Talk:Dual-clutch transmission

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Why is there a paragraph on NVH under the "Suppliers" heading?[edit]

The first section under "suppliers" talks about noise, vibration and harshness (NVH). This needs to be moved to a different section. I'm not computer savvy enough to do that myself without screwing something up, though.

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Deficiencies[edit]

I think this article is pretty much far away from good. What this article does: (Incompletely) list all suppliers and cars with dual clutch transmissions, and provide an inacurate historical overview. I think this type of information is not really that useful. What the article does not do (but what it ought to do) is explain what a dual-clutch transmission actually is, how it works and what it does. As far as I'm concerned, many 1970's high performance tractors made in communist contries (such as the K-700 series derivates) have dual-clutch transmissions that were used for shifting without interrupting the torque transmission from the engine to the wheels. There is only one puny hint that some tractors might have dual-clutch transmissions, (John Deere), but it rather reads like an advertisement. --Johannes (Talk) (Contribs) (Articles) 17:06, 11 August 2019 (UTC)[reply]

While not quite burning trash, the article in current form is useless as an informative encyclopedia entry. It fails its most basic task of informing the layman reader what a DCT *is* (and the accompanying picture might as well be an impenetrable mathematical formula for all the good it does without exposition telling him what it means), and why DCTs are different/better/whatever than manual/standard/automatic/whatever transmissions. Are they more reliable? Are they faster? Bring you the chicks? And the whole bottom half is free advertizing vender-whoring that should be chopped off right now. (We don't have an exhaustive list of brake-pad makers, do we?) --2601:444:380:8C00:714D:E5A8:5A07:75B4 (talk) 18:30, 6 March 2020 (UTC) <just.another.IP.user>[reply]
1292simon Thank you for cleaning up the article, that was really necessary. As I have stated back in Summer of 2019, the article lists manufacturers, but I that is not particularly useful. I suggest removing this (really unnecessary) "information", what do you think? Best regards, --Johannes (Talk) (Contribs) (Articles) 11:45, 23 July 2020 (UTC)[reply]
  • Hi Johannes. Thanks for your kind words, I really appreciate it. Yes, I agree that the Suppliers and Applications sections should be vastly trimmed back to just the significant examples. Now that DCTs are quite ubiquitous, there is little benefit in having details on them all. I'll be having a crack at this in the next day or two, if you wouldn't mind waiting to see what you think of the trimmed version?

    Also, could I please ask a favour? In the Clutches section, I'm not understanding the difference between the two alternate designs. Could you please have a look and see if you can explain it to me? If you know of any examples of these two arrangements, that would be the cherry on the cake! Many thanks, 1292simon (talk) 22:23, 23 July 2020 (UTC)[reply]

Hello Simon, I believe that the article would benefit from virtually any kind of trimming, so take your time and work it out, I would appreciate it. Thank you for your question. I believe that it is actually less difficult than you might think: There are three different designs for DCTs. The "first design" uses a hollow input shaft that surrounds a second "inner" shaft. These two shafts are on the same axis, I'd call it the "flywheel axis". Now in this design, the two clutches are "in the same place", meaning that there is a small inner clutch for the "inner" shaft, and a bigger "outer" clutch for the hollow shaft surrounding the inner clutch. These two clutches also share the same clutch bell housing, as seen in this picture. If you can somehow get access to this book, there is a good drawing on page 233. The "first design" is used in VAG vehicles (Audi, VW, Škoda, etc.) for example. The "second design" is very similar to the first design, but it does not have the two clutches "in the same place" with an inner and outer clutch, instead, the two clutches are behind each other on the same axis. The second design is very common in agricultural tractors, for example, The Fortschritt ZT 320 has such a clutch (picture). The clutches can be in the same clutch bell housing, but they do not necessarily have to be. The "third design" uses two gearbox input shafts that are next to each other. The engine's crankshaft drives both of these shafts (there usually is a set of gears for that), and each of these two gearbox input shafts has its own clutch. Think of it as two regular constant mesh gearboxes which have output shafts that both power the same driveshaft. The only vehicle I can think of with such a design is the Melkus RS 1000, but it has a single clutch only; its gearbox is basically made from two ordinary Wartburg gearboxes to make a short transmission ratio five-speed. Best regards, --Johannes (Talk) (Contribs) (Articles) 17:56, 24 July 2020 (UTC)[reply]
  • Great, many thanks for your explanation. I was stuck in the mindset that the clutches are on the same plane, so the second design makes a lot more sense now. Kudos for the reference to the obscure 1970s sports car, your knowledge of anything involving an internal combustion engine is incredibly broad!

