DOKA Sprinter 4x4 build

[MLu]

I've been looking for the next step up from sleeping in the back of my Discovery II, but I think I may have skipped a few steps on the way...

I bought a 2014/15 dual cab (906.233) 4x4 flatbed Mercedes-Benz Sprinter. The idea is to build it up to be a four-person, four-season, four-wheel drive overland camper, used mainly in Northern Europe. Eventually adding on trips to Russian Karelia and the Kola peninsula, more of Europe, at some point perhaps Northern Africa and the pipe dream always being Mongolia and the 'stans. Compared to the disco, it's certainly no offroader, but driving it around some snowy fields and forest roads makes me fairly confident it'll take me where I need it to go, despite no low range. At least it's leaps and bounds ahead of my dad's RWD Sprinter ambulance-conversion when it comes to clearance, traction and angles.

Aiming at having an onboard hot shower, separating toilet, queen size(ish) bed plus dinette that turns into more sleeping, induction cooking. Looking to keep it electric and diesel only, no gas. No pass-through. All fluids indoors. All this on a 3665mm wheelbase with a crew cab and about 1100kg to work with.

At the time of writing, I'm fiddling with figuring out the layout of the camper so I can start getting quotes for composite panels (anyone know a good supplier in the Helsinki region, hit me up...). I was hoping to do it without an above-cab sleeping alcove, but that's probably not going to happen, so I'm likely to end up in the 3,5 meter height range, unfortunately. The current flatbed is 276cm, I'm looking at having the box end up at about 350cm with the last 50cm over a 45 degree angle, plus probably an alcove over the cab.





First question: do I REALLY need to engineer a three-point or other torsion-free subframe solution?

Between the cab (which I believe is fairly rigidly attached to the frame, please correct me if I'm wrong, but looking a picture I took it seems to be literally welded to the frame) and the rear axle is about 130cm, the total frame behind the cab is something like 240cm. The flatbed that's on it has what looks like a seriously stout subframe solidly bolted to the frame. In addition, the Mercedes Body/Equipment mounting directives (aka Bodybuilder's guide) clearly states that self-supporting bodies can be attached directly to the frame without a subframe, and that ALL assemblies must be attached to all factory attachment points on the frame. Best case scenario: removing the flatbed and subframe and attaching directly to the frame would save me at least 20cm of space; second best scenario: utilizing the existing subframe would save me from designing and building a frame and simplify the construction significantly by not having to make and work around wheel wells.

 

[MLu]

I'll just grab this space for later.

 

[MLu]

I ended up removing the flatbed, mainly for weight savings, and am installing an aluminium subframe. Since the whole front of the vehicle is solidly welded to the frame, and both frame rails come together in the rear with a solid chunk of metal, I decided to go with a standard subframe solution offered by a local truck outfitter. The subframe is solidly bolted to the subframe in the rear and middle, and in the front some thick rubber "washers" serve to give the subframe a little bit of room to manoeuvre.

I decided to go with 40mm fiberglass/XPS composite panels for everything except the floor, which is 60mm, with a couple of added birch plywood supports to attach the subframe. I have yet to order windows and hatches, that needs to happen pretty soon. Before that, I need to finalize planning the interior, and frankly I can't quite decide where to put the bathroom.



Below: Most important things first, of course; a raised air intake and some 255/85R16 Toyo MTs. Floor panel offered up to get a feel for the proportions. The overhang isn't too bad.


Below: subframe mock-up. It's really simple, literally just two rails with attachment points using M8 sized slots. The gunk is Sika underbody protection and cavity wax, the rust conditions around here are pretty brutal.


Below: typical Finnish spring. "I'll just pull out real quick so I have space to cut the frame rails"; cue instant blizzard.

 

[Bernhard]

Hi, I`m Bernhard in Oslo, Norge. I`ve just bought the same Sprinter 2014 4x4 doka 120.400 km and I `ve the same plans. I`ll get the car in beginning of August. My cabin will be made in Sweden by Orustvagnen, very good builders. I also want to save weight and hight. That's the status for your project? Best regards Bernhard

 

[MLu]

Apologies for the lack of updates. I've assembled the box, and went for a quick test run to the Lofoten islands. And took the kids for a short drive around the Finnish archipelago. No squeaks, rattles, hums, whistling or similar issues, thankfully. Right now, it's basically an empty shell, a rather ungainly tent on wheels as far as camping comforts go, but I had test it out.

 

[MLu]

Hi, I`m Bernhard in Oslo, Norge. I`ve just bought the same Sprinter 2014 4x4 doka 120.400 km and I `ve the same plans. I`ll get the car in beginning of August. My cabin will be made in Sweden by Orustvagnen, very good builders. I also want to save weight and hight. That's the status for your project? Best regards Bernhard

Hej Bernhard! The box took a lot longer to assemble than I anticipated, and if I did it again I would probably skip the alcove and work on a raised sleeping solution of some kind, even though it would be difficult to accomplish sleeping for four that way. The alcove adds a lot of extra work, and the wind resistance is pretty bad, as well as the height. It's about 3.2 meters tall, but will end up about 5-10cm taller with solar panels, roof hatches etc.

Currently working on figuring out the interior, the tech, and a good ladder solution to get in and out.

 

[MLu]

Parked next to another Sprinter; same model, wheelbase, color, but 2WD and on stock tyres.

 

[MLu]

This is supposed to be a build thread, so I should probably add some build pics. Below: I decided to vinyl wrap the box; it was expensive, time-consuming despite working with only flat surfaced, and resulted in various annoying mistakes. Time will tell how it holds up.


