Meaning of Numbers (xx-xx)

 Ever heard of a Hart-Parr 12-24? Ever wondered what the 12 and 24 stood for?

The origin of this type of tractor naming goes back to the early years of tractors. It stood for the HP rating of the tractor. In this case 12 would stand for horsepower (HP) at the draw bar (pulling power) and 24 stood for the HP at the belt (production power).

So why is there two different numbers?

Well it had to do with the early tractor's capacity to do work. The configuration of early tractors were to either pull something heavy as in a plow. Or it would be stationary to power, to say, a thrasher. Rarely would the two be used in a single job. So knowing how much the tractor could produce in each perspective job was crucial.

If you only know one number, don't worry, because as a general rule the belt usually could produce twice the amount of power as the draw bar.

This period of tractor naming lasted from about the time tractors became popular and well into the 1920's.

Don't be fooled though. Some manufacturers falsified their tractors capabilities to increase their sales. This was actually a common practice used by corrupt tractor manufacturers and would not be done away with until the Nebraska Tests set a standard for tractor capabilities.