the mandrel all the way into the bearing as far as possible. Using two wrenches start tightening (expanding) the mandrel. It needs to be very tight. Make sure the blade is stable. It is easy to knock the blade off the sawhorses if not prudent.
Once the chosen mandrel is secure and tight attach the slide hammer. It takes a pretty firm hit to break the bearing free. It is important to have the blade secure from sliding off its horses. Two people would be a good idea during this phase of removal. Ensure the mandrel remains aligned vertically and horizontally during each strike of the slide.
The picture on the left illustrates what it will look like after successfully pulling the bearing.
The next step is to clean the bearing recess and remove any burrs. Once cleaned it is time to install the new bearing. Place the bearing on the insertion tool and place, as pictured, into position. The dead blow hammer is used to start the bearing slightly into the recess until the blade attach bolt is aligned with the tool block. The picture shows the bolt in place and tool properly aligned and ready to push the bearing. Note the thin washer hanging below the mandrel. I put this washer between the mandrel and bearing as a guide to indicate when the bearing is flush. Note that there should be a .050" gap between this washer and block body.
With the appropriate wrench start pushing the bearing into place. It should push in smoothly and easily. If not, stop, and review your setup.
Once the bearing is .050" to the flush washer, remove the tooling jig and inspect. It is wise to have the part numbers facing out. In the future it may help you re-order the correct replacements. As mentioned earlier I usually don't grease the bearing until just prior to blade installation. I find this helps prevent contamination from dirt and debris.
As with any aircraft task this is a easy process with proper tooling and fixtures. With any aviation related task, time is not as important as quality. Take your time and do the job once!
Tools required to remove the aligner block bearings are available from Harbor Freight.
The kit is a blind bearing puller.
A dead blow hammer, 11/16" wrench and a locally manufactured press are for the installation phase of aligner bearing change out. The "special" tool can be assembled from a old thrust block, a short length of all thread rod, long nut and a lathed mandrel. I could provide a drawing if requested via email.
To remove the aligner bearing you may need either the large or small mandrel depending on the condition of the bearing. A common failure is that the bearing comes apart during blade removal. In that instance you would need the large mandrel. If the bearing is whole then the smaller one would be appropriate. The wrenches are to adjust the "squeeze" of the mandrel against the bearing race.
Thrust & Aligner bearing Replacement
Aligner Block Bearing
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