Complicated and British...
Posted on 12/09/2024 8:28:32 PM PST by Red Badger
The efficiency of a tooth-on-tooth geared transmission, with the smoothly variable gear ratios of a CVT – minus the belt friction and capable of going all the way down to a zero ratio without needing a clutch. That's a 'holy grail' level promise!
Italian company Alter Ego, led by mechanical and automation engineer Edyson Pavilcu and assisted by kinematic studies undertaken at the Milan Technical University, says it's prototyped a beautifully complex new mechanism – the world's first geared CVT – that's 10% more efficient than a regular belted CVT.
Indeed, the efficiency is on par with some manual transmissions, while offering the ability to smoothly adjust gear ratios from zero all the way up to overdrive, whether the wheels and/or crank are turning or not.
A quick manual vs CVT transmission primer
Why is this a big deal? Well, transmissions are designed to let a drive system – be that an engine, an electric motor or a set of cyclists' legs turning a crank – operate at its optimal speed for efficient torque delivery, while adjusting the gear ratio between the drive system and the wheels to give just the right leverage for the current speed and situation.
Manual transmissions are very efficient, meshing metal gears together to deliver between 95-98% of input power to the other side. But you can only have as many gears as you can fit in the box, and multi-clutch systems aside, you have gaps in the power delivery where you need to friction-clutch out of gear then back in to the next one. When in gear, your ratio is locked, so your engine speed has to vary as you accelerate or decelerate. You can stay close to your ideal engine speed for the conditions, but not dead on.
(Excerpt) Read more at newatlas.com ...
The “complex” description got me - I almost got my wife a Nissan Murano because one of her friends had one and she thought she would like it too. I test drove it and the CVT felt different but smooth - I did some research, and at the time, the CVTs were suffering a lot of problems so I got her a Rav4 with a V-6 - which she fell in love with and it held it’s trade-in value over 7 years when we traded in for a 2016 Highlander - which was also a seriously nice vehicle - even nicer than my 2018 Mercedes GLC300 which cost about the same.
We finally decided to go single vehicle - she doesn’t drive as much as she used to - and opted for a 2024 Rav4 with all the bells and whistles...it may outlast us both as we’ve only put about 1K on it in the 2-1/2 months we’ve had it.
The CVT is interesting - but doesn’t seem to offer any real advantages unless one hates to be able to detect a shift - and the new “upgrades” need to be proven over a few years before I would consider one if I were still in the market.
Did you watch the video?.......
“CAFE standards have been making it difficult for major automakers NOT to go CVT on many vehicles. So now we have transmissions that fail before spark plugs, weird. I’ll take a Mopar three speed torqueflite. Whatever is in my Toyota Avalon works fine, too. Anything more than six speeds is overkill.”
Unless you had a 10 second car with 5.13 gears that really “hooked up”, you could not break a Turbo Hydra-Matic 400 transmission if you tried. Unfortunately, it supposedly took 18 horsepower just to run the hydraulics.
I have a 2013 Nissan Murano and a 2021 Nissan Kicks with CVT’s. Both are running fine but I am wary of them and hate they way they drive. My wife and son drive them.
A friend at work just had her CVT tranny crap out on a 2015 Rogue, almost $4K to replace it.
It was a joy to drive though, until a friend of mine bought a 1999 Lexus LS400. I was living in King George County Va., while he lived in Potomac Md. Probably a 50-60 mile drive, so he asked me to drive his car while he relaxed, theoretically.
I started complaining that everyone was driving so slowly. I glanced down at the speedometer to see I was tracing at 90 miles an hour, but it felt like I was driving about 70 miles an hour at most. That Lexus drove & rode like a dream. I was very impressed.
Well, this gives me some concern for mass production:
“complex”
Yep, reason we ended up going with a Kia instead of a Subaru a few years back was that the Subarus had CVT.
Doesn’t look all that complex to me................
You want something complicated? Consider the Torsen differential gearing as used on the HMMWV. It worked just fine- until it didn’t. It was a bitch to fabricate, and reliability was a little dicey, as it was a real bear to overhaul, the failure usually being the pinion gear and the resulting progressive failure of the seals related to the shaft.
Yes that is very complicated..................
shifty...
Thank you for the info.
No problem, I had to look it up for my own ignorance, so I thought I might as well state what I found. 🙂👍
“Did you watch the video?.......”
No - did you see something amiss with what I wrote?
Ferrari Transmissions are a marvel of engineering. Shift in 0.02 a second. Until you need to get one repaired.
No, there’s nothing wrong.
The CVT’s in the Nissan cars you mentioned are belt driven and prone to failure from wear. That was covered in the video. You dodged a bullet.
No belts in this CVT design, just gears. But it’s just a prototype and hasn’t been proven in the real world yet. It hasn’t been put in a vehicle, tested for wear, torque stress on the gears, etc. But it looks promising, and it doesn’t seem all that complicated, at least to me...........................
Thanks - once it is a proven product, I’ll change my tune - but with complexity come a myriad of potential failure points...It’ll take a few years, after widespread production for it to prove itself. Until then, I’ll stick with more conventional transmissions - 8-9 gears and still durable for decent performance/mileage even with smaller engines.
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