tubing thickness for swing-out gear carrier.

[irish44j]

I'm looking to build a swing-out carrier for half of the rear of my rig. Tire is door-mounted so this won't carry the tire. The plan is to have it about 2' long (off the left end of the bumper frame) with a 2x2 square tube bottom piece and two 2x2 vertical pieces. The verticals will mount a 24" x 16" chuck box (probably some kind of pelican case or similar), and a the top of the verticals I'm basically going to have a horizontal bar that goes across the rear window right above the spare (about 36" long total). See pic below. The upper crossbar will have a gear shelf on it, to hold a 5-10lb propane tank, maybe a cooler, and other fairly lighweight stuff - total less than 100lbs.

See my sketch below

Anyhow, for a tire swing-out I'd definitely want to go with 3/16" or maybe 1/4" tubing, but this is a small rig (2-door Raider/Montero) and keeping things as light as possible is always a goal. So thinking about building this in 1/8", with a few gussets in key places for extra support I just measured the tubing on my 1000lb engine hoist and it's 1/8" so figure that's probably strong enough, since this will only hold a fraction of that weight.

So any thoughts on going with the lighter-weight tubing to save weight (and money, for that matter)? I'm leaning that direction but a sanity check is always good.

general design, minus the gussets, etc. Anything heavy would be on the left side, basically as close to the pivot as possible. The spare tire is in the open area on the right, if you can picture it. The circled numbers are the piece lengths in inches.



back of the rig in question. Spare tire is now moved about 2" to the right, but more or less the same. The upper bar will basically cross over where that antenna platform is in the photo (it has since been removed).

The two uprights will basically go directly on either side of the RAIDER / door latch housing

 

[grubworm]

i'd go 3/16". if you use 2" tubing, that is a little over a pound per foot difference in weight, so what is that...maybe an extra 15 pounds for a much heavier duty frame.
i rarely fab anything of this type nature with anything less than 3/16"...

also, youre going to be driving at highway speeds with this frame loaded and bouncing over bumps and potholes with other vehicles right behind you...i'd go heavier just for the piece of mind. and definitely with you on the gussets...maybe even gusset at the pivot. there is going to be a good bit of stress on that weld tying the frame to the pivot

 

[Dave in AZ]

Here, watch this guys video

 

[irish44j]

i'd go 3/16". if you use 2" tubing, that is a little over a pound per foot difference in weight, so what is that...maybe an extra 15 pounds for a much heavier duty frame.
i rarely fab anything of this type nature with anything less than 3/16"...

also, youre going to be driving at highway speeds with this frame loaded and bouncing over bumps and potholes with other vehicles right behind you...i'd go heavier just for the piece of mind. and definitely with you on the gussets...maybe even gusset at the pivot. there is going to be a good bit of stress on that weld tying the frame to the pivot

yeah, I'm usually one to overbuild stuff as well (like the cage in my competition stage rally car, which is well beyond requirements). The guys I race with always laugh that my car's structural additions are overkill (but in that case, it's my life vs. a tree at 80mph so it REALLY matters to me!)

In truth, most of my concern is with the lower bar - I'm quite certain the two uprights, which will mostly have vertical stresses on them, will be more than sufficient at the 1/8 thickness, especially when gusseted - considering the low amount of weight they'll be carrying compared to some of these rigs lugging 35" tires around plus Jerry cans and such. So I think I will definitely switch that one over to either 3/16 or 2x3 bar at the bottom. Maybe I should bite the bullet and actually use some of those engineering calculations I spent too many years learning long ago, haha.

I didn't note it, but the upper bar will have a platform on it that will itself have a good amount of structural rigidity and again won't be carrying much weight, so I'll think on that more.

The pivot will DEFINITELY have a gusset, though I'm going to use the under-bumper mount, since I want to mount it to some 1/4" tube ooming directly off the frame - the C-shaped mount like the one in the video ^^ won't work well since I have a stock bumper, and I don't want it supporting the pivot.

 

[irish44j]

Here, watch this guys video

yeah, saw that one previously, it's very well-done. Though as noted, my pivot mount won't work well with the C-mount he's using since I"m mounting to the1/4" frame extensions rather than the bumper. I do note he's doing it all in 1/8" according to the comments - which is interesting. If I was doing a full-width swingout like that I almost certainly would go 3/16.

In any case, thanks to both of you for the food for thought, and hope you had a great Christmas.

 

[smritte]

I agree on everyone's advice for tubing thickness. What the video didn't mention was the stress on the bumper to frame mounts. The issue is when your on washboard road's. The leverage is focused on the frame mounts. Quite a few aftermarket bumpers bolt on one side of the frame. I would suggest 1/4 plate on at least two if not three sides. I also suggest a gusset from the wheel mount plate down about 50% of the distance.

Another thing to point out is when you buy your main hinge, make sure they use a common bearing and seal. Pretty much everyone uses trailer bearings but not everyone uses standard sizing. Over the years I've run into two occasions where it was difficult to get a replacement bearing and seal.

The bearings go bad from moisture. I would also suggest a heavy waterproof grease.

 

[irish44j]

I agree on everyone's advice for tubing thickness. What the video didn't mention was the stress on the bumper to frame mounts. The issue is when your on washboard road's. The leverage is focused on the frame mounts. Quite a few aftermarket bumpers bolt on one side of the frame. I would suggest 1/4 plate on at least two if not three sides. I also suggest a gusset from the wheel mount plate down about 50% of the distance.

Another thing to point out is when you buy your main hinge, make sure they use a common bearing and seal. Pretty much everyone uses trailer bearings but not everyone uses standard sizing. Over the years I've run into two occasions where it was difficult to get a replacement bearing and seal.

The bearings go bad from moisture. I would also suggest a heavy waterproof grease.

Thanks, and good thoughts there. For the mount off the frame I used 1/4" 2x2 square tube, welded directly to the frame as well as the factory (bolted-on) 3/16" bumper side brackets, and then also over-capped it and under-capped it (welded) to the frame top and bottom to increase twist resistance. The mount with the long lower piece goes through both walls of the square tube.

Didn't take a pic, but I jacked up the entire back of the truck by the outer end of this bar just to test it. No flex lol.

 

[irish44j]

Just to follow up on this, I did build this thing, and here's how it turned out. I did use the 2x2 1/8 square for the whole thing, and it's very, very solid/strong - granted its not holding very much weight. Anyhow, just to add to the idea pile for those who dont' follow my build thread.