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Rollcage Fabrication Tips, Tricks & Cost

Posted in How To: Body Chassis on March 18, 2019
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If you spend enough time out on the trail you are going to encounter a vehicle that has rolled over. It’s inevitable. If you are unlucky, that rollover was caused by you and/or has occurred in your vehicle. To that end, having a well-built rollcage is an absolute must for any vehicle that sees the trail regularly, especially those with factory soft tops like a Jeep, an FJ-40, a Samurai, a Bronco, a K5 Blazer, and others. Sure, some 4x4s have enough aftermarket support that more than one rollcage kit is available, but often that is not the case. We like bending tubing and welding together our own cages, so even though we know of at least one aftermarket cage kit for our vehicle, we planned all along to build our own.

Like anything intricate, building a rollcage involves specialized tools, knowing which materials to use (we use DOM steel tubing), and more. Some tools are a must-have, while others you can make or do without. But once you’ve made the initial investment those tools are yours forever, and you save money with every project you’re doing at home with them instead of paying a fabricator. Here’s a rundown of each tool we have, how we use it, and how you can make it if it’s something you can make.

A good welder you can trust is a must when building a rollcage. Our Millermatic 190 can weld 5/16-inch plate. Pretty much all we used it for on this project was 1/8-inch-thick (0.120-wall) tubing and a little 3/16-inch plate.

Tools of the Trade

Tools you must have to build a cage.
• Tubing bender
• Carpenter’s square
• 4 1/2-inch angle grinder
• Welder
• Hammer
• Permanent marker
• Level (chances are you can use your phone)
• Handtools
Tools you can make.
• Example bend
• Angle finder tool
Tools that make life easier.
• Chop saw or band saw that you can cut angles with
• Tube notcher
• Air-over-hydraulic setup or hydraulic ram
• Experience can help save you hundreds in wasted materials

