Custom Metal Fabrication and Welding

Steel, aluminum, and choosing the right process

Recreational vehicles mix metals in ways that matter to a fabricator. Trailer and coach frames are typically welded steel, sidewall cages are aluminum extrusion, and van bodies are thin high-strength steel with a factory coating that does not tolerate heat well. Welding aluminum calls for TIG or a spool gun on a MIG machine with the correct shielding gas, and it demands scrupulous cleaning because the oxide layer melts at a far higher temperature than the metal beneath it. Steel is more forgiving and much less tolerant of poor fit-up than people assume.

Joining dissimilar metals is where amateur work goes wrong. Aluminum and steel cannot be welded to one another with any process available in a general shop, and bolting them together without isolation creates a galvanic cell that eats the aluminum wherever moisture reaches. The correct answer is a mechanical joint with an isolating washer or coating, or a bimetallic transition insert. We see aluminum brackets bolted directly to a steel frame regularly, and the corrosion at that interface is usually the reason the part is back.

Heat input has consequences beyond the puddle. High-strength steel used in modern van and truck bodies loses strength in the heat-affected zone, and manufacturers publish specific restrictions on where sectioning and welding are allowed. Excessive heat on a thin panel also distorts it permanently, which shows up as a wave in a finished side that no amount of filler will hide. Planning the sequence, stitching rather than running long beads, and controlling fixturing is the difference between a repair and a new problem.

Frame cracks, extensions, and the load path behind them

Cracked frames on towables are common and they are almost always a design or loading story rather than a metal defect. Fifth wheel pin boxes, the transition where a frame steps up over the axles, and the rear section behind the axles are the three usual locations. The rear one has a specific cause: a bumper-mounted spare, a cargo carrier, or a generator hung well behind the axle acts on a long lever arm and fatigues the frame rail at the point where it is least supported. Welding the crack shut without addressing that leverage means the crack comes back.

A proper repair starts by drilling the crack tip to stop propagation, then grinding a full penetration groove, welding it out, and adding a fish plate or gusset sized to move the stress concentration away from the repaired zone. Where the load path is the real culprit, we add structure that carries the load back to a supported point rather than simply thickening the failure site. That is more design than welding, and it is what separates a repair that holds from one that lasts a season.

Frame extensions and modifications require an honest conversation about limits. Chassis manufacturers publish restrictions on wheelbase changes, section modulus, splice locations, and what may be drilled in a rail flange, and those exist because a frame rail in bending is doing most of its work in the flanges. Drilling a flange for convenience is one of the most damaging things anyone can do to a chassis. Where a customer wants an extension we work within the published guidance or we tell them it is not something we will build.

Rear separation on travel trailers, where the back wall pulls away from the floor and the frame sags behind the axles, is the extreme version of the lever problem. Repair is a combined structural and body job: reinforcing or replacing the rear frame section, re-tying the floor to the frame, and rebuilding the wall to floor joint. It is substantial work, and it is worth doing on a unit in otherwise good condition because the alternative is watching the back end continue to drop.

Hitches, receivers, racks, and carriers

A receiver hitch on a motorhome is not a bolt-on accessory. Rated tongue weight has to be carried into frame members that can accept it, and on many coaches the factory receiver is welded to a light rear extension that was never intended for a heavy carrier or a towed vehicle at the top of its range. We check what the existing structure actually ties into before uprating anything, and where the mounting needs reinforcement we build it back to a supported crossmember.

Ladder racks, roof racks, and awning supports on vans have their own logic. The roof of a cargo van is a thin skin over spaced bows, and anything mounted to it must land on those bows with load spreading plates, not on the skin between them. Bolted mounts with backing plates, sealed properly at each penetration, outperform welded attachments on a painted roof because they can be serviced and they do not burn the coating from the inside. Interior headroom and the finished ceiling are usually the constraint that dictates the approach.

Cargo carriers, bike racks, and generator platforms all fall into the same category and all suffer from the same optimism. The mass sits far from the mounting point, road input multiplies it, and the failure shows up at the weld or at the frame rather than in the accessory. We size members for the dynamic load rather than the static one, triangulate where the geometry allows it, and where a customer wants more capacity than the structure supports we say so instead of building it and hoping.

Equipment installation on work vehicles

Work van and service body interiors are a large part of the fabrication schedule here. Shelving systems, drawer packages, pipe racks, bin systems, and partition bulkheads all need to be anchored into structure with load spreading, because a shelf full of fittings becomes a projectile in a hard stop. We use manufacturer mounting points where they exist and add backing where they do not, and we keep penetrations out of structural members and away from wiring and fuel lines.

Cargo control gets designed rather than improvised. E-track, L-track, and D-ring anchors have published working load limits, and those numbers only mean something if the anchor is fastened into something that can carry them. Bolting a rated anchor into a plywood liner produces a rated fitting with an unrated attachment, which is a common and dangerous outcome. We spread the load into the body structure and document what the completed installation is good for.

Finish is the part that determines service life on all of this. Bare weld metal and grinder-bright steel corrode quickly in a coastal environment, and Southern California is one. We clean, prime with an appropriate primer for the substrate, and finish with powder coat where the part can go in an oven or a durable coating system where it cannot. Fasteners are chosen for the metals they join, and every penetration through a body panel gets sealed rather than left to find its own way.

On commercial units generally, the scope here is body, paint, structure, and equipment installation. We do not perform engine or drivetrain work and we do not perform federal inspection services, and being clear about that up front saves everyone a wasted trip. What we do offer is a bay large enough to take a full size box truck or a 45-foot coach inside and keep it there while the work is finished properly.

What is included

Load path design before fabrication

Members sized for dynamic loading and tied back to supported structure rather than to the nearest convenient panel.

Steel and aluminum welding

MIG, TIG, and spool gun work with process and shielding matched to the base metal and the joint.

Crack repair with stress relief

Crack tip drilled, groove welded to full penetration, and a fish plate or gusset added to move the concentration away.

Dissimilar metal isolation

Aluminum to steel joints made mechanically with isolating hardware so the interface does not corrode itself apart.

Hitch and carrier mounting

Existing rear structure evaluated against the intended load and reinforced back to a crossmember when it falls short.

Coating and corrosion protection

Weld metal cleaned, primed to the substrate, powder coated or finished, and every body penetration sealed.

Signs you need this work

• A visible crack in a frame rail, usually near the axles or behind them
• A rear wall that has begun to separate from the floor line on a travel trailer
• A bumper or cargo carrier that has started to droop or twist under load
• Rust blooming at a bracket where aluminum was bolted straight to steel
• Shelving or a partition in a work van that shifts when you push on it
• A previous weld repair that has cracked again in the same place