|
|
Ernest,
This is something I'm familiar with, but can you tell me who makes this
particular PSRU and how is the sun gear attacked to drive shaft.
See comments below Marked ****:-
Continuing with the theme in my previous email, I spent some time to
dis-assemble my PSRU, to see what it was really made of. The design
boils down to a planetary gear set welded to the wheel hub of a NASCAR
racing car, and held to the engine with custom cast aluminum (LOTS of
custom cast aluminum).
This was put together several years ago, and loosely based on the Ross
unit. There have been several lessons learned since the Ross units
started flying, and I want to make sure I incorporate those lessons into
any modifications I make.
The first question I have concerns the reaction forces from the
planetary gear set. If I understand the mechanism correctly, as the
helix teeth on the sun gear engage and turn the planets, there is a
considerable force trying to push the sun gear out the back of the
unit.
**** Yes!
This force will be taken up by the eccentric shaft and destroy
bearing in the engine unless steps are taken to handle it in the PSRU.
**** Yes! the engine bearings are not designed to take this thrust!
Tracy's solution has been to add a properly rated bearing at the back of
the sun gear, if I'm not mistaken.
**** That's correct, other options have served to fix the Ross gearbox.
The unit I have has a set of ball bearing at the rear of sun gear. They
look to be really heavy duty bearings, but I couldn't find a part number
and didn't want to take the chance of damaging them while removing them
from the housing. Any guesses from the group on whether this setup will
stand up to the reaction forces or not?
**** Firstly plain ball bearings DO take some thrust. Tracy does use one in
the front ( of his PSRU) I believe.
I can't say how much thrust it will take but it appears to be quite large -
take the size to your local bearing supplier and they will identify it and
give you a thrust rating.
I know there's a 1,000 ft/lbs of thrust there, but how much is carried
rearward I'm not sure.
The first picture below shows the back of the PSRU with it's rear cover
removed. The shaft engages the clutch plate. The second picture is
from the other side, and depicts how the sun gear sits in the center of
the ball bearing housing.
Question - is the rear teeth of the sun gear turned down before being
pressed into the bearing - I'm assuming it is.
George ( down under)
----------------------------------------------------------------------------
----
----------------------------------------------------------------------------
----
----------------------------------------------------------------------------
----
>> Homepage: http://www.flyrotary.com/
>> Archive: http://lancaironline.net/lists/flyrotary/List.html
|
|