a1gemmel builds an offroad trailer from scratch

[a1gemmel]

So I kind of flipped a coin to decide which forum I'd post this build thread on. Landed on FR4x4, so either sorry or you're welcome based on your interest in trailer fabrication.
Here's what we're doing:


I need a trailer specifically for a group camping trip coming up, and more generally to fit my outdoorsy needs.
The requirements are roughly as follows:
- sink and hot water, with 10 gallons of water storage
- propane cooktop
- 12v fridge
- onboard air
- 100 watts of hard-mounted solar
- 1000wh of battery capacity
- storage for camping gear
- ability to follow my pickup on 37s through reasonable trails
- future possibility of adding an overhead rack and rtt
- not look like trash on wheels

I've been gathering up bits and bobs and have most of what I need to knock this thing out, so let's get started.

First up, I welded a receiver onto the 1/4" wall piece of 2x2 tube that's going to make up the spine of the trailer. This is massively overkill, but enables pulling doubles or recovering other trucks with a rope off the trailer if push comes to shove.



The next step was to yadda yadda the whole 4'x5' frame construction and forget to take any photos. Note the recesses on the rear of the frame for access to the hitch pin.



I dug around in the Strategic Toyota Reserve (or as my lady calls it - the pile of junk in the side yard) and came up with some leaf spring hardware and a pair of stock leaf springs from the front of my '81 pickup.




The empire of dirt also yielded the right size tubing to accept some leaf spring bushings I cut down in the trusty mini-lathe, and some square tube to make hangers out of.





A critical part of the process is to break your holesaw arbor, fix it in the lathe, then rip the threads out of your holesaw, then weld it onto the arbor. Don't forget this step. Profanity isn't strictly necessary but does help.



All tacked up on the frame. I'm using a 4" drop axle flipped as a sort of trailer portal axle, this gives the trailer axle on 31s roughly the same ground clearance as my truck on 37s. I may switch to spring-over-axle once I get it more fully assembled and right side up to take measurements. The u-bolt plates that came with the axle won't work with the width of the Toyota leaf springs so I need to fabricate some first.



That's all for now, thanks for following along!

[a1gemmel]

Next up... took a leaf out of the pack, made a new pin.



Made some passable u-bolt plates - I've drilled the plate with the option to push the axle back 1.5", which I am doing.




My axle is a custom order 3500lb 4" drop axle at 62" wide. I had to order the 6x5.5 hubs from another source and assemble it myself as I couldn't find any vendor that offered this combo. All in about $300 for the axle and hubs. Once I'm closer to completion I'll post a complete parts list with costs for anyone interested.



The trailer is now trailering... except for a tongue. It's on a set of 31x10.5R15 on stock steelies from the same '87 4runner part-out that donated the suspension hardware.

[TjMike]

Following. Have always thought about an off road trailer and just assumed I'd be buying one.
Looks great so far and really looking forward to seeing your progress.

[Mountaineer01]

Agreed, this looks awesome, excited to see the progress and the end result!

[a1gemmel]

Thanks guys!

Yeah, I looked at buying built offroad trailers but I just can't justify the price. Starting with a utility trailer is also an option but after looking at marketplace for a while I just didn't find anything that was the size I wanted and heavy duty enough for the use case.
This is a project where I'm happy to spend time instead of money, fabrication is fun and I get to try new things.

Mounts from my parts bin and some used shocks will complete the suspension system. They're at a fairly weird angle but I think they'll be good enough for a trailer.







Lookin' good! The ball hitch is kind of temporary, I'd like to make some kind of swivel hitch using leaf spring bushings and common hardware.

[Jim]

Good progress!

[xaza]

I used Lock N Roll for the hitch on my trailer and love it. It is very quiet and does not bind up.

https://locknroll.com/

[a1gemmel]

I assembled what will become the "roof" of the trailer by fitting it up clamped to the frame. I missed taking a photo of the million clamp moneyshot.



The front half gets some bracing as it'll be load bearing for luggage or the moose I hit with my truck.



That assembly now disappears into a corner of the shop for a while as I finish up the frame - I have a few things where I need to flip the frame over to weld the underside, and I want to get that done before the trailer gets too heavy.

The front half of the frame (which will be the storage area) gets some bracing in advance of welding the floor in.

[a1gemmel]

A while ago I snagged a whole pile of steel shelving off of marketplace for a song and a dance. Although I had to buy a lot of the longer pieces specifically for this project, much of the bits and bobs and shorter pieces come from buying lots of off-cuts from local fabrication shops and squirreling them away in my stockroom. If you want to build stuff out of steel without spending a fortune, this is the way to do it. These particular steel shelves will get to live out their retirement serving as the floor of the trailer.



