Oregon Trailer inspired build M116A1 Platform

[aharrow22]

After finding my M116A1 platform back in May and just sitting for 6 months, I decided to use the Christmas season and slow period at work to start on my trailer build. It has been a on again off again build since then with some great progress the past two months. I am gearing up for the maiden voyage to the mountains of North Carolina this fall so with the summer slipping away I am trying to step up my game. I just got around to posting on the forum.

I have used this forum for some great information and learning tools and made plenty of mistakes on my own. Anyone that wants to join me on this journey and is looking at the military platform as a potential starting point, I welcome to follow along.

My inspiration was from Oregon Trailers, love their product, the build quality, ideas and touches that they added, and would have loved to have purchased one, but they are way out of my price range. To their credit they have some great videos on their website.

Here is the Terra Drop that I used as a starting point when designing my trailer.


For the most part I am pretty flexible and this build has been fluid in the decisions that have been made along the way based on my lack of experience in building trailers and research of what I thought I wanted and maybe what I actually will end up with.

So my main requirements were something that was off road capable and rugged that I could put the same wheel and tire setup as my wife's Toyota 4 runner.
- AC and DC power for off grid, shore power hookup when available and future expansion to solar if desired
- Water tank and pump for sink and shower expansion if desired
- Full kitchen galley with plenty of storage
- Cooler for now, potential fridge expansion if desired
- Propane grill
- Queen bed
- Tongue Box to house electrical and storage
- Possible RTT in the future

So I picked up a Army surplus M116A1 trailer from a military guy here in Jacksonville, FL. She sat here for 6 months.




until I swapped out the axle for a Dexter 3500lb and bought the same wheels and tires on the 4Runner. Bringing her home

[aharrow22]

In a perfect world I would have had the local welding company tear off the metal platform that was welded on as it was slightly off level and build me a metal frame for the teardrop. I battled with the decision of wood vs aluminum frame and decided that because I know nothing about welding and I am skilled at woodworking that it was the best route to go for me. Also budget was tight and I could overcome these issue by putting down a new floor and shim the areas that were off.

Starting the frame






So the overall dimensions are 66" wide and just under 10' long. My two big mistakes were not accounting for the mattress to be on top of the wheel wells and the width of the trailer and sheet metal that comes in that size. It wasn't until I went to buy the sheet metal that I found they only come in 49" widths. So for the roof, I had two seams which isn't a huge deal but I would have preferred no seams because of the look and the potential for leaking.

The Bed issue didn't come up until my wife pointed it out AFTER I had framed the entire trailer and was under sheet metal. I realized I had measured headroom from the floor instead of building above the wheel wells. So now when I buy a Queen mattress at 60" x 80" I will have to cutout the foam for the wheel wells and we lose about 6 inches on each side. So the width of the mattress in the narrow part will only be 49" instead of 60". I told the wife it just means we need to snuggle closer.

[aharrow22]

And here began the next challenge, the hatch. Hatch 1.0 was built way too large. Here it is before skinning.





What happened was, when I installed it on the hinges to do a dry fit before skinning, it no longer lined up. I couldn't figure out why until I realized that it was way too large and was flexing as I raised and lowered it. Maybe the skin and aluminum would have tightened it up but I wasn't taking the chance, so I ripped it off and went back to the drawing board.

Hatch 2.0 became much shorter in overall length, so it wouldn't flex nearly as much. Also brought down the weight of the hatch and in the end was a challenge that I was glad we worked out now instead of later.





I also installed the kitchen sink and faucet. I also at this point figured out that I am not going to keep the cooler back here. I can't open the lid fully, so I am going to turn the cooler area into a counter top with storage underneath with pop up lids to access underneath. I will figure out the cooler situation later.

[aharrow22]

Moving right along, Hatch 2.0 was skinned and we cut out doors. If my trusty time machine was working, I would go back and not build custom doors. More on that later.







you can see the white aluminum sheet metal underneath the trailer ready for install



And finally ready to start putting this under skin. So most people skin the inside and do insulation, run wires, etc. and then do the outside skin.

I wanted to do the outside first for two reasons. One to test for leaks and I could easily do that with the inside open and not guessing where the leak is coming from. And two I wasn't ready to commit to what electrical fixtures I wanted and where. I am severely lacking on the electrical side and will have some questions for the community as I near those decisions. Also I wanted to take this out in the wild and use it so I could decide on things I might want to reconsider or didn't think of. I.e. I really should have done "x" but now that the inside is all finished I can't run wires for that or change it. This gives me freedom to do so.

