Here is another picture showing the difference between the
2.85 and the 2.17. The 2.85 is the larger pinion. If you rearrange
the 2.17 gear set you get 3.17 by holding the ring gear and take
power out of the planet carrier. I don't know why anybody with
a rotary would want to use the 1.85 version.

BTW IMHO the best way to hold the ring gear is use six drilled

head

hex bolt set screws in groups of two equally spaced around the

outer

housing and safety wire them.

Paul Lamar

George Lendich wrote:

Paul,
Are we thinking along the same lines i.e. using your suggested bolts

like

the 2.17 toothed flange is used to hold the 2.17 planetary.
If so that a good idea, my only concern is drilling into the ring

gear and

going right through the teeth.
George

Don't drill into it. Just grind a few small shallow depressions where
the set screws go.

Paul Lamar

I had been under the impression that the entire planet assembly was
supposed to have a slight amount of "float" as opposed to being held
rigidly to the case.  The thinking was that this allowed for the

assembly

to self align and prevent any spalling of the gears.  Of course it would
need to be tight enough to the case to prevent any fretting of the
ring/case interface.  Is that not the purpose of the notched flange on

the

2.17 set?

Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR
13B in gestation mode

There are two schools of thought on this. First is the float school
and then there is the precision school. Tracy started out with
float on his Ross. He did not like the wear marks as the 2.17 planet

carrier

moved around in the aluminum case. He then went to the precision idea.
Jury is still out IMHO although Tracy's approach is looking good so far.

As far as practical matters are concerned you could broach the aluminum
housing to mate with the splines on the outer part of the ring gear
at great expense and let it float. Using set screws is a much cheaper
solution. Assuming a 2.85 or a 3.17 of course.

Most of the failures reported in the last 5 years have been due to
inaccurate machining on Ross's part I suspect. That and the missing
helical gear thrust bearing in most of Ross's product.

Paul Lamar

Paul & Mike
I've thought about that a lot and if I could add a little to that response.
In the 2.17 the planetary is floating (a little), to the extent dictated by
Ford.
In the 2.85 the planetary is still floating completely as dictated by Ford.
Nothing different to the gearbox!!
Tracy has followed this approach as well - to my knowledge!
George (down under)

No! Tracy's planet carrier is rigidly attached to the housing in the 2.17.
In his 2.85 preliminary design the bulkhead holding the ring gear is
also rigidly bolted to the housing. As far as the 2.85 planet carrier float is
concerned only the clearance in the aft plain bearing and the spline between
output shaft and planet carrier would allow very limited self aligning. Same 
goes for the sun gear plain pilot bearing.

As far as I know there are no Tracy 2.85's flying. Correct me if I am wrong
Tracy.
 
Here is my sketch of Tracy's 2.17 design.

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2003 All world wide rights reserved.