The Hart-Parr Company really put their heads together when they designed the 22-40. They already had the 10-20 in production, so instead of coming up with a whole new engine design they just used two 10-20 engine blocks mounting them side by side on a single large crankcase. This proved to be very effective and not only did it provide adequate power but it was a smooth and quiet running engine. Hart-Parr called this engine "Twin Two" four cylinder construction. It had the same bore and stroke as the 10-20 but there was four cylinders putting out surplus power over and above its rated horsepower. In the Nebraska tests it delivered 28 max h.p. on the drawbar and 46 max h.p. on the belt.

This tractor used massive 6 spoke cast rear wheels each weighing 804 pounds. Another special design Hart-Parr used was a single Shebler carb for each engine block. This must of proved to be a problem as just the first 168 tractors built came this way. Many of these early models were converted to the single carb at a later date. I assume it would be a trick to keep them sychronized. After serial number 70169 they went to a single carb for both engine blocks, althought a modification was made again at serial number 70244, this pattern continued through the 28-50 models.

The 22-40 was a large, powerful, but yet compact tractor for its horsepower. It was very popular as a road tractor for building roads. It was also a favorite with custom threshers and sawmill operators. It had a roomy platform with easy to use controls. Take a look at the platform here. If you could operate the smallest Hart-Parr tractor you could operate the largest ones as the controls were all the same.