rear Bumper/Swing Gate
Perhaps the most complicated of all of the projects undertaken for the Defender, the rear bumper and swing gate had to be well thought out before getting underway. The reason for this is that it had to interface with the new drop down tailgate on the truck, as well as provide a suitable base for the subsequent roof rack. It also had to accommodate a rear winch and a class 5 trailer hitch. And of course it had to look good to.
The entire construction had to be made of steel so it would be rigid enough to support all of the weight from the spare tire, four jerry cans, tools that would end up being stored inside the thickness of the swing gate itself, and last but not least, the roof rack.
What complicated the planning was that unlike the original Land Rover tire carrier that used the thin aluminum body walls and rear swing out door to support the tire carrier's weight, I wanted everything to be mounted solely on the main steel frame of the vehicle. This way there would be no strain, and consequently, no eventual damage to the Defenders bodywork. To accomplish this, the new bumper was designed to utilize the existing mounting holes of the old bumper, but because our bumper will protrude out further and weigh a lot more, I designed it so that there were also support arms that reached forward under the truck to attach to the underside of the frame where the anti-sway bar is fastened on. This provides a very strong gusset for the entire assembly.
You can look at the photos below individually with the descriptions, or open a "picture only" slideshow here.
Rear Bumper and Swing Gate Build Sequence
As with all projects, it all starts with the layout of the first piece.
The most complicated shapes to be made for the bumper were the two end plates. They were shaped in this way to accommodate a 3/4" recovery shackle that can hang freely.
This disk and belt sanding machine would end up being one of the most utilized pieces of equipment for all of our projects. We bought it right at the beginning as we knew from our manufacturing experience that it was an important piece of equipment for doing prototype work, which is essentially what we were doing.
Once the two mounting arms were built they were bolted onto the truck frame so the main bumper rail could be positioned and tacked in place with the welder.
We made use of the existing trailer hitch mounting holes in the frame's rear cross member as well. It will support our new trailer hitch tube, which will also act as a support point for the future winch mount.
The main bumper assembly is all tacked together, and can be removed for welding.
MIG welding the assembly.
One of the problems with the welding process is that it creates a lot of heat in the base metal being welded. When this happens, the uneven temperatures in the material cause the metal to distort to such a degree that the structure bends.
To return the material back to straight and square, strategic back heating with an oxy-acetylene torch is needed.
After the bumper section was welded and straightened, the next step was to attach the riser section that would become the mount for the swing gate.
To ensure that the vertical post was square to the back of the vehicle, a straight edge was clamped to the riser, and then lined up with the body so the parts could be tacked in place with the welder.
Once the riser was tacked in place, the pivot shaft for the swing gate was positioned. With it bolted in place, a piece of wood was then clamped on so measurements could be taken for cutting the swing gate tubing to size.
With all the parts cut to size and tacked together, the swing gate assembly is welded together.
Here we see the finished assembly with tabs welded on to support the jerry can rack. The pivot shaft and locking tab are also installed.
On the back side of the spare tire mounting plate, a 1" NC coupling nut was welded. This would receive the "lock cover" that would screw into it to prevent unauthorized removal of the spare wheel.
This is a close up of the pivot shaft welded to the end of the swing gate. The tape is on the axle shaft to protect it from welding spatter.
The tab with the four holes is to receive the latch that will lock the swing gate open. Without it, wind or gravity could cause the gate to slam shut, which could cause damage to the swing gate or anyone that might be in the way.
Two pillow block bearings were used for the pivot shaft to turn in. These would later turn out to be a liability. Although they were supposed to be sealed bearings, water and the extremely fine dust found in the desert infiltrated the race and caused them to start seizing up.
They were replaced with a machined plastic bushing that worked flawlessly.
Test fitting the finished swing gate.
The outboard end of the swing gate had to have a secure place to rest when stowed for travel. It needed to be very strong and have points where a lock could be installed.
This photo also shows the finished shackle attachment point on the end of the bumper tube. A large washer was welded on each side of the shackle hole to make the metal thicker. This reduced rattle when driving off road with the shackles in place.
With the swing gate finished and re-tested on the bumper assembly, the final welding of the swing gate mount was done.
On the left end of the bumper, the seat for the outboard end of the swing gate was welded in place.
Once the welding is finished, various areas needed to be ground smooth to facilitate proper operation of the moving parts.
The entire rear bumper and swing gate broken down and loaded in the back of the Range Rover. It's off to the sand blaster and powder coater.
This is the special wheel lock I devised. It was made by welding a piece of plate to the end of a short length of pipe, and then machined in a lathe to make it look nice.
Once that was done, a 1"NC bolt was welded to the inside of the end plate.
The visual outboard side of the lock cylinder. Once powder coated, we applied a Land Rover badge to the flat area to finish it off.
The finished lock mechanism. Even after almost ten years in use, it still looks pretty good.
Back from the powder coater, now comes the careful task of bolting everything together without scratching the finish.
The swing arm with the studs for the spare wheel now in place on the mount.
If you look carefully, you will see that we also machined and installed a flat disk of 1/4" black Delrin plastic so that the wheel would seat up against it rather than against the powder coated metal. This protected both the wheel and the wheel mount from abrasion damage.
Here is the finished bumper in place, but without the swing gate. Before it could go on, we wanted to run the air lines etc., and get that work all finished. It was easier to do without the swing gate in the way.
Here is the finished swing gate resting seat. Again, we installed 1/4" Delrin plastic to keep the powder coated steel surfaces from touching each other.
Once the swing gate was installed, we made up a checker plate cover sheet that was fastened in behind where the spare wheel would sit. This was done in anticipation of later creating a tool storage area on the opposite side of the swing gate.
The black plastic boss in the middle of the wheel mount is so we can lift the wheel up and sit it on the smaller diameter section, and then easily rotate the wheel so the holes line up with the studs. Then the wheel can be easily pushed up the little ramp and straight onto the studs without chipping any of the paint on the wheel rim.
The tire sitting nicely in its new home.
Here you can see that the pillow block bearings have been replaced with the black plastic bushings.
The finished swing gate with the jerry can holders bolted in place, and the centre wheel lock installed.