How to Build a Rear Bumper With Swing Out. (redux)

First off I made a huge mistake and accentually deleted my instructables account. Long story short remember that Autodesk and instructables are the same. The old archive of the article is |here| luckily the internet is forever, well at least the text is.

A few caveats:

1. This is for a body on frame vehicle. The project was specifically designed for 2013 FJ Cruiser.

2. Check your local laws for legality.

3. If you are going to do this you will have to make modifications to fit your vehicle.

Okay, now we got that out of the way, most SUVs now do not come with a tire mounted on the rear of the vehicle little lone a metal rear bumper. This is fine for most people but if you plan on taking your vehicle offroad a metal bumper has saved me a lot of body damage, the rear swing out was mainly to hold gear for me as my FJ came stock with a rear tire carrier but getting that tire out from under a vehicle is good for 2 reasons. (1) While a vehicle is in 4wd you really should have the same size tire on all 4 wheels. Most people I know get larger tires when they decide to build a vehicle for offroading and the spare under the vehicle doesn't get changed. (2) When someone blows out a rear tire in mud and the vehicle drops on to its frame it is a long, dangerous process to get the tire out from underneath the vehicle.

Welder

Angle grinder

Protractor

Hammer

Clamps

Chop saw

Skill saw

Jigsaw

Socket set

Clamps, lots of clamps

The what

You want to build a bumper to protect your vehicle and to carry stuff not on my roof rack or inside the cab.

The why

(I know its out of order but it sounds better as a title)

I want to protect the vehicle is an easy one. I don't want the tire below the frame, up on the roof rack or in the cab. I also don't want to store extra gas up on the roof or inside the cab and occasionally it would be nice to have some recovery gear and maybe some drinks outside the vehicle so I don't have to dig in it all the time to get anything.

The how

The bumper can protect the vehicle, I also want it to wrap a bit around the sides so if I slide into anything it hits it instead of the body. The tire can go on a tire carrier and I can make a gas can holder kinda like a shelf so I can put a cooler there if I don't need gas.

The plan

Ask yourself these questions and it will help direct you to your plan. In my case, at first, all I wanted was bumper the swingout came later, about 4 months later.

The bumper needs to be strong enough to take a hit on something, it won't save you from a 40 mile an hour crash but backing into a tree or falling onto a rock it should do fine. This needs to anchor onto the frame of your vehicle. You also need to choose what part of the vehicle gets cut off to make room for this bumper. Adding a swingout adds a lot of stress to a bumper that makes you need to anchor the bumper on both the top and bottom of the frame.

My plan for this project was a simple sketch with some ideas written on it to keep me on track. The idea was to have a very simple exoskeleton type bumper. I opted to use square tube because that is what I had on hand as left over from my trailer build the year before. This should let me have a strong light bumper that would give me the ability to expand on it later if I wanted.

For my vehicle, I removed all of my bumper leaving only the rear of the frame. I know I wanted to use parts of the plastic to fill in holes so I took my time and took it off whole and putting the hardware in bags as to not lose it.

My vehicle came with an "at the dock" trailer hitch, not a stock Toyota one. In order to still be able to tow I bought the OEM hitch and use the aftermarket one as a base anchor point for my bumper.

Since I was using my original hitch as my foundation it this was an easy step for me. I also added 2 supports that bolted to the frame. I have seen some people weld onto the frame, I personally am not a fan of welding anything to the frame. If it gets damaged its much easier to unbolt opposed to grinding off. Most frames have stock holes for mounting tow bars, I would suggest that being a good start to making a foundation. Grade 8 hardware, while not being a must I highly recommend as there can be some significant stresses in the bumper. Using 1/2" hardware Grade 8 bolts should take somewhere around +90k lbs to pull out and +20k lbs to shear I'm going to have metal failing elsewhere before the bolts do.

I used my existing hardware for the main supports the other 2 I used 1/2" UNC hardware with washers and used 1/4" plates on each side of the frame to clamp it into position. This gave me my hardpoints to start my construction.

For the main braces, I used 3/8" plate and I cut it with a cheap Ryobi jig saw. It wasn't fast but it cut at a decent speed and as long as you use good blades it didn't have a problem with it. Before welding everything together I placed a mocked up the layout on the back of the vehicle then clamped the supports in. If you can't tell most of this build the "measurements" are taken directly off of the vehicle. Since this was a one-off product I didn't have to worry about repeatability.

