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Jeep Flatfender - Garage Project GPW: Part 5

Posted in Project Vehicles on September 1, 2015
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There are a million and one ways to build a rollcage from scratch, and there are almost as many seat options when it comes to assembling an early Jeep. Not all of them will look good or even work in the confined interior of a flatfender. Comfortably fitting in an early Jeep is not an easy task. If you’re any taller than 5 foot, 6 inches tall, you have to be a bit of a clown-car contortionist to even get in and out of a flatfender Jeep. If you’re 5 foot, 11 inches tall like Cappa, then you are near the max-height limit for this ride, unless you plan to cut and extend the body. Over the years we’ve come up with a few tricks to make the seating in an early Jeep more comfortable, while still retaining a low overall ’cage height.

When we set out to build our ’cage, we took the many rollovers of our last flatfender into consideration. There were a few parameters we worked with: the top of the cage had to sit below the windshield frame, it had to mount solidly to the Jeep’s frame, the seats and belts had to be mounted to the ’cage itself, we needed plenty of headroom all around, we wanted to keep it light, and the ’cage had to help make the hacked-up and crumbling 70-year-old body more rigid. We considered building a buggy-style cage but scrapped the idea because we like the look of a traditional dual-hoop ’cage better on this kind of Jeep. A dual-hoop ’cage is also a little easier to build, especially for a first-time fabricator. The main structure is made from about 30 feet of 1 3/4-inch, 0.120-wall DOM (drawn over mandrel) tubing. DOM tubing is roughly twice the strength of HREW (hot rolled electric welded) tubing and worth the small increase in cost, especially when fabricating a rollcage. Chromoly of the same size would be about 20 percent stronger than DOM, but it is significantly more expensive. However, to achieve that increased strength, chromoly also requires welding techniques and processes that are outside the realm of most at-home fabricators. DOM is generally the most cost-effective material for enthusiast rollcages built at home or in a professional shop.

We’re getting near the home stretch of finishing our GPW. Keep your eyes peeled for future installments.

Our first flatfender had a three-hoop family-style ’cage. We don’t plan to carry passengers in the back so we opted for a simpler dual-hoop ’cage that we formed with a JD Squared Model 3 manual bender. We often see people get out of control with ’cage bends. The bends are considered a weak point. Fewer bends is better.
We’ve been using this basic JD Squared TN-100 tubing notcher for over 15 years. It uses common bi-metal hole saws to make notches in the tubing. You use different-sized hole saws to fit the material you are working with. The cutting angle of the TN-100 is adjustable and features engraved degree marks. A single hole saw will last for more than a few ’cages if you are careful and cut slow. It’s best to not use cutting oil because it will contaminate the welds if you don’t clean it all off the tubing.
We used 3x3-inch, 3/16-inch-thick angle iron as the footing for the rear portion of the ’cage. It’s pushed under the body rail so the ’cage is not removable, but it bolts to the body in two planes for extra rigidity and support. This portion of the ’cage is also attached to the frame on the underside.
With only two bends in the A-pillar hoop, we were able to match the angle of the windshield frame and kick the footings forward. This offers more room for ingress and egress on a flatfender, and it gives us the ability to mount the ’cage footings on two planes. The A-pillar is attached directly to the frame from the backside of the slanted footing.
Keep the gaps in the tubing junctions as small as possible. The supporting connections should always meet with another tube directly on the backside. This helps prevent shearing of the tubing in the event of a hard roll.
It’s a good idea to periodically check for head and body clearance while assembling your ’cage. You’ll want to keep the tubes at least 6 to 8 inches above your head. We prefer to keep the B-pillar a long ways away from us to keep from bonking our heads when driving over rough terrain, so we kicked it back to nearly the same angle as the A-pillar and windshield frame. Use wood blocks to mock up the seating position and try several locations for the best fit and comfort for you.
The main structure of our seat mounts is made from 1-inch, 0.120-wall DOM tubing. It’s welded directly to the A and B rollcage pillars. A ratchet strap comes in handy when pulling tubing together and holding it in place to be tack welded. Once the entire assembly is fitted and tacked, you can finish welding. Some areas will need to be welded during assembly because of limited access.
We added 1 1/2-inch 3/16-inch-thick strap steel to our tubular seat mounting structure for a solid flat mounting surface. We also bashed the wheel tubs back a bit for more seat room. A little heat and a big hammer simplify this task. We’ll have to build a transmission cover down the road, but we have an idea for that.
We chose PRP Premier Series low-back suspension seats. You can custom-order PRP seats in many different color combinations and styles that fit your needs. Some people complain that the Premier Series seats are difficult to get in and out of because of the tall bolsters. We spend more time sitting in them than actually getting in and out, so the extra effort worth it to us. The PRP Premier Series seats cradle us and keep us from feeling fatigued at the end of the day. PRP also offers other seats with less bolster support for easier entry and exit. We like to angle our seats back up to 15 degrees. This makes seating really comfortable (for us), increases headroom, and provides more legroom in the cramped quarters of this small Jeep.
PRP seats feature race-style seat-tab mounting. The company offers several different bolt-in mounts and sliders for more popular Jeep models. We like to use the flat-faced universal angle brackets (PRP part number C11) to simplify installation.
We finished off our seats with some vintage-looking AutoLoc lap belts from Summit Racing. Several styles of belts are available in many different colors to match your interior. The AutoLoc airplane lift buckle is made from real metal. They are a bit long but can be made to work in a small Jeep.
We added an Advance Adapters Dual Swing pedal kit (PN 716117) to the firewall of our flatfender. The master cylinder for the kit is not designed to be used with disc brakes, but the assembly gives us working brake and hydraulic clutch pedals as a starting point to build off of.
Most of the hard to find original trinkets had been pilfered from our GPW body tub, but Omix-ADA repops pretty much everything, including this GPW glovebox door. The A-pillar of the cage was in the way, so we stole an idea from a buddy’s Jeep. We cut the offending bit off the door and tack welded it to the glovebox opening, leaving us a fully functioning glovebox.
We wanted a larger and less leaky fuel tank than the stock one mounted under the driver seat. Summit Racing has a lot of fuel cell size and shape options. We found that this RCI 17-gallon aluminum fuel cell (PN RCI-2171A) fit easily between the rear fenders in the back of the Jeep. It is 30 inches long, 7 inches wide, and 17 inches tall. The narrow width and good height will help ensure that the fuel pump doesn’t starve at excessive angles off-road. It features -8 AN outlet, inlet, and vent fittings and comes with a 0-90 ohm sending unit. We cinched it in place with 3/4-wide 1/8-inch-thick strap steel.


Summit Racing
Akron, OH
Advance Adapters
Paso Robles, CA 93446
Suwanee, GA 30024
JD Squared
PRP Seats
Murrieta, CA 1-951-894-

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