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Contrary to popular belief, Hart-Parr did not coin the term “tractor,” although it was one of the first manufacturers to effectively use the word in its promotions.
And while we’re setting the record straight, neither was Hart-Parr the first company to build a gasoline tractor since such machines first began to appear on the market in 1889.
Not having these particular claims to fame by no means diminishes Hart-Parr’s enormous impact on the development of the tractor, however. Numerous engineering firsts (first overhead cam engine and use of an induced draft radiator) combined with the fact that Hart-Parr was the first entity to build a factory devoted to full-scale tractor manufacturing certainly secure its distinction as the founder of the tractor industry, according to noted tractor historian, the late R.B. Gray.
The tractor that put Hart-Parr on the map and firmly entrenched the company as a major competitor in the tractor industry was the 30-60. First introduced in 1907, the 30-60 was part of the third generation of tractors developed by Hart-Parr. Old Reliable, the nickname Hart-Parr applied to the 30-60, lived up to its name by having far fewer breakdowns than competing machines while delivering power above and beyond its manufacturer rating.
This attribute was crucial since so many tractors of that time often failed to meet their manufacturers’ ratings. The 30-60 was an exception in this regard. It turned out 38 horsepower at the drawbar and over 60 horses at its belt.
Built rugged to a fault, the 30-60 established a new standard for reliability in the industry. Much of this success can be attributed to Hart-Parr’s insistence that the vast majority of the tractor’s components be manufactured by the company to their high standards.
All steel parts
For example, almost all the working parts on the tractor were made of steel, which was an exception at this time of cast-iron construction. The engine’s crankshaft, for example, was either fabricated from steel that was dropped or hammer forged from a single billet of open-hearth steel.
And the tractor’s engine was designed for smooth operation. This was accomplished by establishing the centerline of the crankshaft below the centerline of the cylinder which, in effect, greatly reduced operating vibration. And then to simplify engine operation, Hart-Parr engineers operated both the intake and exhaust valves in the two-cylinder power plant from a single rocker arm.
Overhead cam advance
Another industry innovation in Hart-Parr engines was the placement of the power plant’s camshaft between its rocker arms. This advance was, in essence, one of the earliest examples of an overhead cam engine.
True, those engines weren’t spinning at a high speed (more like a rated 300 rpm). But the power plant burned hot, which allowed it to efficiently consume low-quality distillate fuels like kerosene. The challenge for engineers was in keeping water from boiling out of cooling radiators.
Induced draft radiator
Hart-Parr took care of this condition by using oil as a coolant. But oil wouldn’t give up the heat it absorbed in its engine journals as readily as it did water. So company engineers, led by the ever innovative Charles Hart, invented the induced draft radiator design.
This innovation utilized engine exhaust, which was plumbed to exit out of a tapered stack located at the top of the radiator. The rising exhaust would induce a draft that drew cooler air in from the sides of the radiator, effectively reducing the temperature of oil circulating from the engine.
Hart-Parr literature of the time bragged that the cooling oil never needed to be resupplied: “As there is no waste of oil, the original supply furnished with the engine should last as long as the engine itself!”