Whatever happenned to the gearless transmission?

Many years ago I remember reading about a new type of transmission that would allow for an infinitely variable gear ratio (as opposed to a collection of fixed gear ratios).

It worked by having an input disc connected to an output disc by adjustable semi-perpendicular wheels. For a low gear ratio, you’d set the angle of the wheels so they contact the input disc near the edge, and the output disc near the center. Here’s an ascii art diagram, if you’re having trouble visualizing it:



input disc| = |output disc
            ^ the angle of these wheels can be adjusted

Anyway, whatever happened with this concept? Was it abandoned, still in the design phase, or has it actually been released on certain car models?

Sounds like you are asking about a CVT, many cars use them - link.

They’re call a Continuously Variable Transmission (CVT) and they are quite popular. The Wikipedia article states:

ETA: Ninjad while copying and pasting.

I believe that manufacturers intentionally put in a “thunk” in changing gears even in the CVT because it was what the consumers expected.

My brother has an Altima with a CVT and it’s really disconcerting to me as there’s no shift feeling in it whatsoever. He didn’t even notice it until I pointed it out.

Your brother might be better off if you hadn’t mentioned it. Now, he might always notice it as bothersome. Hopefully not.

Electric cars and motorcycles drive similarly - no gear changes. That was a little weird, riding my friend’s electric bike. And also driving my in laws’ Prius, or the Tesla on a test drive. I think people will get used to it. Or at least they can, given time.

That’s for different reasons, though. Your basic Joe-average internal combustion engine has a minimum rpm that it needs in order to keep itself running, and a maximum rpm before it breaks, which requires gearing to keep it in that range. An electric motor produces torque right from a dead stop and all the way through its operating range, so it doesn’t need gearing. A CVT is actually adjusting gear ratios. An electric motor isn’t.

The lack of engine noise also seems weird on electric cars and bikes.

Yeah, not as far as I know. He’s not the type of guy who is bothered by pretty much anything and certainly would let me know if he was.

I suppose this is a good place to ask, and Google wants to tell me the mechanics but not how it works from the user’s end:

What is driving CVT like? “Set it to D and forget it” like automatic, minus clear transitions? What are typical gearbox settings, typical P-R-N-D-n-2-1?

Yes, it’s pretty much as you describe it here.

The transmission settings on my 2001 Prius are P-R-N-D-B, where “B” stands for “Braking.” When the transmission is in “D” you get very little engine braking - the car just coasts when you take your foot off the gas. When you put it in “B” it engages regenerative braking and also forces the engine to spin, giving engine braking. It’s supposed to be for going down steep hills. I never use it, despite the fact that I live in a hilly area.

My Outback has P-R-N-D-M. The M is a M is a pseudo-manual flappy paddle shift set-up that picks 6 or 8 places to act as defined gears. I’ve never used it, and doubt I ever will, I don’t see the point really. I just put it in D and very seldom notice it’s not just an automatic.

I do notice it while paying for gas however. :wink:

Right, but I think that’s just a gearbox choice on some CVT and automatic cars, but neither transmission has that function by default.

Regular automatic transmissions do the same, it’s just a lot more awkward and unnecessary to switch L-2-D-OD.

My wife has an 2016 outback, and uses the paddle shifting descending long hills (we live in the mountains and routinely drive over the continental divide). She seems to like it. I can’t comment as I’ve only driven it a few miles.

CVTs may be popular with everyone – except car reviewers. If you look at the zillion reviews on Youtube, you will hear them railing against CVTs endlessly, though it’s not real clear why.

I have a 2010 Outback and I use it for the same reason. You can also use it in winter to start in “2nd” gear helping to avoid wheel slip, but it’s rarely needed with AWD.

what car enthusiasts want is usually quite different than what the average car buyer wants.

my main complaint with stepless CVTs is that it makes it more difficult for me to know what the drive wheels are doing in low traction conditions.

They seem to get down to 2 things: They’re less fun, which I guess is absolutely true, but meaningless to the “car as a transportation appliance” drivers. And they wear out early, which apparently has been a problem in the past, but has improved.

I find this interesting since manufacturers have been trying to totally remove the “thunk” in automatic transmissions for decades. Wannabe hot rodders have even found ways to defeat the modifications designed to reduce it on the theory that the smoother shift was somehow slower.

I bought a pickup from such a guy once and I had to replace the transmission because the slam from first to second and second to third was just too annoying.

There’s more than one way to make a CVT. One primitive type uses opposing conical drums with a big v-belt between them - the drive ratio is determined by changing the distance between the drums, which changes the diameter at which the belt rides. This type of CVT probably does wear out early. The Prius uses a modified planetary transmission, which is actually very rugged.

Just because you sound super suspicious about these “wannabe hot rodders,” here is a good explanation of why people install shift kits (which I totally understand are not for everyone). A smooth shift is produced via shift overlap, which is essentially like slipping the clutch on a manual – increased friction, wear, and heat, while wasting energy that could be used for forward propulsion.

http://www.mistertransmission.com/what-are-shift-kits