Overview:

There are numerous systems across the Douglas SBD-5 Dauntless which require electrical power to operate—from the fuel pumps, to the engine ignition system, forward machine guns, instrumentation, radios, radar, lighting (both internal and external), and many other items. As a result, there are literally miles of copper wiring running through the airframe, all of which need to be routed through protective conduits and junction boxes to ensure they both reach the correct components and are relatively straightforward to maintain. Several of B-22's original junction boxes are too damaged to refurbish, so Pioneer Aero's Doug Brown—a newcomer to these pages—recently began refabricating some of them. This article will cover some of his work.

Here are three original electrical junction boxes from B-22. The upper example is the main distribution box in the gunner’s compartment, while the lower two are from the pilot's cockpit. Unfortunately, corrosion has rendered all three boxes beyond airworthy use. (image via Pioneer Aero Ltd.)
Here are three original electrical junction boxes from B-22. The upper example is the main distribution box in the gunner’s compartment, while the lower two are from the pilot's cockpit. Unfortunately, corrosion has rendered all three boxes beyond airworthy use. (image via Pioneer Aero Ltd.)

Modern Remanufacture:

Most of the SBD's electrical junction box bodies were made from aluminum sheet, stamped out by the thousand using a drop hammer or hydraulic press during WWII. However, due to the deep draw involved with forming many of these parts, it is far less economical to use the same process for recreating them today.

An appropriate alternative, which Pioneer has chosen to follow, is to cut out the box pattern from aluminum sheet and then fold up the sides into same shape as the original box. After welding the seams shut, the exterior beading is carefully filed down to precisely resemble the original box's rounded edges. Since these parts are not structural, they can be made from an aluminum alloy, such as 6061, which is relatively easy to weld (unlike aircraft-grade 2024) and machine. While Craig Cunha was responsible for the welding, Doug Brown handled everything else.

The original electrical boxes were created via deep drawing, a process used to create three-dimensional hollow shapes (like boxes) from a flat sheet. This is achieved using a punch of the required shape to press an aluminum blank into a matching die cavity. Pioneer could not economically reproduce this process, so chose to cut out a pattern, fold up the sides and weld the corners to create the required box shape instead. This image shows a cut out for a rectangular box prior to folding the sides up. (image via Pioneer Aero Ltd.)

Here we see an electrical junction box during its fabrication process. The sides have all been partially bent up to allow access for starting each of them, after which they will be folded up through the complete 90 degrees. Note that the part number, 4094852 is inked on the inside to help with box identification during the process. (image via Pioneer Aero Ltd.)

Here we see the box after each fold has been completed. Note that there is gap at each corner; an intentional decision to allow space for the next step. (image via Pioneer Aero Ltd.)

Here is the box after having the edges from each corner rolled inwards so that they butt together with a rounded shape—the earlier gap now being far narrower. (image via Pioneer Aero Ltd.)

A view of the electrical junction box after having each edge welded shut. Note that the box is slightly taller than actually necessary so that the welding could proceed smoothly past the intended lip and conclude before reaching the edge. The box will be trimmed to shape afterwards, and any excess welded material will be ground away to provide a rounded external corner with the same profile as the original box. (image via Pioneer Aero Ltd.)

Here we see the electrical junction box after having had the external welds at each seam ground down to re-create the original, rounded profile. (image via Pioneer Aero Ltd.)

Here are another three original electrical junction boxes (and one lid) from B-22—thankfully all of them are reusable. There are several boxes shaped like these in the Dauntless. The wiring linking these boxes is protected by flexible, braided conduit and crimped-on end fittings. The end fittings sit in the larger holes, with each being held in place by a nut inside the box. (image via Pioneer Aero Ltd.)
Here are another three original electrical junction boxes (and one lid) from B-22—thankfully all of them are reusable. There are several boxes shaped like these in the Dauntless. The wiring linking these boxes is protected by flexible, braided conduit and crimped-on end fittings. The end fittings sit in the larger holes, with each being held in place by a nut inside the box. (image via Pioneer Aero Ltd.)

Here we see a sheet of aluminum after having had the outline for one of the "house shaped" electrical junction boxes marked out on it in preparation for cutting. The same construction process used with the rectangular box will be followed in its fabrication—except for the extra side, of course! (image via Pioneer Aero Ltd.)

Here we see a blank for the "house shaped" electrical junction box after it has been cut from a sheet of aluminum. The sides will be folded up in due course. (image via Pioneer Aero Ltd.)

Here is the "house shaped" electrical junction box in the process of having its sides folded around the forming block. (image via Pioneer Aero Ltd.)

Two electrical junction box lids. The lefthand example, from a donor airframe, appears airworthy but awaits confirmation after bead blasting. The righthand lid is original to B-22 and clearly has some corrosion issues; a decision will be made soon regarding its potential refurbishment. (image via Pioneer Aero Ltd.)
Two electrical junction box lids. The lefthand example, from a donor airframe, appears airworthy but awaits confirmation after bead blasting. The righthand lid is original to B-22 and clearly has some corrosion issues; a decision will be made soon regarding its potential refurbishment. (image via Pioneer Aero Ltd.)

Here we see a lid for an electrical junction box in the process of having its edges rolled. The aluminum blank was clamped against a steel forming block in the shape of the lid. The edges and corners have been beaten around the block; because it is shallow, the shape can be induced without causing creases or cracks. (image via Pioneer Aero Ltd.)

Here is another view of the junction box lid during its fabrication; the curve at the corner is very evident. (image via Pioneer Aero Ltd.)

The junction box lid is seen here after forming is complete; its shallow nature being obvious. (image via Pioneer Aero Ltd.)

Another view of the junction box lid after forming process was completed, this time from the outside face. (image via Pioneer Aero Ltd.)