HINTS AND TIPS

The Buttons below will take you through the different hints and tips that I feel will make your helicopter safer and more reliable.

Elastomeric Bearing

The Rotorway Factory builds and supplies one of the best main rotor systems available for a kit helicopter.

One reason for this is the elastomeric bearings that provide a very rugged and reliable pitch bearing for the main rotor blades. If they are properly cared for they have a long life and provide an amazingly smoothe rotor system.

 

Elastomeric bearings age

  • Insure that the calendar life of your Elastomeric bearings is within that allowed by the factory
  • Insure that absolutely no grease is able to get onto the elastomer (rubber/brass shim) surfaces. Keep them clean.
  • I like to place a micro thin layer of grease on both flat surfaces of the outer bearings. This allows the elastomeric bearing to slide into itís neutral position when the rotor system is running down. If you hear a loud "twang" from the blade area on run-down, it is an indication that the elastomeric bearings are snapping back into place instead of sliding, this could be hard on them and shorten their service life.
  • If you find that your ship seems to fly fairly smooth when in a hover and then once it enters translational lift it becomes very rough, the problem may be that your elastomeric bearings are worn out.

2/27/09 I just returned from a trip to instruct Raymond Butler in his newly completed 162F. Raymond did an outstanding job constructing his ship and there were only a few items that needed to be tweeked before we began the main and tail rotor balancing.

First we did a very precise static lead-lag adjustment followed by static balancing the main rotor system. We attached the computer balancer to the ship and began the dynamic balancing. In a few hours we had the vibration level down to .2 ips which is just within the acceptable limits and could not get the vibration level any less.

As we began Raymond's hover transition training I was really bugged about a two-per vertical hop felt in the cockpit. We used the tracking lights and got the tracking perfect and yet the vertical hop persisted. It was not severe at all, just annoying and not within my standards. I told Raymond that I had adjusted everything that could be adjusted and since we still had that annoying hop I suspected that the new (5 years on the shelf during construction) elastomeric bearings were failing.

Raymond called Robin at the factory and she was her normal accommodating self when she overnighted a new set of elastomeric bearings to us. When they arrived we pulled the main rotor blades off the ship and the following photo shows one of the old elastomeric bearings next to one of the new ones. Both of the older ones looked the same.

In the photo above you can see the left elastomeric bearing that was only 5 years old and never before used. The elastomer has deteriorated to the point that it overheated in use and boiled the black elastomer out from between the brass shims. The bearing on the right is one of the new ones that we recieved from Rotorway.

Once we had installed the new elastomeric bearings the ship flew rough again at .7 ips. We once again installed the tracking lights and found that with the new elastomerics the blades needed to have the tracking readjusted. This eliminated the vertical hop that was still present after the bearing change. We then retracked and balanced the main rotors and tail rotor blades and the result was .o6 ips to .1ips.

With the bad elastomeric bearings we had made adjustements that somewhat compensated for them. Once they were replaced, we had to remove the compensating adjustments to bring the ship into perfect balance. We were happy with the final results and continued Raymond's transition training with a very smooth flying ship.

Update 3-6-10

Raymond was flying his helicopter and having the time of his life. During the take off run at approximately 100 feet above the ground the ship began a violent shake so he did what I had taught him to do "when in doubt, auto out". He immediately entered an autorotation but with trees directly in his path he pulled a very steep flare dragging his tail stinger in the dirt. The the set down was hard bending his skids, landing gear, and rear gear supports on the frame.

Raymond found that he had experienced just one more valve train failure which is common with this engine. He was able to keep the helicopter upright but spent several months repairing it. At this time is was near the 100 hour mark so he performed all of the 100 hour maintenance items including replacing the aligner block bearings.

When he began to fly again he was plagued with a strong vertical hop and cyclic shake. We corresponded for several months and everything Raymond tried resulted in the same result, that annoying vertical hop. Last week Raymond gave up and asked me to return and give him a hand. We removed his blades and inspected the elastomeric bearings which were now only 1 year old. They were covered in grease because Raymond over-greased the bearings in the thrust blocks, and as the rotor spun up the grease migrated from the bearings over the elastomerics.

When we cleaned the grease off it was evident that some of the elastomer was deteriorating and we thought that we had determined the cause of the hop. We called Rotorway and found that they had a long backorder for these bearings so we decided to verify if they were indeed the cause.

Dave Forester has been hangaring his 162F in Raymonds hangar so with Dave's permission we removed Daves main rotor blades with their respective elastomeric bearings and installed them onto Raymonds ship. The main rotor system now required re-tracking which we did. When we brought the ship up into a hover it had the same annoying hop, just like it did with Raymond's blades and elastomerics.

We removed Daves blades and found that his elastomerics were really bad with black seepage around the edges as can be seen in the photo below. Raymonds one year old elastomeric is on the left, Dave's 4 year old bearing is on the right.

We then installed Daves blades with Raymond's elastomerics and found the rotors to fly very smoothe. This told us that Raymond's elastomerics were good but still somewhat damaged by the grease as seen in the photo.

We then took a closer look at Raymond's aligner block bearings. We found that they had been installed with only .045" protruding from the block instead of the required .050". This caused the aligner block bearing to rub against the blade adustment pin mimicing the effect of a bad elastomeric bearing. We reinstalled the aligner block bearings with the proper clearance and the rotor system was perfectly smoothe. Mission accomplished.

 

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The material on each page is the opinion of the author only and any actions taken by the reader relating to information on this site is the responsibility of the builder.