The reason we are discussing dirt bike clutches is because your original question references all these concepts…as it contains one of each example.
The auto trans clutched planetary gear sets…with bands on the outside of the planetary to switch the ratios…the clutch pack is in the center of it all…to uncouple the thing at will.
Its all extremely clever if you ask me…surely is not cutting edge as these are old designs…
Amazing I say
Ok, I actually need a little bit of help here. I know how a one way sprag clutch works. But I think what I need to know is if the sprag clutch’s outer race is held stationary. I think what i would like to know is exactly what it does, I know it only allows rotation in one direction, but how is it used (like, how is it actuated to provide smoother shifts)? I think I know that the inner race is attached to the input shaft. I can’t find any videos that show exactly how it actuates or anything.
Both inner and outer races are held to their respective elements with the clutch between them. The outer race might be interference fit, inner race with a keyway for example. Only way the driven element can be tied to the ouput element…
Makes sense. On a roller one way clutch, the outer race is splined to the transmission case. I think that a sprag clutch also has splines on the outside of it, but I’m not sure where that splines up to. Maybe it splines to the clutch drum.
Thats why those cutaway… exploded parts views are so helpful. Many items in the trans are not immediately understood conceptually just at a glance.
You really do have to pay attention… there are a lot of clever things going on in there. I’m still amazed every time I have to look at some of those drawings etc…
Those picture diagrams are available… use the internet…
Ok, I think I understand now. So the transmission i looked at was a AA80E, and it’s one way clutch is only used to help make the shift from 1st to 2nd nice and smooth, but only manual mode. From what I can see, it only helps the B2 Brake in stopping the center planet carrier, and is used for nothing else other than that. In other words, it basically is a B2 Brake helper and it doesn’t do anything more than that. It also makes it so that the planet carrier can’t turn the opposite direction. The B2 brake also engages in first gear in low range. Nothing else changes when you put it into low gear. The only issue I think I’m having is now I’m questioning my assessment on how it works, since in the operation chart, it labels the One Way Clutch as a circle, not a triangle, which means it engages even in Drive. Here’s the Operation Chart. 
You can have first gear braked by a one way clutch in parallel with a brake bands/multiplate clutch, where the one way clutch is used for normal forward drive. Engine brake in 1st and reverse are provided by the actuated brake.
It was designed this way before the age of fast electronic that can open and close the first gear clutch precisely. And you want to be able to disengage first gear while coasting because such low ratio provides in significant amount of engine braking if the clutch remain engaged, especially in a modem 8 speed.
In that chart that you shared, the 1-2 shift is achieved by engaging b1 and releasing b1. If you get the timing wrong at such low ratio, you’re going to feel it, which is bad for a transmission meant for the lexus flagship. Using a one way clutch for first, b1 can progressively take the load as the one way clutch releases naturally
Also for cars with auto engine shutoff or hybrids, using a one way clutch rather than hydraulic actuation is one less load imposed on the engine/electric motor when it starts up
A one way clutch allows the stator of the torque converter to freewheel during low slip operation, making the torque converter act like a fluid coupling.
So, in other words, the one way clutches inner race, which is connected to a planet carrier, never actually stops spinning, (unless B2 is applied) it just absorbs the shock impact of the B1 brake applying? It basically just takes the shock of the B1 brake applying so that way the shift becomes less jerky?
Yeah, I know about the one way clutch in the stator…
It wants to spin in reverse in first gear while under power. After you pick up some speed, around 10mph, and release the throttle, the engine drops to idle and the tires are driving the carrier forward. That’s when the one way clutch releases.
If you’re going down a steep hill and have manually selected first, the carrier is driven forward by the tires. But the b2 clutch is engaged to lock the carrier.
So in a sense, the one way clutch just prevents the carrier from spinning backwards, and when you pick up some speed, the carrier starts spinning because of the wheels, so then the one way clutch releases it’s grip and then the one way clutches’ inner race just spins around without doing anything else. So in other words, it just locks the carrier in place until the wheels get momentum, and then it releases since the tension is gone?
EDIT: Ok, I rewatched a video on the subject and this guy is saying that the one way clutch mainly activates during acceleration. If so, that also confuses me as to how it is activated in only 1st gear.
For this transmission, from the calculated kinematics of that carrier, it only wants to spin in reverse while accelerating forward in first gear. From 2nd gear onward, that carrier turns in the forward direction
Alright, thank you! I understand the concept now. So it basically holds the carrier from turning the opposite direction, preventing a really hard shift from 1st to 2nd.
@chunkyazian gave you some excellent insights. It would help if you actually held a planetary gear set in your hand…and imagine what power inputs and torque loads would be trying to do with each component.
Then you can layer in why clutches and one way sprags are sprinkled where they are etc… A clutched, sprag’d, planetary is deceptively complex and very elegant in design.
I find it very entertaining personally.
I guess what I was trying to figure out was just exactly what it was there for. In the AA80E, it has one one way sprag. Also, assuming that the AA80E only has 3 planetary gear sets, it would make sense for the middle ring gear/planet carrier to want to spin backwards under acceleration.
Before you try to wrap your head around this Aisin 8 speed, I would suggest that you study how the Ravigneaux gearset works. This is a 4 speed units from the 50s. After you study this, then study the Lepelletier gearset. Lepelletier figured that adding a reduction gear before the Ravigneaux results in a 6 speed. Once you understand the Lepelletier, you can study the AA80E. Aisin, amongst others, figured out that adding one more clutch results in an 8 speed
Are you telling me, that these amazing devices I am so enamored of, are French in origin @chunkyazian?
Not in a million years would I have imagined this…
Now that @chunkyazian has given you the proper names of what I was simply calling a “planetary” gear set… You can type those names in a search and you will find all sorts of diagrams and better still animations of those gears in motion. There are tons of them to view.
This is but one of them that directly addresses many of your questions…
I watched a video on the AA80E from WeberAuto, and the guy went over the Lepelletier gear set and the Ravigneaux gearset. It’s a fairly in-depth video, he goes over the entire structure of it piece by piece. It’s an hour long video, but he shows what happens when gear shifts occur, and what clutch packs apply during shifting. By you explaining that the middle planet carrier wants to spin backwards when starting off in 1st gear, it suddenly rang a bell in my head as to why the one way clutch was there. I think I understand the AA80E fairly well, as it’s design is actually fairly simple. It really is quite a feat of engineering