OT engineering fastener load calculation stuff

[wheelieking71]

I'm still waiting on the winch manufacturer who thinks this is legit...

It isn't the winch that is the problem. And I am not tossing names around.

 

[CarbideBob]

If you are going past the strength of 4 3/8s mounting bolts how big is the cable on his monster?
Bob

 

[Milland]

If you are going past the strength of 4 3/8s mounting bolts how big is the cable on his monster?
Bob

Snatch blocks.

Can I use that word?

Well, try and stop me!

Blocks! There, I said it...

 

[wheelieking71]

If you are going past the strength of 4 3/8s mounting bolts how big is the cable on his monster?
Bob

It isn't the bolts I am worried about. It is the U-nuts. These: Amazon.com: The Hillman Group 58456 3/8-16-Inch Regular Extruded U-Nut, 15-Pack: Home Improvement
And the size of the holes this hardware occupies.

 

[dian]

U-Nut Retainers On EFC International

why not use larger back-up plates with welded nuts?

 

[BT Fabrication]

That is exactly what I was thinking! And why I was pretty much dumbfounded when I saw them intended to mount a winch bumper.

I know EXACTLY why they are using them: the design of their bumper makes a proper nut/bolt a bitch (I know, because I did it).
So they are after ease of installation (and probably less complaints from customers who don't know any better).
The cherry on top is using 3/8" hardware in existing holes that will accept 1/2". Again I know because I did it. (factory is 12mm fine-thread)
When all they really had to do was a proper weld-nut. I am sure the tolerances on the vehicles frame are tight enough that they would not have had problems.
I worked with these guys a couple years ago on a project. They sure put on a good show that they knew what they were doing. And that their stuff was top shelf.
Their facility is very nice and well equipped. I was pretty comfortable I was buying good stuff. I should have done more research!



Why yes, it is. Why?

I work on them all the time adding aftermarket goodies, and jeeps tend to do stupid designs all the time like this from aftermarket cheap manufacturers.

thats why i like metalcloak bumpers and warn winch stuff only and nothing from china.

 

[BT Fabrication]

People tie off vehicles to winch all the time.
Some things just need to be built/assembled for the worst case scenario. I think this is one of them.

In the big picture, opinions don't really mean shit. Even/especially mine. This is why I was digging for actual specifications on these fasteners.
We have both ends of the spectrum in here already for opinions.
Cole thinks those U-nuts will hold as much as the bolt that is threaded in to them. Over 6,000lbs if I am understanding him correct.
BT Fab thinks they are good for about 750lbs. Which I am sure is an educated WAG.
I tend to think BT is much closer to reality! Especially considering the size of the hole they are sliding that thing over.

and yes its a somewhat educated guess, being the failure point probably being the sheet metal or the sheet metal nut deforming. Breaking of the 3/8" bolts is pretty low as I believe they are rated breaking strength of actually around 3200# each. the 5/16" cable on those is rated for a bit less on working strength of i think 8900 and breaking around 18,000. usually the winches dont have enough juice to pull that much weight when fully spooled out of the drum.( most of the pulling rated strength is max dia of the spool drum)
once you are down to the last wrap it drops significantly from 10K down to about 3.5K

 

[Clive603]

In the absence of better information I'd treat them as Riv-Nuts, Clinch nuts or similar. Basic engineering layout and load paths when installed are very similar.

Riv nut data is pretty easy to find and seems sensible :- http://www.rivet-nut.com/assets/rivnut_mechanical_properties.pdf

Clive

 

[mjr6550]

I didn't read all of the posts here, so maybe someone mentioned this. The proof load of a 3/8 grade 5 bolt is 6600 pounds. That is the maximum load before permanent deformation occurs. Depending on the application difference factors of safety would be applied.

This link shows some different options for fasteners in blind applications. The ones you referenced quite likely don't have a strength rating. If they do it should be available from Hillman. If they don't they should not be used in any application where strength matters.

 

[neilho]

Going to a larger diameter seems like a good idea. Switching to grade 8, not necessarily. They're generally more brittle than grade 5, so if the two bearing faces aren't parallel (ie, not machined), the fillet is more highly stressed in one spot of its circumference. Grade 5 is more ductile, so can accomodate the stress.

