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Off-Topic Posts / Re: Florida Bridge Collapse
« Last post by 70cj428 on Today at 09:08:35 am »
When they tried to tension the over stressed rod more- it broke.

On one of the news videos, there's a great shot of about 12 feet of the rod sticking straight out of the concrete support with the hydraulic tensioner still attached. (The rods are slid into tubes and just anchored at the ends, so it's pretty apparent that the rod failed prior to the collapse, If not it would still be anchored in the support member). It seems that with current computer aided stress analyses, engineering design is moving more toward higher stressed components with less of a safety factor built in. This saves money (and weight) in your design but you end up with more critical components in your design. Sometimes, you can't avoid critical components, like cables in a suspension bridge, but it's usually prudent to build in redundancy when you can. I'm especially aware of this as I see both sides of this ( My old profession, Mech. Engineer, my new profession, Firefighter) . Ask any engineer about engineered truss construction and they love it, it's light, rigid, strong overall and cheap. Ask any firefighter about it, they'll tell you about sudden catastrophic failure within minutes of significant fire exposure.....

A good example of this is the World Trade Center collapse(s). those buildings were built with cantilevered  poured concrete floors supported in the center by the elevator towers, and the outer ends supported by the stressed structural steel skin of the building. Great idea as the corrugated steel is light and strong, allowing more usable space and load in the building, and a taller skyscraper. Unfortunately, steel loses a ton of it's strength when it's heated. Someone realized this and came up with a way to start a large fire on the upper floors. Within hours, the steel skin failed, the floors started sliding down the center support and the rest is history. Traditionally constructed buildings generally won't do this. A couple examples, a B25 hit the Empire state building in the 40's in a very similar scenario to the WTC without collapse. Here in Philly, we had a fire on the 22nd floor of a highrise (One Meridian Plaza, google it ....) The fire burnt 8 floors of the building over a full day, and although there were fears of a collapse, the structure withstood the massive fire load. (Unfortunately, we lost 3 firefighters in the incident, after becoming lost on a floor above the fire)

I'm pretty sure I'm preaching to the choir, but sometimes the old way of designing things is better .....

Just rambling.....   John
Off-Topic Posts / Re: Export brace quailty
« Last post by Badcatt on March 23, 2018, 10:35:13 pm »
I have that one on my 70 Cougars. one is a convertible and the other is a hard top. I have not added on e to my Q code Cougar yet. But all I will use is the Scott Drake reproduction or an original. They look correct in every way and on my cars they went on with no problems.
Dale; maybe I missed it...  did your POP end stands get under the PBF C7 chrome valve covers ?  Did you switch vc's, or did you do some grinding ?  I see that the HS rocker arm ratio is 1.76 ?  Nothing to be concerned about ?  Thanks, Brian
I went through this a couple of years back.
I ended up going with the Harland Sharp and the POP stuff.

HS Rockers.

Ditto.  And I think the HD shafts or the end stands (not necessarily both) are prudent upgrades in any CJ build.
Off-Topic Posts / Re: Florida Bridge Collapse
« Last post by rockhouse66 on March 23, 2018, 08:55:28 pm »
I suppose in a sense you could say it was the "perfect storm" because they had that curb issue which changed the geometry of the support vehicles but ....expletive deleted....they must have had an entire team of engineers who were invested in this project who would monitor such things during installation.  The references to "the specifications" in the video is, in my experience, what happens when someone is passing the buck (or the hot potato).  When you have to go back and read the specs after the fact and/or read the commercial terms of the contract, then it is the start of the blame game rather than the "what did we do wrong?" analysis.  CYA.
I went through this a couple of years back.
I ended up going with the Harland Sharp and the POP stuff.

HS Rockers.

Off-Topic Posts / Re: Florida Bridge Collapse
« Last post by Chris Teeling on March 23, 2018, 07:35:50 pm »
You would think it would take more than one overstressed rod to bring it down but I suppose it is possible

Agreed, A good design will accommodate a single failure mode without catastrophic failure.

 I am not familiar with the design of that bridge but competent structural engineering oversight and addressing items uncovered in an FMEA would be normal practice prior to fabricating or something as critical as a bridge.
Went to the POP site to check out the items Royce mentioned and looks like they have everything you would want to build your own rocker assembly ?  I am particularly interested in the end stands for my own set-up.  I have heard and read about the possible deflection in the unsupported ends.  The end stands look pretty nice and are a little pricey at $140 for 4.  Those roller rockers are looking pretty nice to.  So my question is are they, the end stands, really needed ?  I have read, FE Forum I think, they become necessary if you are pushing 500HP or there abouts ?  I don't believe my motor is in that HP range and I don't take it over 5K even at the track.  Thanks, Brian
Off-Topic Posts / Export brace quailty
« Last post by preaction on March 23, 2018, 05:56:13 pm »
I need to get a new export brace to use as a template for checking shock tower movement is the Scott Drake repro the best one out there ? In the NPD catalog they claim theirs is exactly like an original strength and thickness wise.
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