Internal/external balancing
Why should they be made thicker? The BHJ I have is the same as stock, the fluid damper is thicker but center is stock thickness, the ATI is also the same as stock. Just looked at all 3
Then you have a FD with a recessed face.
They are made thicker because you generally can’t make them bigger in diameter. The OE damper is made for the OE application. That means OE materials, OE stroke, OE RPM, even OE cylinder pressures. All that is considered, and probably more that I’m forgetting.
That means when you go from an OE 1018 steel forged crank (that is twisted to get the 90* offset on the rod throws) to say...a 4340 non twist forging, even at the same stroke, you change the resonance frequency of just that part. That means the OE damper is no longer tuned for that. Now change the connecting rod material. Same thing. Change the bobweight...same thing (a I knew I was forgetting some other parameters). Every time you change any part in the system, you change the requirements of the damper.
An OE damper is tuned for all of the above, plus the elastomer type dampers ALL have a relatively small tuning window so they are tuned for an RPM where they spend the most time...which is steady cruise RPM. Transient RPM out of tune is much less destructive than steady state out of tune issues.
That means if you are using an elastomer damper and the manufacturer doesn’t ask you about your RPM, bobweight and such, you have no idea at what frequencies the damper will be in and out of tune.
To that end (this is covered in the Chrysler engine manuals so it’s not a speed seceret) as all those parameters change, the damper has to change. That means it generally needs to get heavier. Since you can’t make the diameter bigger, it has to get thicker.
If you want to see cheap assed engineering, look no further than the SBC. There were at least two diameter dampers. The low RPM, low performance engines got the smaller damper, while the higher performance engines got the bigger damper. Once you get the damper to the maximum diameter you can’t get it any heavier unless you make it thicker.
That’s why the FD is thicker. To get it heavy enough to dampen across a broad range of RPM it had to be thicker. I can’t say for sure, but I think the Innovators West damper is thicker than OE too.
Again, if you buy an off the shelf elastomer damper and you have change any or all of the above pieces, you can bet that damper is compromised before you take it out of the box.
Luckily, the cranks and stuff are over engineered so you don’t always see crank failures from improperly tuned dampers. But, almost all crank failures are damper related.
