Hi
egn,
Thanks for that feedback – it moves things along nicely. Just some more questions, and in the fourth section, an observation.
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1. The Second Choice?
In the last section of my post above, I wrote that most potential customers shopping for a very large, UniCat or ActionMobil type motorhome, are probably not interested in rock-crawling, nor extreme, Ralleye-style off-road travel. And that, as such, a Unimog might be overkill. It seems that most potential customers would opt for the second choice, in your list of choices. Do you agree?
It seems to me that you, personally, have opted for the second choice with your MAN-KAT, because as you explained in the
“pivoting frames and mounting campers” thread, you deliberately lowered the distance between the rear tires and the lower edge of the platform:
My cabin was originally about 2.48 m high and the total height at 18 t with 14.00R20 tyres was 3.90 m. An unloaded KAT has its platform at about 1.70 m. I didn't keep the original distance between the rear tyres and the lower edge of the platform, but reduced it about 5 cm to save height. This is no problem because we our motorhome is not intended to be used in the extreme situations, where this extra space is needed. It is designed as overlander and we wouldn't risk it by pushing it to very extreme terrian where crawling is necessary. The risk causing damage would be much to large. It is our home and not an off-road rallye vehicle. Other people installing 16.00R20 tyres on an old KAT will have the same problem with platform distance.
As I added solar power in the meantime, the total height is now about 3.95 cm, when it is fully loaded with 1300 l fuel and about 650 l water and other supplies for a total weight of about 18 t. Even if I wanted I couldn't install 16.00R20 tyres.
There is still room between tyres and cabin when the suspension limiter is hit on both sides. But the tyres will hit the cabin when we would crawl through extreme terrain, where one side of the axle is going up and the other side is going down into extreme position. The cabin is protected against collision by a 4 mm thick aluminium plate at the lower side. With hydraulic suspensions of an SX the height can be kept constant independent from load. A friend, who is also one of the best KAT mechanics available, has installed a hydraulic suspension to his 4x4 and can control everything regarding suspension.
– see
http://www.expeditionportal.com/for...35?highlight=pivoting+frames+mounting+campers.
I get the impression that you are a fairly typical sort of customer for this range of the market, and that's why having these leisurely discussions with you are proving so valuable!! :ylsmoke: It's still 5 or 6 months away from when my thesis project "officially" begins, but in the two weeks that I've been blogging on the ExPo forum in earnest, I feel that my thinking has advanced by many additional months.....
So if you are in fact typical for this market-segment, then the second choice is probably where my design efforts should be targeted, right?
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2. Length Questions
You personally opted for 9.3 m, and you and your wife are happy with this length. But you also think that the vehicle should
not be designed around the size-limitation of European RV-park camp-sites. So are there any other reasons why 9.0 m long would be preferable to 10.0 m, or 10.0 m preferable to 12.0 m, the upper legal length-limit?
If ferry toll costs were not an issue, does a 12.0 m length make sense? And if not, why not?
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3. All-Wheel Steering
I agree with you that systems should be as simple and robust as possible, so that nothing critical is likely to break down far from civilization.
However, that's exactly why I was so stunned when I came across the literature about all-terrain cranes. These things are really robust, they are built like tanks, and they are built to work. They are commercial vehicles that have to be on-site and working properly 24/7, so that their operators can recoup their investments and turn a profit. Often they will work at considerable distance from any kind of paved road, so if they break down off-road, it will be a big hassle to recover them, and the down-time will cost their operators plenty.
The all-terrain crane “market”, in short, probably forces crane manufactures – and ZF industries – to produce very reliable products. Furthermore, because time is money, the newest cranes can also travel at comparatively high-speed (65 mph) on paved roads and highways. When you described these cranes as slow, I think you might still have in mind the off-road cranes of 20 years ago?
The only question is whether they can travel at
high speeds off-road. The SX-45 and the Tatra 815 series not only can handle off-road terrain, they can handle it
fast – see
http://www.tatratrucks.com ,
http://www.tatratrucks.com/trucks/customer-segment-catalog/defence/ ,
http://www.tatratrucks.com/trucks/c...ity-heavy-duty-universal-cargo-troop-carrier/ ,
http://www.tatratrucks.com/trucks/product-catalog/t-815-7/ ,
http://en.wikipedia.org/wiki/Tatra_815 , and see the dynamite video at
http://www.tatratrucks.com/about-th.../vojenska-rada-tatra-t-815-7/?section=defence . Also see:
SHORT VERSION:
LONG VERSION:
I fully agree that the frame of an all-terrain crane is much too heavy. Such a frame is designed to bear the weight not just of the vehicle, but also of the huge crane on top, and whatever load it might be lifting.
But the frame of an offroad crane does
not interest me. It's the ZF-industries all-wheel-drive/all-wheel-steering that interests me.
