pivoting frames and mounting campers

[Victorian]

Please excuse my simple answers as I'm not an engineer... My knowledge only comes from being around expo trucks for many years and working together with one of the best Expedition Truck Engineers in Germany.
Anyhow:
Every truck manufacturer has a "truck body builder" guideline. Within that guideline (together with tire sizes and required clearences) the manufacturer is telling you where you can mount truck bodies or other accessories. Most of them only talk about commercial truck bodies. Mercedes and MAN for excample have special guidelines for offroad trucks. To my knowledge, only qualified outfitters are able to get that info.
In other words, trying to figure out by yourself how to build a subframe that will protect your truck and the camper body is not easy and could be potentionaly cost a lot of money in repairs.
My advice is always to hire someone that has designed and build them in the past AND can proof that his designs are without fail.

 

[Sitec]

Twist...

I've been trying to work out the best way to mount my body, and have been looking into 3 or 4 point mounting and how and where to mount the points... I think the easiest way to describe twist is to find yourself a 300mm/12" long standard plastic ruler... Twist it over its length (like a truck chassis off road) and watch what happens... The center line is the only 'plain' that stays in the same place. The left edge and the right edge stay relatively straight but not in the same plain. They work in opposite directions. With this in mind, wherever you mount your body on the outside edges of the chassis will be the section that the body will follow. If you want the cab and body to have minimal twist difference then your two outer mounts should be close to the cab... (but you must then allow for lots of chassis twist clearance under the rear of the body, especially in the rear wheel arches where the tyres will be). Going back to the ruler principal, if your cab is mounted at the front (1cm point), and you have two outer chassis to body mounts so the body stays upright (around the 12cm point on the left and right edge on the ruler), then your 3rd and or 4th body mount can only be and must be in the center of the ruler (around the 20cm and or 30cm point). This is not possible on the ruler, but it is possible on a chassis. One mount could be just in front of the axle, and the second could be at the rear... giving you a 4 point mount that spreads the body weight over the length of the chassis, whilst letting it flex like it's designed to. This is exactly how I plan to mount my body on my Merc 1222. I plan to have my two front outer mounts approx 24" behind the cab, with the 3rd just in front of the rear axle, and the 4th about 36" behind the rear axle. The only thing I plan to add is two sprung cab shock absorbers between the outside edges of the chassis rear and the underside of the body. These will give the body a bit more support when on highways (hopefully lessening body roll), but being soft enough to compress and stretch allowing chassis twist when off road... Attached is a pic that I have borrowed from a book I have :-

https://haynes.com/en-au/build-your-own-overland-camper

If you have not seen this book, buy it. It has so many things I've not thought about, including the pic below and a section on chassis twist and body mounting. It clearly shows the chassis center line and also the deflection if you don't get your mount ********** in the center of the chassis. Hope my different approach at describing the twist makes sense, and if needed I'll sketch my mounting plan and post it here for comment/criticism/praise!

 

[IdaSHO]

And that's why I only use bushings, as opposed to bearings.

Even when designed correctly, there is always a chance that certain deflection can cause binding.

 

[Sixinarow]

https://haynes.com/en-au/build-your-own-overland-camper

If you have not seen this book, buy it.

I bought this book after seeing your post. Great book!

 

[Sitec]

I've also ordered this one...

https://www.amazon.com/Motorhome-self-build-optimisation-Ulrich-Dolde/dp/3981855310

It should arrive tomorrow or Monday.. I've been told there's a lot more detail on stuff so I thought I'd buy it. I'll let you know what its like too...

 

[Sixinarow]

I've also ordered this one...

https://www.amazon.com/Motorhome-self-build-optimisation-Ulrich-Dolde/dp/3981855310

It should arrive tomorrow or Monday.. I've been told there's a lot more detail on stuff so I thought I'd buy it. I'll let you know what its like too...

Thanks. It's pricey!

 

[Neil]

Hi. Come in very late on this discussion.
I am not an engineer but can only tell you my experience over the last 8 months on corrugated graavel roads in South America.
People really worry about twisting and I did. I lost sleep over this.
However, It never entered my head that the pounding applied to your vehicle ove thousands of kilometers on Ripio ( Corrugated washboard gravel Roads ) would prove to be 10 time more destructive to your vehicle that twisting has been so far.
All I would add to this great thread is that any mountings you put your cabin on must not only be ably to cope with the twisting but more importantly must be able to cope with the relentless hammering on threee or four mountings . Ie 2 to 3 tones smashing into 3 points for 5 hours a day for weeks . It has to be good.

I am quite glad that I chose not to have a three or 4 point mounting and opted niavely to go for the rail on rail system as it spreads the smashing and has coped with all the twisting perfectly

I was a bit lucky as ripio roads didnt even enter my head when making these choices .

