Mercedes LAF 1113 B family truck

[Christian]

Hi All!

I've been here for 10 years this february!

And we finally got the dream project, a Mercedes LAF 1113 B from 1979.

I am starting this thread partly to document the build, partly to ask questions and get help.

First of all, a bit of background, feel free to jump past the boring parts.

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My wife is 41, I'm 43, and we have two daughters, 3 and 7. We're danish and live just north of Copenhagen.

We had a motorhome long before the kids, an old wreck of a VW LT31 we got driving and toured Scandinavia in.
After that we wanted something else, and fell in love with the portal axled Volvos and got a TGB1314, the 6X6 variant.
We spent a lot of time on it, including converting it to a more reliable Toyota Diesel driveline.
But when the kids came along, we found the cab too small, and the center engine config wrong for our use.
So we sold it, unfinished 2½ years ago...

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We needed something bigger, but still old school and taxable in Denmark...
So we fell in love with the shape of the old Mercedes L series trucks and here we are today, with a lovely 4X4 LAF 1113 B with 4.2m wheelbase (13 feet 9 23⁄64 inches for the US crowd), new turbo and servo!



Its from 1979, and 12 years ago a bunch of guys from Holland bought it from Wiesbaden fire department and used it as a support truck on the Paris - Dakar.
Despite the trip to Africa, the truck has only done 33.000kms...

The plan is to make a cab over with the grown ups sleeping over the cab, and the girls in bunks in the back.
All in all pretty standard - except I want the cab and camper part fully integrated!



Its not perfect, but it is a work in progress!
As you can see, i want the original cab and the new box integrated.
And I do know this will pose some problems, and I have been told about all the downsides.
Nut for us that is ideal. So I am looking at ways to go about it, including 4-point subframe, fixed subframe etc.

But I am leaning towards a semi 3-point system which can take into account that the linkages from the cab (steering column, gas pedal, gear shift etc.) has limited movement...

Feel free to comment!

 

[LostInTheWorld]

That is such a cool vehicle to build from. It will be a lot of work, but it will be really cool when finished. I look forward to seeing it transform.

Before settling on our current Unimog, we very briefly considered a Bedford. I always loved the classic sheet-metal curves of older trucks like Bedfords and the Mercedes L series.

Michael

 

[Christian]

That is such a cool vehicle to build from. It will be a lot of work, but it will be really cool when finished. I look forward to seeing it transform.

Before settling on our current Unimog, we very briefly considered a Bedford. I always loved the classic sheet-metal curves of older trucks like Bedfords and the Mercedes L series.

Michael

Thanks Michael!

Coolness was a major factor, but others were:
A really big cab with room for four+ and a dog etc.
No engine box in the cab means that you use it as a regular room.
No tilting cab means a cabover is not a problem.
I know you can get a lot of that in the big pick ups you guys in the states has, but we can’t get those here, and if we could, I could not afford one!
Besides, the big pick ups, the Dodge 5500, Ford 650, Chevy Kodiak or what have you just doesn’t have the charm ;-)

 

[Sitec]

Great looking trucks the Bull Nose Mercs! There's still a lot still earning their keep in Africa! Re making your body/cab all one piece, that's a huge ask of the body and cab. I'd be having a rethink there. While you still have the original body on, take your truck off road (or just jack one side of one axle up) and see how much movement there is between the top of the cab and the top front of the body... (set two tape marks up there first). I think you'll have 150mm (6") + of movement to contend with... Have you thought about building your body, and then building a separate 'pod' on the top of the cab that can be lighter as it does not have to be structural, but make it's shape match the cab so it looks like it's all one. You could then have the usual 'crawl thru' between the cab and living, and access the large sleeping pod from inside the cab...

 

[Joe917]

Crawl thoughs suck. walk through should be the minimum. Crawl throughs end up never being used.

 

[Sitec]

If it's 800mm wide by 1200mm tall (or whatever the cab allows) then it is usable... Id rather that personally as it's at least closable, as in a hot country the cab AC isn't trying to cool the whole box, and in a cold country at least you have a chance of still heating the cab... The logistics of making that double cab part of the body is massive, it could be done by removing the cab and making it part of the body incorporating it into the 3 or 4 point mount... Just my preference though.

