Monday, June 28, 2010

Painful Progress

The evolution of farm tractor design must have been a painful process for engineers who were competing for farm customers. There is a bewildering variety of designs for us to admire at engine shows, and there were many designs so unsuccessful that none survived for us to see in modern times. Hart Parr began with behemoth tractors which were rugged, successful machines for big farms, sawmills, threshing, etc., but they soon came out with tractors which were more suited for replacing horses in row crop agriculture on small farms.
This four cylinder, cross motor design was designed to be maintained easily by the farmer, with all of the working parts accesible for maintenance. You should note that there is no oil sump under the crankcase. This engine has a mechanical oiler that pumps clean oil to all of the lubrication points. You never change the oil in this engine, but you do have to fill the lubricator regularly.
Only one man is needed to operate a tractor like this one, a big departure from earlier tractors which more resemble a steam traction engine than a farm tractor.

Click the photo to enlarge. This photo illustrates just how difficult evolving machine design can be. The valve covers tell the farmer to watch his valve clearance, which is good advice; and valve adjustment is a basic skill that every mechanic needs, but the engineers who put this together still had not grasped the necessity for clean air to feed the engine. The dirt that these engines inhaled wore the valve guides, the valve faces, the valve seats, and the pistons, rings, and cylinders. A simple air cleaner would have drastically reduced the frequency of needed valve adjustments, and for valve and ring jobs. It seems simple to us now, but someone had to figure out this problem 100 years ago.



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