Crankshaft hArmonics

[hotrod]

Think of the crankshaft being made of rubber and remember that peak torque is approximately 2-5x the torque registered on the dyno, at the point max cylinder pressure and best mechanical advantage occurs in the engine (depending on the engine cylinder count and firing order crankshaft design).

Yes long cranks at high power wind up a LOT which is why they started putting "harmonic balancers" dampers on the front of crankshafts to help control those rotational vibrations to manageable levels.

An interesting read on dampers.

http://www.bhjdynamics.com/downloads/pdf/tech/BHJDynamics_Damper_Info.pdf
http://www.moparmusclemagazine.com/techarticles/engine/mopp_081027_crankshaft_damper/

Larry

[WOODY@DDLLC]

I used to design automatic production crankshaft gauges for the big three in a former life! (I did the Olds diesel but that's another story!) 
We would turn the crank at 50 rpm with a hydraulic motor and measure the mains & throws while it was turning. All to the OEM's statistical quality standards. 

I always enjoyed asking the crank guys what those standards really meant when I was in the passing lane trying to get around an 18 wheeler! I always got the look ..........

Mechanical engineers can learn just about everything they need by studying the statics and dynamics of fasteners and cranks! 
E.g. Glorified springs and rubber whirl-a-gigs! 

[manta22]

During the 1950s, Mercedes-Benz developed their 300SLR which was powered by a straight-8. To reduce crank torsional flexing, power was taken from the middle of the crank by a gear instead of at the end of the crankshaft. In effect, it was two straight four cylinder engines connected back-to-back.

[Seldom Seen Slim]

Doug:

What mile marker ae you near?  We're just about to Billings and staying in Belgrade tonight -- but where should we look for you when we go past in an hour or two?

Sorry for the hijack --

[SPARKY]

Dang HR those hurt my head 

[Rex Schimmer]

Larry (Hot Rod),
That article by BHJ Dynamics was one of the very best I have ever read on the subject of crank dynamics. Thanks a ton for posting!!! I down loaded and kept a copy for reference.

Rex

[SPARKY]

The isssue I MAY be having is--  I run a flexplate without a converter---I am suspecting that my rear main  has not been anchored the way that article indicated because I do not have as much mass to gyroscopically anchor it---I am thinking of running a flywheel to drive my automatic trans pump--- circle track type coupler or pump drive. 

If we get to run this thing this year I will pull the mains a check them


Thanks to all who post with their comments and links   we have so many who have nice orderly minds--- and we have others who just have minds that wander into unknow areas and have trouble getting out---this thread will let me revist enough times to be come conversant and provide enough understanding to at least get back out of this mental trap --- thanks guys 

[Buickguy3]

  Jon,
   Sorry I missed you we are located at about the 405 mile marker. At Belgrade you are close to Pedro from The Montana Dodge Boys. See you on Friday.
  Doug