Modern Off-road Trailer Build

[mhnudi]

Hello all. First post here and first time going through the diy teardrop/camper build myself. My wife and I have been wanting to build something to go on longer trips with us and our two dogs, and it finally seemed like a good time to get started. We really liked the general design of the Polydrops trailer, so this build is going to be themed after that.

A few things we want in the finished trailer:

- 500ah LiFePo4 batteries w/rooftop solar
- 12v air conditioning unit
- Hot water for outdoor showers and heated cabin
- 12v refrigerator
- Induction cooktop
- Storage
- Interior and exterior lighting
- Fresh and grey water tank

We’ll be packing a lot in here but we’ll see if it pans out during the build! The first step was to get the trailer built. I started off with some 2x2” tube stock from the local MetalSupermarkets here in Charlotte. Most of the stock is ⅛” wall thickness, and the main 12’ long beam is 3/16” wall. To weld the frame I’m using the Harbor Freight 140 multiprocess welder in MIG mode.



To cut the metal I’m using that harbor freight horizontal bandsaw. This thing isn’t going to win any awards but for $300 it did a nice job with a little bit of setup. Here I’m using the level which had been zeroed against the cutting base of the saw to make sure the cuts were perpendicular.







One of the key items which I got for this welding project was the fireball tool mega square. This thing is amazing to prevent those off planer welds I would get sometimes on past projects, particularly when I didn’t have a flat work surface. I have been eyeing one of these for a long time and glad I finally took the plunge.


Lots of tacking…


Another great Harbor freight purchase is these little 3ton daytona jack stands. $30 a pair and they worked great to elevate the frame while I progressed with welding everything up.


Decided to add some plates to the 3 main joints at the front of the trailer for a little additional strength. This is ¼” steel plate I cut out using cutoff discs and the angle grinder.




Welding on the after chain attachment points


At this point I skipped a few steps and did the rough installation of the timbren suspension.




The base trailer frame was now completed and it was time to add on the front and rear extensions




Just a few planning diagrams for some of the angles on the front of the trailer. This was done using the ipad app shapr3d which is a fully featured CAD program for ipad users.




Rear extension tacked in before welding




And the front extension welded in place. At this point the trailer structure is complete.


After grinding all the top-surface welds, I started with a self-etching metal primer on the frame. Doing one side, then flipping after 24 hours and doing the other.


For the coating, I decided to go with the spray-on Raptor liner. It was easy to apply and seems to be pretty robust.


At this point, the lining was complete and the timbrens were installed and properly torqued to spec. At this point I mounted the cross member support and bolted it in place.




Started on the wiring for the tail and side marker lights. I was particularly proud of this wire routing through the tube.




And here’s just an initial preview of the overall shape and some interior components as I’m working on the build plans. Lots more planning to do, but happy to have a trailer base that’s finished and ready to build from.


Thanks for looking!

- Matt

[Capebuild]

Very nice..... nice job! I had thought about getting one (or 2) of those Fireball squares, but never did. They look handy. And that Raptor paint finish looks great.
Again, nice job!

[mhnudi]

Very nice..... nice job! I had thought about getting one (or 2) of those Fireball squares, but never did. They look handy. And that Raptor paint finish looks great.
Again, nice job!

Thank you! After using just one of these squares, I’m thinking the next time I do a welding project I will probably grab the largest version of the one that he sells. I particularly like being able to get to the inside of the corner as well while welding.

I have never used the raptor liner before, but based on the reviews I’m hoping that it holds up well enough. It has a nice professional finished look to it so I’m interested to see how it holds up!

[mhnudi]

I’ll try to post these periodically with a list and links of all parts that have been used in the build. Note these are NOT affiliate links of any kind, I just buy a lot of stuff off of amazon due to limited availability nearby.

Trailer and Suspension
Timbren Suspension - https://www.etrailer.com/Trailer_Axles/Timbren/ASR2KHDS02.html
Ark Articulating Coupler - https://www.etrailer.com/Straight-Tongue-Trailer-Coupler/Ark/AR44FR.html
Idler hubs (toyota wheel pattern) - https://www.amazon.com/dp/B088ND7XXN?psc=1&ref=ppx_yo2ov_dt_b_product_details
Toyota style lugs - https://www.amazon.com/dp/B07FVF28SR?psc=1&ref=ppx_yo2ov_dt_b_product_details
Curt weld-on jack - https://www.amazon.com/dp/B004QEM7HK?psc=1&ref=ppx_yo2ov_dt_b_product_details
Curt weld-on hitch receiver - https://www.amazon.com/dp/B001GN6L4Y?psc=1&ref=ppx_yo2ov_dt_b_product_details
Weld-on safety chain retainer - https://www.amazon.com/dp/B091G2JSBT?psc=1&ref=ppx_yo2ov_dt_b_product_details
Raptor liner kit - https://www.amazon.com/dp/B01CKE7B1E?psc=1&ref=ppx_yo2ov_dt_b_product_details
Safety Chains - https://www.amazon.com/dp/B07GF2PG5Q?psc=1&ref=ppx_yo2ov_dt_b_product_details
Grade 8 Hex Bolts - https://www.homedepot.com/p/Everbilt-1-2-13-x-3-1-2-in-Zinc-Plated-Grade-8-Hex-Bolt-810118/204225710
Grade 8 Washers - https://www.homedepot.com/p/Everbilt-1-2-in-Yellow-Zinc-Grade-8-Flat-Washer-3-Piece-807128/204276487
Grade 8 Nuts - https://www.homedepot.com/p/Everbilt-1-2-in-x-13-in-Zinc-Plated-Grade-8-Hex-Nut-816468/204275970

