[SEL] Did they ever make?

jbcast at charter.net jbcast at charter.net
Sat Jan 1 06:41:34 PST 2005


>  Now, here's the big question, the 30 and 50 both have 
> a counter balanced crank, the 20 doesn't.  This looks like it would be 
> just the opposite of what it should be.  If there is a reasoning for 
> this, maybe this is one of the reason's JD did it the way they did, to 
> prevent from having to do additional counter weighting of the crank.
> 
> Tommy Turner
> Magnolia, KY
> 
> 
The 180 degree cranks are mechanically balanced, but fire unevenly. It's impossible to completly balance an engine with counterweights, you're trying to balance reciprocating motion with a rotary weight, it will always be a compromise. If you put too much weight on the crank it will start to wobble as it goes around. Alluminum pistons did wonders for balance, reducing reciprocating weight. A 180 crank allows one cylinder to offset the other, but you still have an engine that's trying to rock back and forth, as one piston reaches the top and the other the bottom the engine tries to follow it, the opposite happens on the next stroke. 
J.B. Castagnos




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