360 Crank Sequence? I'm Confused.

[quote="acotrel"
My problem is that I cannot imagine how the crank should be balanced, what sort of two into one exhaust would work. The cam grinding if I wanted to find the best , would be a killer.

Dave Nourish made a great many 270 degree cranks, and most were balanced dynamically at 54% unless a customer asked for a different factor.

Two into one exhausts with such a crank are somewhat difficult to design owing to the leading firing cylinder back pressurizing the trailing cylinder over part of the engine speed range, but above or below this range the situation reverses, and the trailing cylinder becomes the dominant power producer.

Today's cam grinding shops can produce whatever the customer wants, but you have to find one who will take on one off jobs. Megacycle do cams already so nothing to stop a project from getting started. A purpose designed camshaft is a different matter, but people are around who will do the design work, all you have to do is produce a billet shaft and the profile design data, and it's really a very straight forward job for a cam grinding shop - anyone that is except Tighe cams !

I think part of what causes confusion is that many people do not understand that a 4 stroke engine makes two revolutions per cycle...I actually had a (doofus) engineering instructor mark my solution incorrect on a thermodynamics problem and AFAIK I was the only one in the class that got it right, the instructor and my classmates all used 1 rev/cycle for the incorrect solution for rpm...I'd been working on engines for years so I knew better (granted this was at a terrible engineering school, San Francisco State FWIW)

Now that's sticking to your guns bluto. I've had similar happen in science classes to learn teachers and judges can get away with it in their kingdoms. if y lug your 360 twin it does sort of feel like pumping bicycle peddles along. Naked Olympics does mimic our engines some when run into the elastic-erotic zone.

Time Warp said:

dennisgb said:

In searching for information on when modern balance shafts were designed into engines the earliest reference is for an automotive engine built by Mitsubishi in 1975 "Silent Shaft". Motorcycle engine balance shafts came later, long after Norton was out of business. The Commando was designed in 1967.

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The TX750 was a Yamaha motorcycle made in 1973 and 1974. It was loosely based on the XS650 but had what Yamaha called an "Omni-Phase balancer" to counter vibrations which are inherent in a parallel twin with the crankshaft set at 360 degrees (both pistons rise at the same time). Using a pair of balancers (one to stabilize the imbalance of the cylinders, the other to counter the rocking caused by the first balancer), Yamaha’s Omni-Phase balancer essentially eliminated vibration in the TX750, producing a smooth ride previously thought possible only in a triple or a four cylinder.[2] This new system was a first for a Motorcycle but resulted in massive failures for the first model year. Although, these problems were fixed in 1974 sales never picked up and the machine was shelved.

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She'll blaze down the highway at 80, very smooth!