For this stage, I took a full 10' stick of 1 1/4" square tube measured it out to be centered on the frame and started cutting and welding on the truck to maintain the shape of the frame. I used clamps to get the bumper to the right position then welded it together. Note I did not weld to the supports so I can move the bumper off with ease.

Scrap templates might be one of the easiest ways I know how to make a complex shape with a square tube. Take a piece of scrap, in my case I used 1" wood strip, to act as a template. Move the scrap to the location you want your next part of the bumper to go and clamp it down and mark it with a pen. Take off the scrap and mark a line square to the metal at the end of the line you marked with the scrap. This is your new baseline. Take your protractor to find the angle of your original line, half the angle and use the protractor or angle finder to give you your new cut lines on either side of the new line. Cut out the notch but leave the "pivot" side of the square tube intact, this acts your hinge for the fold. Leave a small gap I did around 1/8" since I was using 1/8" thick material. Weld it up and you have your new angle. I like the method since you can measure out the exact place you want your metal to go.

I wanted the rear bumper to go nearly to the wheel well to protect the whole rear of the vehicle. One thing to note is with a frame on body vehicle the body flexes in relation to the frame. This bumper is mounted to the frame and wraps around the body, for this, I wanted the metal bumper to clear the body by about 2".

I have more details on how this is done on the next step.

Sorry I did this set of drawings in cad and I don't have the orginals.

Step 1: Here I found I needed a 54 degree angle.

Step 2: Make your new baseline on the material.

Step 3: Mark 2, 27 degree lines either side of the new baseline.

Step 4: Cut the V

Step 5 Fold on the open edge.

If you want you can cut the whole thing but for what I needed cutting 3 out of 4 sides worked well for me.

If you noticed in the sketch I had the idea of 2 square tubes running parallel to make my frame. For this step, I took off the top of the bumper I just made, cleaned up the welds and used it as a template to make the bottom rail. To make sure the two rails were close as I could make them to being the same I cut and clamped the rails together and tacked each fold then bent as I moved down the square tube. Finally, I bent the ends up to meet up with the top rail.

The rear of the vehicle has vents in it to allow the AC, airbags, and doors to function correctly. These are covered with the plastic wrap around that used to be my bumper. I did not need the center of the bumper or the plastic winglets that just get ripped off by most people wheeling FJCs, but I needed/wanted to reinstall the plastic pieces that protect my vents. There are a few protrusions to these plastic parts so I wanted to fit it before I finish making my bumper wings.

The wings themselves were made with the same method I used for the top rail of the bumper.

If you haven't noticed everything so far is relatively parallel with each other its good in the looks department but it will not hold up to any offroading. The wings need to be triangulated to have the strength needed to stay functional and to not fail and cause more damage in an accident. This is also where the bottom rail came in, the bottom rail is below the side plastic so this allows me to triangulate and place a piece of metal under the exposed body of the vehicle.

At this time the bumper is nearly done if you want to keep it as a bumper. At this time I remounted the bumper to the foundation supports, lined it the bumper up and checked if everything is still square. When you weld things tend to warp. Once I was satisfied I tacked the foundation to the bumper and then unbolted the foundation from the frame. A mostly complete bumper was done. I capped the ends did final welding and touch up then primed and painted the bumper.

I left the bumper at this state for several months. I took it on a few trips on its first outing at Lone Star Toyota Jamboree in Gilmer, TX it paid for itself as I drug the rear of the vehicle along some staircases (rock ledges) and rubbing the walls. Other than 2 flat tires which the bumper couldn't protect all the only damage the bumper received was some scratches which were fixed with some spray paint.

The bumper proved itself as a bumper but I quickly learned a swing out completely changes the loads put on the bumper. Before most of the load would be from behind or below making the existing 3/8" supports plenty. Now there is a tire load elevated 20 or inches above the bumper along with any other loads you plan on putting on the structure. Supports were needed to be added to resist rotation of these new loads but I'm getting ahead of myself.

Choose a hinge style

There are 2 predominate hinge styles, dual shear, and spindle. A dual shear has 2 plates and the hinge rests between it, similar to a door hinge. The other is a spindle, I choose spindle as it doesn't require as much support structure to mount it.

Mounting the spindle

I used the same 3/8" plates to make to matching triangles to mount the spindle, the spindle passed through both and welded the spindle to both of them and then to the bumper. I took the top of the spindle and mounted it to a 2"x2" square tube mounted it into position. I also painted it so it won't rust while I'm working on the bumper since I'm was attempting to not take off the bumper so I can make sure what I was building was where I wanted.

