Bull Bar

Increased Collision Protection

Although the top of our newly fabricated front bumper stands a full three feet off the ground, road hazards exist that this bumper on its own can’t fully protect us from. We’re not talking about those made of metal and polymer, but rather those often unseen obstacles of the flesh and bone type.

This graphic shows the size relationship of a mature bull moose in front of our truck.

Many parts of the world have hazards from the natural world that pose a significant risk to vehicle travel. For many people, they think of Australia with large red kangaroos bounding across highways and colliding with vehicles. In those cases, the largest wandering roo might weigh as much as 90 kilograms (200 pounds) and stand 4 to 6 feet tall at the top of the head. But the reality is that in areas like North America and Northern Europe, much larger animals exist and wander the landscape at will. Dwarfing the largest kangaroo, moose can stand as high as 2 meters at the shoulder and weigh over 500 kilograms (1200 pounds). Other large animals include elk, caribou, bear and bison.

Even the largest truck when confronted with a large moose inside the braking limit of the vehicle will suffer catastrophic damage if not adequately protected. But even with this extra protection, significant damage is guaranteed. The objective, however, is to keep the vehicle in some form of drivable condition so it can make it to a population centre where help can be secured. This is the reason we designed and built a substantial bull bar to compliment our heavy duty steel bumper.

Design Considerations

Original Design

Final Choice

We went through several design iterations in the process, mostly trying to follow the unique look of the grill on the front of our Volvo VHD. Unfortunately, to make the bull bar with the outward leaning vertical posts just wouldn’t work. The width of the frame rails was such that we would be starting from a width at the bottom that would make the top of the bull bar far too wide, and would look odd. It would also mean a joint where the vertical posts bent outward, and this would seriously compromise the strength.

We also ultimately decided to go with horizontal cross rails as it tied the two verticals together better from a structural perspective. We also added the diagonal to the grill area so as to match the signature look of the Volvo identity. It also adds a diagonal gusset to help eliminate a parallelogram deformation if the bull bar is struck on the end of the outrigger bars.

The Fabrication process Begins

Here are the water jetted outrigger end plates and their two foot plates.

Outrigger bar end plates

Since the bull bar, like the bumper itself, was being built in our garage with limited equipment, we chose to have the outrigger arm end plates cut out by the same water jetting company that did the bumper brackets. The reason for this is that these end plates were made from 3/4” thick 6061-T6 aluminum plate and would have decorative horizontal slots to match the aluminum lift platform on the back of the truck. Although I could easily cut the outer shape myself, the slots would be time consuming if a proper job was to be done. We’d also have to find the aluminum plate, which in small pieces is expensive when bought from a metal retailer. The water jetting company keeps this material in stock, so it was much easier, and indeed cheaper, to just give them the .dxf file for these parts and let them supply the material and do the work for us.

Here are the finished end assemblies prior to welding the foot perimeter.

Once we got the plates back, it was a matter of dressing them up and then attaching the foot to the vertical plate. The connection was done both with fasteners and weld. Since this end assembly was a structural member of the bull bar, we wanted a secure attachment. Something we didn’t want to rely solely on the weld to perform. After all, it is an aluminum weld, and not very large.

Dressing was done first by draw filing all of the inside surfaces of the slots. This eliminated any stop/start rough points from the water jet cutting. Then, by using a router with a round over bit, all the sharp edges were shaped to radius all the corners. After this, the routered edges were lapped with a hand abrasive cloth to smooth them out, before sanding the faces with an orbital sander.

The edge radius was done using a wood router and round over bit. It was easier to move the material than the router.

Inside edges were also radiused, but after the inside faces were draw filed.

After the router work, the edge was sanded to remove router marks.

Here is a good before and after comparison of the edge.

One down, one to go.

Both edge finished and ready for face sanding.

Securing the feet

Since the joint between the side plate and foot is a structural one, we took extra care to ensure the joint would remain intact in the case of an impact. To this end, we used both mechanical fasteners and tungsten inert gas (TIG) welds.

One of the advantages of using the mechanical fasteners is that it is a more precise way of securing things than trying to just clamp pieces together before a weld process. Eliminating the clamps also makes the welding process a lot easier. The fasteners we chose are a grade 10.2 flat head 3/8 fine thread machine screw. They thread 1-1/4” into the vertical plate, and we used six of them in each assembly.

The screws had to share the foot real estate with the two 1/2” diameter pins that will lock the foot to the bumper.

This is how the dimensioning ended up after drilling the screw and pin holes.

After the holes were drilled in the feet, the feet were clamped to the vertical plate so they could be used as a guide so a hand drill could transpose the holes to the plate.

