High-strength steel combine harvester design earns award

January 2012 – Developing lighter equipment with steel may sound like an oxymoron, but that’s exactly what engineers Kent Brown and Corwin Puryk did when they designed the header and draper for a new combine harvester for John Deere Harvester Works, East Moline, Ill., a facility of Deere and Co. Brown and Puryk combined high-strength steel with a new design to reduce the weight of key components on the harvester by 50 percent, increase load capacity and improve productivity by as much as 40 percent. The design also allows the harvester to meet new engine emission requirements.

In November, John Deere won the Swedish Steel Prize 2011 for its design. SSAB, Stockholm, established the prize to promote and educate industries about high strength steels and the potential to develop lighter, stronger, sustainable products. SSAB is a global leader in value-added, high-strength steel and is the parent company of SSAB Americas, Lisle, Ill., the leading supplier of steel plate in North America and Latin America.

Breakthrough design
Conventional approaches to harvester designs have tended to counterbalance increased header or draper weight with material added at the rear of the combine for stability. Brown and Puryk took a different approach. The two engineers considered aluminum initially but determined the material couldn’t handle the forces generated if a single control arm on the harvester was required to manage the weight of the entire head. Switching to thinner plate and lighter materials wasn’t sufficient to meet the weight reduction goal. “It was soon very clear to us that high-strength steel was a requirement for us to achieve our goals,” says Brown.

The engineers looked at locations on the header and draper where strength and fatigue were critical properties. SSAB’s Domex 700MC advanced high-strength steel allowed John Deere to switch from standard Grade 50 steel to Grade 100. More than 100 components were made with the new steel.

“For small grains and soybeans, the float arms of the HydraFlex draper platform are located under the wide belts feeding the cut grain to the feed drum and into the combine feederhouse,” says Puryk. “The arms are attached to the harvester in the back on the platform. At the front edge, the arms are loosely attached to the cutting mechanism, which allows the arms to carry the weight of both the grain and the platform while following as close to the ground as possible during operation to minimize loss of crops. The arms also help stabilize the conveyor belt. The design is unique and a key factor in making this harvester more efficient than other machines on the market.”

Global impact
The draper’s float arms originally were made of 6-millimeter thick standard steel, and welded together to form a closed structure. The new arms are formed from 2.5-millimeter high-strength steel. Although the reduction in thickness is significant, engineers were able to optimize the design of the float arms to take advantage of the advanced steel’s higher strength. “Stamped parts, less welding and simpler assembly allowed us to achieve the economic targets by a wide margin,” Brown says. “They gave us cost savings that offset cost increases in other areas of the machine.”

The combine harvester is also a breakthrough in terms of customer perception. “Farmers rarely regard lower equipment weight as a benefit,” Brown adds. “In this context, weight often represents strength and stability, but our development team sees the new combine harvester as a breakthrough for new ways to design agricultural equipment.”

The lighter machinery will save fuel, reduce pressure on the ground and increase load capacity. The new combine currently is in full-scale production at John Deere Harvester Works; however, the equipment already has racked up thousands of test hours in the field along with accelerated fatigue tests to ensure the machine carries the same high level of quality as its predeccessors. According to Brown and Puryk, the project also has a global impact. “The world population is growing dramatically,” they say. “To ensure enough food can be produced to feed people in the future, greater efficiencies in agriculture are a necessity. The new combine and front-end equipment can increase productivity by 15 to 40 percent.” MM