So over the spring I'm going to try building & mounting bolt-on 4-point rollbars. The idea isn't to make the truck racing legal or anything, just a) think they look cool and b) want to add a slight measure of protection in the event of a rollover since I've never driven anything so top-heavy (I have a 3" lift & 33" tires).

As I'm sure most of you know, there's nothing ready-made available other than the Go Rhino! bars, which I'm not interested in, so I'm gonna go the DIY approach. Not sure I'll want them forever, so don't want to weld them directly onto the frame. From what I've gathered, the best solution is to weld "outriggers" (right word?) onto the frame with mounting holes; then just drill 16 small holes through the bed & mount 'em up, with rubber (either washers or a plate) below the feet.

I know that for looks alone I could just bolt 'em directly to the bed, but will the design below be sufficient to tie them to the frame such that they won't just fly off (or worse, into the cab) during an accident? Don't worry, I won't come sue you if you're wrong (not least b/c I'll be dead), I'm just looking for feedback from folks who understand the physics better than I do.

Sorry for the crappy image, hope it makes sense.

 

Is this going to be a "show style" bar that sits outside of the cab, inside of the bed?
Where exactly do you want to attach these feet for the bars?
The floor of the bed sits rather high so your "outriggers" or frame plates will have to have some elevation, and sit pretty high. This will require quite a bot of fabrication.
andwich through the bed and attach to the frame, why not penetrate the body and extend the tube with another tube to attach to the frame. This eliminates large bulky plates. If you sandwich the body between two plates just make sure that you use different size plates on either end of the body. In other words do not make your plates from the same sized piece. This will act like a sheer and cut the body. While it really wont make a structural diffrence, it will ruin the body. By making the plates slightly different sizes you will eliminate this problem.
Attaching directly to the frame will be the strongest.

 

DO NOT weld the outriggers to the frame, especially the stock frame (tube frames setup for race vehicles is a different setup) instead weld them with braces to a flat plate and bolt them to the frame.
Here is a picture of how I did mine on the race truck to give you an idea of what I am talking about and it DID survive a rollover. It's not real clear but you can see it to get the idea



Then the tube of the roll bar extends through the floor board and is welded directly to the outrigger part.

 

yes, outside the cab, inside the bed...

if i'm understanding you correctly, it would work like this? makes sense...

 

monsterbaby- only saw your response after i'd posted. makes a lot of sense. am I right that to remove the bars later you'd need to cut through them before removing the bolts? i don't have a problem with that, just trying to get the picture in my head.

 

In the case of my setup yes you would need to cut the roll bar tubes loss from the out rigger part to before unbolting it from the frame, BUT in the case of that particular mount it is also the body mount so you don't want to unbolt it.
BUT like I siad that is on my truck which doesn't translate perfectly since it is a race only vehicle, but the idea for the outrigger will work for you.

 

Going retro? Here is my "rollbar."

 

The outriggers can be welded to the frame if you use a larger plate (4"x4" square or larger at the mounting location. The reason MonsterBaby is saying don't weld to the stock frame is that most people just weld the outrigger tube (typically 1.5" to 2") to the frame. Just the end of a tube hitting the frame is not a large enough attachment area (not enough surface area of the outrigger touching the frame) and in a hard roll over the outrigger tube might rip off the frame, or rip a hole out of the frame. This break will be AT the weld if your welds are inferior, or just outside the weld (in the HAZ or "Heat Affected Zone") if the welds are correct.

Adding a plate at the attachment point will spread the load applied to the outrigger end/frame and will prevent the ripping holes in the frame.

A bolt on outrigger setup is still a good idea if you think you will change your design at some point. I try and make most everything I do to my trucks a "bolt on" type deal. It makes it easier to change later after a re-design, or rebuild after a roll over.

Also - if you have a tube from your outrigger ending at a plate that is bolted or welded to the frame - don't forget to gusset the attachment point!