Countersinking the holes was the next step after transposing the foot holes onto the vertical point.

Since we have a small drill press, we had to get creative in order to drill the plates with this machine.

Here you can see one of the guide holes (2nd from the right) that were drilled into the plate using a hand drill and the foot as a template.

After drilling, each hole needed to be tapped to receive the screws.

This shows how much of each screw will thread into the vertical plate. It’s a full 1.25” of thread engagement.

All threaded in, the assembly is ready for welding.

Because the aluminum is so thick, and our welder is only 200 amps, we needed to preheat the assembly so it was hot enough to form a good weld pool.

Here is the final weld. It’s not robot perfect, but it’s pretty good.

The foot to vertical plate weld is a full perimeter weld that will provide substantial strength, especially when combined with the six high strength screws.

Main Vertical Posts

There are different ways of designing the main structural component of a bull bar. Most of the bull bars that are made today consist of a heavy vertical flat bar with a thinner flat bar strap wrapped around it and welded to it to give it three dimensional thickness. It’s a quick and inexpensive way to build a bull bar. But it’s not the strongest design, nor does it have the most appealing appearance.

The higher quality, higher strength commercially made bull bars are all made with a box construction vertical member of differing shapes. Unfortunately, these bull bar/bumper combinations are expensive. They’re worth the money, but it certainly hurts the old pocketbook.

Since we are making our own bull bar, and our hourly shop rate basically boils down to coffee and cookies, we elected to go the more time consuming route of a shaped box section vertical. Above that, we decided to shape it to compliment the front profile of our engine hood.

To create the shape we used 1/4” thick 6061-T6 flat bar. The sides came from 8” wide material, and the front from 2-1/2” wide material. The back face was developed from 3” channel, as it was needed for structural reasons.

The first step to creating the vertical posts was to print out a full size graphic of the post layout. This way we could easily transfer the curved shape of the post front onto the aluminum flat bar. It also gave us all of the attachment points without having to transfer each individual measurement.

Using the paper template, the shape was transferred to the flat bar.

The actual shape was scribed into the metal, and then rough outlined with felt pen to make it easier to rough cut on the table saw.

Since the saw only cuts a straight line, multiple overlapping cuts had to be made.

Here’s the rough cut blank with the cut off wedges beside it.

The first blank was finished completely and then used as a hard template to layout the other three.

Here’s the finished first side ready for scribe tracing.

After the three remaining blanks were rough cut, the first was set up as a router template so the router court quickly trim the rest to final finished shape.

This shows the amount of material that the router would be trimming off.

Vertical Post CoNstruction

Now that the post sides are finished, it’s time to start constructing the post’s three dimensional shape. This begins by laying out the placement of the internal components. These components consist of the pivot tube at the bottom of the post, along with three braces made of aluminum square tubing.

The aluminum braces do several things. First, they provide the spacer to position the two side walls a precise distance apart so the perimeter strips can be welded in place. Secondly, they provide additional structural strength against sideways impact deformation by transferring the forces through the width of the post, and then by the cross rails to the other side of the bull bar. By doing this it reduces the chance that the perimeter flat bar welds might fail.

The paper printout makes positioning the internal components easier.

The heavy square tubing inserts are strategically placed so they end up between cross rails.

With the paper template positions transferred to the aluminum by felt pen, all is ready for assembly.

With the aluminum inserts properly positioned, all is clamped ready for welding.

This shows the structural inserts tacked in place and ready for final welding.

The pivot tube is 1-1/4" Sch 80 aluminum pipe, and is welded on both sides of the side walls.

The pivot tube allows for the 1-1/4" O.D. stainless tube that forms the pivot axle for the entire structure.

This shows the inside and outside welds of the pivot tube.

With all the inserts welded in place the structure is still perfectly straight.

All ready for outside weld dressing.

The best way to dress down the weld is to use a router with a flat end bit. These rails support the router.

A standard dado bit is used to machine the welds.

A sturdy router is needed when machining aluminum. Aluminum is much tougher than even the hardest woods.

Raising the router up on the rails allows it to slide over the raised weld so the cutter can work, without the router baseplate hitting the weld.

This is how the weld looks after the router bit has done its job.

After the router has trimmed the weld, the final raised few thousands of an inch are removed by draw filing.

Once leveled with the draw file, a quick touch with a Scotch-brite abrasive disk finishes the job.

Both assemblies ready for the next step of attaching the perimeter flat bar.

After all that welding, you can’t get much straighter than this.

Adding the vertical post perimeter

With over 16 feet of continuous weld per post, care must be taken to balance the stresses in order to keep the post straight.