Since I originally made this as just a bumper, not something that will take a swing out I had to strengthen it. These pictures will be a bit out of order as I strengthened the bumper in stages.

Step 1: Tie to the two square tubes together and box in the spindle plates.

Step 2: Double up the top rail on either side.

Step 3: Mount a permanent clamp from the top rail to the frame keeping the bumper from rolling. This was done on both sides. The portion of the clamp that mounts to the frame uses existing 2 holes in the frame to clamp down to. It also wraps the frame to keep it from sliding. The Portion mounted to the bumper wraps the bumper too but it is welded into position.

Step 4: Wing plates, I took some cardboard and traced out the shape I needed to fit the bumper then drew it in auto cad and had a company cut 2 1/4" thick plates, 1 for each wing. Welded these in along with a matching angle to allow me to clamp the top of the bumper down on to the frame.

Yes, its a bit overkill but the last thing I wanted was a part of my bumper breaking damaging my vehicle or worse hurting someone. Remember this is on the back at all times including going down the highway at 80 miles an hour.

I am breaking down the swing out into 3 sections. The arm, the tire holder and the equipment holder.

The arm design

I wanted the arm to be strong but not huge and I commonly enter the rear of the FJ so I wanted a simple latch to allow me to quickly open and close the arm. I'm saying this because a lot of "kits" out there have a threaded bolt closing the swing out, it's strong but not fast.

The arm itself is 2" square tube like I said earlier, I put a small upwards bow on the arm because as it takes weight it will sag. Metal is strong but all metal bows. This was done by cutting a slit in the metal like I did with the bumper and rewelding it so there is a slight upwards track to the arm.

I tested it the only way I thought reasonable to do. I sat on the arm 90 degrees out from the vehicle, the weakest the arm can be. I don't recommend this as I nearly died on that swing out arm since there were no stops and it had fresh bearings in it. You can see even with my 220 lbs it bowed the bumper down. This was partially because at the time of the test I didn't have the bumper fully reinforced.

The latch

The toggle is a locking toggle I ordered from McMaster-Carr. Its mounted on an angle to the receiver. This is done so the arm is pulled in both directions into the holder locking it into position. Both the receiver and the arm have a 1/8" thick stainless steel plate lining them since paint would constantly be worn off. Others have used plastic here and plastic is quieter. It was simpler for me to weld on a strip on either side. Much later I put a ramp on the receiver side of the latch to allow the bumper ride up into the closed position.

The assist

You don't want this arm singing all the way out and knocking out a tail light likewise you don't want it closing on you. Both of these can cause vehicle damage or bodily harm. Many people choose to use a drop in a pin to lock the swing arm open and have a mechanical stop to keep the swing arm from going too far. I chose to use a gas strut. I chose a 240 lb gas strut to hold my arm open, I chose this much as it can hold my arm open on if I am on a 30 degree angle, also with the leverage of a 5 foot long arm it takes around 40 pounds of force to close the door, it is not a small amount but its easily done.

The swing out is designed to hold a tire and either jerry cans or a cooler now time to design those parts.

Tire carrier

The tire needed to be positioned as far over to the driver's side as possible to allow room for the can/cooler mount. I also opted to have the tire closer to the pivot because it will always be mounted. The can/cooler will not always be in position.

The carrier itself was a simple 2" square tube that mounted up to 2 1/2" square tube. The 2 1/2" square tube was carved out so it would slide over the 2" tube so I could get an angle I wanted and a significant amount of welding around the joint. I put the tire on a bit of an angle so I could get some load over the swing arm not having it all 6-7" out. I also added 2 diagonal supports to help strengthen the beam holding the tire. The plate is some more of that 3/8" plate I used to make the main mounts for the bumper. The studs are welded to the back of the carrier can easily cut off and can weld new ones on if they get damaged. (they have)

The Can/Cooler tray

I wanted to make the tray itself as light as possible everything not directly holding the cans/cooler up is flatbar. It is tied into the main tire carrier but unlike some people's carriers I couldn't have any supports at the far end because it would block my license plate. I chose to have 3 supports hold up the can holder and it has done fine for a few years now.

I would suggest you slowly load up the rear carrier and see how it handles on your vehicle. I posted this article like nearly everything went as planned but I did slowly load the rear swingout and over a course of a few weeks added the supports to the bumper that I posted over time to stiffen the bumper. I also removed a tie rod I made that tied the swing out to the rear door, cool in idea but horrible in practice. It was so due to the insane mass of the rear door, and swingout while it was on I never wanted to open my rear door. I chose to use a gas strut in the end and it has been great.