The problem with CVTs is lack of slippage under heavy torque load. This can easily be dealt with by spinning it at very high RPM by engine design (turbine or Wankel rotary) or increasing gears before the CVT and with reduction gears after either way.
26th July, 2012 @ 8:11 p.m. (California Time)
Slowburn Its not the CVT that's a problem its the inadequacies of the ICE which has limited torque in all but a certain RPM range. Any slippage in the transmission is inefficient,creates heat and is undesirable. A CVT by design overcomes most of the ICE's shortcomings by allowing it to reach its peak torque while the tranny changes ratio controlling the speed of the vehicle for a set accelerator position. It already does this better than any other means of transmission system to date.
Can't really see your point.
27th July, 2012 @ 4:49 a.m. (California Time)
Not the first Honda CVT design.
Back in the early 1970s they made a 175cc scooter with a coaxial swashplate pump/motor device on the end of the crankshaft, with the angle of the pump swashplate, hence the gear ratio, controlled by a left-hand twistgrip.
By setting the angle of swash to zero, this also eliminated the necessity for a clutch.
The above design is identical to that used by DAF for many years, the vehicles using it had the interesting ability to go as fast backward as forward.
Various early motorcycles such as the highly successful Rudge Multi used a similar mechanism.
This design of transmission has also been used in industrial applications for decades, incidentally.
27th July, 2012 @ 8:55 a.m. (California Time)
So, for non-engineers, the question would be: if they're so good, and they've been around so long, why aren't they being used everywhere already?
27th July, 2012 @ 11:45 a.m. (California Time)
The whole point of the various ratio transmission is to deal with the narrow torque bands that most prime movers have.
ICE with a transmission became the standard prime mover for cars because they were superior to steam, battery based electromotive, and far cheaper than ICE powered electromotive. This brings us back to mechanical transmissions; clutches and fixed ratio gearing take high torque loads well but require gear changes, power converters have lousy efficiency, and CVT slip under high torque loads. To prevent the CVT from slipping and the resulting wear run it in a high RPM and low torque mode and then use a consonantly engaged reducing gear to lower the output RPM while raising the torque. Because the problem with CVTs is they do not perform well under high torque loads.
re; Rich Mansfield
Because they only work well and efficiently under low torque loads and everybody likes to mock the guy with unconventional solutions before he finishes his explanation and nobody likes to admit that they were wrong in their mocking.
Therefore innovators have to be able to produce their demonstration model on their own, or function well enough without radical innovating to be given free rein to his work.
27th July, 2012 @ 3:25 p.m. (California Time)
Great and all but today's torque converters are a dead end until the contact patches grip (and slip) without wearing out. Otherwise we might as well use the old snowmobile belt and inertia-based variable diameter pulley. At least we can perform a simple belt replacement as necessary - making the belt the sacrificial element.
27th July, 2012 @ 5:59 p.m. (California Time)
This doesn't negate the inherent flaws of ICEs requiring transmission because ICEs can't supply maximum torque at zero rpm.
Transmissions for ICEs are inherently complex as a result for that sweet spot, which STILL reduces the mechanical efficiency and will eventually fail from wear. Replacements and lubricating oils brings more money to the greedy big oil and automotive industry coffers, which is what is fueling their industry all these years.
Slowburn: Previous generations of steam engines are inferior to ICEs because they require dangerously high pressures and tight tolerance manufacturing and expensive materials to be efficient and is significantly more obvious for automobile application : MORE THAN 50 YEARS AGO.
Today's cumulation in advances in such as technology computer aided design and manufacturing, new manufacturing processes and materials such as ceramic bearings and increasing use of easily mass manufactured and formed aluminum alloys has allowed the development of new generation 'steam engine' for automobile use that uses both rankine and diesel cycles with heat salvaging and regenerative abilities.
It has multi fuel multi mix capability - any type of combustible that can be atomized and burns them cleanly in a centrifuge, doesn't use polluting engine oils (uses deionized water instead), no catalytic converter, no miscellaneous filters and oils and the best part is that it has maximum torque at zero rpm, which means NO TRANSMISSION. Check out cyclonepower. It is being developed on submersibles, self powering robots and electrical generators for the US military because the automotive industry is too greedy to let you and me have this proven technology because they're still busy effing around with earth polluting inefficient 'suck-squeeze-bang' engines that wastes 2/3 of it's heat, runs in access of 650 rpms DOING NOTHING during stoplights, and intentionally burns excess fuel in the exhaust because there isn't enough time to burn it all.
28th July, 2012 @ 4:27 a.m. (California Time)
As a car owner, driver, worker, enthusiast i want to say that i love and hate CVT's.
Yeah you can be in the PERFECT part of the torque curve under all acceleration but they are somehow MORE boring than a standard automatic to me. I love to feel the engine's output characteristics while driving, even just doing it around town.
Also, remember how you could save money AND gas by getting a manual? This also forces you to understand cars, friction, ratios, your car's limits, etc. the moment you're forced to ride around on your own in one. MT's are becoming a rare find in cars because people go in to buy a car, realize they can't text without a free hand and get a slush box instead.
Anyone ridden in any nissan in the past 5 years? The only news here is that honda has ALSO decided to ruin their cars (while long hailed as having the best MT's on the market, oh god please don't stop offering the MT).
29th July, 2012 @ 3:16 a.m. (California Time)
...most of the Nissan product line is equipped with CVT, and shipping world wide since the 1990's -- Honda is just now marketing a Japanese prototype?
29th July, 2012 @ 5:03 p.m. (California Time)
None of which alters why ICE became the industry standard. I did forget one item of importance why ICE became the industry standard: Henry Ford, if he had been building steam powered cars instead of ICE powered cars we would all be driving steamers but he chose the then best solution.
29th July, 2012 @ 7:58 p.m. (California Time)
Altima has this already!, since it's compact it would work well in a small sports car, that would be pretty..
10th August, 2012 @ 8:15 p.m. (California Time)
Take a look to this new transmission design. Is a continuously variable transmission CVT gear only (the only one functional in the world), very compact and lightweight, and which could replace the current systems both for efficiency, simplicity and not least the costs.
Because this CVT work only with pinions is better the all other systems by efficiency and high torque transmission.
In the web page you will find more explanations, drawings and a short video of a basic prototype.
The first prototype will be ready for tests during this year.
20th January, 2013 @ 1:09 a.m. (California Time)