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why Flat 6

5035 Views 2 Replies 3 Participants Last post by  soggybottom
As I was having coffee with two long-term low-milage (read HD) riders. One asked why I was so partial to the flat six configuration. I gave my "standard six cylinder engine, done right, needs no counterbalances" and, although true, I just could not elaborate. Here a few days later, Big Larry, over on the F6B board posted the following:

"A flat-6 or horizontally opposed-6 is a flat engine with six cylinders arranged horizontally in two banks of three cylinders on each side of a central crankcase. This should not be confused with the Opposed-piston engine. The pistons are mounted to the crankshaft such that opposing pistons move back and forth in opposite directions at the same time, somewhat like a boxing competitor punching their gloves together before a fight, which has led to it being referred to as a boxer engine.
The configuration results in inherently good balance of the reciprocating parts, a low center of gravity, and a very short engine length.
The movement of the pistons in a horizontal engine is all in the same plane, so it creates less vibration than in a V-configuration engine; particularly one, like a V6, with an odd number of cylinders on each side of the engine. Unlike the V6 but like the inline-6, the flat-6 is a fully balanced configuration which is in perfect primary and secondary balance. The three cylinders on each side of the crankcase tend to have an end-to-end rocking motion, like a pair of inline-triple engines, but in the usual boxer engine configuration, the imbalances on each side cancel each other, resulting in a perfectly smooth engine.

The flat-6 is also smoother than the flat-4 or inline-4 because the power strokes of the cylinders overlap in a four-stroke cycle engine. In these four-cylinder configurations, pistons are 180 degrees apart in crankshaft rotation and start their power strokes every 180 degrees, so each piston must come to a complete stop before the next one commences its power stroke. In the flat-6, each power stroke begins 120 degrees after the previous one starts, resulting in 60 degrees of overlap between power strokes and a much smoother delivery of power to the flywheel."

I am not an engineer, but I did sleep at home last night.
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Whatever the reason I will have real trouble going back to any other engine if I had too. For the 12k service I was given a v-twin loan bike. Started it up.... "wtf... oh yeah this was normal".

No more pains in my hands hands or feet. I always took that as part and parcel of bike riding. Stuff character, I'm over that :D
The Goldwing flat six is the finest motorcycle engine ever designed, bar none....
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