9th April 2015 by David Mason
Last week, we took a look back at Multimatic’s 2014 Enlighten Award entry where the company had optimized a front lower control arm to successfully reduced weight by 30%. This week, it’s the turn of powertrain specialist, MAHLE North America.
For MAHLE’s entry, they focused on the development of a new connecting rod for Polaris Indian Motorcycle. The connecting rod is part of the engine combustion system. It transfers the resulting forces of the combustion energy from a translational (up and down) movement into rotational movement of the crankshaft. The lower these oscillating masses, the better the noise, vibration and harshness (NVH) behavior; the lighter the masses the better the impact on friction and fuel consumption.
The original baseline conrod set was developed as a fully machined component out of steel. The new set of rods is aligned to a modern, highly sophisticated, cost effective steel forging process where cycle time, rough part tolerances and machining process are state of the art.
The weight of the new connection rod was reduced by 31%. The old connecting rod total mass was 1488 grams (two rods) and the new MAHLE design is 1020 grams (two rods). Additional weight reduction will be achieved by adjusting the crankshaft counterweights for mass balancing (customer responsibility). MAHLE used advanced simulation technologies to overcome the challenge of forging the long slim I-beam structure from center-to-center.
In its entry, MAHLE highlighted that this is the first lightweight connection rod of its kind that is in production and meets all the customer requirements.
In the past, a vehicle’s engine and associated powertrain components were not the focus of much attention when it came to saving weight. It’s easy to see why. Engines present a complex problem with a huge array of oscillating forces and NVH characteristics to consider, adding more and more variables into the design. However, the powertrain also provides a huge opportunity for weight engineers as a lighter engine can lead to a lighter supporting structure leading to a cascading effect of material saving.
Interestingly, a research project by DuPont highlighted powertrain and transmission as the industry’s primary target for lightweighting, beating out chassis and body-in-white which came second and third respectively. It is thanks to the ever increasing power and accuracy of simulation technology that this is becoming possible. Changes to the design, be it material substitution or material removal, can be quickly assessed and analysed, making these complex systems a feasible target for design exploration and weight saving for manufacturers.