Paul, do you or anyone on the group remember the change in crankshaft
resistance after torquing down the RD 1C 12" an4 bolts at final
assembly?
The assembly instructions show a trial fitting without the 5 1/8 inch
ring gear spacer o-ring. This worked well on my unit, with the
crankshaft turning easily by hand. However I found this oring was
missing from my unit.
Tracy's specifications are for a 5 1/8 inch outside diameter and
0.190 inch thickness, which corresponds to an AS568-351 (3/16"
thick). I ordered some of these, but found that the actual thickness
is 0.21 inches, not 0.190". I cannot find any metric or other
equivalent size that exactly matches the 0.190 specification.
When tightening down the drive bolts to the final torque, the
resistance to turn the crank shaft roughly doubled. I can still
detect just a little bit of backlash play, but the torque required to
turn the crank shaft without spark plugs installed is approximately
20 foot pounds. It appears this is due to the resistance of the ring
gear pressing on the O-ring against the adapter housing.
Does anyone know if this amount of resistance is normal, or perhaps
Tracy was using some o-rings that are exactly 0.190 inches in
thickness?
Thanks!
Scott Gettings
I assume that is the late one that does away with the torque
damper. I have no experience with that one. Send me a dwg or sketch
if you can. A picture or two would also help.
Typical of O-ring dimensions. It gets real critical when you are
dealing with the rotor housing O-rings. Too big and it will crack the
cast iron.
I this case it's not that bad.
Paul Lamar
The RD1 C still has the 4-bolt damper that mounts to the flex plate.
I added AN 970 large washers to the bolts on the engine side to the
plate, which was obviously highly stressed by the bolts and standard
washers on that side. It is also easy to inspect.
I have attached the expanded view of the RD1-C. The ring gear has a
45 degree cut on the outer circumference to accept the o-ring. The
oring just pushes against the solid adapter cylinder (the part that
bolts directly to the adapter plate), thus keeping the ring gear
tight. It seems this oring spins against one or the other surface
when running. So when trial assembling without the oring, the gears
spin freely. With the oring in place, there is pressure on the ring
gear as the bolts torque down.
Here is the scan and adapter pix.
Thanks, Scott Gettings
The ring gear is stationary. The bulkhead the ring gear splines on
is bolted to the gear box case. Nothing critical about that O ring.
Those bolts are flat heads screws. The early ones where known to
shear. I think the diameter was increased in the later versions.
The stock Ford bulkhead is powdered metal and SUPER hard. Makes a
good bolt shear :-)
Old message:
"I found that seven (7) of the eight (8) 1/4-20 bolts holding the
ring gear to the casting were broken. Only one bolt was still in
tact, and it was loose. After discussing this with Tracy, we agreed
to drill and tap them to 5/16-20 which I did. "
Please take one of those screws out an measure the diameter for me.
After you fly it for a few hours it disassemble the gear box and
check those bolts that bolt the ring gear bulkhead to the gear box
case.
Paul Lamar
Will do.
Scott Gettings
Paul,
I opened my RD1-C drive, and have included some pix. The ring gear is
on a splined shaft connected directly to the prop hub. It is not fixed
to the case and does not have the screws mentioned above. The ring
gear can easily be pulled out, as per the pic. The planet carrier is
fixed to the �spacer� part of the RD case (against the flat adapter plate).
You can see the location of the o-ring. When in place, it sticks up
about 0.03� before compression. Since the surface on the spacer/planet
carrier where the o-ring contacts is rough (see pic) , it appears that
the ring gear must rotate along the fixed o-ring surface. There is
nothing else other than the o-ring holding the ring gear from impacting
the prop side of the planet carrier.
Turning the engine over without compression requires about 10 ft-lb of
torque. When the o-ring is compressed, this doubles to about 20
ft-lbs. Do you think this is an acceptable amount of drag?
Thanks again?
Scott Gettings
Aw so my mistake. I thought all C versions were 3.12 to one. You have
a 2.12 to one I think.
Power is out of the ring gear rather than the planet carrier as in a 3-2-1.
An O-ring used in that fashion is very very unusual to say the least.
That is not what they are designed for.
Maybe Tracy did that to dampen some vibrations. I have NO idea what he
was thinking :-)
Paul Lamar
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