Rear wheel hub issue

[mm1ut1]

Took my 77 out of storage yesterday and was cleaning the road grime off the rear wheel when I noticed that a piece had broken off the rear outer hub. Ever see something like this ? Looks like I will be hunting down a rear wheel or hub soon !

 

[Its been a long time]

Yes my 77 has the same issue but not to the same extent as that.

 

[DogBunny]

I wonder what causes that damage.
I have a 70-71 front drum wheel that has damage in the same place, but much smaller (I got the wheel like this). I showed it to 2M, and he gave a lengthy explanation of why it was nothing to worry about.
The two broken pieces were still attached, but very much pushed in. I broke them off, dressed the distorted edges as best I could, and glued them back. This was purely for cosmetic reasons. I don't remember if I used JB-Weld, or Super Glue, or both.

 

[Jan_P]

Can be many reasons but I will try
In many metal materials there is the fatigue life span .That is and was difficult to foresee
Designers rarely get it so wrong that the design breaks immediately I have no experience in these materials
The men here from Flying sector might know more
Low loads longer life more load shifts before crack Higher loads fewer load shits before cracking

These cracks appears to be close to the spoke insert and there is a force going in there

Furthermore in the manufacturing process ..there can be some kind of heat process If these are cast
It is a hot fluid that goes to solid and when cooling down and solidify it shrinks in volume .And if it is fixed at another point it can create internal stresses
Well know in fex Welding " Heat Shrinkage "

Welding heat shrinkage is the contraction of metal as it cools from high welding temperatures, causing the weld metal to pull surrounding base material inward. This process leads to distortion, such as buckling, bowing, or angular changes, resulting from tensile stresses. It happens because the heated metal expands, then contracts more than the surrounding cold material allows, causing structural deformation

Then in steel there can be the heat affecting the grain size .. Steel mills sells " High Tensile " steels used in excavators
but the specs is as delivered :What the strength is after welding is mostly unknown especially fatigue strength .
Since the grains are affected even if perfect welds.

To sum it up ( my guess )
This being old machines the Fatigue life span at these positions can be used up more or less
A place with the spoke force who knows if correct
It is tightened and inserts that "pulling " Force but it will flex a bit when the load varies.
And some internal stresses from the Manufacturing process possible

If the spoke holes is drilled after said Heat Stresses the Drilling can relax internal forces.
There can also be casting defects don't know the English word ? " Slagg "

 

[Wingedwheel]

Higher loads fewer load shits before cracking

Sounds painful!

 

[DogBunny]

Can be many reasons but I will try
In many metal materials there is the fatigue life span .That is and was difficult to foresee
Designers rarely get it so wrong that the design breaks immediately I have no experience in these materials
The men here from Flying sector might know more
Low loads longer life more load shifts before crack Higher loads fewer load shits before cracking

These cracks appears to be close to the spoke insert and there is a force going in there

Furthermore in the manufacturing process ..there can be some kind of heat process If these are cast
It is a hot fluid that goes to solid and when cooling down and solidify it shrinks in volume .And if it is fixed at another point it can create internal stresses
Well know in fex Welding " Heat Shrinkage "

Welding heat shrinkage is the contraction of metal as it cools from high welding temperatures, causing the weld metal to pull surrounding base material inward. This process leads to distortion, such as buckling, bowing, or angular changes, resulting from tensile stresses. It happens because the heated metal expands, then contracts more than the surrounding cold material allows, causing structural deformation

Then in steel there can be the heat affecting the grain size .. Steel mills sells " High Tensile " steels used in excavators
but the specs is as delivered :What the strength is after welding is mostly unknown especially fatigue strength .
Since the grains are affected even if perfect welds.

To sum it up ( my guess )
This being old machines the Fatigue life span at these positions can be used up more or less
A place with the spoke force who knows if correct
It is tightened and inserts that "pulling " Force but it will flex a bit when the load varies.
And some internal stresses from the Manufacturing process possible

If the spoke holes is drilled after said Heat Stresses the Drilling can relax internal forces.
There can also be casting defects don't know the English word ? " Slagg "

This may well be the case for the OP.
In my case, I think the hub received a blow. Very possibly while it was off the bike -- that was a wheel only, that I bought on eBay.

 

[Its been a long time]

I think the damage to my rear hub in that area is down to rough handling of the wheel. That is a very fragile part of the hub.

 

[AUTOMAN]

A stone got in there and flipped. Poof comes the collar.