A premium brake solution and its variants: Wet multi-disc brakes in industrial trucks
visionary forklift concept by Still, nicknamed "the egg"

visionary forklift concept by Still, nicknamed "the egg"

Forklift trucks save people's lives on a daily basis in every warehouse or logistics operation. How so? Quite simply by stopping both reliably and precisely several thousand times a day, therefore keeping personnel out of danger. Low-maintenance premium brakes from KNOTT have become an established feature of countless commonly used forklift trucks: They not only do their job safely, but are also extremely economical and operate without the loss of braking force - in a wide range of different applications.

Wet brakes - a long term solution
Multi-disc brakes, which are cooled by immersion in an oil bath, are a special solution which was actually developed by KNOTT for use in agricultural machinery. In many modern tractors, the stack of brake discs mounts on the axle drive shaft and provides perfect braking for the life of the tractor. In both economical and technical terms, this could be seen as the ideal braking solution for vehicles. Completely encapsulated preventing dirt and dust penetrating the assembly, wear is so minimal that the issue of repair, maintenance or exchange generally never arises.

Unbeatable - in slow moving vehicles
The technical skill of wet multi disc brakes with the braking action occurring over the entire disc surface is one which lends itself ideally to slow-moving trucks and drive motors. However, the faster the axle turns - and consequently the disc stack rotates - the greater the heat dissipation to the oil which can result in cooling problems. In addition, at higher rotation speeds, the resistance created by the brake oil also consumes an increasing proportion of the drive energy. Finally, there is a risk that the discs could run dry, should all the oil have been dispersed to the extremities by centrifugal force. Many of these effects could be solved technically; however this would come at a price. Consequently, the principle of the oil bath cooled disc brake is ideally predestined for wet brakes used in slow moving vehicles. The maximum speeds for wet brakes in agricultural vehicles is currently 50 to 60 km/h.

Four good reasons
There remain a few forklift truck veterans in good running order who are still happily braking using what is known as the "coach box brake", a primitive ancestor of the modern brake whose origins lie in the rim block brakes used on early bicycles. Modern forklift truck brakes have to be capable of far more.
a) Clean braking: Many warehouses are used for storing high-value goods or food products. Here, the introduction of dust must be minimized. This is achieved using special tyres, clean burn engines, exhaust filtration systems and electric drive systems. The use of multi disc brakes from KNOTT whose full encapsulation ensures minimal contamination is fully compliant with these endeavours.
b) Safe braking: the wet multi disc brake supplies consistent braking performance throughout its entire service life. For all forklift trucks which pick up heavy loads and move them at speed, the maintenance-free brake with constant braking performance is a highly attractive option. Added to this is the capability for integrating a fail safe parking brake function, which prevents the truck from accidental rolling away.
c) Low-maintenance braking: Many logistics companies working multiple shifts aim to eliminate or at least minimize maintenance activities. On principle, the KNOTT brake requires hardly any maintenance: no downtimes.  
d) Anywhere braking: The opposite end of the scale from the clean warehouse would be a contaminated location such as a fish market. Here, organic waste, decaying material and brine will radically accelerate up the ageing process in any forklift truck. Conventional braking systems will require constant maintenance shortly after commissioning. Wet multiple disc brakes are capable of weathering even this type of extremely erosive environment.

Part of a vision
The visionary forklift concept by Still, nicknamed "the egg" which has received awards for its outstanding design, was fitted with an equally forward-thinking brake solution supplied by KNOTT: A single wet multiple disc brake functioning via the ball ramp principle with an integrated spring-applied combination brake cylinder. A forklift truck fitted with such a failsafe parking brake was revolutionary at the time - and is still ahead of its time.

Between two drive motors
The virtuosity of the custom brake designer and manufacturer is really highlighted on the closer examination of the brake developed for a 2-ton electric forklift truck with two drive motors on the front axle.
In this case, only one displaceable brake disc is used on each side. These are located between the two drive motors and apply their braking effect equally on the left and right wheels. The method of actuation is another innovative aspect: The discs are actuated mechanically using Bowden cables. Instead of wedge actuation, rotary cams are used to expand the discs. The outstanding benefits of this concept are its simplicity, its economy and the fact that the brake provides identical braking forces in both drive directions.

Perfectly fitted into the load-wheel
With this design concept for a three-wheeler forklift truck, the multiple disc brake is integrated in a complete hub and stub assembly. The brake is actuated by means of a ring piston with a spring-applied parking brake also incorporated into the system.

Simple choice for forklift truck clients:
Premium brakes from KNOTT or low-cost drum brakes
Many 4 to 5-ton capacity gas / diesel forklift trucks utilise drum brakes. In the main, these are scarcely modified brake assemblies originally designed for commercial vehicles which operate close to their limits in heavy duty applications.
Designed to occupy precisely the same mounting space as a drum brake, KNOTT has designed a complete wet running brake within an integral housing. Excessive over heating of the brake oil due to comparatively high average speeds is negated by the KNOTT designers incorporating an external oil cooling system with selective oil circulation within the brake housing. This development allows the forklift truck client to simply choose between the simple or the premium braking systems depending on the specific duty cycle and operating environment he has in mind. For the forklift truck manufacturer, this client-specific adjustment involves hardly any additional activities, as all the dimensions and fixing points for the two axles are identical whichever brake solution is specified.

Survival by innovation
KNOTT brakes are found not only in forklift trucks but in construction machinery, agricultural machinery, military vehicles and a variety of special-purpose machines. Right from the start, the company opted to specialize in vehicle-specific custom brake solutions far removed from the world of mass production. The KNOTT Group with its current workforce of over 1000 has dominated many of its chosen niche markets for many decades. The company offers an almost unlimited availability guarantee on practically every spare part required for its brake solutions.
The deceptive facade of what appears to be an idyllic farm building conceals a frenetic hub of activity spanning design, development, an in-house testing department with test rigs plus manufacturing all under a single roof. Simultaneous engineering is deployed to reduce the time required from the original concept idea to the volume product. Continuously pushing out the boundaries of innovation, the company builds on a foundation of good, rapidly implemented ideas, new patents and products as well as highly flexible production ethos.  

We thrive by being challenged
Whilst KNOTT may appear to be cherry picking from the brake development pie, in fact custom brake solutions are anything but an easy option. The other side of the coin are highly complex terms of reference, tight timing schedules and what can frequently be enormous cost pressure. But this is just the type of tough challenge KNOTT excels at: coming up with intriguing, often surprising and superior solutions.

Knott GmbH
Kathrin Knott
Obinger Strasse 15
D-83125 Eggstätt

Tel: +49 8056 906 245
Fax: +49 8056 906 103
E-Mail: k.knott@knott.de
Internet: www.knott.de

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