Broken Crankshaft Alt Fire Cam

[Dave c]

Jeremy has steel rods that work with the Winberg crank that you can run on the street

So does wade. He also mods the factory crank to work with most of his ideas..Not sure why everyone has the idea that wade only does aluminum rod stuff and racing only stuff. I've seen everything from land speed engines to marine stuff there.

 

[S Phinney]

So does wade. He also mods the factory crank to work with most of his ideas..Not sure why everyone has the idea that wade only does aluminum rod stuff and racing only stuff. I've seen everything from land speed engines to marine stuff there.

I only spoke from what Wade and I had discussed before. Maybe he does have that now and I wasn't aware if it. I know Wade builds many different applications.

 

[S Phinney]

Nothing against Shane but I think tuning has a big part of it. You can break anything with bad tuning! Not saying that's what happened here at all. I know it's an extra $1000 but I will only start with a new crank now.

I am going to give my opinion now about why I think it failed. The number one reason that I feel it failed is the crank probably was stressed from previous use. I don't believe it was tuning related in my case what so ever. Unless you want to claim tuning as the cause for the high power. This truck was ran on low pw and low timing in comparison to the standard of most tuners. In respect to tuning itself my philosophy is conservative to moderate. I don't feel you have to be on the extreme side to make power. Drivability is a high priority for me. Making power is the easy part of it but the power without everything working right together is useless in my opinion.

 

[Yellow Jacket]

I am going to give my opinion now about why I think it failed. The number one reason that I feel it failed is the crank probably was stressed from previous use. I don't believe it was tuning related in my case what so ever. Unless you want to claim tuning as the cause for the high power. This truck was ran on low pw and low timing in comparison to the standard of most tuners. In respect to tuning itself my philosophy is conservative to moderate. I don't feel you have to be on the extreme side to make power. Drivability is a high priority for me. Making power is the easy part of it but the power without everything working right together is useless in my opinion.

Yeah, I get a kick out of people who jump on the "tuning" is the issue band wagon.......LMAO!!! I've seen multiple tunes from multiple "big dollar" tuners.

And I too have broken a new crank that never seen more than 1650us duration but seen pretty high timing at 5500 rpm, lol...I do know that the biggest "feel" in smoothness and reduced vibration was the Internal Balance and Altered Firing order seemed to reduce it also...and this is in a pulling truck with engine plates mounted front & rear straight to frame...you can feel EVERYTHING.

 

[Burn Down]

what i have always wondered when Guy at Socal pointed it out to me is why a wider #1 main isnt being made/used. i understand in a stock truck application as keeping them all the same size is more economical, specially if it holds up just fine but in our cases i see it benefiting. there is plenty of room up there to add a wider one.

or maybe thats not enough support?

I'm not sure on the wider bearing? I have heard of it but have no idea what it would take to implement it?

One thing that keeps ringing in my ears, is where most of the breaks occur, in the front half of the crank. Which makes me think that a support for the front of the crank or perhaps a wider #1 bearing would help prevent the over flexing of the crank. I discussed this issue (broken cranks) with a Large Engine Engineer from Cat. He expressed concerns with the loads placed on the front of the crank IE, CP3/CP3's, water pump, oil pump, serp belt, & cam. So maybe the support idea has some merit...

 

[countrycorey]

Didn't Banks have a crank support on it's twin turbo/supercharged marine motor? That might be a starting point.


Corey

 

[S Phinney]

The problem with custom bearings and they are available from what I hear, is the quantities that have to be ordered to get them. It's around 10 thousand sets plus or minus 25 percent is what I was told. I do believe that could help. You have probably near .5 inch that the front bearing could be wider.

 

[Fingers]

you guys realize everyone jumped on the "AF is a major help to the crank" after Jon's thread about it possibly improving the harmonic issues seen by his computer simulations and then, based on the little sample size we have here on this site, it was said it keeps them from breaking.

since that was done by Jon, the post on here and other forums about it FIXING broke crank shafts is rediculous and yet, no one jumped on them letting them know that its not a guaranteed fix. Now that we on this forum have actually seen a failure from our small sample size, its assumed that we all imply a AF cam does NOT help the crank. No one has said that and i hate to say it but implyed posts are where people take that info and run with it like a cummins external oiling system.

I see this happen all the time on forums and since i feel this forum is one of the top one for good, reliable info, id like to think we all look at both ends of the spectrum to put together our facts by a very well done deductive reasoning.

no hard feelings :hug:

I've seen my name thrown around a bit here so I guess I should say a few things.

First, I didn't / don't have the answer. If I did, I would be rich right now.

Second, I like the torque application to the crank better with the Alt-firing order than stock. However, and I've said this before, I don't know that it will save cranks. Feedback from those that have been in the position to use Alt and Std order cams back to back indicate that the Alt-fires are smoother. That alone is one reason to go alt-fire, but is says nothing for the crank longevity.

