Opinions on the Flywheel of the Hart-Parr Tractor

Lewis H. Cline shares his opinions on a previous article concerning the old reliable Hart-Parr tractor.


| March/April 1967



16-30 Hart-Parr

Photo courtesy of Warren King, Adrian, Michigan.

PHOTO: ROBERT GRAY

A reader's opinions on the Hart-Parr tractor. 

I found the article by Wilfred Koskela, page 11, November/December G.E.M. to be very interesting. He had a question regarding the counterweight cast in the flywheel of the old reliable Hart-Parr tractor (bottom of page 14 of that issue). Here is my answer to it:

While it's true that a counterweight here does not seem necessary, the throws of the crankshaft being opposite, on investigation you will no doubt find another at the other end of the crankshaft, (perhaps out of sight, inside of the clutch) (which if I'm not mistaken is inside the belt pulley) These counterweights are opposite (180 degrees from) the crankshaft throws. True, the throws of the crankshaft balance each other, but this is a static balance (balanced only while the crankshaft is not turning). On large bore motors, especially those not of the opposed type, where the cranks are far apart (lengthwise of the crankshaft) considerable vibration would be set up while running. These counterweights overcome a large part of this. A rotating counterweight will not altogether counteract the vibration of a reciprocating piston, but will materially reduce it. By making them of the proper weight the engine can be made to run much more smoothly. On engines of this size the centers of the pistons must be 16 or 18 inches apart, so they would not balance each other very well, being so far apart, while running.

I purchased used, a number of years ago, a John Deere Model B (1936 vintage) and one of the first things I noticed about it was that it vibrated badly. I took the clutch out of the belt pulley and noticed that the pressure plate (which was counterweighted) which was mounted on the splined end of the crankshaft had been put on wrong. The instruction book mentioned a rivet and a short spline on crankshaft which should be lined up when reassembling. The mechanic? either did not notice this or disregarded it and when he tightened up the nut on the end of the crankshaft sheared off the rivet, and had die light side of die pressure plate nearly opposite the crankshaft throw. Reassembling it correctly overcame the vibration.

The flywheel of these has a hollow spot on the back side of rim to offset the weight of the crank throw at other side of the engine.

I hope this answers his question.