 

[wheelieking71]

why not use larger back-up plates with welded nuts?

Your guess is as good as mine.

 

[wheelieking71]

Guys, lets not focus on the bolt. Was it not obvious in my very first post that the bolt was not necessarily my concern?

The stupid U-nuts are the point of focus here.

 

[Illinoyance]

I am no a fan of extruded threads on the clip. Why not eliminate all the fuss and use a standard nut and flat washer?

 

[neilho]

Guys, lets not focus on the bolt. Was it not obvious in my very first post that the bolt was not necessarily my concern?

The stupid U-nuts are the point of focus here.

Only speaking for myself, but IIRC, you wrote that you replaced the recommended, supplied fasteners with a grade 8 bolt and nut. At this point, since that went in the assembly by your decision, isn't that what you should be thinking about? It's what you're on the hook for.

You already rejected the friggin' u nut (with good reason, IMO) and it's not in the assembly.

 

[wheelieking71]

Only speaking for myself, but IIRC, you wrote that you replaced the recommended, supplied fasteners with a grade 8 bolt and nut. At this point, since that went in the assembly by your decision, isn't that what you should be thinking about? It's what you're on the hook for.

You already rejected the friggin' u nut (with good reason, IMO) and it's not in the assembly.

No. As a matter of fact that is not what I should be thinking about. I did it so I don't ever have to think about it again.

The whole point of this thread was me asking if there was anybody much smarter and more experienced than I that could help me understand how this company could send this bumper out the door with the mounting hardware that they did. Because seeing it made my feeble brain scream "WTF?! Are you kidding me?!".

The only logical conclusion I am able to come to is that the only thing they care about is that their product looks cool, and sells well.
With the highest profit margin (dirt-cheap hardware). Safety be damned!

 

[plastikdreams]

It isn't the winch that is the problem. And I am not tossing names around.

Wait...isn't that what we do here?

I had a 17.5k winch on a 2500hd, mounted with a weston winch mount. We tried pulling an oak stump, my truck chained (gr 80) to a tree and a 20k strap around the stump. Let er eat and nothing let go...Including the stump lol.

 

[CarbideBob]

What is the give up point of the u-nuts?
Is it under a normal nut? How thick of a nut? How many threads needed to hit the max of the bolt?
How good are the threads in a u-nut vs a normal nut? Is the for sure bad looking u worse, better or equal to a normal nut?
Fully agree that to the eyeball such look like poop cheapo stuff. But engineering wise not so sure.........

You are worried that the yucky nuts will give up and fail pulling the bolt though them and cleaning their clock?
Bob

 

[neilho]

No. As a matter of fact that is not what I should be thinking about. I did it so I don't ever have to think about it again....

I get that you just ain't gonna. No problem. And I do hope you never have to think about it again.

 

[TDegenhart]

Now that I understand what you were referring to (U-nuts) I would agree this isn't a good application. Look else where.

Why do I say that? I've been in manufacturing a long time. We engineers can concoct neat designs that are simple and cheap to make and they can be made to satisfy performance requirements in the lab. But that doesn't account for the applications that no one thought about or variations in manufacturing.

Tom

 

[wheelieking71]

What is the give up point of the u-nuts?
Is it under a normal nut? How thick of a nut? How many threads needed to hit the max of the bolt?
How good are the threads in a u-nut vs a normal nut? Is the for sure bad looking u worse, better or equal to a normal nut?
Fully agree that to the eyeball such look like poop cheapo stuff. But engineering wise not so sure.........

You are worried that the yucky nuts will give up and fail pulling the bolt though them and cleaning their clock?
Bob

RED ^^^^ That was my original question. I didn't think it was as hard to understand as it seems to have been. But what do I know?

BLUE ^^^^ That or? Yea, with only 4-1/2 threads at best in questionable material, I don't think it would take that much force to pull the bolt right out of the nut.
Or, with the nut being slid over such a large hole, pull the nut right through the hole.
The hole measures about .540". The widest part of the nut's flange measures about .940". So, a 3/8" bolt in a .540" hole. "hot-dog in a hall-way"

I was just looking for a spec. or reference where I could figure out what kind of loads those things are rated for as I couldn't find anything.