Our tubing bender is an old JD Squared Model 3 unit with a Swag Off Road air-over-hydraulic ram mount. We’ve abused this setup for years. Lots of what we will show you applies to other makes or models of benders. The first step to bending anything is to create a test bend. This will help you get a feel for your bender and measure where bends need to go. We like to try to do a 90-degree bend and mark where the tube enters the bending die as shown. Draw the line around the circumference of the tubing. You can make a more permanent mark by scoring with a pipe-cutting tool. Flip the 90 in the die backwards and mark the same spot on the other leg of the bend. Some folks mark the spot where the tubing is slightly deformed by the bending die about an inch toward the bend from our mark. That works too; you just have to be consistent with your method. You can now measure from the mark to the face of the 90-degree bend and duplicate bends by measuring straight stock between the marks.
Now when you bend your first 90 you will probably bend it to only about 87 or 86 degrees. That’s because steel has a memory and “springs back.” It must be bent about 3-4 percent past the angle you want it to stay at (we usually bend it past by about 3-5 degrees). So if you bend to 94 degrees using the degree ring and pointer set to 0 degrees when the material is installed in the bender, you’ll get an honest 90-degree bend.
The idea is to use the example bend to figure out where you need to start a bend. In this example we hold the 90 where we want to make our first bend in the A-pillar riser bar of the cage. We won’t be bending it to 90 degrees, but at least now we have a mark to measure the length of the first leg before the bend.
Another tool you can easily make is an angle finder, or angle meter. Ours is pretty simple and is made of some 1/8x1-inch bar stock with one end rounded and drilled for a 5/16-inch bolt, washer, and nylock nut (and it doesn’t actually tell any angle measurements, we just use it as a template). It will pivot at the bolt, and we use it to get a good idea of how much bend each bend will need. Here we’ve placed it where our first bend in the A-pillar will be, and with the two legs parallel to where we want the tubing to be we have a good idea how much bend to put in the tubing.
We use the angle meter to eyeball the bend. With the degree ring on the bender set, we can duplicate that bend an infinite number of times in this tubing. Just remember that you’ll always have to bend the tubing past your angle by about 3 degrees on a small bend like this. Use your “eyecrometer” to check that the edge of the tubing lines up with the edge of the angle meter.
Here’s our first bend in the A-pillar. We used some welded-seam tubing (instead of DOM tubing, which is stronger and more expensive) to build a template for the A-pillar (we will make final versions out of 1.75x0.120-wall DOM). We did that because from here on out things get more and more complex and interesting. Well, just about every 4x4 you’ll ever meet requires you to make compound bends or bends that are out of plane from each other. That means you will have to spin the tubing slightly in the bender between bends. That will allow the part of the A-pillar next to your windshield to lean in like the side of your windshield does, but still allow the top A- to B-pillar bar to parallel the roof (rather than turn inwards). We go into compound bends a bit deeper in the online version of this article, but for now were going back to the basics of cage building.
Each foot of a rollcage needs to be welded to the frame, or to a pair of foot plates sandwiching the vehicle’s thin sheetmetal. We got these foot plates from our local steel supply house, and added a slight break in them to match where the A-pillar landed on the floor. The bend also makes the foot plates a little more ridged, so that’s a bonus. Ideally the outside dimensions of the top and bottom foot plates would be different, unlike with our plates. You also want to make sure that neither foot plate has a sharp edge that could cut the sheetmetal it is sandwiching. Foot plates of different size top and bottom and with rounded edges will help prevent the plate from tearing a “cookie cut” piece of the thin sheetmetal out of the body of the 4x4 during a roll.
The other side of a foot plate needs to be tied to the frame somehow. If you want your 4x4 to stay as vibration-free as possible you’ll want to add a length of 1.75x0.120-wall DOM with some leaf spring bushings and tabs. We are trying to keep this rig as light and strong as possible, so we just tied the foot plate directly to the frame.
Once you’ve gotten the hang of bending tubing, you’ll have to get comfortable with coping ends of tube to fit together into weldable junctions. There are several ways to cope tubing, but probably the fastest and easiest is with a tube notcher like this one. It’s an old TN-100 Tubing Notcher from JD Squared. Ours is as old as our bender, if not older, but it works great, especially with a couple of new parts from JD Squared. The company still sells and supports this tool. You can also learn how to cope with a chop saw, a band saw, a saber saw; an angle grinder with a flap wheel, stone, or cutting wheel; hell, even a hack saw (if you have a year to build a cage).
We built seat mounts into our cage using some 1.5x0.120-wall DOM, tied to the main structure (made of 1.75x0.120-wall DOM). More info on that is in “Junkyard Seat Swap." These pieces need to be bent precisely and notched at angles to meet the other tubes. You can see that we used heavy tack welds to hold the whole cage together until we were done with it. That makes correcting any mistakes much easier and yields a better-looking final product.
Remember high school physics class? Nope, neither do we, but they did tell you something that is very useful when building parts for your 4x4. Tubing is strong, especially for its weight, but how you tie it together makes a huge difference (and we don’t mean welding versus using epoxy to join the tubes). Triangles made of tube are very strong. Boxes are OK, but you have to assume that the junctions at the ends will fail first, and in that case a square is fairly easy to collapse, flat. One way to build a stout cage is to build triangles into it. Now, it’s easy to go overboard with tubing, but we do like to add triangular gussets when we can. There are a dozen or more ways to build a corner gusset, but coping a 9-inch length of (in this case) 1.5x0.120-wall DOM is maybe the easiest way to make a corner much stronger. Sure, it would be better to build an “X” between all four corners of a box like this, but when you need to access an area, that’s not always realistic.

