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Advanced synchronizers from Oerlikon Graziano provide fuel savings and easier gear shifting on heavy trucks

New generation synchronizers from Oerlikon Graziano featuring integrated activation system with optimized clearances to give smoother shifting and reduce drag. Click to enlarge.

Oerlikon Graziano has developed a family of advanced synchronizers for heavy-duty truck transmissions. The first application of the technology, on new 9-speed and 14-speed premium gearboxes, has contributed to transmission efficiency improvement, helping to fuel saving and emission reduction.

The new synchronizers save fuel in two ways: by optimizing the shift to minimize torque interruption and by reducing steady-state drag torque in the transmission. They combine the high durability and high performance of Oerlikon Graziano’s existing Long Life synchronizers with a new internal activation system, the use of optimized clearances and lubricant paths for higher efficiency.

During a gearshift, synchronizers manage the speed difference between the previous gear selected and the next one, to ensure a smooth, quiet shift. In a typical transmission, all the gears are in constant mesh but only one pair is driving because in each pair, one of the gears freewheels until connected to its shaft by a synchronizer.
The hub of the synchronizer is splined to the shaft and carries three equi-spaced struts around its perimeter, on which the selector sleeve rides. In order to connect the synchronizer hub to the gear and engage the chosen ratio, the sleeve is moved towards the selected gear when the driver operates the gearshift lever.
Fine internal teeth on the synchronizer sleeve connect with opposing external teeth on the side of the gear to transmit power. But the sleeve cannot simply engage with the gear because they are rotating at different speeds. To prevent grinding or crashing of the synchronizer teeth, two further elements are carried between the hub and the gear: a synchronizer ring and one or more cone clutches.
The synchronizer, or blocker, ring carries fine external teeth matching those of the sleeve and the gear. It blocks the sleeve from travelling into full engagement until the speeds have been synchronized. The cones provide the necessary friction to adjust the rotating speed of the gear until it matches that of the shaft. At this point, the friction on the synchronizer ring decays and the ring’s external teeth line up with the sliding sleeve, allowing it to complete its travel and fully engage the teeth of the selected gear.

The new synchronizers are configured in single and double cone arrangements, each with the same external geometry to allow flexibility in transmission design. In all, four different synchronizer specifications are used on the 14-speed transmission and three on the 9-speed.

The synchronizers have exceptionally high torque capacity—up to 18,000 N·m (13,276 lb-ft) in the first applications—and use molybdenum-coated steel cones for high durability with optimum friction. Future developments include the potential for carbon coating. A key feature of the new technology is the integrated activation system which provides outstanding durability and ease of assembly.

By increasing the speed of a manual shift, Oerlikon Graziano has been able to reduce the torque interruption, keeping the engine at optimum efficiency for longer and reducing engine transients to save fuel.

Whichever gear is selected, large differences in rotating speed can exist across the other synchronizers. With a conventional design this leads to significant drag losses which impair efficiency, but the new synchronizers greatly reduce this effect to further improve fuel economy.

The new synchronizers improve the shift process during three distinct phases. Prior to synchronization, the integrated activation system provides optimized load characteristics to give improved consistency and outstanding durability, compared to a standard design.

The second phase, synchronization, has been shortened by the use of multi-cone technology, best-in-class friction materials and the optimization of geometries and tribological properties.

The third phase, from synchronization to engagement, has been improved by incorporating new internal features allowing smoother travel of the sliding sleeve, avoiding blocking problems and providing a more friendly engagement feel to the driver, and finally making this solution even more attractive in applications which are usually manual shift with air assistance, so any shift problems can immediately become obvious to the driver. The new system ensures a fast, smooth and reliable shift under all conditions, making it an attractive alternative to a powershift system as it packages into a much smaller space.



Small (50 KW) in-wheel e-motors on all (6 to 20) wheels could give diesel-electric large trucks all the traction required without mechanical multi-speed transmission. Diesel-electric locomotives have done it for 50+ years.


A truck is not a locomotive and in-wheel engines are more hype than really good idea because increasing weight of un-sprung mass is a very bad things when it comes to rolling efficiency and thus fuel efficiency. Not mention problems of exposure to dust and waters and vibration.


Diesel-electric locomotives require transmissions that can handle a huge amount of horsepower and deliver it to MANY wheels - they use electric transmissions for initial lower cost and reliability - NOT for efficiency.

And they do NOT use in-wheel e-motors.

And 18 wheelers do not have a significant traction problem.

In-wheel e-motors would be a lose - lose.


TT...never say never. In-wheel, much lighter, e-motors will be common place by 2020/2025. It will be a win-win solution.


Never say "It will be".

Say; "I think that".


TT....some 400,000,000 e-bikes with in-wheel e-motors have already been built in the last 10 years or so and are in daily use. The next step will be to use in-wheel e-motors for 400,000,000+ e-cars of all size and shape in the next 15 years or so.

Meanwhile, the number of e-bikes with in-wheel e-motors will double to 800,000,000+ by 2025. It may be large enough to convince the skeptics.


The number of e-bikes with in-wheel e-motors MAY double to 800,000,000+ by 2025; MAY.

This may be large enough to convince the skeptics to make locomotives with only 2 wheels, or it may not.

Henry Gibson

The Artemis and perhaps the undemonstrated NOAX hydraulic hybrid technology would be more efficient and could apply regenerative braking to all axels. ..HG..


Why apply regenerative braking to all axels?


A problem for introducing technology into the trucking industry is that the trailer is often used for storage and is not owned by the tractor company. Therefore you need to diminish the cost of the trailer. For that reason it is unlikely that the expense to install induction motor drive to the rear wheels will be justified.

However I am still of the opinion that electric transmissions in the tractor unit make sense since the top speed range is much lower than for cars, 110km/hr, this encourages the adoption of a single gear ratio to be optimised for the acceleration needed at the lower speeds. Also an induction motor can hold its max rpm indefinitely unlike a reciprocating engine. Furthermore that speed can extend out into the 10k rpm range which multiplies the power of the motor. Eg a 50Kw frame size traction motor for 1500rpm becomes a 350kw motor at 10,500rpm, same weight and cost just different winding and a rotor balance.

The same speed advantage can be used for the generator itself which would be geared up 1:4 from the diesel engine by a planetary perhaps a tad larger than the coke can sized Prius planetary which handles only 100Hp but nothing as large and as heavy and as complicated as a modern 14-speed mechanical unit.

I would be remiss also if I didn't mention that traction motors are capable of delivering full torque from rest and in fact can deliver up to 300% torque with a 30 sec rating without requiring a corresponding increase in torque from the diesel although the engine controller may require it to run faster at this time.

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