All very nice Scot, but it still doesn't answer my basic question which is why would I want to buy an SE Compensator. H-D's been making compensators since like forever and they've changed maybe three times over the years. The current flat internal spring design came out somewhere in the 70's I think.Before that the spring was a separate piece and they were a bit of a pain to work with, so that last improvement 35-40 years ago was great. It works quite well and you know it's hard to beat tried and true so I'm like what's the big deal on the SE thing .So why a new mousetrap when the old one catches mice fine ? I'm behind the curve on this SE Comp thing. Help me out ok ?
B B
Oh... I thought you were heading another direction....
The short answer is the crank failures that became more common starting in 07...
Here's the long answer... A number of things happened in ’07 that seem to coincide with the current crank issues. In ’07 the Cruise Drive was expanded from the Dyna Platform to include all Big Twins. It seems that the new larger motor sprocket would easily max out the capacity of its shock absorbing compensator. This is evident by the sound made when the mechanical stops are reached at maximum travel. Crank failures and starter failures began to occur in increased numbers...
When problems became evident in 2007, one of the first countermeasures was the torque smoothing calibration. This was intended to prevent the engine from pulling down hard at extremely low RPM. The resulting powertrain snatch would hammer the crankshaft off the compensator's mechanical stops resulting in severe torque spikes at the crankpin, ultimately shifting the flywheel assembly.
One of the next countermeasures was the Isolated Drive System introduced on 2008 touring platform machines. The IDS is also offered as a retrofit for 2007 touring machines. This device absorbs shock loads generated from the powertrain, reducing stress at the crankpin.
The next countermeasure that followed in 2008 was the high capacity compensating sprocket - the SE compensator. It can handle 7x the torque spikes over the stock compensator.
Regarding other internal countermeasures; I've been led to believe from an engineering friend at the MOCO is the interference fit of the crankpin into the flywheel doesn't tolerate being disturbed after it has been assembled. My understanding is that if the joint is moved after assembly, even for truing, the integrity of the joint will be compromised, reducing the torque capacity of the assembly.
Somewhere there is a "calculation" based on production variables that results in the substantial number which is used to specify "acceptable" trueness of this assembly. So far it seems in practice that this number is not representative of a quality component.
My sense is that the increasing flywheel shift issues beginning in ‘07 are the result of drivetrain changes coupled with higher engine output which was not met with adequate torsional dampening of the drivetrain.
My take on the crankshaft issues that began in 2007 are:
The crankpin was moved further from the crankshaft center, increasing the stroke and the mechanical leverage of the flywheel’s inertia over the crankpin. This reduces the crankshaft’s capacity to resist high torsional load spikes.
The longer stroke results in increased mechanical leverage resulting in higher torsional loads throughout the powertrain.
The overall gear ratio changed substantially with the advent of the Cruise Drive to a numerically lower ratio. This change resulted in a substantial increase in load throughout the powertrain.
You have a scenario whereby the engine has increased capacity to produce high torsional loads; the crankshaft has reduced capacity to handle these loads and the drivetrain and chassis have less capacity to absorb and dampen these torsional load spikes. The engine makes more power, and the rest of the powertrain and chassis absorb and dampen less
So that's why you may want to consider the SE Compensator....
Author
Topic: Latest dissapointment (Read 5379 times)