Usually I don't get asked to install gooseneck adapters. They are simple to install and most folks don't want to pay what I charge, so when one comes along, I am always suspect.

Today I got a call asking me to do one. As those of you who use them know, they bolt up and then you are supposed to drill and install four grade eight 1/2" bolts up through the adapter and pin box plate for safety. The newest wrinkle is this called asked me to do one the way he had just seen done by someone else.

Instead of using grade eight bolts, someone is using standard self-tappers. Just doesn't seem right to me and sure is not what I read in the instructions. I know there is darn little chance an adapter will ever break free, but if it did, I would want the grade eights through bolted rather than grade five self-tappers.

May want to watch for it.

Steve

 

I am not a big fan of gooseneck adaptors anyways , way to hard on a fifth wheel....

 

so i work at a refinery in Wa. state, we very rarely use grade 8 bolts as they are too hard and can be britle. They have great clamping/holding force but break relatively easy with a small amount of side load. agrade 5 will tend to bend with side load before it breaks, a grade 8 will just snap. 75% of the fasteners we use are grade 5 . the others are stainless in varying grades. I would use grade 5 in that situation, not self tappers though.

 

Thanks, manufacturer sends grade 8s so that is what I go with. You may well be correct, but liability is too great to buck manufacturer's recommendations.

Steve

 

I'd opt for the grade 8 as well. Especially if I was working on someone else rig that I could potential be held liable for a failure.

 

I did one better than that. I installed all of the bolts, tightened the adapter down and then welded all four sides of it to make sure that it never came loose. On a side note, the trailer that we purchased a while back came with a free 5'er hitch, and it's much easier to hook up than the gooseneck was.

 

You may want to read this article:
ROCKCRAWLER.com - Grade 5 vs. Grade 8 Fasteners

 

The engineer in me says that he did the math right, but there's something still not "right" with his logic...

I'm still trying to put my finger on it...

I don't know if it's that he didn't discuss shock loading on the bolts, or that he glossed over the importance of proper torquing....

-blaine

 

I spent roughly 30 years doing material testing, including fasteners for a major defense contractor. There are a number of things here, first shear strength of the fasteners, second yield strength of the fasteners and third ultimate tensile strength. As the link MisterCMK provided shows, there is a fairly good difference in the properties of Gr5 and Gr8. The other issue that rears it's ugly head is fastener quality. There are a lot of counterfeit fasteners floating around, I personally buy my stuff from Fastenal simply because of my background. I know they can provide me with proper items, they, MSC Grainger etc. do carry "imported" fasteners, but the respective catalogs reflect this.

If you are in doubt on the "pedigree" of fasteners, Google "fastener quality act" and you can find several large documents with manufacturer's ID markings. I will not use any bolt or nut with no ID on it. BTW, nuts are graded also, using a Gr8 bolt and a Gr2 nut, the nut will fail by stripping under tension.

As the link also shows, and was mentioned, proper torque is very important, over torquing will stretch the bolt, resulting in early failure, under torquing can lead to "shock" loading as the components slightly separate and close back up.

The "self-tapping" bolts are a fairly hard steel, they have to be in order to cut threads, the problem is, they may be a high carbon, case hardened steel which is very brittle. One of our load indicating device manufacturers changed the material in pin that rides in a pair of roller bearings from AISI 4340 (nickel chrome moly steel) to AISI 8620 (hardened high carbon steel) probably for cost reasons, the end result was interesting, the older pins would bend quite a bit, taking over 3 times the capacity of the unit, the new pins would fail catastrophically at around 1.5 times the capacity. End result, we downgraded the nuclear working load of these units.

Sorry for the long dissertation and somewhat vague references on the load equipment, but I don't feel at ease giving the company names out.