    I'll have a crack at rewording the descriptions in the Design section, please feel free to fix up anything I get wrong. Cheers, 1292simon (talk) 04:40, 25 July 2020 (UTC)[reply]

Hello Simon, you are welcome! Your changes were good, and I appreciate them. Something that still needs some fixing is the "automatic" thing. Dual-clutch transmissions don't necessarily have to be automatic, but the article does not explain that; currently, the article's first sentence reads „A dual-clutch transmission (DCT) (…) is a type of automatic transmission in automobiles“ – you could say that it's misleading or false, but either way, I am very unhappy with that. In the Fortschritt ZT 300 (and ZT 320) tractor(s), the dual-clutch transmission is operated manually, and it works differently from what the article explains. I hope this is not too confusing, I'll try to explain it briefly: In the ZT 300 there are two clutches (dual-clutch transmission I guess?), the first clutch is for transmitting the torque to a three-speed gearbox with an additional range selector with three ranges, giving it 3×3=9 gears; the reverse gear is in an additional reverse gearbox, and you can choose range 1 and 2 in reverse (3×2=6). So effectively, there are 9 forward, and 6 reverse gears. In addition to that, there is a so-called „Unterlastschaltstufe“ (ULS), a German word that literally means "underloadshiftgear", and it means that it is an additional reduction gear that can be activated without having to interrupt the torque transmission from the engine to the wheels (which is something that you would usually do when pressing the clutch pedal). The ULS is activated when pressing the clutch pedal half-way down, which activates the second clutch. The ULS has to be pre-selected, but that's it. Now this is different from what this article is about, but it technically is a dual-clutch transmission, and in German, this clutch assembly is called „DK 80“. DK means Doppelkupplung (Dual clutch), and 80 stands for, well, nobody knows, 2×40 cm diameter? 2×40=80 kp·m of torque? But it is a dual-clutch, however, not exactly what this article is about… And that is this article's problem. It is too focussed on cars; and I don't even know what the word "automobile" is supposed to describe in this article. Motor vehicle? Car? Lorry? Who knows. Best regards, --Johannes (Talk) (Contribs) (Articles) 22:02, 25 July 2020 (UTC)[reply]
Yes, the description of "automatic" needs a better explanation so that the tractors are not excluded (although IMHO it should be explained that this is a niche usage). I also think that a Tractor section would be useful. Regarding the manual operation, are you aware of any cars where the DCT does not have a fully automatic mode? Cheers, 1292simon (talk) 22:54, 25 July 2020 (UTC)[reply]
I agree, nowadays, that is just a niche usage, but back in the 1960s, it used to be the main usage for DCTs. I am not aware of any cars with manually operated DCTs. And that makes perfect sense to me: A regular, synchromesh gearbox is the cheapest to make, most reliable, lightest, and most efficient gearbox for cars. Its only downsides are that it doesn't shift automatically, and it is slower than a car dual-clutch transmission. A car DCT is more expensive to make, possibly less reliable, and heavier. It can shift automatically, and it does so very fast. A maual DCT (with clutch pedal(s)) would be very difficult to operate and possibly lose its speed advantage to the regular synchromesh box. This is why I believe that a clutch-operated car DCT don't exist. Only reason why car DCTs exist is that they have a better efficiency than regular hydrodynamic torque converters, and that they work with front-wheel drive cars. Best regards, --Johannes (Talk) (Contribs) (Articles) 09:15, 26 July 2020 (UTC)[reply]
Great, thanks for all the info. It is very interesting how the trend between DCTs and planetary automatics waxes and wanes through the years. Personally, I really like the concept of the CVT, however the reality when driving one is often quite unpleasant (although I think that's because they are often put in the situation of an undersized engine trying to move a heavy car, which isn't going to be fun for any type of transmission). Cheers, 1292simon (talk) 10:32, 26 July 2020 (UTC)[reply]
CVTs are really only then necessary, whenever a very fine speed adjustment is desirable, and when tranmitting much torque is not required. Otherwise, they don't make that much sense: Their efficiency is low, transmitting much torque is an issue, and they are too expensive compared with regular constant-mesh gearboxes. In theory, CVTs would be ideal for tractors, but in reality, they don't work as desired. Combine harvesters (and other types of harvesters such as forage harvesters), however, usually have CVTs. You will find regular transmissions in very old (1940s) combines only. Virtually everything built from the 1960s and onwards has some sort of CVT. In cars, a hydrodynamic torque converter makes more sense in my opinion, if an automatic transmission is desired. Best regards, --Johannes (Talk) (Contribs) (Articles) 00:36, 28 July 2020 (UTC)[reply]
Ahh, very interesting. Now that you mention it, the precise speed control (under varying loads) is one big advantage. But for use in cars, perhaps when a torque convertor auto can have 10 gears these days, that's probably as close to infinite ratios for practical purposes anyway. Cheers, 1292simon (talk) 08:53, 28 July 2020 (UTC)[reply]

Fuel economy?[edit]

How does the fuel economy of a DCT compare with that of a conventional (hydraulic) automatic transmission? (And why?) ---Dagme (talk) 00:51, 5 December 2021 (UTC)[reply]

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