Forum Discussion
- Gotcha Rick, I thought you were serious. I agree its absurd. Anytime there is a test that touts one as the best, or competition as worse then the brand loyalists come out. I am just trying to provide a moment of relief from commercials that prove nothing through random "tests".
- Hey I thought we were talking about frame flex, I just wanted to join in on the conversation. I think you guys are taking this way too serious.
- Really Rick... a picture of an OBVIOUSLY overloaded Superduty is the best you have? Did I write or imply in any way that the Ford F250 was capable of carrying an infinite amount of weight?
If I remember correctly, my argument was that the F250's frame is satisfactory for its rated and intended weights and for its expected service life. I'm sure I can find a photo of some hillbilly that overloaded a GM frame (they are better right, less flex) and snapped it in half. I'm sure I could find a Volvo longhaul with a damaged frame too. Just cause their are idiots out there that overload a truck doesn't mean that it doesn't work to its engineered specs... - If you have a vehicle with high frame flex, it will drive its self on uneven roads when loaded heavy. The frames will flex and affect the steering geometry. Any engineer should know this.
MM49 - When will people realize that marketing will manipulate photos or videos for their purpose? If we wanted to show frame failure, there are plenty of examples from any manufacturer.
http://www.youtube.com/watch?v=WBNll0bTYZo
You have to decide whether this is typical or an anomaly. I am not trying to pick on any brand and can provide examples from any of them. ktosv wrote:
Spoon, your understanding of fatigue is flawed .
Therefore, your statement about engineers allowing for flex to prevent failure (from fatigue) is flawed. They may allow for this flex, but they better be accounting for the fatigue life based on the deflection and cycling.
You sound much more knowledgeable that I am, so I defer to you. My understanding of the exact science behind it is flawed, but the end result appears to be the same. These frames were designed to handle the stress and still have a long service life.
This "test" doesn't make GM's frames any better than Ford... it simply means that it doesn't twist as much.- Ummmmm. I prefer Mike Rowe.
- Fords frame bending has to do with all those 6.4 radiator failures. The link a few pages back really was interesting. GM really beefed up those frames in 2011 and they did a good job.
spoon059 wrote:
Basically the argument is that steel needs to have some flex. Without flex it bends. When it bends it becomes fatigued. When it has fatigue, it is more likely to fail. To prevent it from failing, engineers allow for some flex.
Spoon, your understanding of fatigue is flawed . By definition fatigue is the failure of a material due to alternating or cyclical loading. This loading will cause some level of deflection, which would be referred to as flex if it was less than the yield strength and permanent deformation if it is greater than the yield strength. When it flexes back and forth it is actually causing fatigue regardless of the amount of deflection. The material will eventually fail at a load/stress much lower than the materials ultimate strength. Therefore, your statement about engineers allowing for flex to prevent failure (from fatigue) is flawed. They may allow for this flex, but they better be accounting for the fatigue life based on the deflection and cycling.
Your link that you posted even included this information: "and fatigue is the behavior of a material when subjected to cyclically applied stress, which can result in a crack and failure.
“Fatigue is what kills truck frames — not tensile strength or yield strength,” he said. “Fatigue is when you bend something until it breaks. Every material has an elastic zone. If I bend the material and don't exceed the yield strength, it will come back. If I get past the yield strength, I've strained it. It doesn't go back to the original shape.”