Perhaps the trickiest part of the whole build is attaching the perimeter flat bar to the post assembly. This is because it’s welded in place, and so much weld, if not done correctly, can create tremendous stress in the structure which shows up as unwanted distortion. The preferred and necessary straight vertical post could end up looking like a banana.

The first thing we had to do was remove some of the material where it backs up against the angled bumper.

The material was cut away with a hand held jigsaw.

To ensure our spacing was correct we test fitted the pivot axle and post onto the bumper parts.

We also welded into the 3’’ channel strongback a threaded plate that would receive the pivot safety lock.

The strongback was then tack welded into place on the the post assembly.

This shows why there was a complicated cut away needed. All because the bumper front angles away toward the back. We didn’t want a large gap.

This is the cut away section that fits around the bumper face and top.

Quite a few pieces are cut and fitted into place to close in the bottom of the post around the pivot area.

The front of the post was closed in using 3/16” x 2.5” aluminum flat bar.

The welding is done 3” at a time, at all four corners of the post in alignment with each other. This balances the stress.

It was important that all the welds were full penetration, since the outside surface would be trimmed off so it’s smooth.

This shows the complicated area around the bumper face all welded up.

Welding the structure took some time because of the constant rolling of the post to weld all sides evenly.

Here I’m welding the front face of the post.

Here is the post structure all fully welded.

Vertical Post Weld Dressing

A before and after image of weld dressing and surface sanding with an orbital sander.

After the welds were all completed, they all needed to be dressed to make them disappear. The objective was to make the structure look seamless, like it was not a fabricated component.

The primary tools for this kind of work, on aluminum, is a hand router with a flat end, chamfer or radius carbide cutter, a coarse and fine flat file for draw filing, various lengths of abrasive cloth in a fine grit, and an orbital sander with 100 and 150 grit sanding disks.

Before we can radius the edges, we have to flatten the side faces.

You can see the notch cut out of the router baseplate that allows the cutter to get to the weld bead.

The first job in the dressing is to make the side faces smooth and level so the router base plate can run easily along it to radius all the corners. To accomplish this we have to customize the router baseplate so it will run along the smooth side of the face while the flat end of the cutter can remove the top of the weld bead.

Routing off the weld bead can be tricky when using a cantilevered router bit. One can easily slip and drop the router bit below the base metal surface.

It took a while to do this because we also had to remove some of the strong back material as well.

Draw filing came next to remove the router marks. First a coarse file, then a fine one.

Although the weld still looks visible, this just because the various metals have different densities and crystal structures. Once sanded, they all blend in.

The next step was to radius the edges with a router round over bit.

A new base plate was used for this operation so we had better support.

This is the finish that’s left from the router bit.

Care had to be taken to leave the sharp edge where it’s needed for other reasons.

This shows the raw edge from the router on the right and the strap sanded edge on the left.

With the edges all done and the faces sanded, a nice uniform look overtakes the parts appearance.

Creating the bull bar cross rails

Paper cutouts show the size and location of the cross rails.

The next job in building the bull bar is to create the cross rails. Now this might not sound overly complicated. After all, the cross rails are just rectangular tubing, right. Well, not quite. You see, the bull bar verticals change dimension front to back, as measured from top to bottom, and we wanted the cross rail depth to be spaced evenly. So to do this we would need to use rectangular tubing of differing dimensions. Unfortunately, for perfect spacing, the tubing sizes we wanted don’t actually exist. This meant we needed to actually fabricate two of the four cross rails.

The top two rails were simple enough, as they were standard tubing sizes. But the bottom two rails had to be created from other parts. The third rail was fabricated from two pieces of rectangular tubing. One cut down along its length and then the two welded side by side. The bottom rail, however, had to be made from four pieces of flat bar the way the vertical posts had to be done.

Third Rail Construction - this rail was made from one piece of 2”x2”x3/16” tubing and one piece of 2”x4”x3/16” tubing. The 2”x2” tube was cut lengthwise into the shape of a “U”. Then the two were welded together and dressed down.

Two lengths of tubing to shortly become a single, wider tube.

Once the smaller tube was cut to a narrower dimension, the two pieces were tack welded together.

Just like the vertical posts, the welding here had to be done in 3" sections and then the tube flipped to do the other side.

All welded and still nice and straight.

The excess weld bead is removed with the router the same as with the vertical posts.

Draw filing the surfaces was next to remove the router marks.

After the draw filing, sanding of the entire surface was next.

All finished and ready to be assembled in the final structure.