 

[Christian]

Great looking trucks the Bull Nose Mercs! There's still a lot still earning their keep in Africa! Re making your body/cab all one piece, that's a huge ask of the body and cab. I'd be having a rethink there. While you still have the original body on, take your truck off road (or just jack one side of one axle up) and see how much movement there is between the top of the cab and the top front of the body... (set two tape marks up there first). I think you'll have 150mm (6") + of movement to contend with... Have you thought about building your body, and then building a separate 'pod' on the top of the cab that can be lighter as it does not have to be structural, but make it's shape match the cab so it looks like it's all one. You could then have the usual 'crawl thru' between the cab and living, and access the large sleeping pod from inside the cab...

Hi Sitec,

First of all, thanks for taking the time, not only to comment in detail, but also the sketch. I do like your thoughts, and if I give up on my own idea, that may well be the way we go. I really like your idea about access from cab to bed, that would effectively make it a two bedroom truck

I do know that I'm on shaky ground. But there's actually several reasons why I want to integrate them. I want to be able raise the bed over the cab, so there's as much room as possible in the cab, when the bed isn't used, so we can use the cab as a separate room. I think that's a good idea with kids, so we don't have to sit together all the time. that also means that we can lower the bed a more than below the roof line, so there's plenty of room in the alcove when sleeping. Plus I want to be able to use the entire truck when driving. So there will be seatbelts at the benches in the back too, and a more open connected feel.
I do know heat and cold might be an issue, I fear condensation most. But I hope I can control it with adequate ventilation.

Mechanically I believe it is possible. i have tried your test, and they do move a lot! But the are also attached at opposite ends. I have been told that the frame may twist as much as 20 degrees.
Right now the cab sits on rubber mounts at the front and disc springs at the rear. The box is solidly mounted at the rear, and disc springs at the front.

I propose making a 3-point system with the pivot above the rear axle. If you look at our truck from the side, you'll see that the current cab actually ends approx. 1~1.5m from the axle. This means that we are already almost there, and a complete subframe for both cab and box only have to lenghtened 1~1.5m to reach the pivot point. The part of the subframe and bottom that extents rear of the pivot have to clearance the movement of the chassis, but that is doable.

Am I mad?

 

[grizzlyj]

That is a lovely truck
I don't see why using it as you describe requires the two halves to be rigidly joined though? Why not just doors that allow free movement between but no actual connection?
You can't effectively insulate all that cab glass so travel in cold places will be cold throughout rather than having a nice cosy rear end (!) and cooler sleeping space in the front.
And you'd have to lift the cab and back section off, make one huge front to back (and so heavy and curving) sub frame and then get all the controls to work in their new relative positions, rather than just adjust how you think you may use it and leaving as is? Whatever supports the cab now won't be strong enough to extend, roughly doubling its span to the back of the truck perhaps?
There are one or two older Unimogs made with one piece bodies despite the flex but I don't think any were as long as yours will be.
A friend sleeps out in his uninsulated unheated Landy in northern Scotland year round and the only way he can avoid condensation is leave the windows ajar all night. Chilly.
Re-making a sub-frame that your seats and belts(?) are attached to might fall foul of whoever is responsible for proving such things are strong enough?
Good luck with making it even lovelier what ever you do
Jason

 

[Wazak]

That is a lovely truck
I don't see why using it as you describe requires the two halves to be rigidly joined though? Why not just doors that allow free movement between but no actual connection?
You can't effectively insulate all that cab glass so travel in cold places will be cold throughout rather than having a nice cosy rear end (!) and cooler sleeping space in the front.
And you'd have to lift the cab and back section off, make one huge front to back (and so heavy and curving) sub frame and then get all the controls to work in their new relative positions, rather than just adjust how you think you may use it and leaving as is? Whatever supports the cab now won't be strong enough to extend, roughly doubling its span to the back of the truck perhaps?
There are one or two older Unimogs made with one piece bodies despite the flex but I don't think any were as long as yours will be.
A friend sleeps out in his uninsulated unheated Landy in northern Scotland year round and the only way he can avoid condensation is leave the windows ajar all night. Chilly.
Re-making a sub-frame that your seats and belts(?) are attached to might fall foul of whoever is responsible for proving such things are strong enough?
Good luck with making it even lovelier what ever you do
Jason

