bertsmobile1
Lawn Royalty
- Joined
- Nov 29, 2014
- Threads
- 64
- Messages
- 24,705
Failure analysis is a hands on experience thing .
It is not all that difficult but only if the failed item is in your hands.
Cracks will tell you a lot as will the shape of the fracture surface, which side of a conrod has the little neck, weather there is necking or bending.
Then there is metal pick up, the direction of metal pick up and oxide colours where there should be none .
However to do it properly you need to be at one with the engine and understand exactly how each part interacts with other parts .
So for instance with a broken rod you fist look to see if it rotates freely on the big end and if the piston rotates freely on the little end.
Then you look at the oxide colours on the underside of the piston .
Big end is free bit little end is frozen & the piston is blue so you look at the oil slinger / pump .
Teeth missing and the surface is slightly rounded & polished a little then it was a cause, teeth fracture surface clean with no damage, happened during the failure . etc etc etc
And thus it goes on.
In a different life I did occasional overflow work for a tutor who had a contract with the police forensic lab .
Around this time of year you get a lot of car smashes when little Johnny is high as a kite but daddy big time lawyer is busy trying to shift blame anywhere else .
A common trick, before ABS came in was to rev the engine hard then slip your foot across and jump hard on the brake when you had maximum boost on the brake servo.
This will generally pop a seal somewhere in the braking system so little Johnny can claim brake failure
If you get Air Crash Investigations over there binge on a few hours of it and fast forward through all the bull to the bits where they show you how they determined a missing washer caused an engine to self destruct.
It is very accurate, quite a surprise for a TV show.
Even then they ignore the technician who spent hundreds of hours cutting up critical pieces of the wreckage, doing micro analysis of the crystal structure and hardness testing
It is not all that difficult but only if the failed item is in your hands.
Cracks will tell you a lot as will the shape of the fracture surface, which side of a conrod has the little neck, weather there is necking or bending.
Then there is metal pick up, the direction of metal pick up and oxide colours where there should be none .
However to do it properly you need to be at one with the engine and understand exactly how each part interacts with other parts .
So for instance with a broken rod you fist look to see if it rotates freely on the big end and if the piston rotates freely on the little end.
Then you look at the oxide colours on the underside of the piston .
Big end is free bit little end is frozen & the piston is blue so you look at the oil slinger / pump .
Teeth missing and the surface is slightly rounded & polished a little then it was a cause, teeth fracture surface clean with no damage, happened during the failure . etc etc etc
And thus it goes on.
In a different life I did occasional overflow work for a tutor who had a contract with the police forensic lab .
Around this time of year you get a lot of car smashes when little Johnny is high as a kite but daddy big time lawyer is busy trying to shift blame anywhere else .
A common trick, before ABS came in was to rev the engine hard then slip your foot across and jump hard on the brake when you had maximum boost on the brake servo.
This will generally pop a seal somewhere in the braking system so little Johnny can claim brake failure
If you get Air Crash Investigations over there binge on a few hours of it and fast forward through all the bull to the bits where they show you how they determined a missing washer caused an engine to self destruct.
It is very accurate, quite a surprise for a TV show.
Even then they ignore the technician who spent hundreds of hours cutting up critical pieces of the wreckage, doing micro analysis of the crystal structure and hardness testing