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Dented pushrod

rjcthree

rjcthree

Well Known Member
Hi everybody, I'm hoping to confirm what I've already decided.

I just unwrapped the 96" AT6-049x1.20 tubing used for aileron pushrods inside the wing. One tube is dented but not bent. The dent is greater than the wall thickness. Back when I was an engineer (as in before I became managment and had my lobotomy) the rule of thumb for thin-wall tubing was if the dent/distortion/damage was > wall thickness, it was scrap, especially if it was used in compression (pushrod, truss member).

I was going to replace it.

I don't think I'm overreacting.

What do you think?

Rick 90432
 
When in doubt...

I find that I don't lose as much sleep over the possibly good part I've decided to replace as I do over the possibly bad part I've decided to keep.

Usually by the morning I've decided to replace the possibly bad part.

Jim McChesney
Tucson, AZ
-7A finishing kit
 
Well, the actual forces the tube will be subjected to are pretty small. If the dent is small and didn't bend anything, I wouldn't be too concerned. I mean, you end up drilling 8 hours in the tube before you are done, so think of that dent as just another small hole. Most of tube diameter is there for stiffness, not strength. Before you toss it, at least call Van's. Also, if the dent is near one of the ends, note that you will end up trimming off 6" or more, to that might solve your problem right there.
 
One of my pushrod tubes was also dented at the end. Ended up cutting off some of it to make it the proper length, so don't bother sending it back until you measure.

greg
 
Dent

Sorry guys, dent is dead-center. Right where it would buckle. I haven't run the theoreical bucking loads. I thought about reinforcing it, but it's worth the $20 to replace, I think. A hole and a dent resolve into very different resultants - especially with thin wall.

Just for grins, I may have the resident FEA guru model this, we'll see. Thanks for all you thoughts!

RIck 90432
 
rjcthree said:
Sorry guys, dent is dead-center. Right where it would buckle. I haven't run the theoreical bucking loads. I thought about reinforcing it, but it's worth the $20 to replace, I think. A hole and a dent resolve into very different resultants - especially with thin wall.

Just for grins, I may have the resident FEA guru model this, we'll see. Thanks for all you thoughts!

RIck 90432
Click to expand...
Rick,

You paid for a dent free tube and you should get one. Call Van's, they are good about these types of things.

Besides, you will have enough worries on your first flights, you shouldn't have to worry about this tube.
 
My elevator pushrod tube was dented when recieved from Vans with the fuse kit.

I emailed Vans support and they said that it should be replaced if there was any visable damage whatsoever.

They sent me a brand new one immediately no questions asked.

I even got to keep the dented one.

2000604703229200496_rs.jpg


2006208618609625399_rs.jpg
 
Any dent near the middle portion of the tube could substantially reduce the load at which the tube would buckle. There is no easy way for us to know how much the max load this tube would ever see, or at what load the damaged tube would buckle. Cut the tube at the dent (so you don't inadvertently use this one), and get a new one.
 
ordered new

I ordered new, so that's a done deal . . . . they made me pay for it though. $36!!! A/S only wanted $22! Oh well. I needed a couple other things too . . . a hundred dollars here, a grand there . . . who's counting? I stopped, for sure. It will take what it takes.

Thanks for everybody's thoughts.:(

Rick 90432
 
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