High Alpine Cabin on Wheels 7X14 Cargo Trailer Conversion

[PbCabinOnWheels]

The goal is to provide a tiny home on wheels for seasonal work in the Colorado Rockies. The trailer is going to be driven from the homebase in Portland, OR to the worksite in Colorado 1-3 times per year with each work-season lasting approximately 3 months. Ideally the trailer should be able to accommodate the 3 month stay on-site with no need to drive to town for provisions. The site is located at high elevations (10,000+ ft) and will need to operate in all seasons.

For some background, I have been offered a seasonal job located just outside of Leadville, Co. My wife and I currently live in Oregon so I will have a home base and shop to work on the CTC. This is not a full-time (365day) build as I will be returning home multiple times throughout the year. However, each stay will be long-ish at 3 months. I have a place to park the trailer at the work site where shore power, water and sewer will be intermittently available but not guaranteed. There is a yurt on-site as well which is heated and quite comfortable year round so if the CTC has some catastrophe I can stay at the yurt if there is any failure or whatever.

This is my first build for something like this and I expect it to be a rather challenging one. I am going the CTC route because I don’t trust the pre-built travel trailers and have always been a DIY kind of guy anyways. For now I have access to a shop which I can use to build this out.

I am looking at a 7 X 14 Interstate Tandem Axle LoadRunner Cargo Trailer as my starting point. To be towed by my 2014 Tacoma with the factory tow package. Tacos are fairly anemic when it comes to towing with a max tow cap at 6,500lbs and a easily overloaded rear axle. I don’t want to go over 4,000lbs fully loaded just in case. I think I am pushing the limits with the 7X14 trailer which is listed to have a dry weight of 2,100lbs but I think I’ll need the space. Especially considering I am planning on putting everything within the insulated interior (no external tanks). Also, my wife is giving hints that she is super jealous and may join me inside the unit in the future adding more need for space.

I plan on putting my build progress here. So I can share and get feedback. Thanks for looking!

Initial concept sketch:

[PbCabinOnWheels]

I bought the trailer and got it home safely. First time ever driving a trailer so I white knuckled it all the way home through rush hour traffic. By the end I was gaining confidence.



The first thing I did was tear down the paneling to prep for insulation.



All walls removed.


Next I am going to put 1" furring strips in to fit a total of 2" of insulation panels in the walls.

[PbCabinOnWheels]

The build is mostly finished and i've moved the rig from my home base to the over wintering spot in the Flat head region of Montana. Life managed to kick me in the ass during the build so I didn't have any time to post updates as I was going along. I did however take ~100gigs of pictures and videos of the build that needs to be edited and organized. I'll post a detailed breakdown of everything i've done in this thread.

Here is a brief look at what I slapped together.

[PbCabinOnWheels]

Here is some CAD work. Since I tore the whole trailer apart I took the time to map out the location of everything on the trailer down to the mm. It's been extremely helpful.

[noseoil]

Looks nice & functional for your needs. Did you get a rolling weight on it yet? I'd go with empty tanks for the mountains & towing, every little bit helps when towing in higher elevations. From sea level to our new elevation of 6,500' here in Raton we lose about 18% of our horsepower (3% per 1,000' is the rule of thumb). On Monarch pass this summer in Colorado this summer it was 11,200' at the summit, so use your imagination...

Not sure how the Taco will like pulling at those elevations with the load, but if the rear end is sagging a bit with the full load, think about a pair of airbags. We added these to our Nissan Frontier & it's a great addition for towing. Basically, we would load the trailer & hook up, add the stuff in the bed of the truck, then check the read end "squat" with a stick I kept in the glove box. I cut a stick to length to go between the top of the tire & the inside lip of the fender well. If it was too low (yes, it usually was) I'd hook up a bicycle pump to the air fitting & my wife held the stick. I'd just put a few pumps on the 'bag until it was back to level again, do the other side, then we were ready to leave.

I went to the 2019 Ford Ranger with the EcoBoost motor (only a 4 cylinder, but...), after I was towing in the mountains of Colorado this year with the teardrop. The 4 cylinder Nissan wasn't up to the task in those high hills & long, steep grades. It would do the job, but I didn't want to beat an older 2007 truck to death while towing. Your Taco with the V6 motor may do a bit better than the old Nissan, just watch temps on those grades & give it a rest if you need to on the long pulls. Hopefully, you have a brake controller on the truck, you'll need on for the down-hills with that much weight. Best of luck!

P.S. Take a look at an Intel-NUC computer if you need to upgrade at some point, it will shave off a lot of weight & take less space from your area (4" X 4" X 2"), also draws less current than a desktop or typical laptop (https://simplynuc.com/8i3behfa-full/).

[PbCabinOnWheels]

Another view from the back

Did you get a rolling weight on it yet?

Fully loaded (tanks full, food stocked) was 4350lbs with 500lbs on the tongue. First stop out of the shop was the weigh station then straight to the mountains after. Took the time to take it off the hitch for proper measurements on the tongue.

Dry curb weight Taco:
Front Axle: 2000lbs
Rear Axle: 2000lbs

With trailer hitched and truck loaded with supplies:
Front Axle: 2450lbs
Rear Axle: 2950lbs
Both truck axles: 5450lbs
Trailer axles while on tongue: 3850lbs
Trailer axles while off tongue: 4350lbs

I am still trying to wrap my head around the physics on these measurements. But I think I got the basic numbers right. The above numbers are just read straight off the billboard at the weigh station.

