Not a challenge, but a plea: where's your source(s) for this? I'm about where you were, but would love to know more about the internals so I can make an informed choice when my current (ICE) car dies.
The wikipedia page is quite in depth [0] but is quite dense and took me a few goes to understand. They're fascinating to understand, and they really are mechanically simpler than a standard ICE + gearbox drive line. I got nerd sniped one day figuring out how my Toyota Crown "gearbox" worked only to discover it doesn't really have one. They don't even have a real neutral gear, the wheels are always mechanically linked to the engine.
They require much more active computer control to work though so they aren't logically simpler in my opinion, but mechanical simplicity is what makes the biggest difference.
There are certainly better more approachable sources though so I leave this as an option as the info is there, but can take a moment to understand.
The way I think of it comes from the old ME degree I got. You can analyze assemblies by the number of degrees of freedom. Three degrees of freedom, like three linkages pinned at the corners is a triangle and the relative positions of each element are fixed.
Four axis, like a square pinned at the corners if you know the relative position of two elements you know the position of the others. This is the basis for most traditional machines.
Five axis is floppy. And usually avoided traditionally.
The synergy drive is a five axis machine mechanically. But has two electric motor generators. By varying the speed of the motors you can control the gear ratio of the mechanical path. Since the motor speeds are indignantly variable so is the mechanical path. You end up with continuously variable transmission with a mechanical power path and an electric one in parallel. And it doesn't suck like pure mechanical ones.
I’m with you in general. Though, with the amount of electronics and “computer-complexity” that modern ICE cars have, I’m not sure there’s a meaningful difference!
That's really good, I watched one of their older videos to understand what I was getting into before I bought a Toyota a few years back. For those reading, the video is from Weber State University, they have a series of hourish long detailed videos on various automotive components including different versions of the Toyota electric transaxle and rear electric drive unit (mechanically separate but present in the AWD vehicles).
My takeaway was the same as some of the other posters here, the system is an engineering tour de force. Simpler than the gas version, proven reliability, and efficiency not too far off the theoretical limit of gas-burning drive trains.
This video cleared up my confusion and corrected my misconceptions, giving me enough knowledge to hold a one-hour discussion with an actual Toyota mechanic.
Also, YouTube helps. Search for “Power Split Device” or “e-CVT”.
Regarding other hybrid tech, it’s a bit of a crapshoot. I basically use ChatGPT with search enabled to have sources, and then ask how the system works. It’s never in the marketing materials, I guess most don’t care.
Respectfully, why are you asking for sources on an already high effort subjective post instead of verifying the info yourself? Wikipedia is a great place to start with car spec stuff.
Because when I ask questions like that in this forum, I get great answers (as you've seen). And, other visitors with the same interests can benefit from those answers.
