Flatbed Bolts, How Tight?

[wicked1]

I checked the bolts on my camper, and none were free spinning, but they were all equally loose. I didn't really have a wrench big enough to tighten them, and had some other work to do on my truck, so got a BIG socket wrench. (A flatbed to frame bolt was cracked off, and a few other bolts loose).

With this wrench, I am able to tighten these too much! The first one, I wasn't really paying attention and just kept turning the thing, w/out much effort.. Then noticed the aluminum plate the bolt goes through was warping! So, I guess tight enough! The others, all loose enough for me to turn w/out any effort w/ my about two foot long socket wrench. I don't want to break anything. I was expecting to turn these until I couldn't turn them anymore.. But w/ this big tool, I guess I could pull the bolt right through the aluminum bed frame!

I'm new to large engineering and repair.. (I'm an EE, so lifetime of building and repairing small things, but I was never really in to vehicles until now)

 

[kmacafee]

I assume this is a FWC? One of the reasons I didn’t buy a FWC flatbed is the attachment method. Trying to line up 4 bolts to keep that camper secure is, in IMHO, ridiculous.

I purchased a Bundutec and it’s mounted on an aluminum flatbed. Mine is attached using Fastguns that use the jack brackets of the camper(probably it’s strongest point) and run them directly to the flatbed. In 60,000 miles, much of it off-road, I’ve never had an issue of it moving. I can easily remove and install the camper when needed. It might be a solution and I have attached a picture to show how it works. I can take more photos if needed.

 

[Dirtroadsavant]

I have never had an issue with the bolts loosening. When I reset them, which I’ve only done once in 3 years, I use your basic 10 or 12 inch wrenches and take it one grunt beyond flattening the split washer. I don’t know how big your wrench is, but if it’s longer than that, you can just choke up on the handle to reduce your leverage so you don’t over do it. Someone out there may know torque specs, but the one grunt method has worked for me.

 

[wicked1]

Thanks, I could definitely make those work. Although personally, I don't plan on removing the camper. Maybe more bolts would be a good idea.. I saw someone else post that their 2015 camper was held down w/ 6 bolts.. Mine is also 2015, but they only used four.
I haven't had any problems, but was just looking over things. They might have been fine, but w/ this big wrench, they didn't seem tight.

My primary concern has now shifted to the flatbed to frame mount.. I mentioned in my first post, there's a broken bolt. There's a gap I can't close.. Maybe it was always there, and that's why this particular bolt snapped. But I'm not sure.. And no amount of force I can apply is bringing it back together.. Wondering if I should make a shim.



Edit to reply to dirtroadsavant, there was no grunting.. Just lightly pushing the wrench around and around, until I noticed the aluminum plate was becoming V shaped. So I guess I need to choke up on the handle a bit . Well, that's basically what I did w/ the other three bolts.. I'm sure they're fine.
In contrast, the steel frame gap I mentioned above... No amount of tightening would bend that steel plate of similar thickness.

 

[pvstoy]

2015 Hawk flatbed I have 6 bolts.

Consider grade 8 bolts with equal washers along with grade 8 nylocks ( or oval nuts). The nuts should be a one time usage. There are tables for torque vales for the hardware you are using if you wanted to use a torque wrench.

If your aluminum plate is becoming "V" shaped then there is a problem. The backing plates with a proper washer sized should be flat allowing a spread footing effect to have the load evenly distributed by the whole surface area of the plate. Your area under the plate is not flat and you should make it a flat area. So yea if there is a gap fill in that gap so there is something there to accomplish clamping force.

The torque on the nut should be enough to stretch the threads so they can not back off. This is where the nylocks give extra assurance of not backing off.

The bolts / nuts and backing plates achieve a clamping force to prevent movement. Done right will hold the camper to the bed and in a accident you might have shearing forces of the bolt or pull out forced ripping out . Enough clamping force areas of contact adds more protection.

 

[wicked1]

About the V shape plate... I bought this truck used in Oct, so I don't have all the details.. The flatbed appears to be made from aluminum tube, laid side by side, similar to how you'd lay a wood deck, then welded together. There are definitely plank sections of aluminum, all welded together. So, I'm assuming those are aluminum tube, and I was just tightening the bolt and compressing the aluminum decking.
But.. I guess I should take it off and have a look.

 

[rando]

If you are compressing the flat bed deck tubing, then you may want a larger and thicker backing plate that spans the aluminium tubes. On my flatbed, the four bolts are each backed up by a 6" x 6" x 1/4" aluminium plate under the flatbed deck (which is also made up of Al extrusion deck planks) and a large fender washer on the floor pack of the camper. The bolts are positioned such that they go through ply wood skids on the underside of the camper, and through the center of the flatbed 'planks' so there are no voids that the bolts span. They are M12 bolts with nylock nuts, and I have checked them a few time in the 5 years I have had the camper, and no evidence of them shifting or loosening.

If you don't plan on removing the camper often, then the through bolting is a clean (invisible) solution that works very well if done right.

 

[wicked1]

Thank's rando.
I think you and I have quite similar vehicles..

 

[nico]

I assume this is a FWC? One of the reasons I didn’t buy a FWC flatbed is the attachment method. Trying to line up 4 bolts to keep that camper secure is, in IMHO, ridiculous.

I purchased a Bundutec and it’s mounted on an aluminum flatbed. Mine is attached using Fastguns that use the jack brackets of the camper(probably it’s strongest point) and run them directly to the flatbed. In 60,000 miles, much of it off-road, I’ve never had an issue of it moving. I can easily remove and install the camper when needed. It might be a solution and I have attached a picture to show how it works. I can take more photos if needed.

C3FA4CFF-D8D1-4528-A87A-F8DCDC11FC8F.jpeg

I like your setup with regards to tying the camper to the flatbed. Is there a reason you couldn’t of done that with a fwc? I have a flatbed grandby being built and I intend on coming up with a system like yours as I’ll be removing the camper frequently.

 

[kmacafee]

I don't see why not. FWC have jack brackets. The only issue might be the flatbed - is there a good place to attach it.

 

[Jon R]

One can do a lot of damage to surrounding truck body sheet metal or aluminum camper frame structure by just cranking down a high grade M12 or 1/2 inch bolt. Bolts of that size can generate well over 5000 lbs of clamping force. You do not want to torque such bolts to high levels when working with a truck body or camper. If you really want to engineer what you are doing, you would decide on the clamping/tension force you want, use the right bolt table to determine the corresponding torque needed, and then address prevention of loosening with some appropriate method. I have no idea how much bolt clamping force FWC intends to be used mounting their campers, but maybe Stan can answer that question.

If you have one corner of your camper that can't be drawn down to contact the bed, something is not straight. My first guess would be the "flat" bed of the truck isn't really flat. If that's the case, shims would be appropriate as you suggested.