Fractured chassis 2010 Escape 19' just behind the front jack on driver's side. - Page 4 - Escape Trailer Owners Community

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Old 11-09-2015, 01:12 PM   #31
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Ahh... Kind of what I was thinking. Those jacks can generate a lot of torque and if cranked hard the break would be behind it because of the trailer weight. Also one more reason why all frames needed to be 4". Maybe one of you engineers could weigh in here but I would be suspect of the jacks as a contributing cause.
Tim - I went down and looked to verify what I remembered - but on my 17B, the jack mounting plate straddles the weld joints for the cross member so it shouldn't put extra stress on the welds there anyway.

That's behind my curiosity on where the cross member is in relation to this crack. My old welder self looks at this and it looks like cracks I've seen on the edges of welds - cold cracks I think is what they are called. If the cross member is just on the front side of that crack that would be my guess (and nothing but a guess - I never finished my engineering degree program) As Brian mentioned harder steel alloys be can more prone to brittleness when welded. The more powerful jack could have been a contributing factor if there was brittleness there. If there is no cross member there, than I supposed it is possible the weld of the jack mounting plate right at the edge of the crack could have been the starting point.

Or I could just be completely wrong - won't be the first time!!

Whatever the cause, I second Ron's suggestion of welding completely around the tube.
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Old 11-09-2015, 02:52 PM   #32
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Tim - I went down and looked to verify what I remembered - but on my 17B, the jack mounting plate straddles the weld joints for the cross member so it shouldn't put extra stress on the welds there anyway.

That's behind my curiosity on where the cross member is in relation to this crack. My old welder self looks at this and it looks like cracks I've seen on the edges of welds - cold cracks I think is what they are called. If the cross member is just on the front side of that crack that would be my guess (and nothing but a guess - I never finished my engineering degree program) As Brian mentioned harder steel alloys be can more prone to brittleness when welded. The more powerful jack could have been a contributing factor if there was brittleness there. If there is no cross member there, than I supposed it is possible the weld of the jack mounting plate right at the edge of the crack could have been the starting point.

Or I could just be completely wrong - won't be the first time!!

Whatever the cause, I second Ron's suggestion of welding completely around the tube.
I agree. I believe these frames are T1 alloy steel (ASTM A-514) which has a very high yield strength at 100 ksi and is quiet difficult to weld. Crack is likely as you say a cold crack (hydrogen crack) at the toe of the tack weld and these are usually a result of a lack of pre heat prior to welding. So likely been there since day one and propagated across the bottom flange of the C channel then up the web over a long period of time as a result of the low cycle high stress loading when jacking (minor)combined with the considerable dynamic loads imposed during towing (major).

As Jim points out its a heads up that all trailer owners should carefully inspect there trailer frame annually as part of there ongoing maintenance.
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Old 11-09-2015, 03:19 PM   #33
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propagated across the bottom flange of the C channel then up the web over a l[/QUOTE]

Is it channel? The close-up photo in post #23 looks like it but I thought it would be rectangular tube. Maybe the fracture isn't completely visible. Or did ETI go from 3" channel to 4" tube?

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Old 11-09-2015, 03:28 PM   #34
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Is it channel? The close-up photo in post #23 looks like it but I thought it would be rectangular tube. Maybe the fracture isn't completely visible. Or did ETI go from 3" channel to 4" tube?

Ron
Aren't all the frames rectangular tubes? My 2010 17B is and all others I've seen have been.
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Old 11-09-2015, 04:04 PM   #35
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Thinking as I go here, but it seems like there would be more stress on the frame when it's supported by the ball as in towing, since that's a longer lever arm producing a greater moment in the area of the crack. Unless the front jacks were used as a sole source of support (no tongue jack) and this particular side was regularly cranked down tighter, supporting most of the trailer weight forward of the wheels. I'm falling into the camp of it being a metallurgical (or welding) issue, assuming there there wasn't a lot of extra weight added to the tongue while towing.
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Old 11-09-2015, 05:57 PM   #36
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Parker that makes a lot of sense to me. I've always struggled with the concept of even the heavy duty jacks being able to actually do damage to the frame, when as you say, the lever arm compounding the tongue weight when towing should be capable of putting much greater stresses on the frame. But maybe it is that the frame is specifically designed to withstand the forces from the tongue and the jacks could put on an entirely different stress. I think I need a beer now before I hurt these old brain cells.
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Old 11-09-2015, 06:26 PM   #37
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Let's see now....start drawing moment diagrams, consulting stress/strain curves...... or have a beer. Hmmm...
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Old 11-09-2015, 06:27 PM   #38
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Let's see now....start drawing moment diagrams, consulting stress/strain curves...... or have a beer. Hmmm...
And lets hope RWD gets it fixed soon and heads off on that trip to Florida.
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Old 11-09-2015, 06:56 PM   #39
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Let's see now....start drawing moment diagrams, consulting stress/strain curves...... or have a beer. Hmmm...
Wow, I can't believe you are struggling with that decision. I say beer for the win.

I remember studying bending moments, and understand very well how the are derived, but boy o' boy, if I had to calculate them now, I would be driven to drinking too.

I don't believe that the jack loading has anything to do with the crack either.
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Old 11-09-2015, 07:23 PM   #40
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The fracture and seperation occured on the frame of a 2010, 19 that has less weight on the tongue than the last 19' production trailers with a 3" frame supporting a storage box with a 100 lb capacity, 2 batteries, and two LP tanks.
Note the rock shield and stinky slinky storage tube on the tongue in one of the photos.
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