Crank Analysis - Opinions?

[Busstom]

Not the drug, you speedsters    Counterweighted crankshafts...

So I just unwrapped my new 82mm CB crank.  Standing it next to my DMS crank, I became curious as to how/why the counterweights on welded strokers are so substantially larger than the integral mass forged into the typical new crankshaft.

Yes, I noticed in photos that Scat, Bugpack and CB cranks all have much smaller counterweight masses than welded stroker cranks, but I am curious if anyone has any insight as to the functionality or significance of one design versus the other.  How do the new, forged crank designs get away with so much smaller weights and still remain a dynamically "balanced" or "optimum" crankshaft mass?

Any thoughts?  Let's hear some opinions out there, in addition to any known facts based on scientific testing.

Thanks!

[Ohio Tom (DdK)]

That's a good question. I'm not sure about that one.
I will say that even thou they look small, they balance out just fine and revv past 8,000rpm w/o tearing up bearings or pounding cases.

[martin]

I'd like to see a pic with them side by side to compare the difference. If someone can weigh them that would be interesting too.

[Donny B.]

Berg cranks have much bigger counterweights and some Scat cranks do as well.  The generic made in china forging usually has smaller counterweights.  Remember it's the mass that counts not the size.

[Clinton DdK]

All I know is they fit in a case a lot easier. I didn't have to clear a thing for my new 84mm crank. This is just the crank no rods, I know that with the rods it will be a different story.

[Sam]

yup i love that they are smaller, if a feller brings me a welded 82 or 84 crank he gets charged a good bit more for labor, due to the pain in the rear clearanceing for them.

Years back I pulled a 78.4 welded demello crank out of my engine and put a Scat Pro comp 84mm in I had to touch some areas for the rods, but it basically slid right in.

A case is pretty butchered up when you get a welded 84 in it. 

[Busstom]

Here's a pic of the two...you can see that the welded CWs are a half-circle, while the other design is essentially a 1/4 pie shaped wedge.

Interesting point about the clearancing though...perhaps that's the main driver behind the design.

[maui]

Let's see as I recall some long time ago in the 70 and 80s,it was a Bergman 78 and a Okrassa 78.4 I noticed that at about 100,000 miles of heavy use that the welded one never have so much wear on the center main as the other and so I never had to align bore the case and the other I had to go 20 case and 10 crank so I say the extra on the cw,s is a good thing and I wen notice the clearence on the case was the same. This was the days when I only used straight 30 or 40wt oil.