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A thermoplastic oil tank for dry sump engines

News International-French

6 Oct 2015

Hummel-Formen, a brand by ElringKlinger develops a reservoir, which weighs around 2.6kg, is made from Ultramid A3WG7, a BASF polyamide 66 with 35% glass fiber reinforcement which is resistant to oil and thermal aging.

The tank is therefore 59 percent lighter than previous steel or aluminum welding constructions and has an improved, multi-functional oil separation system which is integrated in the tank. The complex plastic component is used in the new Mercedes-AMG GT, which has been available since spring 2015 and is the second car that AMG has developed itself.

The oil reservoir is noted for its ingenious geometry: It comprises ten different, injection-molded polyamide parts, which are joined together with 13 further elements like sensors, sieves, covers and screws to form one component. This is done by vibration welding and various snap-in mechanisms. By optimally using the available space, a lot of different functions could be integrated: Apart from the mere storage of the oil, the component deals with the ventilation of the crankcase including the oil separation, makes possible the filling and changing of the oil as well as controlling the oil level and its quality. Furthermore, it also slows down and roughly filters the incoming oil.

The Ultramid used shows high resistance to oil and corrosion, is thermally stable up to 180°C (for short periods even up to 240°C) and contributes to a favorable vibration and acoustic behavior because of its high damping and stiffness. This means that the plastic oil tank is considerably quieter than metallic versions. The tried-and-tested PA66 also displays the rigidity required for this application and necessary to withstand the requested burst pressures.

"With the new oil tank made from BASF plastic, we are not simply remodeling previous aluminum welding designs," says Thomas Wolf, head of technical sales at Hummel-Formen. "We optimized the structure of the component in such a way that it is now lighter, quieter and more compact and can be fitted in the middle of the engine compartment, below the fender. The refined internal structure with various elements and functions for the integrated oil separation would not have been possible with metal." ElringKlinger is responsible for the entire tank – from the initial idea, calculation and prototypes through to the series mold and fabrication. The development work from the 3D model through to the first functional samples made with silicone molds took 12 weeks. The production of the first parts made with serial molds took about a year.

The bigger engineering effort provides among other things better driving dynamics for the Mercedes-AMG GT: The vehicle has a lower center of gravity, therefore sits better on the road and reaches higher speeds around bends.

Dry sump lubrication: oil tank replaces oil pan
As the Mercedes-AMG GT was developed for also driving the race track, it requires an appropriate lubrication solution, namely dry sump lubrication. In contrast to pressure lubrication, which is normally used in car engines and works with an oil pan, dry sump lubrication originates from motor racing: This is where the oil pan is replaced as oil reservoir by a separate tank, which has a tall and narrow design. The oil tank is configured so that the pressure oil pump is always able to reliably suck in the oil even in extreme driving situations, such as driving around bends at high speed or heavy braking.

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