First sheet of aluminum taped and ready to cut out.


First routed edges. Holy smokes that was crazy. I read many articles about eye protection and the metal flakes but man was it raining hot metal, even with my protective gear on.







Fully under skin and ready for a test run around town

[aharrow22]

SOOOOO Glad I did the outer skin first. Had two leaks, one was so simple from not putting in silicone on one of the screws on the roof. Easy fix but I would have never found that if the skin was on. The other was the hatch at the corner where water runs off. I simply forgot a piece of rubber trim on the underneath along the hinge. Easy fixes for both and we were good to go.

Now we come to the section on the doors that hold a special place in the pantheon of curse words I never knew before. This presented my first major hurdle and was so problematic I was ready to throw in the towel at one point. My door once cut out, warped slightly so there was a gap in a few spots where the door met the trim ring.

I was cursing myself that I should have bought the prefab doors with windows but @ $370 each I just couldn't justify it. And building doors looked so EASY!

Once I installed the windows in the doors, I went through 3 different types of rubber trim until finally figuring out the correct one along with installing a drip cap above the door to divert the water. I was really hoping to not install the drip cap but unfortunately I had to. I also had to reshim one of the door hinges to try and close the gap on the passenger door. Certainly would be unacceptable for a professionally built trailer but hey I am an amateur and as long as it doesn't leak I am good to go.





And finally this brings me up to date with the tongue box build.

[aharrow22]

Here is the galley as we stand today. I am going to build a counter top for the area where the cooler was originally going to go. I have changed my mind on this because it is difficult to access the cooler as the lid doesn't open all the way. so I will either store the cooler in the back of the 4Runner at night and during the day have it tucked under the trailer or get a bear proof cooler like a Yeti or something. I am having a difficult time paying for a cooler at those costs but that will be a decision for later once I get out and use this a couple times and see how bad my current one is.





Picked this up at Home Depot for 60% off and it didn't have a scratch on it. It was in the return section so I asked the manager about it. It is larger than I wanted but for $40 couldn't pass it up.







Also I might make the one exposed cubby for the water pump or other electronics to hide not sure yet. The reason it doesn't have a cabinet door is the faucet I bought was too tall and a cabinet door wouldn't open. Ouch, poor planning there.

I also plan to get stainless steel sheet and cover the counter areas with metal instead of paint like they are now. The paint will never hold up and isn't food safe anyway. So I will next purchase the stainless to do that along with possibly the side walls with the left over. It only comes in 4 x 8' sheet so I think it would be cool to skin the white walls to add some protection and make it look more professional.

Items to tackle next:
- Tongue box completion - Plan to use Linex or some kind of truck bed liner roll on compound. Still researching. I will use diamond plate or get more white aluminum if the cost is agreeable but I think the best would be to LineX it from a durability standpoint and taking the abuse on the road.
- Electrical plan - I am going to need help with this and will warrant a separate post to get ideas
- Water tank and pump installation - Once electrical is done I can tackle this. for the 1st camping trip I will take water jugs.
- Propane installation - Most likely will mount it to the tongue box but I really want to mount it to the rear outside wall.
- Table construction - I want to make some tables that can utilize the ledge that runs around the trailer with fold down legs or something. I have a few ideas here but they would be storable when not in use.
- Mattress purchase - Plan to cut the mattress in half and cutout the wheel wells. This way I can fold the mattress when not in use and utilize the front area as a cargo trailer. I plan to put down rubber floor and tie downs along the edge that will be underneath the mattress when it is in use. This will double my trailer as a hauler as well by simply removing the mattress if need be. Gives me some flexibility.
- finish the cabinets in the sleeping area and insulate and skin the inside with flexible plywood or some other kind of material. Might look at getting some flexible foam panels for insulation and noise. Still researching options on this.
- Going to look at Roto packs for additional water storage or jerry cans. The military trailer came with Jerry can mounts so I would just need to paint them and get Jerry cans for water and fuel.
- Axe and shovel mount for the outside
- subtle graphics created from a designer friend. I work in the printing industry and can print some repositionable wrap material for free so I want to do something small and subtle. To be determined

[soapcreek]

Your build is looking really nice.


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[aharrow22]

Thanks soapcreek!
It has been a fun project. Trying at times and I am sure there will be more frustration as I progress.

Your build is looking really nice.


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[twisted lines]

Thanks for the Gally tutorial, answered so many unknowns for me; Nice build