Self Build Guide - 4. Chassis and Suspension.

This is part of a series of articles on building or rebuilding a caravan. You can find the whole series here: Ever Wanted To Build or Rebuild a Caravan?

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The caravan chassis is perhaps the biggest hurdle home builders have to overcome. There are a few options on how you can tackle it.

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Build Your Own From Scratch

If you are already a competent welder then you can probably do the whole thing yourself. We can tell you the basic principles and materials, but you need to closely look at the design of a commercial caravan that is built to the conditions and weight you expect to be. Axles and suspension can be purchased and attached.

If you are nervous about building your own chassis, we don't blame you, luckily there are other options.

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Pay The Professionals to Build It

There are many professional chassis builders around, you will find them with a quick google search. One is G&S Chassis in Victoria. Chassis builders may cost a bit more than your local welder would charge but they will be able to help with the design and strength choices.

There are also standard chassis available to purchase from most trailer manufacturers and even on eBay.

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Reuse an Old Caravan Chassis

Another option is dismantling an existing caravan for the sole purpose of building on the existing chassis. This can give the option of changing the layout and perhaps reusing some components and materials.

The two main advantages of going this way is that:
(i) you are using a proven chassis and
(ii) as you dismantle the caravan, you can examine the way and the order it was put together.

This reverse engineering should not be underestimated, you should resist the urge to demolish the cabin to get to the fun part of building.

The disadvantage is that some of the very old caravans may have brake systems that are no longer legal, or the chassis strength may not suit the very popular 'outback' style, if that is your intention. If your intention is to get to the more remote areas, then a complete custom build maybe the answer.

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Suspension & Axles

While you do need to have a good strong suspension system, that doesn't mean it has to be the fanciest or most expensive.

Many modern Off Road Caravans have independent suspension but in my experience it can be more of a marketing feature than completely necessary.

I won't try and talk you out of one but if you have limited money you will be much better off going for a high quality standard Rocker Roller spring and solid axle than a cheap independent system.

One of my greatest worries is breaking a specialised suspension component in the middle of no where. Every bush mechanic can get leaf springs repaired.

But don't use slipper springs on a caravan, they are cheaper but best reserved for your 'On-road' camper trailers.

My latest personal van has Rocker Roller springs and solid axles, it recently did the Gibb River Road with no issues.

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Standard Design & Materials

My current caravan is 20' long and a semi-offroad. The chassis was based on Roadstar Caravan.

A-Frame is 150mm x 50mm RHS, 3mm thick. It has a lower offset tension strap 30mm x 5mm.
The main longitudinal chassis rails are 100mm x 50mm RHS, 3mm thick.
The first half of chassis rail has an additional 100mm x 50mm RHS welded under the main chassis rail.
Behind the full suspension mounting, is a 3000mm long , 100mm x 6mm flat bar that is welded to the inside face of the main chassis rail.
The cross members, between the chassis rails are:

50mm x 50mm RHS x 1.5mm for each floor sheet join.

50mm angle x 3mm for intermediate floor supports

The outriggers protrude outwards from the main chassis rail to the wall supports:
These are as above
The floor side support is 25mm x 3mm angle
The Wall supports are short 50mm long, 25mm x 3mm angle.

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