Below: glueing the aluminium profiles to the floor. I used Sika 221, with 207 primer on both the alu and the GRP, in addition to using an abrasive pad and cleaning using isopropanol. Before attaching, the glue is sprayed liberally with water. The pre-drilled holes are 5mm, and I glued spacers to the holes to give the Sika space and to avoid or lessen the "wave" effect when attaching the aluminium rivets. I decided more glue = better.


Below: excuse the mess. I started by attaching the subframe, the floor, then the front wall, then the sides.

Below: lifting the 450x210cm roof three meters up in the air went surprisingly smoothly, with a little help. I attached the aluminium to the roof before lifting it, to avoid having to work as much on a ladder, and to give a rail for the roof to follow when lifting it into place. Visible on the floor are the holes to the attachment points; about 20 stainless M8 nyloc nuts and bolts hold the floor to the subframe through the plywood reinforcements. The raised sections of floor accommodate the wheel wells.


Below: I then worked on the alcove; the floor and the front walls.


Below: next up; the rear lower 45 degree wall and rear wall.


Below: marking and cutting the door.


Below: making the door frame.

Below: getting the angles even kinda correct around the alcove was a pain. Mistakes compound...

 

[MLu]

I attended a meetup of an overlanding-themed Facebook group arranged by a local supplier of 4x4 stuff. There was, obviously, some offroad-stuff as well. The measured Ramp Travel Index of this particular Sprinter is a whopping 157 (a stock Wrangler will do 500-600), but we all knew this thing is about as flexible as.. well, a delivery van. All the off road people I talked to made various non-committed sounds in the theme of "sure you could try it I guess" on the subject of taking it up the "easy overland vehicle route". After a couple of failed attempts at getting up the very first obstacle, a bunch of people with a bit more experience and two trucks with winches made me think it was a good idea to give it another go, so I did.



Below: yeah, about that articulation...

Below: screenshot from a video clip


So yeah. At one point there were two vehicles with winches pulling me up a hill, at another point there were four people holding up the truck to keep it from tipping over and at some point I made the heavy steel C-channel rear bumper rather more banana-shaped than before, and I think I gave my poor clutch about two hundred thousand kilometers worth of abuse. And the interior looked like it had been through a blender. Did I mention this thing has no low gear and a manual transmission? The box held up well, there doesn't seem to be a single failure anywhere.

All that being said, I'm fairly impressed. It did far better than I had expected it to do, but it's definitely no off-roader. The articulation is non-existent, the approach angle is decent, the ramp-over is not brilliant, the departure angle is awful, the traction control system is garbage, and using first gear people had to run out of my way while I bumped and jumped over rocks behind them, but the short-ish 144" wheelbase and ok ground clearance makes up for some of it. An old Iveco Daily 4x4 with a smaller but similar camper box did the same track without so much as a hiccup and without engaging the lockers, so where the Sprinter was right on the ragged edge of what it is safely capable of, the Iveco was literally taking a stroll through the park.

 

[MLu]

Next, the spare tire carrier. I'm semi-consciously trying to avoid having to get into the water, heating and electrics, which are where my efforts probably should be right now.

I've looked at various ideas on how to accomplish this. The over-sized tire (255/85/16) no longer fits in the original space between the frame rails, so it needs to go somewhere. The roof? Too high. Under the camper? Doesn't fit, and where it does I might need to put other stuff. On the front? Not interested in figuring out the legalities of that, and will mess with the approach angle and winch. Inside? That space is too valuable to use for a spare, and it would mess with the layout.

That leaves the rear. The lower 45-degree overhang-bit would be the best choice for weight distribution. However, I met a guy who had done that on a similar build, and getting the wheel on and off the holder looked like a chore and a half at that angle. And it messes with the already poor departure angle. I've had this idea in my mind to continue the end of the subframe rails (that's sort of why they are sticking out like that) into a carrier, but the geometry of the cabin and the rails would make it a cantilevered engineering disaster that would still require the wheel to be attached to the rear wall somehow. And probably fairly heavy.

So, I made it as simple as I possibly could. Two pieces of (I think 3mm) aluminium diamond plates, 221'd to the inside and outside of the 40mm rear wall, and attached to each other with two M14 rods, nuts and washers. My reasoning is that the wall itself is held onto the rest of the build by enough aluminium and glue to probably safely hang the whole truck from it, and the 40mm composite material is strong enough to drive over without compressing - so with a big enough washer, ie. the diamond plate roughly the size of the 16" steel wheel, I should be able to just hang the wheel onto the studs, screw it in, et voilà; a spare tire carrier.



Below: the inside, a thermal bridge of nightmarish proportions that I will need to insulate and hide behind the sofa backrest.


I still need to probably rethink the nuts, also considering upgrading everything to M16, and the spacing between the wheel and the cabin needs some consideration to make absolutely certain it can't move, and probably a few pieces of diamond plate to keep the tire's sidewall from resting on the camper's vinyl wall.

 

[KiwiMtnClmbr]

Have you read up on or followed this build?

C'est parti mon kiki mais est-ce raisonnable ? - Casa Trotter

If your school french is as bad as mine, use Chrome and the translation feature will get you through nicely.

The builder has had many growing pains with the Ford platform, but also used a solid mount - albeit with an extensively custom composite floor/bottom.

 

[MLu]

Have you read up on or followed this build?

C'est parti mon kiki mais est-ce raisonnable ? - Casa Trotter

If your school french is as bad as mine, use Chrome and the translation feature will get you through nicely.

The builder has had many growing pains with the Ford platform, but also used a solid mount - albeit with an extensively customer composite floor/bottom.

Mon francais est un peu merde, but I think I got the gist of it. Thanks for the link, there's a couple of interesting things there... those interior panels, for one.

 

[MLu]

Progress is slow. Winter is here.