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
- 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
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.
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.
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.
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.
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.