Terry Owen

The absorption fridge

Invented just over 100 years ago (1922) by Swedish inventors Baltzar von Platen and Carl Munters, the absorption fridge has arguably contributed as much to RV’ing as any other invention. This is because it can cool without the need for electricity, thus opening up a wide range of camping possibilities.

Unlike previous fridges that relied on the mechanical compression of gases, the new device relied solely on heat as the energy source and had no moving parts. This meant it could be fuelled by LPG which, by the 1930’s was becoming widely available.
For decades RV absorption fridges were powered solely by LPG but in the early 1980’s, as campsites with mains hook ups became available, electric heating elements were added. This provided a useful dual fuel ability, saving on gas when it wasn’t needed. About the same time 12-volt heating elements were added too, such that fridges could be powered from the vehicle’s 12-volt system when travelling. This is how the so-called three-way fridge was born. It quickly became the ideal fridge for RV use and that’s why it has dominated the RV market until recently.
Now, advances in compressor technology along with improvements to batteries and solar panels, are allowing compressor fridges to gain more of a foothold. Despite this, the good old absorption fridge looks to have plenty of life left in it yet.

Platen and Munters’ invention was put into mass production in 1923 by the AB Arctic company. Two years later the company was acquired by Electrolux. The rest, as they say is history, with Electrolux, and later Dometic (who bought Electrolux’ Leisure Appliances division in 2001), going on to become one of the world’s largest producers of absorption refrigerators. Thetford began supplying the market with absorption fridges in 2002, following their acquisition of North American speciality fridge maker, Norcold.

The drop-down bed

Lippert’s Toscana drop-down bed can be either manual or electric

It’s difficult to say exactly when the first drop down bed appeared in an RV but Bürstner was a pioneer of the technology. In 2008 the Bürstner Ixeo became the first semi-integrated low-profile motorhome with a drop-down bed and the following year, their Averso Plus became the first touring caravan to be fitted with a drop-down bed.

A further development came in 2015 with the electrical drop-down bed. This made operation a breeze and was height adjustable. In many cases the bed could be lowered down to the height of the seats, eliminating the need for a ladder.
Today the drop-down bed can be found in a wide variety of motorhomes as well as some campers. However, the concept has not really caught on in the touring caravan market, where weight and height are more of a problem.

The big challenge for every RV designer is to maximise space efficiency. The drop-down bed can make a major contribution to this goal whilst retaining most of the advantages of a fixed bed layout in terms of comfort and convenience. Usable floor space is increased and a feeling of spaciousness created by removing the bed from sight during the day. Of course, the bodyshell of the RV has to be strong enough to cope with a drop-down bed and this adds a little to the weight but, for many, the compromise is well worth it.

AL-KO’s Motor Chassis (AMC)

AL-KO’S Motor Chassis (AMC) has perhaps done more for the world of motorhomes than any other single invention, at least in Europe and Australasia. It replaces the original chassis of the base vehicle with a lightweight ladder frame chassis, set lower down, and with independent rear suspension. This generates a significant number of advantages.

Firstly, it creates a better driving experience with enhanced roll stability and a lower entry height (up to 220 mm) for the motorhome. Secondly, the lower chassis height can permit a lower overall vehicle height, or be used to construct a false floor above it, with useful space between. This space can accommodate heaters and tanks, or simply be used as additional storage space.
The rear suspension is based on torsion bars, which are much more compact than leaf springs, thereby allowing the height reduction. If needed, the suspension can be uprated with air springs to allow heavier loads and a more compliant ride.
Other advantages of the AMC include its lightweight construction, which saves up to 50 kg in weight, allowing for a greater vehicle payload. Also, full galvanising meaning that rust should never be a problem. What’s more, the chassis can easily be fitted with additional support brackets specific to the motorhome that will be built upon it.

