Intro: Custom Steel Bumper for Off-road Truck
This is the custom steel front bumper that I made for my truck, to replace the stock bumper, which is made mostly of plastic. Instead of merely giving specific directions for my 2007 Toyota FJ Cruiser, I will outline some useful and somewhat more generalized guidelines for those interested in making a custom front bumper for any make and model of 4x4 truck, for the purpose of four-wheeling and off-road recreation.
After a last-minute decision to take a week-long trip to Moab, Utah, for some epic four-wheeling with a group of friends, I realized that the stock bumper of my Toyota FJ Cruiser just wasn’t going to cut it. But I wasn't up for spending $1000++ on an existing after-market bumper. As a product designer and former metal fabricator, I figured I could design and build a highly functional one with all of the features that I desired, while infusing the design with my own personal aesthetic. I collaborated with a friend who also drives an FJC and has plenty of metal fabrication experience -- and a water jet cutting machine.
This project was a significant undertaking on a very short schedule -- 2 weeks from beginning to end, including design time. The difficulty of your project will depend upon your specific bumper design, skills, and fabrication processes. You can tailor your design to your skill level, access to tools and fabrication processes, functional needs, aesthetics and budget.
Why on earth would I need a bumper THIS beefy on the front of my truck? Check out the video to see the kind of extreme challenges I had in mind when I designed it. A friend posted a video on YouTube of some of my rock-crawling stunts on a recent trail run which reveal just how much abuse this solidly built bumper can withstand.
Step 1: Tools, Materials, and Safety Equipment
The tools needed for this project will vary based on your specific design, as well as the make and model of your truck.
TOOLS USED FOR MY FJ CRUISER BUMPER:
cold cutting metal saw or chop saw
water jet cutting machine
tube bender (external vendor)
1.75" diameter hole saw
drill press, drill bits and countersink bit
angle grinder with grinding disc, sanding discs and scotch brite pads
protractor or angle measure
thread gauge (for measuring existing tapped holes in frame)
long straight edge
socket wrench set
long furniture clamp
dead blow hammer
Philips screwdriver (for removing existing bumper trim)
3D modeling software
a couple of strong friends for the installation
OTHER TOOLS & PROCESSES YOU MIGHT USE FOR YOUR BUMPER DESIGN:
MATERIALS FOR THE FJ CRUISER BUMPER:
3/4" steel plate [(2x) shackle mounts] -- 5" x 8"
3/8" steel plate [(2x) plate uprights, (2x) frame horn mount plates] – 16" x 30", and 8" x 12"
3/16" steel plate [(2x) cheek plates, bash plate mount tabs] – 16” x 24”
1/4" steel plate (winch mount plate and stiffeners) – 36” x 10”
1/8" steel plate [deck plate, bash plate, (4x) winch plate gussets] – 33” x 10”, 33” x 30”, 20” x 10”
1.75" OD steel tube, 0.120" wall – 15’ approx.
1.5" OD steel tube, 0.120" wall – 15’ approx.
1.25" OD steel tube, 0.120" wall – 32.5" [reinforcing cross-member]
high strength bolts and nuts
Earplugs or other hearing protection
Long sleeves or welding jacket
Step 2: Basic "look and Feel" Design Sketches
Research: Search online for existing after-market bumpers that are manufactured for your vehicle (if any).
Look around: When you're out and about, or if you're in a four-wheel-drive club, check out bumpers on other trucks. Take pictures, and ask questions of the owners to learn what they do and don't like about their bumpers.
Ideate: Come up with a few basic ideas. Take some preliminary measurements off your truck, and start sketching.
IMPORTANT DESIGN FACTORS TO CONSIDER:
A) Type - There are tube bumpers and all-plate bumpers. I decided I wanted to make a tube/plate hybrid for my truck.
B) Overall weight vs. structural rigidity and resistance to damage
C) Approach angle - The approach angle on a stock 2007 FJ Cruiser is 34 degrees. Not bad for a stock SUV, but that will certainly prevent you from trying a lot of fun, challenging obstacles on the “difficult” rated trails in Moab and OHV parks. A shallower approach angle means that your bumper is more likely to scrape, drag and get hung up.
