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Zeroshift AMT

by Rafael Seidl

The Zeroshift system consists of 2 drive elements mounted on a common hub. Each element is double-faced where one face can only drive in one direction and the opposite face in the opposite. When paired back-to-back, they both provide either a direct-drive or a ramp face depending on drive direction configuration. Click to enlarge.

Zeroshift, a UK company, claims to have come up with a novel two-step synchronization mechanism for automated single-clutch step-by-step transmissions. When combined with slight feathering of the dry clutch, this is supposed to permit gear changes that are faster than a DSG and smoother than a traditional AT with torque converter. We’ll have to wait for independent confirmation of these aggressive claims.

Step-by-step transmissions are among the simplest—read: cheapest—yet most efficient designs available. Conventional automatic transmissions provide greater torque from a stop because of the torque converter, but they waste significant amounts of fuel until the lockup clutch is engaged, at which point the impeller and pump wheels of the converter are bypassed using a wet clutch.

In many designs, that doesn’t happen until the vehicle reaches approximately 40 mph. Some, e.g. Mercedes-Benz’ 7-gear transmission, do engage the lockup clutch even in first gear, however.

The other advantages of replacing a conventional AT with a sufficiently comfortable single-clutch AMT would be:

  • Substantially lower cost of manufacture;

  • Smaller package size and weight;

  • Same 0-60mph acceleration with a slightly less powerful engine; and

  • Very efficient freeway cruising via longer gear ratios and rapid kickdown.

On that last point: it’s not immediately clear if Zeroshift’s system can handle aggressive kickdown procedures, e.g. from 6th directly into 2nd gear. The required severe step change in engine speed would require unusually tight integration of engine, clutch and synchronization controls.

Similarly, satisfactory single-clutch AMTs would eliminate the possibility of increased fuel consumption of cars equipped with manual transmissions, at a much smaller premium than dual-clutch designs.

Many Europeans, especially older drivers, still don’t shift into higher gears as early as they could. In part, this is because many of them are still unfamiliar with the substantial low-end torque available in modern turbodiesels and boosted gasoline engines. Another reason may be that maintaining the same vehicle speed in a higher gear currently requires a larger, less comfortable angle of the gas pedal. Also, frequently having to kicking down manually is a chore many choose to avoid.

More details to come at the SAE World Congress in April.



Roger Pham

Thanks, Rafael, for the report on this interesting automated-manual transmission. Seems like a logical move in the age of micro-processor and drive-by-wire throttle. For a long time, I have been wondering when auto mfg's will start to move away from the Hydramatic design and move on en mass to this simpler, lighter and more efficient design. The Hydramatic design was invented before the micro-processor age, when the complex hydraulic valving circuitry is acting like a combined analog computer and servo actuators. Quite ingenous, but also a compromise on efficiency. More internal drag than manual transmission and the precise gear ratio is difficult to setup. Then came the torque converter lockup clutch and then ECT, or electronic-controlled transmission, using the smarter microprocessor brain to control the dummer hydraulic computer to approach the efficiency of a mannual transmission but with increasing complexity.
Finally, back to basic is the simplest.

old news

This is really old news. Check out their site. It hasn't been updated since 05

Rafael Seidl

Old News -

yes, the company has been working on this for a number of years, including, apparently, ramping up the manufacturing capacity. I suppose someone forgot to change the copyright disclaimer but the reference to the SAE paper is definitely recent.

The real question is if they will be prepared to let others manufacture the widgets under license or, let themselves be bought by one of the majors. Automotive startups that insist on being the sole supplier for anything critical tend to have zero chance of commercial success (cp. Coates rotary valves, Rosen Motors superflywheel etc.)

Barry R. Guthrie

This seems to be a very good improvement in performance and in manufacturing requirements compared to current transmission technologies. My question is how close does this Zeroshift technology come to surpassing a CVT type transmission? As a driver I like to be able to interpret the road and driving conditions and select the gear I want to use. This is a nice fit for this type of driving. An automatic and CVT type transmissions us a set fixed profile curve that makes the gear changes and ratios automatically when you reach certain operating points. Everyone has different driving standards and expectations. This becomes somewhat of a statistical analysis in matching the transmission shift profile to their target customer's driving characteristics. The Zeroshit type of transmission seems to provide the shifting smoothness and very quick shifting performance like and automatic and CVT, but lets you determine what gear you want to use and this is ok by me.

If this does meet the performance expectations in the design claims, then I see no problem for this company direct manufacturing this AMT and selling it directly to the automotive or other industries. The market is too competetive. Any breakthrough technology that does have a big impact on performance and manufacturing and reducing fuel costs will be highly sought and bought by someone. The prize goes to the ones who catch the time and chance. ~ Ecclesiastes 9:11

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