What's behind the increase in farm machinery reliability?

Saturday, August 8, 2015

Quality control, accelerated testing and metallurgy improvements have all contributed to the great strides in farm machinery since those early farm tractors of the 1940s and 1950s

by RALPH WINFIELD

Some of us older people remember when we changed engine oil every 1,000 miles and ground the valves every 10,000 miles. That was pretty much standard procedure for cars in the 1950s.

A similar service interval was required for those early farm tractors that appeared in the late 1940s, often the first farm tractor on many farms. Trust me, I worked in a rural repair garage and did many valve jobs on both cars and tractors.

New developments, such as hydraulic valve rotators, did much to reduce the need for head-off valve grinding. Interestingly, I recently acquired an operator's manual for a Titan 10-20 tractor that was built by International Harvester around 1920. Guess what it said? At the end of each working day, it was recommended that you manually rotate each engine valve to clear carbon and other materials from the valve to seat contact area.

This was not a big job as the two large horizontal cylinders were positioned with the heads and exposed valve springs pointing directly toward the operator platform. It was a five-minute task to turn the four valves, but was it done regularly by the busy farmer who was more probably more inclined to stop the tractor and get on with other daily chores? Not likely!

But wait. That operator's manual also explained with illustrations the procedure for removing the heads and grinding the valves using a standard drill brace with a flat screwdriver bit!

A few mechanically inclined farmers were dedicated to keeping those older tractors running well. They were often the owners of the threshing machines that moved from farm to farm leading the threshing circuits.

As a result of the labour shortage caused by the First World War and the great increase in off-farm jobs, almost every Ontario farm obtained at least one tractor by 1950. Some also acquired a pull-type or self-propelled combine. The many first-time tractor owners provided a significant service demand at local dealerships and rural garages.

This, in turn, brought on the demand for longer-life engines as the tractors took on a multitude of farm tasks. Early tachometers and hour meters allowed tractor owners to record usage and keep better records of oil change and other service records.

At some point in the 1950s, the Ontario Department of Agriculture appointed a Farm Machinery Board to investigate the reliability of farm equipment. This was a result of many complaints about the reliability of farm machinery and parts availability, primarily for tractors and combines.

Reliability of all types of machinery became a major concern and a high priority for the designers and testers of all types of farm machinery. Special test tracks and laboratories were used by every farm equipment manufacturer to "shake down" their equipment before offering it for sale. For example, the Massey-Ferguson group maintained a test farm and track near Markham, as well as a test laboratory in downtown Toronto.

Creating component failures on a test track was an onerous task for the operators as the bumps were designed to create machine fatigue, which also created operator fatigue.

To a great extent, the cost and time lag of reliability testing using the test track brought about accelerated testing, which could often be done faster in a test laboratory.

Accelerated testing. If, for example, you needed to do a performance test on a specific driveline component, it could often be done in multiples. Let me give you an example. Consider a right-angled gearbox that could be used on a pto shaft to turn power 90 degrees near the point of use. One example would be the common 90-degree gearbox for a typical rotary mower.

With a little creativity, four gearboxes could be tested simultaneously for a 50 horsepower rating, using only a one horsepower electric motor. Gearboxes could be the same or possibly have two to four different gear/bearing sets as long as they had the same gear ratio, which would be one-to-one for our example.

Let us assume the input/output speed would be the standard pto speed of 540 rpm. The horsepower rating would be 50.
Thus using HP = 2 ϖ NT / 33,000, we can calculate the torque load that would be required.
It would be: T = HP x 33,000 / 2 ϖ N
= 50 x 33,000 / 2 ϖ 540 = 486.55 lb-ft

(Does that high torque value show you why the standard pto speed was increased to 1,000 rpm when the power requirements exceeded 50-60 horsepower? The higher pto speed reduced the torque by almost 50 per cent!)

Since all the gearboxes are of a 90-degree configuration, the test engineer would set one at each corner. Three standard drive shafts would be used to interconnect the four gearboxes in a square configuration. The fourth interconnecting drive shaft would have to be of a special design that would allow for a "physical twist" to apply the required torque loading of almost 500 lb-ft.

Finally, a pulley needed to be put on one of the shafts so that the shaft and all the gearboxes were rotated at 540 rpm by a one-horsepower electric motor. Isn't that a sneaky way to create a high horsepower load without high horsepower and high energy use? Trust me, the concept does work and can be used for many types of gear drive units.

Many other machine components can also be endurance-tested in an accelerated manner in the test laboratory. Belt drives and slip clutches can also be loaded and cycled to establish "life testing" prior to being purchased or used on a combine, baler or other farm equipment. Hydraulic quick connectors can also be tested for performance and life-cycle testing in the laboratory.

Metallurgy improvements. Engine life has been extended multi-fold, primarily by improvements in metallurgy, machining and induction component hardening.

Many tractor engines now perform well for thousands of hours without the head or oil pan being removed. When was the last time you had an engine taken apart to grind valves, replace piston rings or do other major repairs? If it happened, it probably occurred early in the engine life due to a faulty component or an assembly error. This assumes that you changed fluids and filters as specified by the manufacturer.

I have had two personal experiences that were very interesting and informative. One was contact with an engineer who was responsible for induction hardening of engine and other components, such as engine camshafts or tie rod ends. What he admitted to me was that, occasionally, a pallet box of items would inadvertently bypass the induction hardening process. Within weeks, each and every one of those items would be returned to the manufacturing plant under the now common warranty program offered to the supplied company.

The second example was when I purchased a new car about 10 years ago. Within a few weeks, one tie rod end started to make a noise. It was removed and returned to the component supplier by the dealer. That was the type of item return that allowed the induction hardening engineer to find out exactly how many items were in that bypass pallet box. The replaced tie rod end lasted for years.

Assembly problems. More and more, we are seeing and benefiting from very precise hydraulic components. Many of the new components in hydraulic pumps, motors and valves are fitted to microns of clearance. There is absolutely no tolerance for contaminants in pumps, hoses, fittings or controls. Components must be clean, capped and kept clean during assembly. Airborne or fluid contaminants not visible to the naked eye will cause component jamming and serious operational problems.

If, for any reason you take apart hydraulic components for maintenance, including hoses, be sure that all open ends are capped. Similarly, make sure that all new hoses made up with crimped end fittings are cleaned and capped. All hose suppliers have, or should have, flushing facilities prior to capping hoses or components.

Let us also take a quick look at newer hydraulic system clearances. Many new high-pressure piston pumps and motors are fitted to tolerances of less than five microns. What is the smallest particle that you can see? About 20 microns! If you are a field sprayer operator, you will know that it is those very small droplets under 20 microns in diameter – the ones that you cannot see – that move off target and cause damage.

Those of us who are somewhat older have seen and experienced many significant improvements in mechanical and hydraulic technology. The benefits are indeed worth the extra effort and, in some cases, the extra costs.

An important rule that I have always followed: do not buy low quality hydraulic oil and filters or cheap "off-shore" roller chain. The savings are not worth the risk of a breakdown or component failure. Any machine out of service at critical times is a liability! BF

Agricultural engineer Ralph Winfield farms at Belmont in Elgin County.