**My new bumper design has a 43 degree approach angle, which gives me a huge advantage out on the trails! Compare the stock bumper in the photo to the new approach angle in the diagram above.
D) Aesthetic considerations
E) Winch - Decide if you want to allow room to mount a winch. The standard four-hole mount pattern for a winch is 4.5" x 10".
F) Engine ventilation and radiator protection
G) Shackle mounts/recovery points - These are heavy plate eyes (3/4" or 1" plate) with holes for attaching shackles or D-rings in the event that you get stuck and need to be towed out. Unless your stock vehicle already has these welded onto the frame at the front of the truck, you will need to include these in your design. In order to gain more ground clearance on my truck, I cut off the heavy round bar loops welded on to the frame by the manufacturer and added the shackle mounts a bit higher up on my bumper.
H) License plate mounting holes - Check the laws where you live. In the state of California, you must display a front and rear license plate. They should be bolted or screwed on.
Step 3: Obtain Frame Geometry and Accurate Measurements
Many newer SUVs, like my FJ Cruiser, have large plastic bumpers. Beneath this is the "real" bumper structure--a sheet metal rectangular tube attached via mounting plates to horns that extend forward from the truck frame. We removed both of these pieces in order to obtain accurate measurements and locations for the frame members, existing mounting plates, available mounting holes in the frame, radiator, front body panels and grille.
We used the existing frame horn mount plates as a starting reference point. The truck was parked on level ground, and we measured tire size, axle location, and front fender flares. Using a long straight edge and a Sharpie, we drew a straight line across a small curved piece of sheet metal on the body as a reference while trying to measure the curve of the grille and angle of the turn signal lights. Distances between available holes in the frame were carefully noted, as well as their distance to our reference point at the frame horn plates. A thread gauge was used to ascertain the thread pitch in tapped holes, so that appropriately sized bolts could be matched to them.
I then used these measurements to create a 3D model of the basic frame tubes and the frame horn mount plates to which the "real" steel stock bumper had been bolted.
We double-checked our model of the existing frame horn plates by creating a water jet file from the 3D computer model and cutting a test piece in plywood. We matched the plywood piece to the truck frame horn plate to verify the geometry.
Step 4: Finalize the Design
Using your preliminary design sketches, combine your design concept with the modeled (or carefully drafted) geometry and measurements of the front components of your truck. If you're like me, this will take quite a bit of time, thought, and bouncing ideas off of other people. Being able to view my design in a 3-dimensional format proved to be a great visualization tool for me, and I made a lot of design revisions based on being able to see the design from many viewpoints.
My final design combined bent tubes and steel plate. The 3/8" steel plates that extend upward from the frame horn mount plates are quite unique. Their truss-like appearance really distinguishes the bumper from other ones on the market.
Another unique feature of this bumper is that the design allows for the winch to be unbolted and removed through the front of the bumper (after unbolting and removing the bash plate). Winches are very heavy and add a lot of extra weight while just driving around town, so it's nice to have the option to remove it when you're not out wheeling. Many winch bumpers require that the entire bumper be removed and the winch inserted or removed through the back side of the assembly. This provides theft protection but means that the bumper is more or less permanently installed. When I install a winch on my bumper, I plan to use vandal-proof Torx screws and nylock nuts.
Some bumper designs have a winch plate assembly that is separate from the rest of the bumper and bolts directly to the frame of the truck. Some plate bumpers allow the winch to be bolted onto a flat space on the top of the bumper.
You may find the steps following this one (Step 4) helpful in learning more about other design factors--in addition to winch mount plates--that influence the overall bumper design. You can then make more informed decisions about what you need and want in your bumper design.
Step 5: Part Fabrication: the Plates
Using my 3D model, I exported files in .dxf format for cutting on my friend's water jet machine. This included the 3/8" bumper mount plates that match/attach to the existing truck frame horn mount plates, the 3/8" truss-like plate uprights extending vertically from the frame horn mounts, a 1/4" mount plate for a winch (which I hope to own someday) with stiffener ribs across the length and width, 1/8" gussets to support the winch plate (added to the design much later in the process -- see Step 9), 3/16" cheek plates which bolt to existing unused holes in the side of the frame and to which the tube knee braces are welded, and a 1/8" deck plate (added at the very end -- see Step 11) which spans the gap between the top tubes just below the grille.