Good luck with it all

Neil

 

[Sitec]

So Sixinarow, yup it's pricy, but I think it's worth it. The way I look at it is if these two books (both very different but both worth their weight in gold) save me making several potentially costly mistakes in my build then they are money well spent. Steve's book is nice and simply laid out as you know, and has all the basic key points covered. Ulrich's book has a nice introduction on him, his wife, the truck, and past stories etc, and then leads into logical detailed sections of his build. The original book has been added to with notes and now translated into English (which has been done well I might add). There is a lot of detailed info in it, including access to some on line build planners. So far, the only thing I think he's missed is details on Composting Toilets. (He does however state at the beginning that this is the 3rd or 4th version of this book and it is continually evolving). The two books are very different, but again I think you would find money well spent with this. He talks about composite builds, steel frame builds, cab to body access etc etc... Wiring diagrams, plans, for's and against's, what to carry and what not. There are a lot of very good pictures too, involving his build and others, chassis choices and why. I've had my head stuck in it since it arrived yesterday! For the American market conversion will be needed as everything is in metric (which suits Europe, Australia etc..). Enjoy!

 

[Joe917]

Just to add another idea to the mix.
The Mercedes Truck body builder also accepts a solid mount system. You will loose the chassis flex, but for a bad road vehicle that is not really an issue. The box has to be very well built as it will be heavily loaded. This construction has the advantage of making a very stable vehicle.

 

[Sixinarow]

So Sixinarow, yup it's pricy, but I think it's worth it. The way I look at it is if these two books (both very different but both worth their weight in gold) save me making several potentially costly mistakes in my build then they are money well spent. Steve's book is nice and simply laid out as you know, and has all the basic key points covered. Ulrich's book has a nice introduction on him, his wife, the truck, and past stories etc, and then leads into logical detailed sections of his build. The original book has been added to with notes and now translated into English (which has been done well I might add). There is a lot of detailed info in it, including access to some on line build planners. So far, the only thing I think he's missed is details on Composting Toilets. (He does however state at the beginning that this is the 3rd or 4th version of this book and it is continually evolving). The two books are very different, but again I think you would find money well spent with this. He talks about composite builds, steel frame builds, cab to body access etc etc... Wiring diagrams, plans, for's and against's, what to carry and what not. There are a lot of very good pictures too, involving his build and others, chassis choices and why. I've had my head stuck in it since it arrived yesterday! For the American market conversion will be needed as everything is in metric (which suits Europe, Australia etc..). Enjoy!

Thanks! Yeah, mistakes could cost a lot more than the book! I appreciate the review and help!

 

[mog]

Thanks. It's pricey!

You can get the digital version on his website for 38.90€ HERE

 

[Sixinarow]

You can get the digital version on his website for 38.90€ HERE

Thanks!

 

[Badmiker]

Ok,

After reading the entirety of the thread over several days across a few weeks I feel a bit more comfortable with the mounting ideas for habitats. Personally on the base vehicle we are looking at and the builds I have seen using them, I am looking at a 4-point system (diamond/Unimog style).

There are advantages in every mounting system and corresponding disadvantages too but at the moment this feels like the best compromise for our vehicle plan.

I do have a ..... silly thought though. Has anyone added leveling jacks under a pivot frame? Rather than try get the vehicle level by driving it on blocks/ramps use a jack to level the subframe. Would that work? Stupid idea?

Not to crank the thing 20 degrees or anything but just to lightly adjust the sitting angle of the habitat.

 

[Joe917]

We had leveling jacks(solid frame mount), but I removed them. They hung down too far, were not worth the extra weight and we rarely needed them. Blocks are simpler and lighter.

 

[Coachgeo]

Ok,

After reading the entirety of the thread over several days across a few weeks I feel a bit more comfortable with the mounting ideas for habitats. Personally on the base vehicle we are looking at and the builds I have seen using them, I am looking at a 4-point system (diamond/Unimog style).

There are advantages in every mounting system and corresponding disadvantages too but at the moment this feels like the best compromise for our vehicle plan.

I do have a ..... silly thought though. Has anyone added leveling jacks under a pivot frame? Rather than try get the vehicle level by driving it on blocks/ramps use a jack to level the subframe. Would that work? Stupid idea?

Not to crank the thing 20 degrees or anything but just to lightly adjust the sitting angle of the habitat.

Not a bad idea...... and unlike a jack to the ground... could be potentially very compact since you could just jack to bracket mounted between the chassis to the habitat. That being said though..... if you do NOT go to ground; though you can make it level.... you may still be little rocky in the habitat cause tires and suspension still come into play.