"Kai M. Radicke" wrote:
> As I was trying to fall asleep last night, I began to wonder why the crank
I'm glad I'm not the only gear-head that goes to sleep thinking techno-stuff.
> for my inline six (TR6) motor has all of the journals in the same plane (I
> suppose you could argue that there are two planes though). Would it not be
> more efficient (for multiple reasons, getting at them later) to create a
> crank shaft with journals say within three difference planes, all separated
> by 120 degrees?
The issue is primarily one of balance. Yes, the TR6 and MG "B" engines
are single plane crankshaft designs. They are rather well balanced but
not so much so as a 6+ cylinder. The big Ferraris use, in essence, two inline
sixes sharing a crankshaft (and little else). They are really smooth. Another
name for the single plane crankshaft is a "flat crank." My Ferrari 308 is
a transverse, mid-engine V8 design but it uses a flat crank as opposed to the
90 degree crankshafts of American V8 engines. It's why the Ferrari sounds
so different. In fact, the closest sound to the Ferrari 3 liter V8 is the
Offenhauser
V8s used at Indy back in the 60s and 70s. The Offenhauser V8 is also a flat
crank design. The V angle is also a issue and is of course related to the
angles
between the planes of the crankshaft -- if there is more than one. Some of the
V12s are 60 degree Vs. The Formula one cars are V10s! Want to work
out THAT balance problem?! Yikes!
> Is there some reason why multi-plane cranks are not more popular (again,
> like I said I know nothing about modern day motors)... ? Obviously, I am
> not talking about motors with V blocks either.
So to sum up; Four cylinders, four stroke Otto Cycle engine, power stroke
every OTHER stroke and, in the advanced designs, V angle. It's about balance.
Balance makes the engine more manageable to use and it also minimizes wear.
Rick Lindsay
Diamond Geoscience Research
5727 S. Lewis Ave., Tulsa, OK
Voice: +1 918-747-3456
Fax: +1 918-747-8599
|