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
------------------------------------------------------------------------
There are two drawbacks to this box Scott.
Number one: the prop rotates in the wrong direction. I suspect but
I could be wrong props like that are hard to find. I happen to
have a nice one that I am willing to sell. Here is a picture. It is
a Warnake.
Number two: you will be quite a bit down on power. A turbo would
be cheaper than a new box if you can find one.
I have a box just like yours. I have new bearings on order with
the idea of upgrading it to 3-2-1. I need to check with my bearing
supplier tomorrow.
I'll have more info on this in a few days. It will need a new prop
shaft and prop flange.
Paul Lamar
Paul,
When I purchased my drive I specified the 3.2:1 configuration, but
it has been a long time. I will put it back together and measure
the actual ratio.
I will also check to be sure there is nothing else preventing the
ring gear from touching the planet carrier except for the o-ring.
If the latter is the case, would a Viton o-ring be a better option
than Buta-N? These are available, but have a 0.21� actual thickness
(vs. the spec of .19�.
My aircraft is a pusher that uses a Warp Drive prop, so I should be
OK with the prop.
Scott Gettings
I did not realize Warp drive made pusher props.
I guess that is what Ken Welter used. His belt drive
rotated in the same direction as the E-shaft. Namely
counter clockwise when standing behind the air craft and
the back of the engine.
If the intake is on the right (and it is ) when sitting in the drivers
seat the engine
rotates counter clock wise. Turning it around on a vertical axis
it becomes clock wise like a tractor aircraft engine. All well and
good if the PSRU rotates in the same direction as the engine.
Your pusher prop will rotate clock wise while the engine is rotating
counter clock wise. Same as a tractor. So the same blades can be used.
You are OK.
In a pusher standing behind it the intake is on the left.
I find all that very difficult to conceive all that in my mind :-) Maybe
it is just
me.
Paul Lamar
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