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martes, septiembre 19, 2023
HomeOff-Road Vehicles53 "CJ3BL" Build Thread | Pirate 4x4

53 «CJ3BL» Build Thread | Pirate 4×4

Front Bumper

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Thanks for all the comments everyone! I agree, a3dhunter! I’m sure partial towards my 3B.
Here’s the first installment of some build pics.

I started with the bumpers and frame rails. The frame rails are 2″ x 5″ x 0.120″ A 500 Grade B. Both bumpers are 2″ x 5″ x 0.188″. Since 2″ x 4″ is more typical, I thought I might elaborate on why I went with the 5″ height material:

I like the 5″ «kick» height of the stack rail front and rear for better axle/steering clearance at full stuff- it’s about the same as the original frame elevation over the axles ( I measured my old frame at 5.5″ at the arch). The larger section also increases the 2″ x 5″ x 0.120″ stiffness to about the same as 2 x 4 x 0.188″ but with less weight. I plan to build somewhat buggy style with no separate body mounts. I like the idea of tying in the roll cage to the frame directly, and having decided that, it didn’t make sense to me to have flexible body mounts with a body assembly and cage that move relative to each other to fatigue the body metal. Since there will be no body mounts, I get rid of the original 1″ of mount pad and underfloor bracing above the rails. The bracing will be flush with the top of the rails. The height from the rail bottom to floor surface will be essentially the same as stock, but with stronger 1″ taller rails. Lastly, I think the proportions of the bumpers and rails will fit well with the tall grill/tall hood 3B appearance. It will be interesting to see if these ideas all work out!

Since I laid out my design measuring and mocking parts up first, I decided to put D-Ring mounts, winch mount, pintle hook, and fuel tank mounting elements together before the bumpers are attached to the rails, as it’s much easier to manipulate.

Some folks have commented on other threads that they like to see step by step how to info, so I tried to take plenty of photos. Let me know if this amount is of interest, or too much to wade through!

Here’s the finished Front Bumper. It’s 50″ wide. I’m trying to keep the overall vibe in a «beefed up traditional» direction.

Here’s step by step shots:
Taper cut to bottom ends, showing chamfers for good weld penetration. Caps for the end taper (shown later) are cut from the same tubing and include the tube radius and chamfered edges.

Winch is mounted so fairlead is under bumper, like Meiser’s Rango lay-out, to keep weight low and provide better airflow to radiator. I also benefitted by using Meiser’s countersunk socket head screw concept on the upper two mounts. I have an old Delta wood lathe from the 40’s that has a gear reduction and cross slide to allow simple metal turning, so I made these up on that.

Lay-out and starter holes drilled for cutting holes for through-bumper D-Ring mounts from TMR:

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I cut the holes using a portable jig saw, with the blade shortened by cutting it off with a grinder. This keeps the blade from banging into the opposing wall of the the bumper tube.

Filed for close fit, while checking with a combo square to assure the mount will be perpendicular to the face of the bumper.

D Ring Mounts welded front and back:

Cut out winch plate from 0.250″ 1018 cold rolled plate with jig saw:

Winch plate and mounting boss welds. I fixtured the plate with some short lengths of square tube clamped to the back to keep the fairlead flange from warping inward while stitch welding to bumper. Decided to stitch weld rather than welding full perimeter of plate to reduce heat and bumper warp. Will seal unwelded edges with body sealer before paint to minimize rust. Gussets are curved to provide smooth edges at sides beyond fairlead.

Ground and filed winch boss welds to make pretty (they don’t see much load) The tape is Gaffer’s tape. I put it around hole to keep from scratching up the surrounding area while filing the welds. It comes off when done without gooey mess.

Tacked and welded Taper caps, then cut ends and fit end caps, which were also cut from the same tubing preserving the edge radius, then chamfered, tacked and final welded end caps. Finished bumper picture above. Now on to the rear bumper…

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