Trailer Wiring
7 pin wiring harness & junction box - https://www.amazon.com/dp/B07L8Z88XK?psc=1&ref=ppx_yo2ov_dt_b_product_details
Trailer side marker lights - https://www.amazon.com/dp/B01N5PWDHG?psc=1&ref=ppx_yo2ov_dt_b_product_details
Trailer rear brake lights - https://www.amazon.com/dp/B07V7BF18S?psc=1&ref=ppx_yo2ov_dt_b_product_details
14 gauge trailer wiring kit - https://www.amazon.com/dp/B00L3LKURI?psc=1&ref=ppx_yo2ov_dt_b_product_details
Self-drilling screws - https://www.amazon.com/dp/B00GYL9C1W?psc=1&ref=ppx_yo2ov_dt_b_product_details
Cable wrap - https://www.amazon.com/dp/B07FW86XV6?psc=1&ref=ppx_yo2ov_dt_b_product_details
Heat shrink tubing - https://www.harborfreight.com/42-piece-marine-heat-shrink-tubing-67598.html
Insulated clamps - https://www.harborfreight.com/18-piece-rubber-insulated-clamp-assortment-67657.html
Heat shrink butt connectors - https://www.harborfreight.com/30-pack-watertight-heat-shrink-butt-connectors-66729.html
Wire terminals - https://www.harborfreight.com/520-piece-terminal-set-67686.html
Rubber grommets - https://www.harborfreight.com/180-piece-harness-grommet-set-67582.html

And finally, here are the overall dimensions on the trailer base (units here are in inches)

[Onajourney]

Looking great mhnudi! That is some frame. Wondering if you weighed it? Thanks for adding the parts link and that frame wiring is pretty impressive.

[mhnudi]

Looking great mhnudi! That is some frame. Wondering if you weighed it? Thanks for adding the parts link and that frame wiring is pretty impressive.

Thanks! I have not explicitly weighed it yet, but based on the metal invoice which included total weight from the metal supplier, I would estimate that it’s around 450lbs based on the amount of remaining material. I’m expecting that the total build will be on the 2000-2500 pound range, but will have to see later on.

[JasenC]

Nice trailer fab.

For some of us this is a 10lbs of crap in a 5lb bag scenario, I went through 7 designs trying to get it all in there.

[mhnudi]

A few more detail photos of the wiring for the tailgate and marker lights:









Up next is building the floor. First is the bottommost layer which is a 3mm thick panel of corrugated aluminum composite panel (ACM). This should provide a completely waterproof base that also adds a lot of rigidity:



After that I’ll be building the framing inset ¾” form the edge of the ACM paneling to allow for a mount point for the walls. I plan for this to be 2” thick and filled with 2” solid foam in all of the openings.


After that, I plan to cap it with 7/16” plywood. Hopefully will have the floor built out over the next week or so.

[JasenC]

Is it san optical illusion or is the side not flat, I'm seeing 3 panels coming to a shallow point over the tire.

[mhnudi]

Is it san optical illusion or is the side not flat, I'm seeing 3 panels coming to a shallow point over the tire.

That’s right, the sides will come to a point to add a large insulation buffer on the side walls and also just add to the aesthetics. I’m not 100% sure I’ll go that route but if I can figure it out I will probably do it.

[JasenC]

Is it san optical illusion or is the side not flat, I'm seeing 3 panels coming to a shallow point over the tire.

I’m not 100% sure I’ll go that route but if I can figure it out I will probably do it.

You could place a board at that point and attach a block to create your junction point and then pull string lines from each perimeter location back to the point to help sort it out, plus you can easily move around the layout till you get it just right before you commit materials to it.

Mine changed 5 mins into starting on the floor, and there's a few more up coming changes as well.

[mhnudi]

Up next was cutting out the 3mm aluminum composite paneling and rough aligning it on the base. The ACM is pretty impressive and the result is a relatively rigid structure considering it’s thickness. I aligned the cutouts to minimize the amount of panel seams which don’t directly sit on a solid piece of the trailer. This is going to get seated with VHB tape and then sealed with zip sealing tape on the top side seams.

The track saw makes this work much easier and helped with quickly templating out the wheel well cutouts. Once I get this secured I will move on to the wood frame of the base.

[ukh87]

Interesting build and I love it. Just out of my curiosity, where are you planning to throw a 500Ah battery?

[chopperwalker]

Nice looking build. Are you planning to use ACM for the exterior walls as well?

There are some very cool things you can do with ACM and v-bit in a router. It allows you to fold seems easily at corners or just general bends for design features. I'm guessing from your design that you might be aware of this and/or planning for it.

[mhnudi]

Interesting build and I love it. Just out of my curiosity, where are you planning to throw a 500Ah battery?

The plan is to have them along with all the other electrical components in a slim compartment between the interior of the trailer and the kitchen in the back. It will include the AC unit on the bottom, then another tier with the batteries, inverter etc. mounted above it. This will leave enough room in the main sleeping area for ~a queen size mattress (a little wider on the sides). I'm working on a more detailed interior plan but the initial layout seems to indicate that they will fit, and the weight will be aligned along the wheels for balance.

The left here is the combination hot water/cabin heat unit (similar to the Truma combi unit), and room on the right for a Dometic CFX3 55 fridge.


Here, the bottom is the floor-mounted AC unit, and above is the approximate size for 5 100ah wired batteries.