Standard bed MAN HX60
As described in an earlier post, we decided tot use the standard platform as the base to mount our Box on.
This means that we have a rather stiff platform that will not twist a lot. It is a rail on rail system with captive springs. It is designed bij Rheinmetall – MAN for off road military (transport) use, so we thought that it would do for our purposes.
The platform already has four build in twistlocks and for us the perfect solution to mount our Box.
Stiff Box on a stiff platform.
The platform itself is stiff, so we needed a Box that is stiff as well. The floor of our Box consists of 12 cm. thick steel beams welded in waffle form. This caters for a very strong and stiff floor. This floor is placed on the bed of the HX60 and fixed with the existing twistlocks.
This all adds to the stiffness of the total construction. We have very little flex – or twist in the bed (and Box), just what the captive springs allow, so most flexing and twisting has to come from the springs of the truck. It also means that we will loose a ‘foot on the floor’ sooner than someone with a four point subframe.
Another tradeoff is weight. The bed is supposed to weigh around 1.000 kgs (I did not weigh it) and a decent subframe will be around 300 – 400 kgs (I guess?) so we are 700 kgs heavier than could be. On our total travel ready weight of 15,5 tonnes it is not a dealbreaker. More importantly, we have a perfect weight distribution of 47% on the front axle and 53% on the rear. The total weight makes the suspension more comfortable and our Mountain Yacht never feels too heavy.
Little flex, off road problem?
Is it a problem that our HX will lift a leg sooner? Our Mountain Yacht is mainly build for (off road) travelling and is our home away from home. This means that we will not go rock climbing or cross the harshest marshlands. So for us the off road capabilities are just as important as the on road manners as we will be spending most time on tarmac – getting to destinations.
I have driven four point subframe trucks in the past, very good at keeping all feet on the floor, but wobbly in corners (we do a lot of hairpins) and less stable at high wind high speed travelling.
Furthermore: our MAN HX60 has differential lockers all around, so lifting a wheel is not the worst thing, the locker will make sure the other wheel gets the momentum needed to keep on going. We also have the Rotzler hydraulic winch as a last resort rescue option.
20.000 km. down the (off) road
It is November 2023 and we have done almost 20.000 kms, we bought the truck unused. We have been travelling all over Europe, mostly the Alps in winter and we did a roundtrip Germany – Switzerland – Italy – Greece and the Balkan countries in summer. Our Mountain Yacht has been in temperatures from -18C. up to 45 C.
We have been in severe snow storms on narrow mountain passes and on extreme soft sandy beaches in Albania. Up to now, we have never been stuck (yes, we know, that day will definitely come) and our HX60 has been performing really well off and on the road. For us it is sufficient, when we wanted ultimate off road capabilities we would have bought a MAN KAT.
Where does this setup shine?
Our rather stiff setup totally shines when it comes to very stable behaviour in any conditions: on road with extreme winds – no wobbling, on- and off road in (high speed) curves: very secure and relatively flat. It feels like I can just point and shoot, almost like a regular car, although not as light footed.
As we travel the most km’s on tarmac or decent dirt roads (most of us do) these rock solid driving qualities are very important to us. And horses for causes, when you want to go rock crawling, you definitely need a four point subframe, and not our Mountain Yacht.
We read somewhere that a four point subframe would give too much stress on the chassis of the HX60, which is not build to withstand the extreme torsion and twists that a four point subframe can give. We do not know whether this is true but it certainly was no consideration for our decision making process. Anyone ideas or first hand experience on this?
I think that this video of a dirt bike race track shows it very well. The Box (and bed) move very little and the suspension does all the work. We drive at a decent speed, especially at the end of the video, in the last corner and the right turn just past the bridge you can see just how stable it is.
We are very happy that we have chosen the existing bed as the platform for our Mountain Yacht. Compared to a four point subframe, we traded some off road capability for fantastic (off)road behaviour, especially in short or longer corners. It also excels at higher speeds, especially with strong winds. And last but not least, we saved around € 9K not choosing the four point subframe. For us this ticks all the boxes and after almost 20.000 km’s we believe that we made the right decision for our kind of use. The fact that more and more Box builders are going the same direction (for example renown Bliss) only confirms our decision.