Eagle Forged Stroker Crank CRACKED

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thomasfouraker said:
Pro Race Balancer. I haven’t pulled the motor yet but hopefully within the next week or two I can have it broke down and inspected.

Aside from component defect, any thing else I should be looking for as a contributor?
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The damper you used was barely acceptable to begin with. After X number of miles it was junk.

That crank did NOT fail and I don’t care who says what. There isn’t a pinch of **** difference between all those China forged cranks.

You are seeing exactly what I’ve been bitching about since ATI tried to jam one of their one size fits all but doesn’t fit anything worth a **** dampers up my ***.

Any and by any I mean ANY elastomer damper has a very narrow tuning range and it starts to degrade they day it’s made. The degradation continues on apace and exponentially until some failure happens.

Not many understand the Pro teams using the ATI damper pay engineers to change the tune of the damper on a constant basis. And they run the engines in a relatively narrow RPM range. Plus they rebuild them on a regular basis as part of routine maintenance.

You had a damper failure that killed your crank. It’s a damned shame the crank is getting blamed for a failur caused by a piece of crap damper.

The ONLY thing the ATI damper has going for it is you can tune and rebuild it. Of course, you need a PhD level engineer to do it.

The rest of the vulcanized rubber dampers are a complete waste of money.
 
Rat Bastid said:
The damper you used was barely acceptable to begin with. After X number of miles it was junk.

That crank did NOT fail and I don’t care who says what. There isn’t a pinch of **** difference between all those China forged cranks.

You are seeing exactly what I’ve been bitching about since ATI tried to jam one of their one size fits all but doesn’t fit anything worth a **** dampers up my ***.

Any and by any I mean ANY elastomer damper has a very narrow tuning range and it starts to degrade they day it’s made. The degradation continues on apace and exponentially until some failure happens.

Not many understand the Pro teams using the ATI damper pay engineers to change the tune of the damper on a constant basis. And they run the engines in a relatively narrow RPM range. Plus they rebuild them on a regular basis as part of routine maintenance.

You had a damper failure that killed your crank. It’s a damned shame the crank is getting blamed for a failur caused by a piece of crap damper.

The ONLY thing the ATI damper has going for it is you can tune and rebuild it. Of course, you need a PhD level engineer to do it.

The rest of the vulcanized rubber dampers are a complete waste of money.
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So what damper do you recommend? Fluidamper good?
 
justinp61 said:
Are you positive that's a forged crank? On the front of the first counterweight it'll say 4340 and have the p/n under it.

Looking at the images on Eagles site it looks like a cast crank.
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95% sure it’s forged…….I vaguely remember the part number and confirming it was forged but it’s possible it’s not.
 
Rat Bastid said:
The damper you used was barely acceptable to begin with. After X number of miles it was junk.

That crank did NOT fail and I don’t care who says what. There isn’t a pinch of **** difference between all those China forged cranks.

You are seeing exactly what I’ve been bitching about since ATI tried to jam one of their one size fits all but doesn’t fit anything worth a **** dampers up my ***.

Any and by any I mean ANY elastomer damper has a very narrow tuning range and it starts to degrade they day it’s made. The degradation continues on apace and exponentially until some failure happens.

Not many understand the Pro teams using the ATI damper pay engineers to change the tune of the damper on a constant basis. And they run the engines in a relatively narrow RPM range. Plus they rebuild them on a regular basis as part of routine maintenance.

You had a damper failure that killed your crank. It’s a damned shame the crank is getting blamed for a failur caused by a piece of crap damper.

The ONLY thing the ATI damper has going for it is you can tune and rebuild it. Of course, you need a PhD level engineer to do it.

