How about the old Harley V-twin design:
(both rods share the same crank journal)
A piston fires.
The next piston fires at 315 degrees.
There is a 405-degree gap.
A piston fires.
The next piston fires at 315 degrees.
There is a 405-degree gap.
And the cycle continues.
(and yes, the girls tell me they do vibrate quite nicely)
