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  #41  
Old 10-09-2006, 07:17 AM
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Kahuna Kahuna is offline
 
Join Date: Dec 2004
Location: Gold Hill, NC25
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Quote:
Originally Posted by jbDC9
I don't get it... what's with all the hubbub over $45 for a pair of 4130 push rods? All you gotta do is call Vans and get a pair of VA-256 flap push rods, $12 each, $24 for the pair. I bought two but haven't flown 'em yet; they're pretty heavy duty and drilled/tapped by Vans, so I don't have to worry about screwing anything up.

Easy.
When I drilled and tapped mine on the 8, I screwed the bearing in and gave it a test pushing my thumbs and prying it back. SNAP!. I quickly went with the hex rods after that. I can easily see how they would fail. The average joe like me drilling and tapping round tube leaves a lot to be desired and plenty of room for dorking it up. I could feel a lot of slop in the bearing threads when screwed in. It was pretty easy to tell I did not do a good job. I tossed em in the garbage and put the hex rod on.

During installation, it became necessary to bend the hex rod a bit to get the geometry right on the up and down movement clearing the fuse. It took a severe beeting to get the hex rod to bend. Its tough stuff.

I recommend the hex rod as standard installation.
Best,
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  #42  
Old 10-09-2006, 07:34 AM
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Mel Mel is online now
 
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I STRONGLY recommend against bending this rod in any way. All forces on this rod are in compression and any bending will weaken it. It needs to be straight!
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  #43  
Old 10-09-2006, 07:56 AM
Bill Anton Bill Anton is offline
 
Join Date: May 2006
Location: Satanta, Kansas
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Default engineering vs experience

You can do all the engineering tests and math you want but I'm going with experience. There was an accident which occurred on landing to a local RV pilot a couple of years ago. It was during the landing flare and rolled the plane upside down. The occupants survived with no injuries but the plane was badly bent. This was a very experienced pilot with lots of hours. After this the local group of RV pilots started looking at the existing flap rods and found several that looked like they might have a problem. Regardless of why the rod failed, I'll guarantee you that everyone in this neck of the woods have either the octagonal rod that Van's sells or one made from 4130 steel.

Bill Anton
RV-8 77 hours
Satanta, KS
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  #44  
Old 10-09-2006, 08:42 AM
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mlw450802 mlw450802 is offline
 
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Location: Payson, AZ
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Quote:
Originally Posted by Mel
I STRONGLY recommend against bending this rod in any way. All forces on this rod are in compression and any bending will weaken it. It needs to be straight!
I agree with you, Mel!
I am not a DAR and am only a lowly engineer but I would consider not passing a plane where that rod was bent.
I'm sure the design intent was for a pure compression load.

-mike
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  #45  
Old 10-09-2006, 09:41 AM
casper casper is offline
 
Join Date: Jan 2005
Location: Derby Kansas
Posts: 146
Talking

I think this thread has about run its course. Lets talk about something really dangerous like the front gear that has failed many times.
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  #46  
Old 10-09-2006, 11:24 AM
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rv969wf rv969wf is offline
 
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Location: Beaver, OK
Posts: 447
Default Flap pushrod failure while not in motion.

I think this thread has about run its course. Lets talk about something really dangerous like the front gear that has failed many times.
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Doyle Reed, Casper 2


I agree with you Doyle, this thread has run it's course. Just a note and I'll try keep it short. I received lastnight a private e-mail: name withheld, this individual e-mailed me about a flap pushrod failure on his RV-6 while sitting on the ramp not in motion. First he did not build the plane. He told me this happened about a year ago while at a fly-in and he left the flaps up instead of down. Apparently someone stepped on one of the flaps by the large footprint that he noted and when he arrived back to his airplane one flap was dangling down. The weight of the person stepping on the flap pulled the heim joint out of the aluminum tube. He examined what happened and what it looked like to him was that the threads inside the flap pushrod tubes had been tapped without proper lubricant and were very very gouged / rough and sloppy. He later examined the other flap pushrod tube and the same thing, both were tapped with either a bad tap, to large of tap, no lubricant, etc. and the heim when threaded into the rods were sloppy and loose. That's why when someone stepped on the flap it pulled the threads. In flight with flaps down this would have not happened because they are under compression. Just passing on what happened to one individual.
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  #47  
Old 10-09-2006, 04:59 PM
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airguy airguy is offline
 
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Location: Garden City, Tx
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Sounds to me like somebody needed the Stupid Stick treatment for crawling all over someone else's airplane as well.....
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