Would anyone be able to provide some examples of a planetary gear system that enables independent rotation of either the i) ring gear (+planet gears) or ii) sun gear (+planet gears) from a single motor? As far as I'm aware for i) I can't lock the planet carrier since this requires the sun gear to rotate, but I could lock the sun gear and allow free rotation of the planet carrier + gears causing the ring gear to rotate. I am unsure what the sleeve mechanism around the main rod for the planet carrier would look like though. For ii) I imagine I could just use a clamp around the ring gear to prevent rotation and then just use the sun gear as normal.
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Planetary Gears - Independent Rotation
- Thread starter astraios
- Start date
GregLocock
Automotive
Sturmey Archer 3 or 4 speed bicycle hub, any number of automatic gearboxes. From wiki
mfgenggear
Aerospace
op
tons of stuff on YouTube.
exactly what is the intent.
maybe two stage planetary gear set.
tons of stuff on YouTube.
exactly what is the intent.
maybe two stage planetary gear set.
- Thread starter
- #4
I basically need to be able to change between configuration 1 and 2 of the gif GregLocock provided in the simplest way possible. With both 1 and 2 able to go in the reverse direction also.
BrianPetersen
Mechanical
So you want to switch between (1) sun input and locked ring, and (2) ring input and locked sun, in both cases with the planet carrier as output?
It means, conceptually, you need two clutches on the input shaft (one leading to the sun, the other to the ring) and two brakes (one leading to the sun, the other to the ring).
Something to think about also, is how you're going to get the output out without one of the other shafts having to pass through the same space and time. If you have concentric shafts, for example, you can't clutch the shaft on the inside to something that's on the outside of the outer shaft (that's turning at a different speed). Sometimes you can cleverly wrap around the end of the gearset or enclose parts of it ... Not all combinations of selecting which elements are inputs, outputs, or locked are physically possible.
IIRC the Sturmey-Archer bicycle hub always has the sun locked. The mechanism to select whether the input freewheels select the planet carrier or the ring are on one side of the gearset, and the mechanism to select whether the output freewheels select the planet carrier or the ring are on the other side of it, and this way it's easy for the sun to be locked because it passes all the way through the inside of the whole thing from one end to the other, and for a bicycle hub, that's really convenient because it's the same fixed axle through the middle of the wheel that you secure to the frame of the bicycle. None of the inputs or outputs have to "cross over" a different one.
If you need two ratio choices, your life will be much easier if one of the possible choices is 1:1, because then (for example) you could hold the sun locked, always take output from the planet carrier, and use clutches to select whether the input goes to the ring gear or the planet carrier. Or, if you can't deal with a stationary through-shaft or you need a bigger ratio difference, you could always drive the sun, always hold the ring locked, and select output from either the sun (direct drive) or the planet carrier (reduction).
As far as I know, even the simplest 2-speed-plus-reverse planetary gearsets from the early days of automatic gearboxes (e.g. Chevrolet Powerglide) used compound planetary gearsets because of limitations on which inputs and outputs can physically be achieved.
If you want to make your head hurt, study the power flow in a ZF 8-speed. Somehow they managed it using only 5 shift elements (clutches or brakes).
It means, conceptually, you need two clutches on the input shaft (one leading to the sun, the other to the ring) and two brakes (one leading to the sun, the other to the ring).
Something to think about also, is how you're going to get the output out without one of the other shafts having to pass through the same space and time. If you have concentric shafts, for example, you can't clutch the shaft on the inside to something that's on the outside of the outer shaft (that's turning at a different speed). Sometimes you can cleverly wrap around the end of the gearset or enclose parts of it ... Not all combinations of selecting which elements are inputs, outputs, or locked are physically possible.
IIRC the Sturmey-Archer bicycle hub always has the sun locked. The mechanism to select whether the input freewheels select the planet carrier or the ring are on one side of the gearset, and the mechanism to select whether the output freewheels select the planet carrier or the ring are on the other side of it, and this way it's easy for the sun to be locked because it passes all the way through the inside of the whole thing from one end to the other, and for a bicycle hub, that's really convenient because it's the same fixed axle through the middle of the wheel that you secure to the frame of the bicycle. None of the inputs or outputs have to "cross over" a different one.
If you need two ratio choices, your life will be much easier if one of the possible choices is 1:1, because then (for example) you could hold the sun locked, always take output from the planet carrier, and use clutches to select whether the input goes to the ring gear or the planet carrier. Or, if you can't deal with a stationary through-shaft or you need a bigger ratio difference, you could always drive the sun, always hold the ring locked, and select output from either the sun (direct drive) or the planet carrier (reduction).
As far as I know, even the simplest 2-speed-plus-reverse planetary gearsets from the early days of automatic gearboxes (e.g. Chevrolet Powerglide) used compound planetary gearsets because of limitations on which inputs and outputs can physically be achieved.
If you want to make your head hurt, study the power flow in a ZF 8-speed. Somehow they managed it using only 5 shift elements (clutches or brakes).
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