Pulled the trigger

[Neil]

Just a short note to make a correction to my previous post.

We spent a week at 4500m to 5000m and I eventually got the knack of getting the Eberspacher fired up.

You must start it on its minimum settings and even then I think it ran on about 30 % of this power, maybe 800 to 900 watts.

Being below minus 20 once it fired up , which took about 5 goes, we left it running all night and it was enough to keep the cabin and the engine warm.

I now have a bit more confidence in it at altitude if this helps your choices.

Neil

 

[nathane]

Thanks Neil,

I think the Webasto has an altitude adjustment capability, I recall observing this when deciding on this option although I can't see it on the data sheet now.

Whilst I don't currently envisage us going that high, it makes sense to make sure it's possible!

 

[Simon dix]

So first few questions around the build, I'll post them here but more generally too. These are questions that I think are fundamental to the box/chassis integration and component mount location options hence covering them at the start.

1) Lithium Ion or Lead acid for leisure batteries? I'm leaning towards Li. Reasons - weight and longevity. In general I'm hoping to keep the weight of the overall package reasonably low without incurring ridiculous cost or compromising on durability. I know that the Li-ion set us is going to be a chunk of change but feel it's probably worthwhile. Views?

2) Heating. I'm inclined towards an eberspacher hydronic system with underfloor heating matrix. Reasons: single fuel, integration into engine allows water heating from engine, preheat ability for cold climate engine starts, draft free whole box heating. Thoughts?

3) Cooking. Electric with induction and combined microwave/oven. Reasons reduce multifuel complexity, diesel has poor reputation (although I've never used it).

4) Toilet. No idea yet between chemical, tank or compost. In the early years the use case is likely to be Europe and Morocco for 1 month trips. Longer term Australia, remote USA/Canada as a certainty with possibly trans Asia connecting the two in a 1-2 year trip. It may be we need to change because of geography and timeframes as we gain freedom and time to travel. I'd love thoughts on this one.

5) aircon. Yes/No and if yes, cab, box or both. I'm also unsure on this. I'd like to think that we will travel based on seasons and avoid discomfort by being somewhere else! However not sure how realistic this will be. Whaddya think?

All the best

Nathan

Hi Nathane, Nice stuff in your thread. Wrt aircon I am probably going down the route of 24v compressor rather than belt driven. I am discussing with the guy who does all my aircon for my site machines (24volt and 12volt). If all goes to plan I will probably look at installing this in January but my plans often change. When I get more details and info I will post on my thread or if I remember ill let you know. Do you need a CAD drawing for your 1550? PM me your email and I will send you some info

 

[Simon dix]

For our sub-frame, we just modified the stock MB sub-frame that was on our U1300L military troop bed. We cut is down a little to make it about 10 inches narrower, we trimmed off about 8 inches from the front, we removed as much unneeded weight as we could, we added a new perimeter frame (the stock frame also had a perimeter frame), and then we added supports for the fenders and under bed storage (we are using the stock U1300L fenders still). We are running the larger 365/80-R20 tires, but other than that, we will have basically the same axle-to-fender clearance as the stock mog. I like that it's the original sub-frame, so I have some confidence that frame flex will be similar to what MB originally designed and tested.

We had Total Composites put steel hard-points directly over the original MB sub-frame rails, so the loading should be nicely distributed. There are 52 bolts that hold the habitat to the sub-frame.

View attachment 448409

View attachment 448410

Habitat floor hardpoints (note that the floor is upside down in this photo):
View attachment 448412

Michael

Hello Michael, Love seeing the structural work without the sheet metal. I have the ex-military u1300L. I was thinking that If I cut out the sheet metal the sub-frame would distort a bit. Did you cut the sub-frame in-situ? I want to cut out sheet metal but with sub-frame off the truck. Do you reckon it will be safe from distorting in any way or form? Only reason why I ask is because I have removed welded sheet metal from frames and had some issues, but I have never removed sheet metal from a frame of this magnitude and engineering! Cheers, Simon

 

[nathane]

Hi Simon, thanks for posting. It's been a long time since I updated mainly because things have been only moving slowly but also cos I didn't want to put much up until I was confident I was going to get there!