The rest of the vulcanized rubber dampers are a complete waste of money.
Click to expand...
Is there any way Of checking is the damper is good or not?
 
when I bought my R3 block, balanced assembly, and 360-1 Indy heads it came with Eagle crank and rods. They didn’t have their upgraded rod bolts which isn’t a smart move. I’m not an Eagle fan but honestly had no reason for my dislike because I never ran it before. That engine ran a best of 5.98 and five years of 6.0 passes. Now I was only shifting at 6700-5700 rpm. I sold that crank and rods to a friend for a street combo and it will be going together with Molnar crank and rods.
 
thomasfouraker said:
95% sure it’s forged…….I vaguely remember the part number and confirming it was forged but it’s possible it’s not.
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It's easy to tell by looking at the parting line, unless that's been ground off.
 
mgoblue9798 said:
So what damper do you recommend? Fluidamper good?
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That or the Innovators West damper. Both have a much wider tuning range. The FD never wears out. The IW damper has a maintenance schedule but it’s not a continuous degradation issue.

I will not use any elastomer damper even thought you can’t swing a dead cat in the pits and see an ATI damper on most everything.
 
Rat Bastid said:
The damper you used was barely acceptable to begin with. After X number of miles it was junk.

That crank did NOT fail and I don’t care who says what. There isn’t a pinch of **** difference between all those China forged cranks.

You are seeing exactly what I’ve been bitching about since ATI tried to jam one of their one size fits all but doesn’t fit anything worth a **** dampers up my ***.

Any and by any I mean ANY elastomer damper has a very narrow tuning range and it starts to degrade they day it’s made. The degradation continues on apace and exponentially until some failure happens.

Not many understand the Pro teams using the ATI damper pay engineers to change the tune of the damper on a constant basis. And they run the engines in a relatively narrow RPM range. Plus they rebuild them on a regular basis as part of routine maintenance.

You had a damper failure that killed your crank. It’s a damned shame the crank is getting blamed for a failur caused by a piece of crap damper.

The ONLY thing the ATI damper has going for it is you can tune and rebuild it. Of course, you need a PhD level engineer to do it.

The rest of the vulcanized rubber dampers are a complete waste of money.
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Interesting you say that. I just found a post I remember previously seeing. The guy with the broken Eagle crank I posted previously was also in a thread saying he had also a broken rocker arm. Link below, post #41. I am not judging or forming an opinion, but I am hoping the Eagle crap I have works when I get it running. One is a forged 4” with 360 mains.
W2 Heads
 
I have a TCI Rattler on our stock crank 360 for 20 years, we have sent it in for a rebuild after 2000 or so passes, we are doing a freshen up right now, its been through 4 engine freshen ups and has checked out good, so this time we went ahead and sent it to TCI to rebuild it. I had a ATI on my 440 for 3 years, steel crank Indy-1 heads engine ran great up until we sold the car, My son runs a ATI on his 528, its been on for 6-7 years and just had it freshened up and it checked out good.
 
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Agree with Rat Bastid, post #26. Dampener problem because of the location of the crack.

I rebuilt an engine that failed for a similar reason. Owner had warning signs, but ignored them: three cracked crank pulleys.

Dampener was one that was bolted together with Allen bolts & half of them had loosened off....
 
Rat Bastid said:
The damper you used was barely acceptable to begin with. After X number of miles it was junk.

That crank did NOT fail and I don’t care who says what. There isn’t a pinch of **** difference between all those China forged cranks.

You are seeing exactly what I’ve been bitching about since ATI tried to jam one of their one size fits all but doesn’t fit anything worth a **** dampers up my ***.

Any and by any I mean ANY elastomer damper has a very narrow tuning range and it starts to degrade they day it’s made. The degradation continues on apace and exponentially until some failure happens.

Not many understand the Pro teams using the ATI damper pay engineers to change the tune of the damper on a constant basis. And they run the engines in a relatively narrow RPM range. Plus they rebuild them on a regular basis as part of routine maintenance.

You had a damper failure that killed your crank. It’s a damned shame the crank is getting blamed for a failur caused by a piece of crap damper.

The ONLY thing the ATI damper has going for it is you can tune and rebuild it. Of course, you need a PhD level engineer to do it.

The rest of the vulcanized rubber dampers are a complete waste of money.
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What do you think of the TCI Rattler?
 
I will try and pull the motor in the next few weeks. Have to free up some engine stand space.