Cost of a DIY Rollcage

Materials
4 sticks of 1.75x0.120 wall DOM (a larger 4x4 could need 5 or 6 sticks) at $5 per foot, 20 foot sticks$400
10 foot plates ($3 each)$30
Misc other tabs$20
Total$450-$700

Tools
Bender$310-$4,250
Bender dies, each$150-$400
Grinder$50-$80
Welder$969
Notcher ($225 new, but we think we paid $75 used)$225
Chop saw/band saw, new (we paid $100 used)$165
Total assuming a $305 1 3/4-inch die for the bender and used tools. (With a fancy bender, one 1 3/4-inch die, and all other tools purchased new at max price, the total would be $6,094.)$1,649
 
Total at-home built rollcage cost. (Would be higher with a fancy bender and new tools.)$2,099

Cost of a Custom-Built Rollcage

We asked Rob Bonney from Rob Bonney Fabrication what it would cost to have a custom rollcage built. The cost really boils down to how much time the cage will take to build correctly. Bonney reports that you can expect to leave your 4x4 with him for about a week’s worth of work at $65 an hour plus materials. That’s about $2,000-$2,500 for a frame-mounted basic cage with seat mounts.

Parts (from above): $450-$700
Labor (for a cage similar to ours with seat mounts): $2,000-$2,500
Total fabricated cage estimate: $2,450-$3,200


Compound Bends

When it comes to the compound bend needed in this style of rollcage, remember that we were making a template A-pillar out of welded seam tubing. This lets us make a two-piece A-pillar with a sleeve that can pivot, allowing us to figure out how much to rotate the tube between the two bends. Next step is to mark the tubing for the second bend at the top of the windshield.
The two bends are held in place with a smaller-diameter tube sleeve inside them with a small tack weld in the center (just to hold the two pieces apart). That allowed us to rotate the two bends and get an actual angular measurement between the two bends (the distance the two arrows have rotated). The two arrows show where the two bends would be in the exact same plane. We then held the tubing in place with ratchet straps and tacked the two halves together to get our angle between the planes of the two bends (which is right at 16 degrees out of 360 degrees).
We can tell you from experience that the two bends in this style of rollcage are usually between 7 to 20 degrees different from each other. Our two-piece template A-pillar will allow us to measure this so we can duplicate it for the final one-piece A-pillar that will get welded into the cage. Sadly our welded seam template is junk, but can probably at least partially be reused elsewhere (for gussets) or used as a template for our next cage or subsequent bends. Looking down the long axis of the tube between bend one and bend two allows you to see what 16 degrees looks like.
For our actual permanent pair of A-pillars (using 1.75x0.120-wall DOM steel) we tack-welded a small piece of plate onto the tubing to serve as a reference mark for the compound bend. Our bender leans a touch, so we set the plate to the same angle as the die and made our first bend based on our earlier measurements. So we mark for the bend (the one at the top of the windshield) as before and chuck the tube into the bender and set the reference plate (tack-welded to the tube) to parallel with the bender’s die. Our bender leans a bit one side about 6 degrees. Use your level (or phone like we did) to set the plate tack-welded to the tube to the same amount as the die (level with the die; ideally 0 degrees, and in our case 6 degrees). Then make your first bend at the line marked as before below the dash.
We rotated the tubing the 16 degrees down. Our phone said 22 degrees (6 plus 16, even though the picture shows 21—it’s hard to take a pic and hold the phone steady at the same time), but 16 degrees is the difference we found before with the two-piece A-pillar template. We then added the second bend at its respective mark near the top of the windshield. The part was test-fitted to make sure it would work, and then we made a mirror image for the other side.
To do that, we again set the plate to level with the die bending once (6 degrees), and then added the 16 degrees for the second bend by rotating up from 6 degrees down to 0 and then to 10 the other way.
The result are these two A-pillar bars that are mirror images of each other.
Test fitting with some heavy duct tape or ratchet straps shows the two pieces fit as intended, with the A- to B-pillar section parallel to the bodylines of the 4x4.
PhotosView Slideshow

Sources

Miller Electric
Appleton, WI 54912
920-734-9821
www.millerwelds.com
Swag Off Road
Oregon City, OR 97045
541-915-2775
www.swagoffroad.com
Rob Bonney Fabrication
602-370-7955
facebook.com/pages/Rob-Bonney-Fabrication/193559750764429

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