The Taco handled it just fine, except for the 9MPG I was getting. I do have an after market brake controller which definitely helped. I have no way of checking temps which I am kind of wishing I could. Not because I am worried but mainly because I am a nerd for such things. I got the tow package which comes with an extra intercooler just for these kind of things. I have no idea if it actually does anything though because I can't measure.

think about a pair of airbags

I have considered this but had some reservations.

I think I am loosing about 2in in the rear when she is hitched up. Noticeable while driving but not by much. I am skeptical of modifying the suspension while I am in spec according to the manufacturer (taco max is 650lbs on the tongue). I know air bags are super popular but I am not sure they actually "do" anything if that makes sense. Sure they will level out the rig but your losing movement in the suspension, right? If you tighten up the suspension I feel like that must put more strain somewhere else in the system. I don't really care that I am riding high in the front as it doesn't seem to impact handling. If there is no added safety to the airbags why should I go with them then? They can't shift weight to the front axle like a WD hitch would so it shouldn't improve steering or braking performance. So beyond just the physical leveling of the truck what do they actually do?

Take a look at an Intel-NUC computer if you need to upgrade at some point

It's funny to me that you mention these because I am leaving behind my old job as an engineer for Intel so I am definitely familiar with the NUCs. I was on the team designing the CPUs for them (sorta kinda whatever...). I am afraid I am too addicted to my beastly PC though. Over clocked+Liquid cooled all that snazzy sh**. She eats up about 1000watts when I get it cranking. A power hog for sure but it also functions as a space heater so I got that going for me when I get shore power.

[noseoil]

"I think I am loosing about 2in in the rear when she is hitched up. Noticeable while driving but not by much. I am skeptical of modifying the suspension while I am in spec according to the manufacturer (taco max is 650lbs on the tongue). I know air bags are super popular but I am not sure they actually "do" anything if that makes sense. Sure they will level out the rig but your losing movement in the suspension, right? If you tighten up the suspension I feel like that must put more strain somewhere else in the system. I don't really care that I am riding high in the front as it doesn't seem to impact handling. If there is no added safety to the airbags why should I go with them then? They can't shift weight to the front axle like a WD hitch would so it shouldn't improve steering or braking performance. So beyond just the physical leveling of the truck what do they actually do?"

The main reason to level the suspension while pulling is to put the vehicle back to its original or "factory" geometry for steering, handling & braking. It doesn't restrict suspension movement or transfer the load to other parts of the truck (other than the air bag itself, the frame which has the springs attached already & the axle tube), it simply beefs up the rear springs a bit to help with the additional load. It would be like adding an extra leaf to the spring pack for towing, then being able to remove it when it wasn't loaded & you were just doing normal driving. Essentially, it's like upgrading the rear suspension to compensate for the added weight & is infinitely variable for loading. To me, the real benefit comes from the ability to "tune" the rear end for changing load conditions. If you take the load off and go back to a normal unloaded weight, the rear end can be dropped for factory level & there is no down-side to the air bags as they just sit there waiting to be used again for the tow (the Firestones required a minimum of 6# of pressure in their resting mode, which didn't do anything to the ride or suspension).

The old Nissan was sprung fairly soft & after the additional coolers, canopy, dutch oven, generator, etc. etc. etc. for camping or a trip to Bonneville, looked a bit sad when fully loaded. There were a couple of times when loaded, where we actually bottomed out on the frame bumpers, hence the addition of air bags. The Taco is more likely a stiffer suspension for loads.

If you're only dropping 2" with the total load, then I'm not sure it's really necessary unless you want to level it. It sounds like you have done the required weights to see where you ended up with loading. I've seen too many vehicles with a trailer towing with the wrong attitude & there are problems as a result, which could have been remedied with a simple upgrade. Next time you're out, take a look at some of the rigs around you that are towing and ask yourself how much control they have if there is some high wind, bad driving conditions or panic stops involved.

P.S. If you're drawing 1,000 watts with your current system, the Nuc would be maxed out & most likely would be a puddle on the desk at some point!

[PbCabinOnWheels]

I am working on a Youtube series for my build. I guess I might as well throw the links here on this thread in case anyone is interested. Please note I am not an expert on this and I highly suspect I did a lot of stuff wrong without even realizing it. So don't take this as a definitive guide on CTC building but merely as a log of my journey so far.

Here it is with as much detail as I can muster into a video format!

[PbCabinOnWheels]

Ep.0 - Teardown

In this video I am talking about how I tore down the trailer and planned the layout.

[PbCabinOnWheels]

Ep.1 - Roof Racks

How I installed my aluminum roof racks.

[PbCabinOnWheels]

Ep.2 - Windows

Here is how I installed the three windows.

[PbCabinOnWheels]

Ep. 3 - Sealing

Here is a breakdown of how I sealed the trailer against the elements.

[PbCabinOnWheels]

Ep.4 - Furing

Here is how I doubled the thickness of the walls by welding furing strips.

[PbCabinOnWheels]

Ep. 5 - Hatch

How I installed the simple electrical hatch.

[PbCabinOnWheels]

Ep.6 - Vent

I choose a Fantastic vent fan Model #2250 to put in the trailer.