This is the balancer I was using:

0DAD4316-1E66-464D-8F5E-448B24212A49.png
 
Elastomer dampers are tuned to a certain frequency based on the rotating assembly spring/mass system and cylinder pressure. Once you change that system a rubber damper is no longer optimally tuned for that system. Viscous dampers use high viscosity silicone and work over a RPM range. That doesn't mean it's optimally tuned for your particular system. I guarantee most have no idea what the resonant frequency of there rotating system is. Most crankshafts I've seen break due to a improperly tuned damper look just like the OP pictures. 65'
 
Plymouth 65 said:
Elastomer dampers are tuned to a certain frequency based on the rotating assembly spring/mass system and cylinder pressure. Once you change that system a rubber damper is no longer optimally tuned for that system. Viscous dampers use high viscosity silicone and work over a RPM range. That doesn't mean it's optimally tuned for your particular system. I guarantee most have no idea what the resonant frequency of there rotating system is. Most crankshafts I've seen break due to a improperly tuned damper look just like the OP pictures. 65'
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Thats interesting. They market that particular damper for mild street builds up to 400hp. It seemed like I fell within that and while this motor has had some WOT pulls while tuning, it never over 5000rpm or demonstrated any strange vibrations. Its in a 6500lb full size truck 2000 Ram 1500 4x4.
 
kdeboy said:
What do you think of the TCI Rattler?
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I don’t know much about that mechanism, but I think at one time I looked into it and the technology came from air plane engines or something. I’m old and that was a long time ago so…connect the dots lol. My memory isn’t what it once was.

I should look into it again. It could also be an alternative to elastomer dampers.
 
thomasfouraker said:
Thats interesting. They market that particular damper for mild street builds up to 400hp. It seemed like I fell within that and while this motor has had some WOT pulls while tuning, it never over 5000rpm or demonstrated any strange vibrations. Its in a 6500lb full size truck 2000 Ram 1500 4x4.
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Right. But as was noted above, they don’t know Jack **** about YOUR rotating assembly. Bob weight matters. So does the natural frequency of every single part in the system.

So let’s say you start the engineering with stock rods, a cast piston, cast crank and say 6000 RPM max. Then you engineer the damper to dampen the frequencies that that do the most damage.

Now you (not YOU in particular but you as in anyone doing this type of thing) drop in a steel crank. The resonance frequency of the steel crank is far different than that of the cast crank. The damper wasn’t engineered for that particular frequency and bad **** starts happening.

Now throw in a set of forged pistons and a set of 4340 connecting rods, which is not only a different materiel but is a different design. All those pieces now have a different resonant frequency than the parts that were started with, and they could easily pissed off and do very bad things.

As Randy Neal of CWT Industries says…once you excite one part of the system it doesn’t stop.

Damper technology is overlooked. Guys spend thousands building an engine and slap a 200 buck (or cheaper) damper on there and hope for the best.

And cost isn’t the best way to chose a damper either. There are some pretty expensive elastomer dampers (other than the ATI) that I would trust as a door stop.

I put hundreds of runs on stock 318 Poly cranks at 8500 (sometimes a bit more) and never broke a crank. I lost some bearings and hurt them, but I never fractured a crank. And I was wet maging my cranks as part of routine maintenance so if one started getting pissed off I would catch it.
 
Rat Bastid said:
Right. But as was noted above, they don’t know Jack **** about YOUR rotating assembly. Bob weight matters. So does the natural frequency of every single part in the system.
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so RB.. for a 390 or 408 you would recommend a fluidampr for low maint and better protection?
 
Icetech said:
so RB.. for a 390 or 408 you would recommend a fluidampr for low maint and better protection?
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That or the Innovators West damper. It’s probably worth looking into the Rattler too. I know it’s a pendulum design that uses…****…I forget how those little pucks or whatever that call them actually work but from my memory there is nothing in there that can wear out.
 
Rat Bastid said:
That or the Innovators West damper. It’s probably worth looking into the Rattler too. I know it’s a pendulum design that uses…****…I forget how those little pucks or whatever that call them actually work but from my memory there is nothing in there that can wear out.
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well.. if they call it a rattler cause it makes noise.. i'll pass :)
 
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