I'm in agreement with Jason here you're going to have to insulate the cab no matter what you do.
I think that I would be considering a walk through and a large pod on the roof with access from below to bring both the cab and the rear accommodation unit together and either you and the missis sleep up there or let the kids sleep in there. My daughters would have insisted that they slept there, I'd also fit some captains seats, recliners of course and a swivel table for the extended cab area and either a separate diesel heater or integrate the main heater and the cab. We always utilise the cab area of whatever vehicle we have we refer to it as the sun lounge (Marilyn that's my wife is relegated to the the side facing sofa now as my youngest Spaniel claims whichever seat is free)

At the end of the day if you have loads of time and cash to throw at the project then you could build a fully integrated unit as for myself I'm impatient I'd want it sorted ASAP and I've got short arms and deep pockets with naff all in them.
No matter what you decide I'll still follow your progress.
Apologies for my ramblings and thanks for sharing your build ideas on a very nice platform.
Barry

 

[Christian]

No need to appoligize guys! I’m listening to your constructive critisism and I really appreciate your input.
But (there’s always a but, sorry), I have been toying and building this thing in my head for three years.
I believe I have worked out most of the kinks, and I know I have convinced myself (and the wife) that an integrated cab/box is the way to go.
Take a look at that double cab, it extends almost to the rear axle anyway. And rests on disc springs right now.
Jason, I’m going to redo the custom floor and underlying braces anyway, the diesel tank is in the cab. I think I might use 120x60 mm RHS, like Volvo used in the rigid chassis on the 5.4T TGB 20 6x6....
And I know certification is not a problem.
I know insulation is an issue, but I have to noise treat the can anyway, might as well insulate. Windows can be fixed with screens/curtains. And yes, I know condensation is a major concern, but I plan on using ventilation with heat recovery to battle damp air.
And Barry, the captsins chairs are on the list, 4 of them. That’s one of the reasons I want to be able to raise the roof/bed to get a bit more headroom. And be able to lower it to get the same above.
I know these trucks have been done this way before... I simply have to try!
But I do hear your apprehensions, so I might have to find an engineer that can draw the subframe etc. and do a finite element analys.

But look at this, which is the odd one out?

 

[Sitec]

A great selection of truck/busses.... and all but the silver one at the bottom left are either 4x2 for on road use in bus form or 4x4 with split cab and box for off road form. I know where your thoughts are with the length of your cab being already half way along the chassis, but even with the rear of the cab fixed hard to the chassis andthe front of the body fixed hard, even if those points were only 400mm apart you'd still get 100mm+ of movement in a cross axle situation. The only simple way I can see to avoid it is to build a lightweight body suspended off the cab with just a simple sprung support at the rear... How much off road work do you plan?

 

[Neil]

This looks like a great project with a lot of thought going into it. It will without doubt be the best thing you will ever do for the family. We are currently travelling and i have to admit before we set off i would have questioned whether this type of travell was family friendly. We have now met loads of families on the road and my opinion has changed drastically. Building a truck like this is the best family adventure ever.

On a slightly technical note i would add to this thread that whatever mountings you decide. Design them robust then make them even more robust. We all study and design torsion free systems but spend little thought on the impact of corrugated ripio roads that send your vehicle into an un controllable violent shake that can last for days and hundreds of km. This action in my view is far more destructive and damaging than anything else, especially when all the weight is on 3 or 4 places. Mountings of all types are a very common repair. So think big and make it bigger.
I will watch this project with interest. Here in south america this great choice of merc is everywhere, 1113 and 911 so its a good destination .
Good luck

Neil

 

[grizzlyj]

Even if you insulate the cab windows with screens you won't have any heat to recover from your ventilation

 

[Grenadiers]

This is a 1983 MAN DOKA built as a one-piece cab/cabin. Former tilt-cab, whereas now they have engine access from the top, inside the cab. A sliding door behind front seats separates that part to the cabin. Eleven years on the road from Tierra del Fuego , to Inuvik in Arctic Circle. Over the years, cracks would develop, and they would fix them. No subframe.

