Today I took delivery of my brand new car after almost 18 years. It's a NISSAN ALTIMA and it has a CVT. It does a great job of keeping the engine in a low rpm range which obviously means better mpg, less wear and quieter. This engine has 188 hp but at 2.5L has nice torque anyway.
Would such a transmission in heavier duty design be viable in buses? Smooth operation and keeping the engine in the ideal range sounds good. There are pros and cons. Thoughts?
no, because drive belts won't hold up. They do work well with small engines. My daughter has a Honda crv and it works fine.
Several years back, GM was going to offer them on their larger vehicles. Pulled the plug at last minute. Couldn't get durability necessary.
Unsure how large an engine is behind them these days.
NISSAN has it on the MAXIMA which has the 3.5 V6 so it may top out at that.
My ladies new escape with a turbo 4 cylinder, has a cvt, no towing, her last escape with less horsepower and a real transmission could tow up to 2200 lbs...
My Subaru has a CVT. I had an interesting talk with a service tech about it when I first had the car and one of my shift points was becoming harsh.
The things are designed to keep the engine at the optimal RPM. Working on their own, the driver would never feel a shift since these things really don't shift. The engine gets to the correct RPM and stays there and then the transmission does its magic to keep it there as the vehicle accelerates.
However, people are so used to feeling their car shift under them that the engineers had to add artificial shift points into the system. Not feeling the car shift was so disconcerting that people didn't like it.
At some point in the first few years in my Crosstrek one of the shift points got really screwed up and the car lurched from one to the next. It felt like something was mechanically wrong, but all they did was reprogram things. Too bad they couldn't just remove all the fake shift points. My guess is that if they did, it would feel about as close to driving an electric car that a gas car can get with smooth acceleration all the way up the speedo.
down side of a cvt is they are throw a way so when they screw up there is no fix and as my buddy found out it's only 6-9 k for a new one at the dealer at 67k miles ? found one at a wreckers for $2500 and when all was done it cost him 4k . 500 miles later the car was sold
but they have worked awesome on snowmobles for ever but it is easy to change the belt
the wife has the 8 speed 2 clutch auto ( kinda standard ) like a formula one race car and so far it is awesome
dave
I had the Nissan NV200 cargo van with the cvt. I think all Nissans except the skyline use the cvt transmission. At 22,000 miles the cvt went kaput and the dealer put in a new one. Never had the van with anything in it. with the 2.0 litre engine it was powerless. Traded it in for a Ram Promaster 3500 since I wanted towing capability. From my understanding, none of the CVT's allow towing and if they do, it is under 2000lbs. Almost all new cars today are coming with CVT's to meet the required fuel efficiency standards. Personally, I do not like the feel when you get on them. Makes your neighboring lane driver think you are about to race them and off they go leading the way. As said before, they run a series of belts that allow slippage to keep the engine in a perfect power band to road speed. My FIL has a Hyundai Venue with the CVT. Driving it around town it feels like a normal geared transmission. (Many car makers have put a program in to give the feeling of "Shifting") When you need to accelerate on the highway, you need to rev the piss out of the engine. I think more noise than go is what it feels like but in reality, it does pick up speed. (1.5 liter engine on that one)
Thanks guys. Everything has its drawbacks. Time will tell how it holds up for me but it is smooth that way though I will miss the sound of my old GRAND MARQUIS going thru the shift points.
But hey, as long as I don't have to shift it myself, any automatic is fine. Hey think about the long gone DYNAFLOW.
Had a Burgman Maxi Scooter with one. Worked quite well. There was a manual mode you could move rocker switch to allow belt to climb higher or lower. Had to watch revs or it would hit limiter before moving switch. Felt like shifts there. Overall loved it in that application. Always Honda should of gone that way on a Gold Wing. I could easily jump a Harley for 500 feet off a light before he went by. Fun for the shock value for unsuspecting since few knew about them.
The 2011 Nissan Altima with over 170k runs fine. I personally am not a fan for the constant RPM it strives to maintain but it drives fine and goes when you put your foot in it. There is a sport mode and also has manual gear selection so it offers some features for a more active driving experience but still nothing like a manual shift.
I travel frequently for work so I am in a lot of rental cars--no choice of vehicle.
One time I had a Nissan Versa with the CVT.
It accelerated so slow that I was afraid to pull out unless absolutely no cars were coming!
It was scary slow. My Farmall Cub moved faster! I almost got broadsided and it would have been my fault.
That turned me off to CVT's.
Quote from: pabusnut on November 10, 2021, 05:33:44 AM
I travel frequently for work so I am in a lot of rental cars--no choice of vehicle.
One time I had a Nissan Versa with the CVT.
It accelerated so slow that I was afraid to pull out unless absolutely no cars were coming!
It was scary slow. My Farmall Cub moved faster! I almost got broadsided and it would have been my fault.
That turned me off to CVT's.
That was slow because it was a Nissan Versa, not because it had a CVT.
yeah, cvt's aren't slow pulling out. Something was wrong or you are use to a Mustang or something similar.
I'm finding that out that it's a bit slow on response but it doesn't bother me at all since I didn't want nor care for a hotrod. I think as some of you said that we are just so used to a conventional automatic running thru the gears. There is a sport mode that allows the engine to run faster but I don't bother with that.
Makes me wonder if large vehicles with go the train approach with the power plant driving a generator with traction motors. Hey six wheel drive!!!
Some interesting possibilities with a hybrid battery pack.
Yeah it seems that MCI bypassed the whole hybrid option and it going 100% electric on the J4500. Time will tell and as those batteries get old they may put some operators off. But I think those use some form of a CVT or perhaps not. You idea sounds interesting.
