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Tom Wesenberg · 03-12-2015, 05:33 AM

Balanceing a crankshaft and counterweighting a crankshaft serve two different purposes.

You can take a perfect balanced tire and add a two ounce weight on the outside top of the rim and also add a two ounce weight on the inside bottom of the rim. The tire is still in prefect static balance, but way off in dynamic balance, as you would find out by spinning the tire. That same principle applies to the crankshaft. The original crank has two heavy weights near the center of the crank wanting to pull the crank one direction, while the two heavy weights on the ends are trying to pull the crank the opposite direction. These bending forces are what wears out babbit. Sure the Model A crank is heavier than the T crank, but the forces are still there trying to bend the crank. If you add weight directly opposite the crank throws, this will do much to counter the pull trying to bend the crank. I would add counterweights any time the engine is opened up and the crank is out. Besides, once it runs so much better you may want to take longer trips than just around town.

03-12-2015, 05:33 AM	#4
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: crankshafts Balanceing a crankshaft and counterweighting a crankshaft serve two different purposes. You can take a perfect balanced tire and add a two ounce weight on the outside top of the rim and also add a two ounce weight on the inside bottom of the rim. The tire is still in prefect static balance, but way off in dynamic balance, as you would find out by spinning the tire. That same principle applies to the crankshaft. The original crank has two heavy weights near the center of the crank wanting to pull the crank one direction, while the two heavy weights on the ends are trying to pull the crank the opposite direction. These bending forces are what wears out babbit. Sure the Model A crank is heavier than the T crank, but the forces are still there trying to bend the crank. If you add weight directly opposite the crank throws, this will do much to counter the pull trying to bend the crank. I would add counterweights any time the engine is opened up and the crank is out. Besides, once it runs so much better you may want to take longer trips than just around town.