Paul do you or anyone have plans or directions for converting 2.17
redrive to 2.85 Tracey said I could buy the parts but no plans or
directions I have local machine shop and can do some myself or might
be
that some on news letter do the conversion if I can get this solved
then
can look at one of the support plate as it sure looks very good

Thanks Keith

The problem is; you must get the power out of the planet
carrier and lock the ring gear. It takes a different
planet set to do that. The issue then becomes; is the housing
small enough in ID to lock the new ring gear? Take your
2.17 apart and measure the ID where the ring gear goes.
Let me know what that dimension is.

Paul Lamar
-- Paul
The ID of the housing that holds the ring gear is 5 1/8 ID the OD is
6 3/8 Thanks for the help Keith


The six pinion ring gear is about 5.023" OD so you will have to
machine
an insert and install it in the housing to lock the ring gear in place
and take the power out of the planet carrier. The next issue is the
spline of the planet carrier must match the spline on the end of
the prop shaft. Measure the OD and count the teeth of that and let
me know what that is. The six pinion planet carrier I have has a
root diameter of 1.195" and an OD of about 1.320". There are 27
teeth. If all that works you may still have to change the sun gear
on the input shaft. The six pinion sun gear has an OD of 2.474",

Paul Lamar
                   

What is the  "ideal " reduction ratio ?  I have 2.17 to 1, but
wouldn't it be better to
run the engine higher and the prop slower ( like 2400 RPM )  What s
the ideal RPM for the
13b for out put and longenvity/reliability ?  would 3.something to 1
be much better.
forget about gears fitting into housings, what is the best ratio ?
BTW I am working with
two atkins aviation 13b ' s

thanks

Lionel

From the sounds of it you want a cross country airplane. As far as
we can tell
the 2.85:1 has proved to be a rather good ratio for cross country
airplanes.
The rotor bearing loads are a minimum at 6000 RPM. That is were the
weight
of the rotor is balanced by the combustion pressure loads. That
would be
a good cruise 2100 RPM. If you don't mind a modest take off
performance
a 2.17:1 can be run flat out for cruise at 6000 RPM. 2750 prop RPM.

My impression over the last 11 years, using side port engines with
kludged
up intake manifolds and 2.17:1 gear boxes, is people were disappointed
with the performance and HP. My guess is the avg. HP level was
around 150 HP.
A p-port engine would improve that somewhat. Perhaps 180 HP or so.

If you want STOL or sea plane performance you need a large prop for
good low speed thrust so something a bit higher like 3.17 would work
well.

Reno racing on the other hand where you can run the engine at 10,000
RPM for 15 minutes something around 4:1 would give you 2500 prop RPM and
a much higher power to weight ratio. Normally aspirated one would get
well over 300 HP out of a 13B p-port and probably well over 600 HP
turbo charged. Add 1/3rd for a 20B to all of the above HP numbers.

Paul Lamar

You mean to add 1/2 for a 3 rotor right?

Chris Cosman

Right Chris. Brain fade :) Thanks.

Paul Lamar