Cranks
- Thread starter Fingers
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From several runs through the model, it looks like putting an even heavier balancer on the front of the crank would help the reduce the flexing on the #1 journal. However, the fix is RPM dependent as would probably not be practical.
However, another bearing supporting the balancer would be even more effective and add little if any weight.
However, another bearing supporting the balancer would be even more effective and add little if any weight.
That's what we need-a great big trunion bearing on the front of our engines lol. Didn't detroit or mack used to do this back in the day? For crank-driven driveshafts for hyd pumps on cement and dump trucks IIRC.
It wasn't a bearing, it was a mount for the hydraulic pump.
A bearing just inside the front seal would do wonders.
A bearing just inside the front seal would do wonders.
Yes, and no. I am sure we could come up with a modified font seal that could be both seal and bearing. My concerns would be the alignment of that bearing with the rest of the crank shaft.
There are floating bearing systems that use an epoxy to lock the bearing in alignment once the shaft is in place.
The Max load out there would be <<5000# and looks to be more like 1000#. At 1000# the factor of safety at the #1 Rod journal doubles.
There are floating bearing systems that use an epoxy to lock the bearing in alignment once the shaft is in place.
The Max load out there would be <<5000# and looks to be more like 1000#. At 1000# the factor of safety at the #1 Rod journal doubles.
Hydrogen Embrittlement
Is there a way to test for hydrogen infiltration into the metal?
Can passivation be done and not impact the Nitride treatment? They both happen at similar temps from what I can tell.
Is there a way to test for hydrogen infiltration into the metal?
Can passivation be done and not impact the Nitride treatment? They both happen at similar temps from what I can tell.
If it cracks you know there was hydrogen infiltration at some point. On any alloy or steel part a person takes a risk of hydrogen infiltration at some point. Can the risk be reduced? Absolutely.
Just because it cracks does not mean there was hydrogen in the metal or even that it was a factor.
Yes, it can be controlled.
My question is can it be tested for post-mortem?
Still working on the fatigue angle for these cranks. It's gonna require some more analysis with tools I am not very familiar with yet.
Yes, it can be controlled.
My question is can it be tested for post-mortem?
Still working on the fatigue angle for these cranks. It's gonna require some more analysis with tools I am not very familiar with yet.
Fingers, I agree that a crack is not just a hydrogen problem or sign of I filtration.
Hydrogen usually infiltrates into metal when it is hot, real hot, like in the forging process and when several factors are taken into account. I fully understood your question about wondering how to check before the incident takes place.
One thing I do know for a fact, if there is hydrogen infiltration during the forging process any metal will absolutely crack at some time. I'm not a metallurgist, but I do working with many different grades of steel and introduce alloys into those steels at very high tempertures a.k.a. Welding. Hydrogen is the nemesis of a welder and blacksmith.
Hydrogen usually infiltrates into metal when it is hot, real hot, like in the forging process and when several factors are taken into account. I fully understood your question about wondering how to check before the incident takes place.
One thing I do know for a fact, if there is hydrogen infiltration during the forging process any metal will absolutely crack at some time. I'm not a metallurgist, but I do working with many different grades of steel and introduce alloys into those steels at very high tempertures a.k.a. Welding. Hydrogen is the nemesis of a welder and blacksmith.
I've dealt with it on plated parts. Low heat processes that then require Passivation to drive out the hydrogen.
I'm not sure of the source on these these cranks, or even if it is present. That is why I want to chase it down before moving on.
I'm not sure of the source on these these cranks, or even if it is present. That is why I want to chase it down before moving on.
Jon,
From my friend, he's a Large Engine Engineer and has a degree in Metallurgy. Pretty smart dude...
Albert,
The only way to test in a highly accurate quantitative way for hydrogen is to take pins and send them to a lab for testing. The other way is to get the original steel spec sheet which should list hydrogen in ppm. Max is usually something around 2.5 PPM or less. The qualitative way to check after the crank breaks, is to examine the steel at high optical magnification or in an SEM (scanning electron microscope) for what is referred to as hydrogen flaking. It looks almost like little leaves in the steel at different orientations. It is very uncommon today to get hydrogen flaking or embrittlement in steel because of a process called vacuum degassing. They pull vacuum on the steel for several minutes and bubble an inert gas like argon through it to stir the liquid a little. Some alloys are more susceptible to hydrogen embrittlement than others.
http://www.substech.com/dokuwiki/dok...ladle_refining
The other hydrogen embrittlement situation occurs when the atmosphere that the component is in gets very sour (acidic). The rendered hydrogen easily transports into grain boundaries and eventually an intergranular fracture of the steel occurs. This looks like rock candy and will then eventually turn into a traditional cup cone or fatigue crack type surface. This can be detected by looking at fracture surfaces or by cutting a micrograph and etching it. Either way it is destructive testing by nature.
Hydrogen embrittlement to the left and traditional overload fracture surface to the right.
Hope that helps.
Increasing the radius by additional material removal spreads out the stress concentration. Which is good, but it also marginally weakens the crank. If you could leave the material and increase the radius, that helps.
Still, the stresses on the crank are hovering around a safety factor of 2 and concentrated in the fillet area. Fertile conditions for fatigue failures. Reminds me a lot of what I was seeing on the pistons.
Still, the stresses on the crank are hovering around a safety factor of 2 and concentrated in the fillet area. Fertile conditions for fatigue failures. Reminds me a lot of what I was seeing on the pistons.
Do the powerstroke and cummins have this problem with the crank or is it the design of the duramax crank?
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