The AMC chassis dates back to 1979 when it was developed for the Peugeot J9 van. It wasn’t until 1985 that it became available for the Fiat Ducato, Peugeot Boxer and Citroen Jumper. Today it is also available for VW’s T6 Transporter and Mercedes’ Sprinter vehicles. According to AL-KO’s website over 220,000 such vehicles have been fitted with the AMC chassis to date.
Many are fixed to their cabs at AL-KO’s production facility in Ettenbeuren, Germany, shown here on the left.

The cassette toilet

Whilst Thetford’s Porta Potti toilet made a huge impact on the camping market following its introduction in 1968, it was their C1/C2 bench toilet in 1987 that really revolutionised the market.
Not only was it permanently fixed in the RV but it was self-contained and could be fully serviced via a hatch from outside the vehicle. It was true game changer as it abolished the need to have toilet chemicals inside the vehicle or to carry the black waste container through it. It’s important to remember that, at this time, formaldehyde with its all-pervading smell, was still a main ingredient.

Thetford’s C2 bench toilet started a revolution

The C1 prototype went into production as the C2 and became an instant hit with end users such that, from then on, RV manufacturers began to design fully fitted washrooms as opposed to just toilet compartments for portable toilets. Many clever designs emerged with folding sinks and built-in showers. The RV experience had suddenly become much more home-like, and it remains so today.
The cassette bench toilet was a huge step forward but it did restrict washroom, design somewhat. The next milestone came in 1993 with the introduction of Thetford’s C200 swivel bowl toilet. In its own way this was just as ground breaking as the C2. It gave RV designers much more freedom with washroom layouts than the previous bench design. This was because the toilet could be positioned wherever there was space on an outside wall and the bowl swivelled into a comfortable position for use.

Global appliance manufacturer, Dometic, introduced their own RV cassette toilets in 2008 – the CT 3000 series. These were similar in principle to those from Thetford although it was not until the CT 4000 series in 2015 that swivel bowls were introduced. From the start one interesting innovation was the option of a scratch and stain resistant ceramic inlay for the plastic bowl, something Thetford has recently launched with its ‘Twusch’ insert.
Recent years have seen increasing interest in other types of toilet, such as Thetford’s INDUS system and separating /diverting toilets. Nevertheless, the cassette toilet looks likely to retain its pole position for many years to come.

Truma Combi space and water heater

When Truma launched its Combi heater back in 2007, little did they realise just how popular it was going to be. It was the successor to the Trumatic C, launched in 1994, which was essentially a blown air heater with a water jacket, designed for motorhomes. The Trumatic C was great success, with some 500,000 being built, but it was quite bulky and heavy, and it wouldn’t fit under a standard bunk.

The Combi changed all that, with a complete redesign that saw the burner change from vertical to horizontal along with many other improvements. More compact and lightweight, the Combi became available in 2-,4- and 6-kW versions. Each has the option of electric heating elements to provide a dual fuel capability.
It was soon joined by a diesel-powered version which, at 15.8 kg, claimed to be the lightest and most efficient diesel combination heater on the market.
The Combi was an instant hit with motorhome manufacturers but one touring caravan manufacturer spotted its potential too. Coachman in the UK (now part of the Swedish Kabe group) liked the fact that it eliminated the need for a gas fire, thereby saving weight and creating usable space for other things. What’s more the Combi could be programmed to go on and off as needed. The only issue was how it might perform off-grid with just battery power available. Tests showed this would not be a problem and so, in 2012, Truma’s Combi boiler was fitted to all but Coachman’s top of the range models (which had Alde hydronic heating).
Other caravan manufacturers quickly followed suit and today the Combi can be found in many touring caravans as well as countless motorhomes and campers.

The Combi was such a good design it has remained largely unchanged from 2007 until now, although an enhanced diesel version was launched in 2022. However, at the 2024 Caravan Salon, Truma’s owner, Alexander Wottrich, announced that an improved version would be launched in the coming months. As he put it “Many have tried to improve on the Combi, but we have succeeded”. We look forward to reporting on it in this magazine.