Queston for the Lubemaster...

[A930Rocket]

From some of your posts recently, I take it you're a metallurgist?

What would cause the cam below to snap while installing?

I hope forwheeler doesn't mind me posting it here?

cam broke during install

How is this even possible? I was not even near the 110 ft lbs while tightening the nut and then it started getting loose again and then...

It was an SC profile from web cams. It was in the engine for years and then I sent it to web cams to get reconditioned and I was installing it again. They said they have never heard of this happening.
I had the torque wrench set for 110 but I am guessing I had about 75 on it at the time it broke. Yeah I guess it is better it broke now instead of later.
So I will be getting a new SC cam from them. I will need to pay the core charge since I don't have a good cam to send them now. Does anyone have a SC cam good or bad I can send them for a core?

[Joeaksa]

Originally Posted by A930Rocket

From some of your posts recently, I take it you're a metallurgist?

Lube is a pervert who likes to get slick things on his hands and other parts of his body and deflower young virgins!

[porsche4life]

I think he is more of a failure specialist than a metallurgist....

[RWebb]

huh Mike has not posted

IIRC, he has a MS in Chemistry (or was it Chem E?) and works for a small "boutique" quality lubricants co.

[cgarr]

It looks like it broke to me..

[M.D. Holloway]

Was with customers most of the day. Looks like a snap snap you got there! I am not a metallurgist but I am a degree'd chemist with an advanced degree in engineering, that and 0.50 will get you a cup of coffee! Now, back to the matter at hand. Looks like a great example of brittle fracture to me - great image of the crystal structure and no signs of necking (elongation).

This is Ductile Fracture and this is Brittle Fracture

[M.D. Holloway]

Now as to why, well thats a good question. What are the factors effecting metal to experience brittle failure?
• Crystal structure
• Interstitial atom
• Grain size
• Heat treatment
Brittle fracture occurs the metal doesn’t yield before it breaks. Instead of the sheets of atoms in the metal sliding over each other as occurs in deformation, when stressed, the sheets of atoms pull completely apart. This type of fracture most often occurs in metals that are extremely hard. Brittle fracture almost always occurs at low temperatures.

[RWebb]

what metal was it, Mike?

[M.D. Holloway]

Something I came across:

Hydrogen embrittlement is a major cause of fastener failure. Prevailing thought is
that steels with Rockwell hardness above C30 are vulnerable. The phenomenon
is well-known although the precise mechanism has eluded extensive research. A
number of proposed mechanisms have been proposed, and most have at least
some merit. Current thinking is that the susceptibility to hydrogen embrittlement is
related directly to the trap population. Generally, hydrogen embrittlement can be
described as absorption and adsorption of hydrogen promoting enhanced
decohesion of the steel, primarily as an intergranular phenomenon.
Electroplating is a major cause of hydrogen embrittlement. Some hydrogen is
generated during the cleaning and pickling cycles, but by far the most significant
source is cathodic inefficiency, which is followed by sealing the hydrogen in the
parts. Baking is often performed on high strength parts to reduce this risk, and the
ASTM, in 1994, issued a specification for baking cycles, as shown below. For the
production plater, having to remove the parts from the production line to
bake - followed by a separate chromating process - is a laborious process.

For Nearly fifty years mechanical Plating has been accepted as a means of
eliminating hydrogen embrittlement. Today, many specifications reflect industry's
confidence in this unique process. While it is true that mechanical plating uses
inhibited acids which generate less hydrogen, PS&T believes that mechanical
platinng as a process is inherently free from hydrogen embrittlement because the
deposit is porous (as are phosphate coatings), allowing hydrogen to escape through
the coating; in electroplating, by way of contrast, hydrogen is sealed in the part.

[M.D. Holloway]

This is an SC Cam? Vanadium alloy? Not sure.

[A930Rocket]

I don't know anything about it or the background. I just thought it was strange to break like that. Luckily it was during the install and not while running!

[fastfredracing]

I have never seen this personally, but I think I remember a couple of threads in the past where others have had this same cam failure when tightening up the big 46mm nut.

[M.D. Holloway]

The temp cycling is what prolly does the most damage - I wonder if the mfgs of the cam didn't really consider the sort of punishment it would experience and went for weight reduction instead?

Also, the torque wrench could have registered 75ft-lbs but unless it is a really good wrench that may have not been correct. If there is gonna be a failure it can only come from 4 sources:
1) The Man
2) The Method
3) The Machine
4) The Material
Ain't anything else....