When a combine hits the field to gather in the grain, there are competing interests at work. The farmer gets paid by the bushel, so he is interested in how much clean grain he takes to the mill and wants to maximize the number of bushels harvested per acre. A for-hire combine crew, by contrast, gets paid by the acre, so they are focused on harvesting efficiently and minimizing fuel consumption. If the combine crew is employed by a large agribusiness farm, they are interested in maximizing both crop yield and fuel efficiency.
Herman Cease, Project Engineer, and other engineers at the Case New Holland Technical Center in New Holland, PA, have the mission of finding ways to optimize combine performance by experimenting with the distribution of power to the various functions of the combine, testing different configurations in the field, and providing information on optimal setups that is supplied to CNH’s customers and dealer network.
“A combine is a self-propelled factory on wheels that can be readily adapted to conditions with software and hardware changes,” said Cease. “The big challenge is to figure out where to put the power to do the most good.”
To get the answers, Cease needs to measure torque on various pieces of rotating equipment within the combine as it harvests and processes grain in a field. That typically means placing a strain gauge on one of the shafts within the combine and then using telemetry to transmit the data off the rotating shaft to a data collection system.
But a combine, driven by a single 300- to 500-hp (224- to 373-kW) diesel engine, can be a nasty place to transmit wireless data. There are shafts that can run at 50 revolutions per second, and there is a lot of electrical noise. Some parts build up huge static charges. In addition, the equipment punishes any monitoring equipment with large amounts of shock and vibration.
That’s where a digital rotor telemetry system from Accumetrics Associates comes in. CNH owns several Accumetrics AT-5000 EasyApp systems at the Lancaster location (and more elsewhere). The AT-5000 EasyApp is a miniature, battery-powered digital telemetry system that can be applied to rotating shafts of diameters greater than 0.9 in (23 mm) using Kevlar straps and can be used to measure strain, torque, temperature, and other bridge-conditioned sensors. The big advantage of the AT-5000 and other Accumetrics telemetry systems is that they are digital. By gathering data on the rotor and digitizing it before transmission, the AT-5000 system maintains a high degree of data integrity and noise immunity.
The AT-5000 EasyApp components are extremely small and rugged. The transmitting module, which includes a lithium battery, mounts opposite an equally weighted adjustable yoke that maintains balance and strap tension. The combination requires about 0.7 in (18 mm) of radial clearance around the shaft. The Kevlar strap that is typically used has a rated pull strength of 3000 lb and can withstand over 12,000 rpm on a 4-in (102-mm) driveshaft, with other straps available for over 10,000 lb rated pull strength. Battery life can be as much as 150 h on a single lithium battery when used with a higher resistance strain gage.
Other components of the telemetry system include a receiving antenna and a receiver. The crystal-controlled system requires no tuning, and a high sample rate (up to 11,718 S/s) makes it possible to capture data from highly dynamic phenomena.
CNH uses the Accumetrics AT-5000 systems in several different ways. One example is on the shaft used to drive a transmission gearbox for the combine rotor. The shaft is strain gauged, with the resulting torque telemetry signal combined with a speed signal to give the operating power. Different operating crop conditions and combine setup parameters are evaluated for crop production into the combine’s grain tank. There are different setups for different crops such as corn, wheat, rice, and other grains that are used for ethanol, oils, animal feed, and human consumption.
Another example of telemetry use is at the rear of the combine where crop residue is chopped. Again, measurements of the driving torque are used to evaluate different styles of chopper setup. A third example is to measure input torque to a gear case that drives the front header on the combine to optimize the efficiency of the header cutting and gathering the crop into the front of the combine.
Due to the flexibility, ruggedness, and high noise immunity of the Accumetrics telemetry systems, CNH can gather the engineering data needed to develop combine configurations that can harvest grain more efficiently. Accumetrics systems are also available in multichannel configurations for more complex applications.
This article was written for SAE Off-Highway Engineering by Jock Elliott, Accumetrics.