If you have CAD files for the 1550 chassis that would be awesome thanks.

I have 2 aircon systems on the build now. An German military unit previously fitted to a 1300 used in the middle East, originally roof mounted but now replacing the glove box in the cab with engine driven compressor and radiator mounted at the rear of the chassis cools the cab and a dometic freshwell 3000 mounted in the box.

We ended up fabricating a new sub frame specifically designed for the box, aiming to minimise weight and optimise attachment.
I have built the box base which is structural and load bearing roof myself using an Al frame into which a foam carbon epoxy sandwich is vacuum moulded. I sourced walls because I couldn't get a good enough surface finish on large vacuum moulded parts to satisfy my needs. I'll be assembling these in the next few weeks.

I'll do some progress to date updates with photos soon!

 

[Simon dix]

Hi Simon, thanks for posting. It's been a long time since I updated mainly because things have been only moving slowly but also cos I didn't want to put much up until I was confident I was going to get there!

If you have CAD files for the 1550 chassis that would be awesome thanks.

I have 2 aircon systems on the build now. An German military unit previously fitted to a 1300 used in the middle East, originally roof mounted but now replacing the glove box in the cab with engine driven compressor and radiator mounted at the rear of the chassis cools the cab and a dometic freshwell 3000 mounted in the box.

We ended up fabricating a new sub frame specifically designed for the box, aiming to minimise weight and optimise attachment.
I have built the box base which is structural and load bearing roof myself using an Al frame into which a foam carbon epoxy sandwich is vacuum moulded. I sourced walls because I couldn't get a good enough surface finish on large vacuum moulded parts to satisfy my needs. I'll be assembling these in the next few weeks.

I'll do some progress to date updates with photos soon!

Great Nathane, keep up the good work. This stuff gets out of hand with all the info and sometimes lack of time and not knowing whether to put the right foot first or the left ?

 

[nathane]

Well, after a long wait (alright I get that's an understatement) it's finally time for a bit of an update.

Early progress has been super slow, with life kind of been getting in the way of progress, with busy work and much energy on improving my banjo playing. However it's also been hanging on to post until I begin to feel that we might actually make this happen - I didn't want to start posting and find everything petered out!

Anyway I'll make a start in documenting the build now - it feels OK to go public.

 

[nathane]

So as a starting point I should probably talk about planning. We have been thinking about this build now for a couple of years. Have read lots of build threads on here, read Ulrich Dolde's book, looked at layouts and fixtures of the European builders etc. etc.

In the end as you've already seen, we decided to go with a Unimog platform, which we know is overkill for our offroading needs but why not? Alright, comfort, noise, speed, fuel economy, etc. etc. I know, but on the plus side, turning circle, it's a unimog, and to be honest, around where I live, anyone who is anyone has a silver mercedes 4x4 and I'm always up for a bit of competition!

So with platform decided we went to Atkinson Vos in Bentham, North Yorkshire, UK and talked about models specs etc. In the end we chose a U1550 L37 for a few reasons, the longer wheelbase would accommodate a 4.2m box, and it came with a handful of desirable things already factory fitted like central tire inflation and intercooler.

Here's a reminder of the vehicle as it started

 

[nathane]

Despite the fact that this was a great starting point we've done a load of stuff to it - but I'll cover that later.

We were not in a hurry to get everything done and the AV folks very kindly were happy to look after the truck for us until we were nearer needing it. But once bought we thought we better start thinking about the box.

We did a load of drawing and ended up making a little model as a starting point for our design:



This allowed us to play around with where the bigger stuff would fit to get a basic idea in our heads of what it would be like.


