Harmonic Dampners???

With the ATI do you have to drill the crank for the pins like Fluidampers if you run over 3500 Rpm?
 
seeker1056 said:
I have read more than a few places, including a version by Cummins that these motors have a serious (explosion serious) issue at 4200 rpm, after that it slowly goes away - kinda like an unbalanced tire that shakes at a certain rpm only

I can tell you that if you go to the Scat crankshaft website that they will tell you they will NOT warranty a crankshaft that has had a Fluidampr on it as they have proved time and again that viscous dampers can and do cause crankshaft breakage They will only recommend a torsianal rubber style elastomeric damper.

To prove a point - show me a single nascar motor with a viscous damper on it - you wont find one - for the same reasons - they are all elastomerics

the reason a fluid damper or similar damper doesnt work well - like any other liquid - it will roll up and be heavier in places, even if only momentarily - does it do a good job of dampening vibrations - sure - thats what unconnected liquid does - but thats no good if it is going momentarily out of balance all the time
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I'm not saying you are wrong. Just asking a question. Wouldn't a fluidamper be like filling a bucket with some water & spinning it over head? The water stays in the bucket even better with more speed. Doesn't the Fluidamper work on this same principal? I've seen alot of elastomeric dampers fly apart, one costing me a engine. I blew a 355 chevy when the damper blew apart & went flying down the road at 7000rpm.
 
a loaded tractor tire goin too fast and thumpin up n down as the liquid starts whipping is a better analogy

I doubt very much you ever blew up an SFI approved elastomeric damper
 
seeker1056 said:
a loaded tractor tire goin too fast and thumpin up n down as the liquid starts whipping is a better analogy

I doubt very much you ever blew up an SFI approved elastomeric damper
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I never had a sfi approved to be honest. Mine was one of the Summit Racing stock replacement dampers.
 
Thats what the guy from ATI told me on the phone. Most all diesel big rig motors do have fluiddampers but you are talking motors only turning 2000 rpm. The size of the damper for cummins is simply not big enough to control the crank vibrations and that is why you have to do the drill pin deal. It is slapping the weight that is floating in the fluid back and fort hence it needs to be bigger and heavier. For competition, you dont want bigger and heavier and thats why the ATI is simple by design. No moving parts to worry about. The ones on the big rigs are like 6'' thick by 18-24" across.

Did i read the the comp units are lighter than the regular ones? I would think this would translate to less stress on the crank which brings you back to the lighter and simpler ati.

Tim
 
ILLINOISRAM said:
Thats what the guy from ATI told me on the phone. Most all diesel big rig motors do have fluiddampers but you are talking motors only turning 2000 rpm. The size of the damper for cummins is simply not big enough to control the crank vibrations and that is why you have to do the drill pin deal. It is slapping the weight that is floating in the fluid back and fort hence it needs to be bigger and heavier. For competition, you dont want bigger and heavier and thats why the ATI is simple by design. No moving parts to worry about. The ones on the big rigs are like 6'' thick by 18-24" across.

Did i read the the comp units are lighter than the regular ones? I would think this would translate to less stress on the crank which brings you back to the lighter and simpler ati.

Tim
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That is not the case in all competition, from my understanding the modified pullers will weld giant pieces of plate to their dampeners. I am not entirely sure why, maybe to give the rotating assembly more momentum so that it can maintain higher RPM's better?

I would like to try a different dampener on my truck but I just can not see myself spending $400+ on something that may or may not make any real gain...
 
Muddin_dude06 said:
That is not the case in all competition, from my understanding the modified pullers will weld giant pieces of plate to their dampeners. I am not entirely sure why, maybe to give the rotating assembly more momentum so that it can maintain higher RPM's better?
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I've heard of weighted cranks to keep momentum up, but nothing in the way off adding weight to the dampener itself.
 
Adding counterweight to the dampers is if you external balance it. Just like a 400 small block chevy.
 
Weight comes into play with CHANGES in speed. Chop the throttle or have a part failure, and the rotational mass of the damper over-rotates the crank snout. That is why the dampers need pinned, not due to "crank vibrations". And you can not change the laws of physics, remove weight remove damping ability.
 
From what I understand, the big pulling guys especially the tractor guys, add weight to the flywheel, crankshaft, and sometimes the dampner, to help in keeping the momentum of the crankshaft speeds at the big end of the track. I also understand most of them that have done this went away from it soon due to crank breakage and alot of other problems.
 
bh10 said:
With the ATI do you have to drill the crank for the pins like Fluidampers if you run over 3500 Rpm?
Click to expand...

ILLINOISRAM said:
Thats what the guy from ATI told me on the phone. Most all diesel big rig motors do have fluiddampers but you are talking motors only turning 2000 rpm. The size of the damper for cummins is simply not big enough to control the crank vibrations and that is why you have to do the drill pin deal. It is slapping the weight that is floating in the fluid back and fort hence it needs to be bigger and heavier. For competition, you dont want bigger and heavier and thats why the ATI is simple by design. No moving parts to worry about. The ones on the big rigs are like 6'' thick by 18-24" across.

Did i read the the comp units are lighter than the regular ones? I would think this would translate to less stress on the crank which brings you back to the lighter and simpler ati.

Tim
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So you need to drill the pin in with the ATI?
 
I don't believe they offer a kit to pin the damper. The bolts on the ATI are much longer due to the fact it's a multi piece damper with a separate hub. Not sure you could even pin that style hub.
 
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