BMW Working on 7-Speed Manual Without a Clutch Pedal
Patent drawings show a gearbox with an 'electromechanical shift actuator,' meaning it would require no driver skill to operate.
By Sam Smith Jun 8, 2012 4:41AM
If recent patent drawings are any guide, BMW is planning to release a manual transmission with seven or more gears.This is not so much news as a steppingstone to another, more interesting piece of information. This isn't the first 7-speed manual to be developed. Porsche offers a 7-speed manual in the 991-generation 911; it's the first gearbox of its type to be offered in a passenger car, but it is by no means revolutionary. Porsche's 7-speed is built up from the 7-speed used in its PDK twin-clutch automated transmission. If you're not familiar, PDK is the lightning-fast automatic transmission found in the 991. Versions of the technology also appear in other Porsche products.
Porsche's manual is essentially a standard gearbox. Although it shares components with its PDK sibling, it uses a clutch pedal and requires a decent amount of skill for smooth operation. Seventh gear is located up and to the right from sixth gear; the gearbox has a clever mechanical lockout that keeps you from putting the lever in seventh unless you're coming directly from sixth. It's compact and simple, and simply works.
BMW's approach is different. It's simpler at first glance, but it's also far more complex. Are you ready for a manual transmission without a clutch pedal?
Above: Porsche's 7-speed manual shift lever. Seventh gear is directly to the right of fifth. It's unreachable from any gear other than sixth due to an automatic lockout. Before we go any further, it's best to keep in mind that patent applications are not reality. Most patents, even those from carmakers, don't see the light of engineering day. The United States Patent Office, for example, issues more than 150,000 patents per year to individuals and companies worldwide, and only a fraction of those are ever brought to production.
Still, what we have here is pretty cool. Take a moment and read E90Post's look at the patent drawings. The drawings themselves are reproduced below, along with E90Post's annotations.
The pattern above is likely not real -- it's just there for illustrative purposes. In the same fashion, the diagram below is just there for layout. In other words, you will not have a giant triangle in your hand, and no real-life gearbox looks like a geometry-class doodle. But you should be smart enough to know that.
Basically, BMW is working on a manual gearbox -- shift lever, 1-2-3-4-5-6-7 gate and all -- that requires no skill to operate. I find this partly repulsive (much of the joy of a manual is in the skill required to use the gearbox properly), partly intriguing (the tech behind it is pretty cool). When installed in a car, this gearbox would require no clutch pedal and likely no throttle modulation when changing gears -- you'd just move the lever, albeit through a traditional manual gate. If this sounds a lot like an automatic, understand that it's only partly automated: You're still physically picking the gear engaged, albeit not directly. There is no mechanical connection between the shift lever and the transmission; the "electromechanical shift actuator" behind the gearbox itself does the cog-swapping. The gearbox is a standard manual transmission, much like the one used in BMW's electrohydraulic automated-manual SMG boxes of yore.
The "patented shifting module," as E90Post labels it, is the key here. According to the patent filing, this component uses magnetorheological fluid -- the same stuff used in many electronic adaptive damping systems, including the Delphi system found on the Cadillac CTS-V, Chevrolet Corvette ZR1 and Ferrari 599 -- to allow or block entry to specific gears.
The obvious benefit of such a device is to keep people from grossly inappropriate shifts -- a fifth-to-first shift at 60 mph, for example, when the driver really wants third gear. But that's just a side benefit. The greater purpose is to make a 7- or even 8-speed manual more practical.
Think of it like this: The more complex you make a manual transmission, the more space you need inside it -- space for gears on shafts, yes, but also space for the shift forks that move them and the air-space pattern that the lever moves through. Since there's a physical limit to how large passenger-car transmissions can be, there's also a physical limit to how tight a given transmission's shift pattern can get. Past a certain point, you can cram more gears onto an input or output shaft, but you cannot create space for shift rods to move inside the transmission casing. This is why the shift pattern on a 4- or 5-speed manual -- the space the shift lever moves through both in the transmission itself and in the cockpit -- is often tighter than that of a 6- or 7-speed manual.
Confused? Here's a simpler answer: Porsche engineers once told me that the 7-speed manual stretches the limits of a traditional casing. With an 8-speed, the gears would be so close together, and the shifter moving in such a narrow space, that most people wouldn't be able to reliably tell, say, third gear from fifth. You'd go for one gear and get another.BMW's design aims to circumvent that by having a machine do the actual shifting. It should allow for a practical 8-speed manual, which is cool; more gears equal better fuel economy, even if there's a limit to the gain. (Porsche's 7-speed manual, for example, has a seventh gear that is tall enough to be pointless for anything other than highway cruising. If you need real acceleration, you have to downshift two, three or even four gears.)
Regardless, this is interesting. If BMW's idea happens, it'll bring about the skill-free manual transmission. It's also the kind of thing I like to see -- a carmaker acknowledging that driver involvement and entertainment are just as important as performance. As much as I bemoan the waning of the 3-pedal car, a manual without a clutch pedal is better than none at all.
Sam Smith is a journalist, a southerner, and a reformed Alfa Romeo mechanic who spends most of his time mooning over ancient racing cars and small-batch bourbon. A multiple International Automotive Media award-winner, he has written for Automobile Magazine, Car and Driver, and Esquire, among other publications. He once drove 4,000 miles in a weekend for a hamburger and has only been threatened by the German police twice.
Sam Smith is a journalist, a southerner, and a reformed Alfa Romeo mechanic who spends most of his time mooning over ancient racing cars and small-batch bourbon. A multiple International Automotive Media award-winner, he has written for Automobile Magazine, Car and Driver, and Esquire, among other publications. He once drove 4,000 miles in a weekend for a hamburger and has only been threatened by the German police twice.
[Source: E90Post.com]
26Comments
Jun 8, 2012 6:56AM
"As much as I bemoan the waning of the 3-pedal gearbox, a 2-pedal manual is better than none at all."
Um, the gear box doesn't use pedals, the clutch does. The clutch uses 1 pedal.
The question should be more about the clutch actuation. Most of the details provided discuss the connection between the shift knob and the gearbox. Its been levers and cables before and the details provided now show a shift-by-wire set. That is separate from the single pedal used to engage/disengage the clutch.
The clutch is the most citical part for smooth operation, and in normal conditions is only necessary when bringing the vehicle to or from a complete stop. (Though the clutch and synchro gears make it easier to shift.)
I see getting ride of the mechanical linkages and advantage in shift smoothness and layout freedom.
Until the clutch can be actuated psychically, there needs to be a pedal.
Jun 8, 2012 6:00AM
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