We wanted compact - 4.2m long, but with permanent shower and toilet, a small U shaped sofa area and without needing to make the bed every night. As a result we opted for the idea of a lifting bed over the sofa area which is not in the model, but otherwise you'll get the idea of the layout.

 

[nathane]

The balsawood model was great for getting the rough design sorted, but I knew we were going to need much more precision in the design to work out how all the various systems and components would fit and work together. As a result I got started with Autocad Fusion, a fantastic CAD package that offers a free licence for non-commercial hobbyist users. It took me a while to work out how to use it, but I have to say this software is absolutely fantastic. I wouldn't dream of trying something like this again without it. The ability to design everything in correct materials to understand mass, distribution, loading, cog etc is just great, let alone being able to think about how everything fits into such a small space.

So in the end the balsa model turned into this:





This is a component by component design - in its current iteration (version 120 - I save a new version every time I get to a significant stage in the virtual "build" process) it has something like 220 individual components. When you "build" virtually like this it really highlights the complexity of the process, but it also helpfully helps with both the physical design stuff, but also to get an inventory list of all the things you need and helps with getting a budget together.

So then with a balsa model and a CAD rendering we were ready to get started!

 

[nathane]

How does the song go? - Let's start at the very beginning, a very good place to start. I guess for us it was let's start at the very bottom and build upwards!

We had decided to build with an aluminium frame made by https://www.pro-lam.net/en an italian company that makes extrusions and components for building HVAC enclosures. It was recommended by a friend who uses this stuff to make large "containerised" type HVAC units to retrofit onto factories, server farms etc. Into the frame we would fit foam composite sandwich panels.

But to get going we needed to build the floor of the box, which incorporates 2 forklift pockets to enable us to demount the box to fit the whole camper into a container for shipping, and the all important ISO container locks to fix the box the the chassis.



So here you can see the very beginning. This is the base of the box, container locks at the corner, 100mm x 100mm x 4mm profile between them, 100mm x 200mm x 4mm Forklift pockets, glued onto the pro-lam profile that is sitting on the garage floor. We are using SCIGrip SG300 Methyl Methacrylate adhesive (https://www.scigripadhesives.com/scigrip-sg300-high-performance-methacrylate-structural-adhesive/). This stuff is pretty strong and as long as you cap each section of tube, the bonding area on these profiles is large, meaning that gluing should be significantly stronger than welding.



In order to increase the surface area of the bond we added corner reinforcements in to all corners:



All surfaces get washed with detergent and rinsed with acetone prior to bonding as extrusions can be left coated in lubricant from the manufacturing process.

 

[nathane]

With the frame built it was time to add the floor:



This is a 3mm AL skin that will be able to take knocks if stones get thrown up etc.

As before everything is washed and rinsed:



Before gluing:


This SCI Grip adhesive (feels rude to call it glue!) is pretty viscous stuff and to be honest a PITA to apply with a manual gun, but the pneumatic gun was something like £350 and I wasn't going to go for that. Working time of this stuff is 40 minutes so we just went slow on the large joints and ended up with huge forearms afterwards!

 

[nathane]

Having a godson who plays American Football (UK club champions in 2018) meant that turning the floor over to work on the "inside" was easy.

Initially upside down (note the funky clamping arrangements!):



Then flipped:



Maybe it would have been easier if we'd taken the weights off first ? Godson on the right - his muscles came in handy more than once so far!

 

[nathane]

As before corner joints reinforced:



And seams in the floor reinforced:



The white glue is SCG Grip SG300 15 - with a shorter work time of 15 minutes. More useful for the small components where we were able to work quickly.

 

[nathane]

Last job on the Aluminium floor was to put a "lid" on the section between the forklift pockets. This void will contain the retractable folding stairs that will pull out from the floor of the box, rolling on skateboard wheels. "Lid" in place.



and the stairs that will fit into the void (photo showing work in progress, for some reason I don't have a finished photo):

Right, supper time now, that's enough for one day!