Fourth Rail Construction - The fourth rail dimensions needed to be 2.5”x6.5” in cross-section. To get this we used 1/4”x6” and 1/4”x2” flat bar, and to space the pieces accurately we used some 3” aluminum channel as internal braces. This kept the developed tubing from distorting into a parallelogram from a rectangle, because of the welding stresses.

Starting the clamp up process to secure the flat bar in position for welding.

The tube assembly is all clamped and ready for the tack welding.

The tack welding is all completed so the clamps could be removed for final welding.

The assembly is perfectly straight at the tack welded stage.

The time consuming process of welding is all complete. The part is square and straight.

The round over bit is used to dress down the edge weld. The radius was chosen to match the other rail tubing.

Some points along the weld length are not sufficiently proud to route off cleanly.

The low points must be touched up with more weld to fill the voids, and then be routed off again.

The routed edges are strap sanded with the sanding mesh, 150 grit, and then sanded by the machine.

All finished and ready for inclusion in the final bull bar assembly.

Drilling The Cross Rails - The last procedure on the cross rails was to drill in all of the various holes we needed. Some holes were used for attaching the wire chase channels to the back in order to hide any wiring we might want to add for lights or whatever. Other holes we added to fasten snaps so that radiator grill covers, mesh for summer bug protection and solid material for winter cold protection, could be attached as needed. Winter is particularly important because extreme sub-zero temperatures will keep the engine from heating up to proper operating temperature if air is allowed to flow through the radiator and over the outside of the engine surface. We discovered this on our first -25°C trip to northern British Columbia.

Accommodating The Winch Compartment Lock - Since the winch compartment would also store some recovery equipment, we needed to lock it for theft prevention.

To create the lid lock we took a Bolt Lock hitch lock and cut the hitch pin shaft, welding only the locking end to the bumper bracket lid shelf.

Locking the compartment came with one problem, though. The lock we wanted to use was a Bolt Lock hitch lock, which allows us to unlock it with the truck ignition key. The issue is that this lock is on the top of the lid, and this would put it in conflict with the lowest cross bar of the bull bar. So to get the lock off without having to tip the bull bar forward we would have to provide a cut out in the lower rail.

To provide access to the lock for the key, a notch was cut in the back of the lower rail.

The notch not only gives key access, but also provides a place for the lock body to lift into when being removed.

The notch opening into the rail body was filled in using fitted pieces of aluminum and weld.

Looking in the end of the rail, you can see how the internal brace closes off one side of the notch.

The weld was dressed down first with a round file…

…then with a small drum sander powered by a hand drill…

…and then by a sanding flap wheel in the angle grinder.

The finished notch is sealed and smooth.

The radiused edges of the notch allows the powder coating to adhere to the entire notch surface. Powder tends to bleed away from sharp edges.

From the front the notch is barely visible.

From the back one can see how much room is available for the key and lock body.

Bull Bar Assembly

Here we are playing around with the spacing front to back to get the best visual positioning.

This shows the arc of the winch enclosure lid as it pivots forward and misses the lower rail.

Now that all of the parts have been created, the time has come to start welding all the pieces together. Although all the layout was designed on a cad program (a very cheap cad program), mocking up the parts for visual verification was a good double check.

Not only did we need to confirm the rail spacing and front to back position, but we also had to verify that the winch compartment lid, when hinged open, would clear the underside of the lower rail.

The bull bar was installed on the bumper with the cross rails spaced and clamped in place.

The cross rails had to be tack welded in an awkward position.

Once tacked in place, the clamps could be removed and the bull bar tipped forward for full welding to begin.

With the front and back welds done the bull bar was positioned to weld the front to back welds.

At this point the diagonal brace was installed to help hold the bull bar square during full welding. It also acts as the Volvo signature.

All welding completed and we’re on to the next step… the outrigger bars.

Building The Outrigger Bars

Now that the bull bar is assembled, it can be mounted back on the bumper so the outrigger bars can be measured, cut and assembled.

Doing this is a complicated process because of the multiple components that are bolted together to form the completed product, and how the moving parts must interface perfectly with the stationary parts in order for them to be locked in place. This is made even more complicated since the bumper will be disassembled, painted and then reassembled on the truck rather than the bench. So positional irregularities can creep in during installation that might impact the accuracy of the interface points. Bottom line, lots of wiggle room needs to be factored in.

Creating The Horizontal Rail - With the vertical end plate in position and braced at 90°, and a piece of wood clamped to the bull bar vertical at the proper height, the 3” square tubing could now span the gap so the length and end angles could be scribed on the tubing. The tubing was then cut on the mitre saw.

We start with spanning the gap with the raw tubing, then scribe the end angles and length.

Since we wanted a broader attachment at the bull bar, a smaller wedge of tubing was cut and fitted.

