Hi Paul, we meet briefly a couple years ago at OSH. I have about 250 hr.
of
flying on my project and a new web page at www.netlynx.us/sahobby I broke
my Ross redrive a year ago and I'm looking for some inspiration to get
back
to it. Thanks Mark Kirkpatrick
What part broke?
Paul Lamar ...No rotor no motor.
I would use it for a boat anchor and go buy one of Tracy's.
Ken
I love those nice Ross castings. The Ross is the lightest
box around. I would dial indicate the ring gear for run out
and if that was OK I would fix it. It has too many bearings.
All you need is the self centering sun gear and the e-shaft
pilot. Planetary are intrinsically self centering on the ring
gear and that is how the loads on the gears [teeth] are equalized,
If you are throwing it away I'll pay shipping.
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A 20B in and of it self, I maintain, does not have enough
torque to break a Ford four pinion planetary gear set.
The 20B torque is 240 ft pounds max. To prove it set the planetary
up on a bench. Lock the ring gear in place. restrain
the planet carrier from rotating. Allow it to float.
I am willing to bet $100 it won't fail with 1000 foot
pounds of pure torque applied to the floating sun gear.
These planet sets are used with V8 engines that have 400 foot
pounds of torque behind followed by a torque converter that is
putting out about 600 foot pounds or more.
Notice the discoloration the bearing forward of the sun gear.
Perhaps this was putting enough heat into the sun gear to
weaken it. That is one scenario. That is in addition concentricity
problems. Another is the clutch disk used by Ross could be a factor.
Tracy uses a rubber coupling. Vance used to tell me he knew of an
English engineer that was fond of saying: "An ounce of rubber is
worth a pound of engineering" :)
Paul Lamar ...No rotor no motor.
Paul, I too am wondering why it broke. Let me give you a little history on
my redrive. At 125 hrs. the forward thrust bearing failed. When I had it
apart the sun and planet gear had some wear. Not bad but more then I
expected with so little time on them. At that time I replaced the sun and
planet gears and modified the drive to try and oil the gears like Tracy
does. I put a bushing behind the sun gear with an oil passage and drilled
the shaft. There are pictures on the web site
www.netlynx.us/sahobby if my
description is not clear. That mod lead to finding out that nothing in the
drive lined up. The day I got the drive from Chris Ross he told me when I
bolt the drive up, before I tighten the bolts to shove the drive as far to
one side as it would go. That always bothered me. So my train of thought
when modifying the drive was to do a better job of lining things up.
Something you said got me to thinking. You said I don't need these bearing,
and I'm wondering if they may have been the problem. If the shaft is held
firm and is not exactly aligned might it only be loading one or two of the
planet gears? Second question has anyone taking apart the front of there
Ross Drive? I got the two pins out by welding some stainless steal welding
rod to them and making a slide hammer to pop them back out but the shaft
won't budge. Before I take it to the 10 ton press is their anything elsa
holding the prop flange to the shaft?
Mark Kirkpatrick
I think the bearings were part of the problem. The sun gear needs to float
so the loads on all six pinions can equalize. Perhaps some sort of adhesive
like Bearing Lock. Try heating it to about 300 F. If that does not work
make a special tool in the lathe that pilots on the hole in the
shaft and is just large enough in diameter to engage the walls of the hollow shaft.
Paul Lamar ...No rotor no motor.
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