Third, these are obvious fatigue failures. They are happening at the obvious stress riser locations on the crank. The first throw is the primary failure point, but they fail frequently elsewhere too.

Lastly, I have several candidates for root cause, but no proof. Until I can quantify each candidates impact on stressing the crank, they are only theory. I suspect it is a combination.

FWIW, here is what I am actively looking into in no special order:

• Under supported snout of cranks
• Short rod syndrome vibrations.
• Crank rotational velocity changes. ECM based, Short Rod based, and tuning based.
• Thrust loading of the crank.
• External loading. Cam, oil pump, water pump, CP3.

 

[S Phinney]

Thanks for posting Jon. I hope you can figure out other items within reason for use to do to help out with these failures.

 

[Awenta]

Wondering, what does a stroker kit do to our cranks. I'm aware the socal kit comes with a billet crank. I'm just wondering how it gets stressed.

Sent from my SM-N910V using Tapatalk

 

[DBUSHLB7]

I think it would be helpful if someone could mock up a graph or chart to keep track of all the variables that led to the failed cranks... Break location, mileage, new or used crank, HP, cam, number of accessories driven off the front of the crank, year model of crank, and whatever other info may help layout an obvious trend or correlation. It would help tell the story if all the data was gathered and noted.

 

[CarolinaHD]

I think it would be helpful if someone could mock up a graph or chart to keep track of all the variables that led to the failed cranks... Break location, mileage, new or used crank, HP, cam, number of accessories driven off the front of the crank, year model of crank, and whatever other info may help layout an obvious trend or correlation. It would help tell the story if all the data was gathered and noted.

You got the talkin part done, now get to it

 

[ty_LBZ]

I'll be your huckleberry! SoCal 3388AF gonna get push to the limits as soon as Trans is built!

 

[DBUSHLB7]

You got the talkin part done, now get to it

I know I deserved that. I'm not all that great with computers...I am in the construction industry after all. I figure a lot of guys here sit at a computer all day anyhow. Didn't mean to be presumptuous, was merely a suggestion.

 

[CarolinaHD]

I know I deserved that. I'm not all that great with computers...I am in the construction industry after all. I figure a lot of guys here sit at a computer all day anyhow. Didn't mean to be presumptuous, was merely a suggestion.

Wasn't tryin to come off like an ass. Maybe I shoulda thrown in one of these guys

:hug:

 

[Burn Down]

Wondering, what does a stroker kit do to our cranks. I'm aware the socal kit comes with a billet crank. I'm just wondering how it gets stressed.

Sent from my SM-N910V using Tapatalk

They still break in the same location... http://www.duramaxdiesels.com/forum/showthread.php?t=50008&highlight=blackie

 

[nwpadmax]

I see this. But, how can reducing torsional stress in the crankshaft be a bad thing? Is it possible that this (AF cam) along with other solutions will solve this problem? Thanks for chiming in.

I'm not throwing rocks at anyone with this comment, but accurate modeling of crankshaft loads and resulting stresses / deflections / displacements with all the variables we put to it.....FAR exceeds the resources and abilities of anyone posting on these boards.

So to say definitively that alternate fire reduces stresses, at all RPMs, is still a stretch IMO. To call it "the fix" is purely opinion...and everyone is entitled to their own.

 

[nwpadmax]

I was under the impression that the crank and rods are hemi width. And utilize hemi bearing size. This is the exact same set up that handles 10,000 hp top fuel engines. Wade said they had FEA testing done and showed 15-20% stronger by cross section alone. Material improvement was not factored. Neither was fillet improvments. If it were it could be even more of a gain in strength.

This puts more weight on the crank and less weight on the rods further improving balance and hp by reducing enertial (rotating and recipricating )weight.

Iirc there are engine running this set up. I do not know how many or for how long. I would assume it's been at leat two years

I doubt FEA was really seriously done, but I found the following, please verify the accuracy:

Hemi rod journal: 2.375" dia
Dmax rod journal: 2.476" dia

Hemi journal width: 2.060"
Dmax journal width: ~1.97" (not sure how this length is specified, quick measurement on a crank in my shop)

Hemi main journal: 2.75" or 3" dia.
Dmax main journal: 3.145" dia.

So at this point I'm at a loss to see where reducing the Dmax crank dimensions to Hemi sizes move us in a positive direction, let alone 15% more gooder.

What am I missing?

 

[Fingers]

For FEA, the "cheek to cheek" measurement is required for the Static model as well as the bearing contact width and location. The fillet plays in a great deal as far as the intensity of the stress riser. The "meat" at the break point is roughly the intersection of the crank and rod journal circles. So bigger journals or shorter stroke would improve the strength in the suspect area. Thickening the throw would help too, but there is no room in the block for the extra material.

So you're not missing anything.

BTW Matt, I bought the software.

 

[Stancedlb7]

They still break in the same location... http://www.duramaxdiesels.com/forum/showthread.php?t=50008&highlight=blackie

Yep, I'll take my comment back. Even strokers snap, well damn.