With the wedge fitted, we could now scribe the end plate that’s against the bull bar vertical.

After the attachment plate is cut it forms a nice clean fit.

With the wedge fitted and clamped to the main rail, we pre-heat the assembly so our small welder can more easily melt the base metal.

Welding the wedge was the next step.

Welding finished, we now get ready to dress the weld.

Like all the other welds, a router is used to remove the bulk of the weld bead.

Before the router, and after.

Draw filing the routered weld bead in preparation for orbital sanding.

Here is a comparison of what the part looks like mid way through the draw filing.

The raw outrigger and the finished rail.

The rail can now be placed to see how it looks.

The outrigger sweeps rearward as it reaches out to the vertical end plate.

Attaching The Bolt Plate - The bolt plate is what secures the outrigger bar to the bull bar vertical. Made from 3/8” x 3” 6061-T6 aluminum flat bar, it was cut to size with angled ends to match the angle on the various surfaces of the outrigger bar.

Rather than threading the holes in the plate with a tap, we elected to use hardened steel PEMserts, which are pre-manufactured fasteners designed to be pressed into holes drilled or punched into the base metal. They are more precise and far stronger than tapping the holes to create the threads.

Before the bolt plate could be welded to the rail we had to drill and press in the 3/8-16 PEMserts.

When the plate is positioned in place, the PEMserts are invisible.

Care had to be taken to space the PEMserts so they would span the web of metal at the middle of the end assembly.

The pieces were positioned and held in place with weights and props so they could be easily tack welded in place.

All tack welded and ready for pre-heating.

As with the other welding, the assembly was pre-heated before the final welding.

The weld lies nice an flat because of the bevels cut in before welding. It also allows us to achieve 100% weld penetration.

The screws were installed prior to welding to ensure the PEMserts would not be affected by the high heat of welding and loosen.

All that’s left now is the dressing.

The completed end dressing. This design lets the end of the rail to blend seamlessly with the bull bar vertical.

Completing The Outrigger Assembly - The final steps in completing the outrigger is to drill the bull bar verticals to accept the cross rail bolt plate, and then weld the cross rail to the end vertical plate out on the corner of the bumper.

The bolt hole locations were transferred onto the verticals using the outrigger bolt plate as a template, before it was welded onto the outrigger cross bar.

Those hole locations were then transferred to the inside of the vertical by measurements from the outer side.

The holes were drilled using a hand drill.

After these holes were drilled, we were able to attach the outrigger rails for the final welding.

Before welding, we also had to pre-heat the joint to make it easier.

The joint was tack welded in situ.

All four corners of the outrigger tube had to be tack welded.

With strong tack welds complete, the part could then be removed for welding on the bench.

The final welds of the project also happen to be the best. Practice makes perfect.

With the final welds done, the outrigger could be put back in place for final test fitting to ensure weld distortion didn’t muck things up.

Final Pre-Paint Assembly Test

The last thing we did before sending all the parts out for sand blasting and powder coating was to fully assemble the bull bar with the bumper to ensure everything worked perfectly.

Final Installation on The Truck

After getting all the parts back from the powder coater we set about prepping the parts for installation.

Not a lot had to be done other than to add the wire chase channels on the back of the bull bar section, and to add to them the numerous snaps that would be used to hold the bug screen or winter cold cover on when needed.

Attaching the wire chase channels to the bull bar after pop riveting the snaps to them.

The boss all ready to help lift the bull bar onto the bumper.

The pivot axle is actually the 1-1/4" diameter stainless tubing that’s been powder coated to match.

The tubular axle is held in place by a 1" grade 8 bolt. This gives it the strength against impacts.

Here I’m wrapping the bolt heads with masking tape so the wrench won’t mark the powder coated heads.

It’s nice to see that all the calculations for tipping the engine hood worked out perfectly.

We made these light shields to help prevent the auxiliary lights from being broken by flying rocks. They are made from polycarbonate.

We applied masking tape to protect the paint job while test fitting the outrigger bars.

With the outriggers bolted on we could test the tipping of the bull bar and it’s resting fit on the bumper corners.

These backing plates help to displace the bolting forces, and cover the larger holes underneath used for adjustment.

The bar tipped forward exactly as designed.

With all the matching powder coated bolts tight, the backing plates are barely noticeable.

The bull bar is held in place by these custom designed latches.

The latches are held closed by keeper hooks. An added layer of safety.

A side view of the bull bar and bumper.

The wide angle camera lens distortion makes the bull bar look much larger on the truck than it really is.

The bull bar stops at a pre-determined point so the hood can be opened.

The final product of four months isolation from Covid-19.