Press Release


Innovative racing clutch prevents stalling engines

  • Centrifugal mechanism activates clutch
  • Proven friction package guarantees power transmission

SCHWEINFURT – Customers of ZF Race Engineering can look forward to a new era: the innovative Sachs Anti Stall Clutch. This innovative centrifugal clutch prevents the engine being stalled at the start of a race and the resulting potential of major hazards in the field.

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Innovative racing clutch prevents stalling engines

The design is characterised by an array of synergies and other positive effects. ZF Race Engineering combines the advantages of a centrifugal clutch with the proven friction package of a multi-plate clutch and, at the same time, retains the option of manual clutch activation.

The Anti Stall Clutch’s friction package is no longer activated by the familiar diaphragm spring but a new mechanism. The centrifugal forces used in a centrifugal clutch are diverted by a special rocker arm in the axial direction. Despite a net weight in the low two-digit gramme range these centrifugal weights can generate a contact pressure of up to four tons. The reason for these high values is that the centrifugal forces increase to the square of the actual rotational speed.

The engineers constructed a new clutch housing to guarantee the rigid redirection of these centrifugal forces. In contrast, the clutch plates and drive plates of the two- or three-plate clutch modules available originate from well proven product ranges. Each of the 140-millimetre diameter plates transmits up to 250 Newton metres of torque – in other words, the two-plate version transmits up to 500 Newton meters and the three-plate version as much as 750 Newton metres.

Purchasers of the Anti Stall Clutch benefit from many advantages in racing. For example, ZF Race Engineering has retained the design option of manual clutch operation by a pedal. Therefore, in racing series that prescribe a precise starting time, the driver can continue to respond to the start signal with the required precision. The individual wishes of the drivers can be taken into account within very broad limits: the reengagement behavior can be varied from gentle to aggressive by the combination of centrifugal weights and springs. Even in the event of an aggressive setting, gentle starts are possible by gentle throttle application. Race drivers who rely on the new design are subject to significantly less mental stress as they are certain that the engine will not stall. In addition, they benefit particularly on wet tracks from easily reproducible starts.

Thanks to this system the starting procedure can be made with lower engine revs in the future because the clutch prevents system-related rev drops or even the engine stalling. These low revolutions significantly ease the load acting on the friction linings. For this reason, ZF Race Engineering relies on sinter linings for the Anti Stall Clutch. They have a higher static coefficient of friction than carbon clutches. Furthermore, the wear behavior of sintered metal in the case of so-called micro-slip is more favourable than that of carbon fibre. This increases the service life of the design. Customers benefit from this decision in terms of price as well. Despite the greater design complexity of the centrifugal mechanism the price of the Anti Stall Clutch is comparable to that of a depression-operated carbon clutch.

The potential fields of application for the invention from Schweinfurt are wide and varied. The new design can be used in any race format that features standing starts and where the regulations do not exclude the use of the Anti Stall Clutch. Touring car racing numbers among the fields of competition as well as formula car racing, and other attractive fields include hill-climb, rallying and rallycross events.

In addition to ZF Race Engineering customers, the other participants benefit from the innovative idea as well: stalled engines – such as during the start or after a spin – are a thing of the past when using the Anti Stall Clutch. The risk of cars stopping in the middle of the field is thus significantly reduced and safety in motorsport further improved.


Moritz Nöding

Head of Motorsports Communications and Sponsoring

+49 9721 98 2141