Robyn
04-05-2007, 09:00
As some of you may have read I discovered some small cracks in a 599 block I am working to build.
In looking things over I had time to reflect on a lot of things and some teachings from my early days in engineering came flooding back.
The split line on the mains are very sharp and ragged with absolutely no chamfer on the bolt bolts or the sides of the part line.
These areas are as machined and very sharp.
One of the first things I learned about such things was that sharp ragged unbroken edges can and do leave a spot for cracks to start.
For example a journal that a bearing fits on will always have a nice radius in the corner and never be cut sharp.
This is done to reduce the ability of a crack starting.
Any sharp edge thats in an area that is under high stress loading can allow a crack to propagate.
Just like scoring a piece of glass so it will break.
I am of the opinion tha chamfering all the holes on the lower end of these engines is a great place to start.
A simple counter sink and a light touch to the holes with the caps off will do fine.
I also believe that following the chamfering a light touch across the edges of the part lines on the center webs with a file to break those sharp corners is also a step in the right direction.
One does not need to get crazy here but this represents some very old and simple engineering principles that work.
Its sort of like welding all the way around the corner of a gusset, you dont do it in high stress areas as the gusset will crack out at the corner.
If one looks at heavy equipment you will see that the welds are run off from the corner of the gusset and onto the parent metal at about 45 degrees.
The idea is to eliminate forming a stress riser.
During my race days we went to great lengths to shot pean, pollish and a whole host of other procedures to keep various engine parts from breaking due to stress risers left behind during the machining process.
I certainly dont think that what I have described above is the total reason the 6.2/6.5 main webs crack but eliminating every possible item that can further the disructive process is a step in the right direction me thinks.
Just some food for thought.
Robyn
In looking things over I had time to reflect on a lot of things and some teachings from my early days in engineering came flooding back.
The split line on the mains are very sharp and ragged with absolutely no chamfer on the bolt bolts or the sides of the part line.
These areas are as machined and very sharp.
One of the first things I learned about such things was that sharp ragged unbroken edges can and do leave a spot for cracks to start.
For example a journal that a bearing fits on will always have a nice radius in the corner and never be cut sharp.
This is done to reduce the ability of a crack starting.
Any sharp edge thats in an area that is under high stress loading can allow a crack to propagate.
Just like scoring a piece of glass so it will break.
I am of the opinion tha chamfering all the holes on the lower end of these engines is a great place to start.
A simple counter sink and a light touch to the holes with the caps off will do fine.
I also believe that following the chamfering a light touch across the edges of the part lines on the center webs with a file to break those sharp corners is also a step in the right direction.
One does not need to get crazy here but this represents some very old and simple engineering principles that work.
Its sort of like welding all the way around the corner of a gusset, you dont do it in high stress areas as the gusset will crack out at the corner.
If one looks at heavy equipment you will see that the welds are run off from the corner of the gusset and onto the parent metal at about 45 degrees.
The idea is to eliminate forming a stress riser.
During my race days we went to great lengths to shot pean, pollish and a whole host of other procedures to keep various engine parts from breaking due to stress risers left behind during the machining process.
I certainly dont think that what I have described above is the total reason the 6.2/6.5 main webs crack but eliminating every possible item that can further the disructive process is a step in the right direction me thinks.
Just some food for thought.
Robyn