Ford's answers to the NHTSA 6.7 Investigation
There was a request for a link to Ford's answer's to the NHTSA investigation posted on a previous thread, since closed. Here is the link: Ford's NHTSA Answers to the 6.7 investigation This PDF i...
Forum Discussion
*Disclaimer: This is for entertainment purposes only, and not suitable for any other purpose. I can only speak to the 2011 truck sample I am dealing with. There may be things present in my sample not seen in any other trucks due to production batches, internal protocol, specific duty cycle, and too many other things to name. This observation in no way represents or applies to anything other than this specific sample. Keep in mind I am human and may have made mistakes so this entire thing could be wrong. I also cannot be certain of root cause since a variety of different things can trigger the same chain of events and it is not always possible to know the order of components failed in the chain of events. This is an effort to understand through a quantitative approach rather than a qualitative approach.
Digging further in.
1 of the failures was a different failure mode, unrelated to the HPFP altogether. So that one is excluded, but we had another one yesterday so the number still stands at 14 for the 2011 models as best I can determine similar failure modes. Someone fat fingered one of the failure mileages to have 50k more miles on it than it really did so I corrected that one. Failure slope changed a bit with the inclusion, exclusion, and correction of relevant failure mileages, and is now 2.558
Since we are still in the lower sample size of failures, the beta failure slope will dance around the true beta slope with the inclusion of additional failure mileages. This will continue until we hit about 30 failures at which point the beta slope typically zeros in on the true slope and changes very little with the inclusion of additional failure mileages.
In an attempt to understand how the beta failure slope may change as more failures happen and are added to the sample we can remove the first, last, or both failures and see how the slope responds.
Doing so, the beta slope ranges from approximately 2.4-3.0
So what does this mean? Well from pages 2-10 and 2-11 from the New Weibull Handbook by Dr. Robert B. Abernethy we read.
"1.0<4.0 Implies Early Wear Out
If these failures occur within the design life they are unpleasant surprises. There are many mechanical failure modes in this class and beta is predictable for generic failure modes.
Low cycle fatigue-beta varies from 2.5-4.0
Ball bearing failures-beta = 2.0, roller bearings-beta = 1.5
Corrosion, erosion-beta = 2.0-3.5
however stress corrosion will be 5.0 or greater"
There is a whole known beta value ranges database here http://www.barringer1.com/wdbase.htm Great site and lots of resources for anything reliability engineering related.
You can form your own opinion, this is just a preliminary observation.
Digging further in.
1 of the failures was a different failure mode, unrelated to the HPFP altogether. So that one is excluded, but we had another one yesterday so the number still stands at 14 for the 2011 models as best I can determine similar failure modes. Someone fat fingered one of the failure mileages to have 50k more miles on it than it really did so I corrected that one. Failure slope changed a bit with the inclusion, exclusion, and correction of relevant failure mileages, and is now 2.558
Since we are still in the lower sample size of failures, the beta failure slope will dance around the true beta slope with the inclusion of additional failure mileages. This will continue until we hit about 30 failures at which point the beta slope typically zeros in on the true slope and changes very little with the inclusion of additional failure mileages.
In an attempt to understand how the beta failure slope may change as more failures happen and are added to the sample we can remove the first, last, or both failures and see how the slope responds.
Doing so, the beta slope ranges from approximately 2.4-3.0
So what does this mean? Well from pages 2-10 and 2-11 from the New Weibull Handbook by Dr. Robert B. Abernethy we read.
"1.0
If these failures occur within the design life they are unpleasant surprises. There are many mechanical failure modes in this class and beta is predictable for generic failure modes.
Low cycle fatigue-beta varies from 2.5-4.0
Ball bearing failures-beta = 2.0, roller bearings-beta = 1.5
Corrosion, erosion-beta = 2.0-3.5
however stress corrosion will be 5.0 or greater"
There is a whole known beta value ranges database here http://www.barringer1.com/wdbase.htm Great site and lots of resources for anything reliability engineering related.
You can form your own opinion, this is just a preliminary observation.