After draping an old wool blanket over the hood of the truck to protect the paint, we bolted the 3/8" plate bumper frame horn mount plates (the small ones test-cut in plywood) to the existing frame horn mount plates on the truck, added the 3/8" plate truss uprights (refer to first picture in this step) and the 1/4" winch plate, held them all together with a long furniture clamp, checked the angle with a combination square (and tweaked until the assembly was perfectly square) and tacked them together with a MIG welder.
Note: These parts were "keyed" to make assembly easier and more accurate. Keying parts involves making tabs on one part that fit into slots on another part. Note the slots on the 3/8" plate uprights, into which fit tabs on the winch mount plate. Keying parts is not necessary; It makes part fabrication a little bit more complicated, but it sure does simplify assembly and part alignment!
Step 6: Part Fabrication: Tube Bending, Cutting and Fitting
We did not have access to proper tube bending equipment, so we had an external vendor do the job. I created a .dxf file from my 3D model of the tubing to be bent so that the guy doing the bending could print out a full-scale template.
Using my friend's tube rolling machine, we added a gentle curve to the middle of both long tubes.
Where the tubes intersected on another, we used a hole saw to cut a curved notch of the appropriate diameter at the intersection.
The ends of the front tube were cut at an angle to match neighboring truck geometry, capped with oval shaped discs and welded with a MIG welder. The caps were ground smooth with an angle grinder using sanding discs and scotch brite discs.
Then, the tubes were fitted on the plate uprights and tacked in place using a MIG welder.
Cheek plates were added next; They bolt into previously unused tapped holes on the sides of the trucks horizontal frame members, making the mechanical attachment of the bumper structure that much more rigid. Be aware that using this technique may, in fact, reinforce a crumple zone on the front of your frame, which could be a safety issue in the event of a front-end collision. There are more than a few bumper designs out there that already use this technique, and I have been told by many people that this does not hinder the deployment of air bags. ARB is the only company whose bumper for the FJC has actually been crash-tested to prove this. You can recognize a manufacturer's crumple zone by noting little dimples in the frame tube.
Tube knee braces were notched with a hole saw (a somewhat tricky cut-then-test-fit process), then tacked to the cheek plates and fitted to the top tubes.
Step 7: Welding of Full Assembly, Adding Shackle Eyes and Center Hoop
Before removing the tacked assembly from the truck, the 3/4" plate shackle eyes were attached at the corners between the frame horn mount plates and the truss plate uprights and given very strong tack welds. These helped stiffen the structure and hold it firmly square for welding.
We then removed the tacked-up assembly carefully from the truck so as not to distort the geometry. Your tacks should be strong so that they don't break during this process. We used the aid of a forklift to support the weight of the bumper, which was nearing 100 lbs. at this point.
We used a MIG welder for the winch plates and stiffeners. A TIG welder was used for the tube joints to make nice-looking welds that didn't need to be ground down.
The center hoop was notched with the hole saw, then added to the complete welded assembly on the welding table. Before tacking in place and welding, the hoop was laid flat on the table and the bumper assembly was laid on the front edges of the 3/8" plate uprights. This allowed us to use the plane of the table to match their angles.
Step 8: Adding the Skid Plate or "bash" Plate
The bash plate serves as a piece of armor that is often the first point of contact on the bumper when tackling an off-road obstacle such as a large rock incline or ledge drop-off. It must be able to sustain significant impact and slide or skid over obstacles.
The plate should be wide enough to cover the radiator in order to protect it from flying debris such as gravel while on the road, and branches, rocks and kicked-up sand while off-road.
It is highly recommended that you put ventilation holes in your skid plate so that the engine receives proper ventilation. Your stock bumper likely has a mesh or grate panel for this purpose. Mesh and fine grates are not likely to be structurally robust enough to sustain direct impact. Instead, I used a common approach in after-market bumpers; I placed five adequately spaced 3-inch round holes near the bottom of the plate - a shape that maximizes air flow volume without sacrificing much strength in the plate.