As a nice side-effect, the powdercoat on the shelving is a fantastic coating for protecting the bulk of the floor.

[TjMike]

The trailer is looking great and you're making good progress. Good idea with the steel shelves. Have the keep that for future projects.

[a1gemmel]

Next up - fenders.







The fenders will eventually bolt to the frame, that will happen later in the build.

[TjMike]

Looks great. Are you worried about the weight at all? Aluminum comes to mind.

[a1gemmel]

Well since you asked I went out and weighed it...

The fenders weigh 9lbs each. Everything you've seen so far weighs 398lbs. Probably over half of that is the wheels/tires/axle/springs.
She's not going to be the lightest trailer, that's the truth. My TIG machine doesn't do AC so I didn't plan for using any aluminum in the construction. I suppose I could skin it in aluminum using glue+rivets, but the simplicity of all-steel construction is pretty appealing too.
Composites and aluminum are something I'd like to play more with, but probably not on this project.
I'll try to remember to weigh everything once it's ready for paint so I can report the weight breakdown by suspension/construction/components/etc

[TyTheJeepGuy]

Fun fact, the steel shelves also live on as the cowl on my J10 hood that a1gemmel made for me

[a1gemmel]

Let's build some levelling jacks. Why? Because I want my omelets to come out perfect no matter how rough the trail is.

First up, embiggen an rv stabilizing jack.



Some bracing gets welded in, and two drilled and tapped plates.



And... deployed! These use a bar through the holes to gain leverage for extending the legs and jacking the trailer up.



Next I decided to make a completely unnecessary recessed mount for a trailer plug. This uses a bit of exhaust tube crushed into an oval. I didn't put the plug in for a photo because I'm pretty sure once it's in it'll never come out again.

[TjMike]

Like how you're not only building a cool trailer but having fun with it with little details like that absolutely unnecessary plug mount

[a1gemmel]

Gotta make all the other trailer guys jealous somehow!

I got these LED bars in an auction lot a few years ago, so they've marinated on a shelf long enough that by project math they were technically free. They get installed under the floor with rivnuts to serve as rock/camp lights.



Next, I picked up an articulating hitch kit at Tractor Supply (some assembly required). Total cost about $40, all the dimensional steel and plastics are salvaged from my empire of dirt.



Made some parts:



As is tradition, I broke the hole saw again.



Big thanks to forum lurker lyapunov for letting me use his big lathe to make some delrin bushings.





The vehicle side gets assembled - the bolt clamps on the steel sleeve inside the bushing, so the bolt can be torqued down tight and all the swiveling happens with the bushings.



The longitudinal axis does rotate on the bolt, so the nut is welded on solid. That does make this part non-serviceable, but I can make another pretty quick if I need to replace it. There is a grease fitting to keep it lubricated. This uses the same 3" spacing as my ball hitch tongue, so it can be swapped in if needed.



The two assemblies are married with a removeable 7/8" pin. The vehicle side can be unbolted and placed on a different drop/rise hitch mount (or flipped upside down), and the trailer side can be flipped to ride under the tongue, with these options I can configure the trailer to tow level behind different vehicles.



How strong is this? I can start with estimating each axis, since I'm using standard fasteners and can look up their properties.

Horizontal axis: 1" Grade 8 bolt in single shear: 0.606in^2 * 150,000 psi * 60% = 54,450lbs

Vertical axis 7/8" SAE 1020 pin in double shear: 0.601in^2 * 55,100psi * 120% = 39,738lbs

Longitudinal Axis:1" Grade 8 bolt in tension: 0.606in^2 * 150,000 psi = 90,900lbs

In all reality, something else will fail before those numbers. I mean, a 2" hitch mount only uses a 5/8" pin so that's pretty much guaranteed to be the fuse before these fasteners. I suspect the weakest link is the trailer side of the vertical axis, with the tube welded to the bolt head. I did reinforce it with a second layer of steel and there's ~10" of blazing hot weld mating it all together so I'm pretty comfortable with it... I think it'll be fine unless I try to snatch a semi out a snowbank off the back of the trailer. Maybe I'll go hook it to a tree and see how much I can stretch my kinetic rope out as a proof test.

[Jim]

Those LED lights work out to project-free in my book. Or - you purchased them years ago with this exact project in mind.

Nice hitch.