http://machinedesign.com/ContentItem/69974/Flexiblegearsbolsterwindturbinereliability.aspx
Matt Prather.
The best thing I can say about that web site is; it is recalcitrant :)
"The IFB consists of a double-cantilever pin supporting the bearing and
gear.
The cantilevered pin attaches to the carrier wall, and a cantilevered
sleeve
mounts to the free end of the pin. Gears and bearings mount on the sleeve."
"Simply stated, external forces on the gear make "the pin bend in one
direction, the sleeve bend in the opposite direction, and misalignment
angle at the gear face remains virtually zero," says Fox."
Interesting design but certain mechanical things don't scale up well.
Most well designed planetarys have a certain amount of flexibility built
in to handle this problem. They also have straddle mounted pinion shafts.
I was rather surprised when Ford changed the low modulus aluminum for
steel in the planet carrier for the six pinion version.
Paul Lamar ...No rotor no motor.
Paul,
In this case wouldn't the gearbox need to be scaled down? They are
talking about huge wind turbines here. These produce tremendous
instantaneous torques. The engine running the gearbox the opposite way
should be easy. I also think you may have been missing the point of the
sleeves. The ability of the bearing to "settle" on the shaft so the
double tapered roller bearing can transmit max. torque seems to be the
wrinkle. Most planetarys can float the ring gear a tiny amount at best.
This design seems to allow the planets themselves to find best angle so
they transmit equal power. That is different. This may be old hat to
some folks here, but I've never heard of it before. Anything that helps
take up the shock loads and transmit more power sounds good to me!
Bill Jepson
I am not belittling this idea. I just think it is unnecessary for our
size planet sets.
What I meant about scale was; small planet sets work no problem. Scale
them up
and the same percentage of clearances become larger in absolute terms.
Kind of like a turbine engine in reverse.
What I meant was the low modulus (one third that of steel) aluminum planet
carrier allows the planet shaft to move around slightly in all directions
including tangentially. Think of it being made out of hard rubber.
Not to mention the slop in the needle bearings.
One could probably do the same thing buy putting a thin ring of hard rubber
around the end of the planet shaft where it is piloted in the planet
carrier. As Vance's English engineer is fond of saying. "An ounce of
rubber is worth a pound of engineering" :)
The British also made a self adjusting gear mesh aircraft PSRU but
the details escape right at the moment. I have it around here someplace.
Paul Lamar ...No rotor no motor.
Paul,
I understand where you were going with the aluminum carrier. Any
misalignment greater than the aluminum housing would allow would
probably be destructive to the gear set. (Don't think Vance's ounce of
rubber even applies in this case.)I believe the Timken system was of
course designed around their tapered roller bearings. I have always
believed these to be one of the best rolling element bearings in the
world, but they aren't always available in the smaller sizes we need.
Prop shaft, no problem but planets is another story. I would love to see
a herringbone gear set become available in our sizes too, but spur gears
is probably the best we can hope for!
Bill Jepson
I think the ounce of rubber applies. Planetary gear sets are largely self
aligning. Not only the angle of the gear but the radial position of the
planet gear. If you constrain them too much then you get high point contact
stress concentrations. You just have to keep the planet gears from
interfering with each other that's all.
Paul Lamar ...No rotor no motor.
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