 

[Christian]

A great selection of truck/busses.... and all but the silver one at the bottom left are either 4x2 for on road use in bus form or 4x4 with split cab and box for off road form. I know where your thoughts are with the length of your cab being already half way along the chassis, but even with the rear of the cab fixed hard to the chassis andthe front of the body fixed hard, even if those points were only 400mm apart you'd still get 100mm+ of movement in a cross axle situation. The only simple way I can see to avoid it is to build a lightweight body suspended off the cab with just a simple sprung support at the rear... How much off road work do you plan?

Hi Sitec,

Oh I love that video!
And they might be 4x2, but the chassis should be the same, or even softer, according to the german forums. And looking at those buses, I suspect they have seen a lot more terrain than ours ever will. On that subject, I suspect ours in reality will be a bad road vehicle at max, without seeing any serious terrain the next many years. that said, the serious hair pins in Norway will introduce chassis flex. And it is nice to know we can tackle Iceland etc. if it comes to that.
Why do you suggest a spring mount in the rear instead of a 3 point pivot system?

This looks like a great project with a lot of thought going into it. It will without doubt be the best thing you will ever do for the family. We are currently travelling and i have to admit before we set off i would have questioned whether this type of travell was family friendly. We have now met loads of families on the road and my opinion has changed drastically. Building a truck like this is the best family adventure ever.

On a slightly technical note i would add to this thread that whatever mountings you decide. Design them robust then make them even more robust. We all study and design torsion free systems but spend little thought on the impact of corrugated ripio roads that send your vehicle into an un controllable violent shake that can last for days and hundreds of km. This action in my view is far more destructive and damaging than anything else, especially when all the weight is on 3 or 4 places. Mountings of all types are a very common repair. So think big and make it bigger.
I will watch this project with interest. Here in south america this great choice of merc is everywhere, 1113 and 911 so its a good destination .
Good luck

Neil

Thanks Neil! And great to hear that you guys are enjoying it. My wife and I have dreamt of this for years, and with the girls being 7 and 3, we have to get started, while they still want to spend time with us! How old are your kids and how much traveling have you done? We really love the 1113 not only for the looks, but for the Merc reliability, ice-braker factor, the big cab, the engine access from the front, I could go on! And for now, I'm totally bling for the amenities in modern trucks.

On the technical side, I agree. And even though I haven't tried any serious washboard driving, I have seen plenty of it online. I can only imagine the destructive forces induced on everything.
I plan on using rubber mounts of some sort to isolate the cab and camber from the chassis to eliminate noise and vibration (the same almost) and the destructive forces of it.
Something like this:

Can take 1.160 kgs (2.560 lbs) static load. So 4 of them should in theory be adequate. The idea was to use the original possitions on the front mounts and add rubber mounts to the pivot to isolate the subframe.

This is a 1983 MAN DOKA built as a one-piece cab/cabin. Former tilt-cab, whereas now they have engine access from the top, inside the cab. A sliding door behind front seats separates that part to the cabin. Eleven years on the road from Tierra del Fuego , to Inuvik in Arctic Circle. Over the years, cracks would develop, and they would fix them. No subframe.

Hi Grenadiers!

Thanks for your post. The vehicle looks very interesting, is it yours? Just to understand correctly, the fully integrated camper box is rigidly mounted to the frame? I believe tha MAN frame twists as much as the Mercedes one do. Well it just goes to proof there's more than one way to skin a cat!

I did do some sketches on subframe ideas in the fall:

I'm not that good at Sketchup yet. but the idea was to make a 3-point pivot system using the two original mount locations at the front, and place the pivot above the rear axle.

• The reason for going outboard after the pivot was to make room for the chassis to flex, without colliding with the subframe. With a 20 degree chassis flex, the movement translates to 40 cm (~16").
• Going outboard also gives a strong outer lower edge.
• some argue that having the pivot in the rear makes the truck lean more going around corners, actually negating the anti roll bar that is the main reason the chassis flexes instead of the suspension. If tis problem is real, a set of airbags between chassis and subframe in the rear could mitigate this on-road and be deflated off-road. These would alos help reduce stress on rubber mounts and help eliminate vibration.

please let me know what you guys think?

(And d**n, I wish I had the money to get somebody to make some real drawings with motion analysis...)