e-4WD?

I didn't say you did, I said I often needed chains. I don't think they would work well on my prius with its traction control. Have you taken your prius? those tires? I see you get my point. Wasn't trying to argue, just that the prius E four probably is not good enoug for those trips.

Yep. Not trying to argue

I think if toyota has a good e awd system they should sell it here. I just don't think it will be used much in california. I took the snow in a jeep with no chains, but skills, but used chains on fwd and rwd cars. I also flew up a lot in a small cesna, where the summer is the danger not the winter.

 

One simple way to visualize the complex motion of a planetary gear set is to divide it into two simple motions:
1. Rotate the sun gear (=MG1 shaft) Counter-clockwise one turn while holding the gear carrier (=ICE shaft) stationary, the ring gear will turn 1/2.6 of a turn clockwise (2.6 is the ratio of number of teeth ring/sun). Now, rotate the complete set (no relative movement among components) one complete turn clockwise. The end result is: sun: zero turns net, carrier turned one turn clockwise and ring gear turned 1+1/2.6 turns clockwise.
2. Now repeat turning sun another turn counter-clockwise while holding the carrier stationary, the ring gear will turn another 1/2.6 of a turn clockwise.

Now, combine both and you get: in case that the sun gear and the carrier revolve at the same RPM in directions as above - one carrier revolution results in 1+1/2.6+1/2.6 (=~1.77) revolutions of the ring gear (its RPM is in direct proportion to vehicle speed).
Same way if the sun gear RPM is twice that of the carrier (directions as above), one carrier (ICE shaft) revolution will result in about 2.15 revolutions of the ring gear (1+3/2.6).

Worth mentioning here that a planetary gearbox is considerably smaller than traditional step gearbox for the same torque rating. Among other things, the gears are much smaller owing to the fact that in any point in time the load is distributed to multiple teeth so the gears can be smaller (in case of 4 planets set - 4 teeth of each component are simultaneously engaged).

EDIT. Correction to ratio and more clear description (I hope).

 

For size comparisons, shouldn't we include the MG's at least?

 

Interesting and duly noted. Is it always the teeth that is the torque-limiting factor? Like, could the ring gear itself crack? The planetary carrier?

 

On really large gearboxes, torque can be limited by the planet bearings. Power on smaller, higher speed gearboxes is often limited by cooling.

 

Thanks and to state the obvious, it's the "E-Four" in the photo that is of interest, not the lime green (or whatever Toyota calls this color)!

 

E-Four ensures safe driving on snowy roads
For the first time, the Prius will feature an E-Four (electronic four-wheel drive) system, which uses a high-output rear motor to assist the engine and front motor as needed and continuously optimizes the allocation of power between the front and rear wheels. As a result, E-Four delivers levels of power and drivability under bad-weather and slippery conditions that are found only in a four-wheel-drive vehicle.

With a compact size and lightweight design that minimizes any negative impact on fuel efficiency, the system is positioned snugly in the rear of the vehicle to ensure plenty of legroom and luggage space. The luggage area capacity of the model featuring E-Four (with spare tire) is 457 liters, the same as the 2WD model (with spare tire).

Under the Hood of the All-new Toyota Prius | TOYOTA Global Newsroom

 

Yeah, but will it be available in the US? The US press releases don't mention it.

 

Yes that is my understanding too; no Toyota US commitment to E-Four in the 2016 Prius. A bit disappointing for me personally.

 

Surely available in Canada? (the great white north)

 

Actually it would make dollars.

 

So, if you get the E-Four, you won't get a spare? As the rear inverter takes up the space of the spare tire.

 

I wouldn't worry about it. Looks like it's not going to be available in the US at this time (based on the quietness of Toyota US). We won't know for sure until the dealers have the ordering info. Ditto for Canada. Maybe there is an initial limited availability of the necessary parts, or maybe they are just "no brainers".

 

You can thank ThePriusTeam for that, ha ha where are they these days. Leading up to the reveal they were finding it really difficult to keep all the secrets to themselves but now its all out, I would have thought they would be actively contributing to the knowledge pool here. Or are they still under NDA locked up somewhere?