Winch: If you plan to mount a winch on your bumper, you will need to cut a hole in the skid plate for a fairlead (aluminum plate for synthetic cable or a roller fairlead for steel cable). The winch cable will run out through this hole. Check online for dimensions of the fairlead you are planning to use. If you don't know, you can always cut a hole in the plate at a later date with a plasma cutter.
MY SKID PLATE:
Many skid plates are welded to the full assembly, but I decided I wanted mine to be removable. There are two advantages to that: 1) The plate can be replaced if it is badly damaged, and 2) the winch can be removed through the front of the bumper without removing the entire bumper from the truck. Tabs were welded at the front edge of the truss uprights as bolt mounting points for the skid plate. We chose to use carriage bolts in the event that the bolt heads get mashed up on the rocks - an occurrence that would make it difficult to remove a hex or Philips head screw.
My skid plate design called for a couple of bends in the plate. Lacking a press brake, we were able to create these bends by cutting a couple of long slots at each bend location, leaving a few small connecting tabs. The plate could then be bent by hand over the assembly, welded and ground smooth.
Step 9: Part Fabrication: Additional Reinforcement
At this point in the fabrication process, we stopped to assess the structural design. We thought it prudent to add more stiffening members to the assembly.
A reinforcing 1.25" diameter cross-tube was welded on, tying the two 3/8" plate uprights together. It serves to hold the distance between the plate uprights during welding, and it strengthens the back of the bash plate upon impact.
Since the winch is mounted on a horizontal surface, the plate will undergo significant torsional (twisting) forces. Two 1/8" gussets, whose profile echoed the shape of the 3/8" plate uprights, were added which tie the winch plate and reinforcing cross-member together.
Step 10: Painting (or Powder Coating)
Lacking the time to take the full welded assembly out for powder coating, I opted for the quick and cheap solution of spray paint. I used Rustoleum 'paint and primer in one' in metallic "Dark Steel" for the main assembly, and textured black metallic in "Galaxy" for the skid plate and deck plate.
Powder coating will give your bumper a more corrosion-resistant, tougher finish. I plan to get my bumper powder coated eventually. If you choose to go that route, make sure to get matching touch-up paint from the powder coater, because if your bumper sees some real action out there, you're gonna need it!
Step 11: Adding the Deck Plate
Adding the final touch - a deck plate:
Since I painted the deck plate a different color from the main assembly, it was tack welded onto the bumper after painting. The deck plate provides some protection for the winch, and may come in handy on the trail should you need to stand on top of the bumper in an unforeseeable event -- such as getting stuck in the mud, when you don't want to step down into it up to your knees to hook up the tow straps (not until you absolutely HAVE to, anyway). It also makes a nice seat... and a lookout platform! [Oh, and it makes a nice level surface for parking your beer!]
Step 12: Installation
After looping a strap around the bumper, the assembly was suspended from a fork lift and raised to the correct height for installation.
High strength bolts were used (metric Grade 10.9 and standard Grade 8) along with nylock nuts to make the mechanical attachment points as strong as possible. The bolts were started in their respective holes but not tightened until all were in place and aligned. This proved to be a somewhat arduous task. Although all bolts and holes were very well aligned during the initial tack welding on the truck, and the tacks were strong, the structure likely deformed a little bit when the entire assembly was welded up. The smallest bit of deformation can cause holes to be misaligned by the tiniest bit and prevent bolts from fitting. Keep this in mind and oversize holes enough to allow for this, but not so much that the final fit has too much play in it.
The skid plate was finally bolted on using carriage bolts, and the bumper was complete!
Note: If we were to put this bumper into production, we would make some small changes in the design to make the installation process go more smoothly and quickly. These are things we learned only in the process of installing our "prototype" bumper.
Step 13: Go Wheelin'!!!
In Moab, this bumper saw its first real action and performed beautifully. The excellent approach angle allowed me to tackle many obstacles without touching the front bumper at all.
On a more recent run to Bald Mountain, I subjected the bumper to some pretty hard-core action -- the kind of extreme challenges for which I designed this bumper. A friend posted video on YouTube of my rock-crawling stunts on Beer Rock and V-Rock, which is posted on the first page of this Instructable.