Frame Repair / Need Help Identifying Parts

AnOldUR

I'm in the middle of an attempt to install an inverter in my 2020 320S. Dropped one side of the splash guard under the trailer to run the wires and found this. They look like inserts for bolting something somewhere. From the view I have I can't see where they could have come from. If someone could identify them and have an idea how they got under there it may save me the unwanted work of tearing things apart in hope of finding the answer. Getting too old to be crawling under this thing.

dragonsdofly

@AnOldUR lions and tigers and unifentified thingies, oh my!

Maxcamp

@AnOldUR this looks alarming.

Attached is a photo of the structural rivets holding the trailer frame together.  Look forward of the step.  Elec cable is my work.
Red marker is NuCamp inspection in factory, as these are critical.

Please immediately look at the frame exterior on both sides too see if you have missing rivets.  Somewhere I saw an old post from someone who had to rebolt these connections.

Crawling under with a bad back as well. Putting a mic on these I get 0.48 inch diameter at the widest ring sitting against the trailer steel.  Roughly 0.34 at the small end of cone and very roughly 0.24 Dia bolt insert.  These measurements should suffice for you to measure whether your loose hardware matches this function.  They sure look like it!

Good luck.  Call NuCamp to discuss.

AnOldUR

Maxcamp8 said:

... this looks alarming.
Good luck.  Call NuCamp to discuss.

There may be some difference between your 2021 Boondock and my 2020 non-Boondock. I could not locate the area in your pictured on my frame. Regardless, you did point me in the right direction and show me what to look for.

What I found was four holes directly behind the step that look to be missing those fasteners and another place the opposite side with one missing.  The holes by the step were blocked, so I knew there was a problem. I was able to stick my phone under the splash cover far enough to get a picture. You can see that the frame is shifted.

Having recently gotten back from five months on the road, I consider us very lucky.

 

bergger

Well that's concerning.  I guess there is another thing for me to inspected on an annual basis.  Is is common to rivet a trailer frame together?  I thought that if it was not a welded frame they were bolted together with grade 8 or 9 bolts.  Also what are those made of? They look like aluminum but I hope not. 

Grumpy_G

Mine is 5 years older and had a quite a bit of miles on it ....

https://tab-rv.vanillacommunity.com/discussion/15582/psa-rivets-went-awol-disaster-avoided

AnOldUR

@Grumpy_G, I'm relieved to know that this is not that uncommon of a problem or necessarily something that I did wrong. We put a lot of miles on this year and have to admit to accidentally hitting things like railroad tracks and cattle crossing too fast on several occasions. I was going to contact nuCamp today, but the fix that you did looks much better than replacing the inserts that they used. I find it hard to understand why they used those little 6mm bolts for this task, but I'm not an engineer. 

edit to ask @Grumpy_G
Has your repair has held up well? Any shifting since replacing?
Did you contact nuCamp and if so, what was their response?

Dutch061

Yes, the "Huck Bolt" fasteners are very common in assembly of frames. They are used on truck frames up through Class 8 (think semi's). Simple to install with the proper tooling and a very reliable joint, or at least in most cases. 

Without more information, it would be difficult to determine the root cause of the failure. Yes, it could even be that the fastener used is not large enough to create sufficient clamp load. It could be operator issues, tooling issues, or even caused by overloading of the frame - IE the design engineer made an error in the calculation of the actual load.

Brad

Grumpy_G

AnOldUR said:

edit to ask @Grumpy_G
Has your repair has held up well? Any shifting since replacing?
Did you contact nuCamp and if so, what was their response?

It's only been 3 months but so far it held up to the usual bumpy dirt roads. I did not contact NuCamp, the trailer is 7 years old now and I'm not the original owner. 

AnOldUR

This reply from nuCamp has me wondering what "too often" means?

GigHarborTom

Good grief.... A couple years ago, we spent 19K on 1/2 frame rebuild of a trailer we were restoring. This scares me. I am 82 and  thought my crawling under trailer days were over. 

Dutch061

I would not use Stainless Steel Bolts; I would lean towards Grade 8 bolts with Nylock (nylon lock nuts) properly torqued based on the bolt size. Remember that the Torque values given are for tightening from the head of the bolt and not the nut. Sorry, I don't have my book with me, or I could advise you further. 

P.S. Make sure to use hardened steel washers between the head and nut surfaces to contact the frame.

Brad

AnOldUR

Getting ready to attempt the repair. Pulled our trailer out of the garage and up on ramps to make it a little easier to crawl around underneath. Taking a break for lunch, but happy to find that by placing a jack under the frame, I was able to get the holes to line up. If the misalignment had been linear instead of vertical it would have complicated the repair.

edit to add that I'm curious if this could have happened when we had the tire on this side blow out earlier this year?

 

Denny16

Sounds like a possible cause, as the blowout would stress the frame.  Avlever idea using the jack.
 Cheers 

BrianZ

Anyone know the proper pounds to torque grade 8 bolts on the frame for, say, a 3/8" bolt?

Grumpy_G

BrianZ said:

Anyone know the proper pounds to torque grade 8 bolts on the frame for, say, a 3/8" bolt?

The oracle knows: http://www.repairengineering.com/bolt-torque-chart.html

RCB

There are two issues here. Repair and Fabrication. The repair seems (more or less) straight forward. However, this case seems not to be the first. The design of the frame  is probably suitable but the fabrication would seem to be less than acceptable. From the pics of the failures, I wonder how there was not a catastrophic failure. Perhaps the structure of the floor held it all together. It would seem that a periodic inspection is warranted, but difficult if the panels are to be removed. How many such failures have occurred?

AnOldUR

RCB said:

… periodic inspection is warranted, but difficult if the panels are to be removed. How many such failures have occurred?

If you know what you’re looking for, you can see the missing heads of the fasteners without dropping the panel. If I hadn’t found the broken off parts trapped under the panel, I never would have known. I’ve read of three other occurrences, but I’m sure there’s more (maybe unknown to the owner).