The Genius of the Dual Clutch Transmission
The history and workings of a dying transmission.
If you were alive in a pre 2000s era and you wanted a sports car (or rather any car), then you had to be prepared for slow gear changes. If you wanted to change from 2nd to 3rd, then you'd have plenty of time to read a good book or have a nice drink (non-alcoholic of course). But in the sports cars of today, gear shifts are, for the most part, pretty damn quick when compared to the cars of yesteryear. In some of the better cars, the transmissions utilize something called a DSG, or a direct-shift gearbox. You may not recognized this term, but you will recognize that DSG transmissions take advantage of an ingenious invention called the dual clutch. When I was younger, I remember getting excited when one of the Top Gear hosts would say "...and it comes with a dual-clutch gearbox." Granted, I had no idea what this meant, just as I had no idea what taxes were, why people walked around with pagers on their belts, or what Obamacare was. Come to think of it, I'm still not sure what taxes are. Perhaps that's why the IRS keeps showing up to my door. Anyways, all I knew when 10 year-old me heard "dual-clutch transmission" from the TV is that the car would be lightning fast. Back then, I assumed that just meant they used some sort of wizardry to make the car faster, but now I am older and much wiser (probably), and I know that the dual-clutch gearbox is really quite and interesting invention.
History and Invention
The dual clutch was invented by a French engineer named Adolphe Kégresse. While Kégresse was never able to make a working model, he patented the design in 1935. Kégresse called his invention "Autoserve." Personally, I think the name is a bit flashy, but then again, I’m no marketing specialist. Autoserve wouldn't make it into a car for awhile, with the exception of a prototype put into a 1939 Citroen Traction Avant.
1939 Citroen Traction Avant
Then, in the 1980's, Porsche became interested in the transmission for use in endurance racing. That decade, Porsche would install the transmission as a five-speed in both the 956 and 962. The geniuses at Porsche knew that such a brilliant design would need an equally brilliant name. So they called it the Porsche Doppelkupplungsgetriebe (known by its abbreviation PDK). That is certainly a lot of syllables. When you put that interesting mess through Google, you'll learn that it means "double clutch." I wonder where they got that from. Despite its lackluster name, the PDK transmission helped the 956 and 962 dominate Le Mans in the 80's.
The dual clutch had finally seen success more than 40 years after it was conceived. However, asphalt wouldn't be the only surface the DSG would dominate in. Audi took Porsche's PDK and put it in the Quattro S1, the famed rallying legend. The Quattro's success on dirt doesn't need to be restated, but with the 5-speed PDK the Quattro did 0-60 mph in under three seconds, which is still lightning fast today. That's not all though. Audi claimed that the PDK could switch gears so fast that you never had to take your foot off the gas. It is only fitting that such a great transmission should be installed into one of the craziest rally cars of all time.
Audi Quattro S1
The DSG still hadn't made it into a production car, however. In 2003, Volkswagen were the first to give it a shot in their 2003 R32 Golf. The transmission itself was named the DQ250, but advertised as the "S-Tronic". It could handle 350 Nm of torque (That's about 260 lbs/ft for my American brethren), and weighed a measly 90 kg (roughly 200 lbs).
The Dual Clutch Today
The dual clutch is still around in performance cars today, though admittedly, it is not as popular as it once was. Advances in single-clutch gearboxes has narrowed the gap that the DSG once had over the single clutch. On top of that, the single clutch is much smoother and cheaper than the dual clutch is. The DSG does bring lightning fast shifts, but compared to today's standard gearboxes, their changes are jerky and uncivilized. While we may see it disappear in a few years, the dual clutch will always be a legendary gearbox and an incredible invention.
Some cars that offer DSGs today:
Mercedes-Benz AMG CLA 45
Porsche 992 911
Volkswagen Golf R
Nissan R35 GTR Nismo
Volkswagen Jetta GLI
Hyundai Veloster Turbo
Alfa Romeo 4C
How They Work
Every car manufacturer is just a little bit different. Different car companies have special technologies that they claim are superior to their rivals. Therefore, not every DSG system is alike. However, most have basic structures that are, for the most part, universal.
Hyundai’s 7 speed dual clutch for it’s Veloster
This may come as a little bit of a shock to you, but the dual-clutch transmission has a total of two clutch plates. A real shocker, I know. These clutch plates are housed inside the clutch case. One clutch plate is housed inside the other, making one clutch plate the outer clutch and one the inner clutch. Each clutch plate drives its own transmission shaft. The outer transmission shaft wraps around the inner transmission shaft. On each transmission shaft lies a set of gears. One transmission shaft contains all even gears, while the other contains all odd. Both of these transmission shafts are then connected to the output shaft. All this talk about shafts is making me want to switch topics. Lets talk about changing gear.
The DQ 250 from the 2003 Golf.
If you changed gear in a regular transmission, the clutch would disengage from the engine and then reengage when the correct gear is selected. This is a process. The dual clutch works a bit differently. Let's say you are shifting from 2nd to 3rd. The clutch plate containing 2nd gear would disengage, but since the other clutch would contain odd gears, it can start to engage right away. This is why the DSG has such lightning fast changes. Since you are not off the power as long with the DSG, power flow is much smoother and loss of speed during gear changes is far less than if you were using a single clutch transmission.
If you made it this far, thank you for reading my first article! This took me a long time to make, but I can't say I didn't have a lot of time doing it. I'd really like to do more of these, so please leave a like to let me know someone actually found this interesting. Also, please leave a comment if you have any advice or have other topics you'd like me to cover. I think it's safe to say I have some free time on my hands, so I'll definitely look into your suggestions. Again, thank you and stay safe!
Most people know that cars come with two basic transmission types: manuals and automatics. But there's also something in between that offers the best of both worlds -- the dual-clutch transmission. Check it out.
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