100% electric would use wheel motors not a cvt. Good benefit on heavy vehicles to control downhill speed and reverse current into batteries
I believe certain models of case tractors have cvt's. Not sure on hp but above 400 for sure.
Quote from: 6805eagleguy on November 10, 2021, 04:54:25 PM
I believe certain models of case tractors have cvt's. Not sure on hp but above 400 for sure.
CVT has been in farm tractor for 10 years ,John Deere,Case,AGCO and others have the CVT,I know Cat has it in some loaders like the 966 and small skid loaders
I would imagine their belt is a lot more robust than ones in cars, since packaging space would be less limited. Also rpm range would be a lot less than in cars.
ditto Cheese. CVT is old school. Transmissions are gone in EV. Just bolt the motor to the wheel or drive axle. It is definitely a big shift in thinking going to EV as they provide 100% torque from the first spin of the motor and being direct drive in general. Motor to wheel are basically locked together.
I like the idea of putting the motor inside the wheel but I don't suppose that will become practical until motors can be made much lighter. Maybe something like the centerless wheels on video game vehicles. Probably still a couple decades away from that one.
Jim
Fossil fuel power will be around for a long, long time to come, there is nothing in your daily life that is not tied to petroleum.EV's are just a small part of life to me and not enough to worry about
You are certainly correct. The BEV movement is still in the early stages but will increase over time. LION is starting to push a BEV ambulance now. BEV's may work fine for short trips around town like taxis, school and some transit buses, airport car rental/hotel buses and local delivery trucks. But emergency vehicles I would be skeptical as well as that new BEV J4500. Not sure about a long distance charter trip in one. Especially when the batteries get old and don't like to hold charges well anymore.
I think the motors used in bell housings for start-stop technology is a great start for wheel motors that they'll be using in vehicles and have had a few years of use to demonstrate their reliability.
Old news. Lookup vehicle hub motors. There are plenty in small utility vehicles and many are used on bikes and motos. I'm guessing the fundamental problem exists in increasing power in the reduced size, maybe economies of scale costs too. Then there is the obvious, practical factor of needing more hub motors.
Quote from: windtrader on November 11, 2021, 09:22:18 AM
Old news. Lookup vehicle hub motors. There are plenty in small utility vehicles and many are used on bikes and motos. I'm guessing the fundamental problem exists in increasing power in the reduced size, maybe economies of scale costs too. Then there is the obvious, practical factor of needing more hub motors.
Hub motors use old technology from the 20's to get power and speed using the planetary gears or some call it the sun gear they are not direct drive.You ever seen a electric traction motor on train engine you could call those hub motors they been around since the 40's some times what is new is actually old technology
I think rail gun technology could be used on hubless wheels. Either embed magnets in the rim or use induction. Maybe a 3d printed polymer rim with conducting traces printed in place. Then a mating stator connected to the car. We have the technology to do that now, but it'll probably take 20 years to perfect it.
Jim
When I worked for Stewart/Stevenson back in the day they were working on induction motors for the military. They were neat but after 2 years and no telling how money they were tossed in junk pile
My wife misses shifting of the Allegro bus. Probably because she didn't have to. Big Cat engine and 6 speed Allison. She could put it in "D" and just drive it. I get to do most of the driving in the Prevost because I do a fair amount of manual shifting of the HT 740 to keep it in no lug RPM range, That took a bit of getting used to, but I actually like doing it. I would think a big CVT might work on a newer bus if designed for it. But try to add to an old Detroit? Could it keep RPM in the 2000 range? Guess we won't ever know. I expect a Biden mandate any minute the Buses must be electric. At least we have enough space for the batteries and enough roof for the solar panels!!
Well, every 3 phase motor you've ever seen has been an induction motor so I'd say they do have some potential. So are Tesla motors... and a whole bunch of others. If it's brushless it's an induction motor.
Jim
looks like the trend of brushless motors is expanding. Of course that is old news but anyway.
Quote from: Jim Blackwood on November 11, 2021, 03:02:23 PM
Well, every 3 phase motor you've ever seen has been an induction motor so I'd say they do have some potential. So are Tesla motors... and a whole bunch of others. If it's brushless it's an induction motor.
These were huge for military tanks, the small turbine engine was the replacement they were not something you pickup by hand,everyone should know magnetic motors have been around for a long time.They were working brushless generators at the same time, now brushless generators are the better generators
A rail gun is just a brushless motor built in a straight line instead of rotating. You could say it is unwrapped I suppose, or something like that. It also has high speed sequential switching of the windings on the stator. The projectile is the armature.
So, if you put that same technology into a rim motor, you should be able to create a very powerful motor and keep the weight down.
Jim
On farm tractors, don't get hydrostatic transmissions confused with CVT.
Shift points were programmed into the CVT transmissions since it was found that under full power, the transmission lasts longer if it isn't sliding around. And you'll notice (at least on our 2021 Subaru Forester) that each shift has a momentary release of power when the transmission adjusts to it's next "gear".
Nothing can duplicate the efficiency of a multiple gear manual transmission. That's why most automated transmissions now in big rigs are of 12 speed-either direct drive or overdrive final gear. With rear end ratios all the way down to 2.21 now, direct drive is the way to go if you're doing mostly highway miles. Good Luck, TomC
Quote from: freds on November 10, 2021, 09:04:43 AM
Makes me wonder if large vehicles with go the train approach with the power plant driving a generator with traction motors. Hey six wheel drive!!!
Some interesting possibilities with a hybrid battery pack.
Read an article on converting trains to battery power and two engines could powered by one half full rail car of batteries and still meet maximum car weight limits. Of course that would need a hell of a charging station!!!