Does anyone have a suggestion on how to secure the Ford ring gear to
the reduction housing? Milo
You can try this trick. Make the housing bore about .1 inch larger in
dia. than the OD of the ring gear. Glue the ring gear in the housing
with red RTV.
Drill eight holes in the pattern shown in the picture. Use 5/16 18
tap drill "G" size drill.
Drill the "G" 0.2610 dia. tap drill holes down into the OD of the
ring gear about .150 to .2 inch. The ring gear is .3 inches thick
before you get to the base of the gears. Overall thickness is .4
inches including the height of the teeth.
Tap the holes in the aluminum housing with an ordinary 5/16 18 tap
as far as you can. Chase the treads with a 5/16 18 bottoming tap to
the end of the aluminum.
Turn down the treaded end of the socket head 5/16-18 screws .1 to
.15 inches long to a diameter of .2 inches. Start at the ends of the
threads . Or buy them. See the extended point screw attached jpg
from McMaster.
These studs will serve as a fail safe in the unlikely event the RTV
bond fails in shear.
This gives a bit of cushion to the ring gear as planetary's are self
aligning.
Drill the head of the screws and safety wire them.
Paul Lamar
BTW Milo. Install the ring gear last. Attach the planet carrier to
the output prop shaft first. While the RTV is not yet curred rotate
the prop shaft and planet carrier to center the ring gear in the RTV
and housing. Then let it cure.
Paul Lamar
Paul a couple questions,
We have machined the box housing .10 to accommodate the ring gear,
and the RTV for cushioning.
If I understood you correctly the RTV will carry the torsional load,
the set screws are there just in case the RTV shears, is that
correct?
I assume that the set screws do not make contact with the ring gear
in normal operation, is that correct?
We have devised a method to notch out the ID of the housing and the
OD of the ring gear to increase RTV shear strength. Is this a good
idea?
We would like to test the drive with only the RTV carrying the shear
load! Your thoughts! We can always install the set screws later.
We request one and all to suggest methodology for assuring that no
voids occur in the RTV at time of installation.
Milo
Won't hurt to test it on the ground but I would use the set screws in
the flight hardware.
Paul Lamar
After the RTV is in place, place the whole assembly in one of the bags
that are available for storing clothes and pull a vacuum on the bag with
your vacuum cleaner. This will remove any air trapped in the RTV so be
ready to add more if any large voids appear.
Gary Knutson
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