|While I was providing flight training for Mike S.
in Mobile Alabama we experienced some trouble with his new 35mm secondary
shaft. On a new helicopter I will hover it for about 5 minutes initially
and then shut down to check all of the components integrity. On the
first shut down and inspection I noticed that the lower secondary
bearing seal had dropped down and nearly out of its race.
I asked Mike if I could do a slight
modification to the secondary to prevent a re-occurrence of the
seal dropping. It seemed to me that the seal was being forced out
by the expansion of the grease in the bearing when it became warm
as we hovered. I came up with a simple fix. Just remove the grease
fitting, grind the end off just enough to remove the ball and spring,
and then clean and re-install it. Add an 18” piece of clear vinyl
tubing and secure with safety wire or zip tie. This way any extra
grease will evacuate into the tube where you can see it and will
not force the seal out. Just remove the tube to grease and replace
it. This worked like a charm and I immediately shared this issue
with the factory and the Rotorway community. Below is a photo of
the fix and notice the red seal edge is still exposed a little bit.
Thats OK, its the way they are built. Look at the top picture again
and see how much further it came out when it let go!
During the subsequent years
I have seen a few seals that have been forced from the secondary
during run-ups prior to my arrival for flight training. I have posted
a couple of photos below so that you can see the mess made when
this happens. It has been several years since I have seen this problem
reoccur. It is always a good idea to keep an eye on all seals and
bearings in any helicopter.
The seal above was most
likely forced out when the bearing was overgreased and then the
grease expanded as the helicopter hovered. Be sure to follow the
factory grease schedule and watch for any sign of the seal moving
down. I am pleased to note that I have not heard of a seal coming
out of the secondary in the past 5 years.
Installing the secondary:
I have been asked numerous
times about how to get the secondary up into the frame. It will
fit once it is lined up correctly.
First get the upper secondary shaft and
bearing up into the area that the secondary will sit. The shaft
and bearing will need to be on top of the lower square drive tube
and tilted forward enough to allow the rear of the large pulley
to clear the lower rear cross tube of the frame. It is at this point
that most of the difficulty arrises. The upper secondary bearing
housing has a bevel that sits against the front lower square drive
tube that allows the secondary to slide forward just enough for
the rear lower lip of the large pulley to clear the frame member
to the rear. If your bearing housing does not have the bevel, the
secondary will not fit. (I have not seen one without the bevel).
Once the pulley is clear go to the next step.
Get the large pulley over the lower rear
frame member with the secondary shaft tilted forward. you will need
to insure that the lower secondary bearing is out of the way to
give you enough shaft clearance so that the pulley and shaft can
slide aft enough to allow the front portion of the pulley to clear
the front square frame tube that the upper lower secondary bearing
Once you clear the lower square drive tube,
the secondary fits into position easily.