So my only question is whether ZF all-wheel-drive/all-wheel-steering, of the sort used by cranes, could also reliably handle lots of bad-road driving at reasonably high speeds? I don't expect it to handle extreme ralleye-style off-road driving, or rock-crawling. But if it can handle bad-road driving just as well as standard Tatra or SX-45 steering, then why not?
It's also worth noting that both the front
and the second axles of the SX-45 8x8 can steer. Only the rear two axles do not steer. So if the second axle of the SX-45 has already been fitted with steering designed to work in concert with the first axle, then maybe it's not such a small step to add two more steerable axles at the back? This would make a huge difference to the turning radius, and overall maneuverability in tight spots.
So don't worry, I am not so unrealistic as to propose using an off-road crane chassis as the basis for a motorhome!! That's
not the reason why I brought up off-road cranes. I only brought them up because they have all-wheel-steering, and they have all-wheel-steering designed to work hard, and handle harsh conditions.
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4. Why a Fully Integrated Camper?
In a post on the first page of this thread,
grizzlyj questioned whether an integrated design was even desirable. I've been marshaling a long list of reasons in response, and will post my full argument in about a week. But
egn, I very much appreciate your own explanation:
We are still happy with the size [of our expedition motorhome]. I wanted it to be shorter than 10 m because of the ferry tarif, and it made no sense to have more overhang at the rear. 6 m living space inside is a good compromise for us with this type of vehicle. Of course, more is better, but without more length outside. In this regard, an integrated solution would be great. As I wrote, we had an integrated camper in the past with a total length of 8.2 m. The cab was integrated in the living room and it was really nice to use the space above the seats for a pulldown bed. This all gave a great feeling. We had to get used to the shorter room in the new camper.
Now
grizzlyj's comment on Page 3 of this thread got me thinking:
To have a huge all wheel drive camper and consider Euro campsite use seems a bit contradictory though???
I started wondering,
why contradictory?
Sure, expedition motorhomes have big wheels, they are large, and they might not "fit" into the spaces available at European RV-parks. But one of the most important reasons why expedition-style vehicles stand out in RV parks, is because they
look so different. As many have suggested, big UniCAT and ActionMobil vehicles look like garbage trucks. And the main reason why they look like big garbage trucks, is because they have a non-integrated design.
So one major design goal, perhaps, should be to create an exterior for a fully integrated expedition motorhome that will not stand out so much. An exterior that will seem perfectly happy and visually “at home” in an RV park, European or American. An exterior that will only signal off-road capability by the size of its tires, and ground clearance, but little else.
Sure, the lack of suitably large "pitches" or hook-up sites in most European RV parks will still be an issue. But the potential market for such a vehicle is not just European. One can also imagine American buyers who, given a choice between:
(A) a Class-A motorhome that is not off-road capable,
versus
(B) an expedition-style motorhome that is almost as large as a Class-A, and that only looks a bit different because of the size of the tires,
....might choose the latter.
And they might be willing to pay a 10 or 20 % premium for the latter, because it has the added ability to travel outside the United States, for instance, in Latin America.
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5. Fully Integrated Earthroamer
It would be interesting to know how much Earthroamer customers use their vehicles
inside the United States, in comparison to how much they use them overseas. Earthroamers are mechanically designed to handle Latin-American "bad-road" travel. But one thing that makes Earthroamers so attractive, is that they look like visually standard, albeit rather big, truck-campers. And what's more, Earthroamers are very
beautiful truck-campers:
Again, see
http://earthroamer.com ,
http://earthroamer.com/xv-lt/driving/ ,
http://earthroamer.com/xv-lt/driving/on-road/ , and
http://earthroamer.com/xv-lt/driving/off-road/ .
One can then imagine these vehicles fitting in perfectly well in any American RV park. Nobody would ever describe Earthroamers as "garbage trucks". And no doubt their American owners probably
do use them as "double-duty" RV's: as motorhomes for both American
and foreign travel. In America, at least, there is probably nothing "contradictory" about using these huge, all-wheel-drive campers on standard RV campsites.
Egn, you wrote a bit about cost, and don't worry, I will be keenly aware of overall cost. In terms of market-demographics, I think the target should be exactly the same age-cohort and income-bracket addressed by ActionMobil, UniCat, Earthroamer, and up-market American Class-A manufacturers. But even this market demographic usually cannot afford to buy
two big, expensive motorhomes, one for the First World, and a second motorhome for the Third World. So if it were possible to design a fully integrated motorhome that functions well in
both contexts, and that costs roughly the same as an ActionMobil, it might prove a popular product…..
In a nutshell, the design challenge -- as I see it -- is to create a
"fully integrated Earthroamer". The design challenge is to create a
"go anywhere" motorhome that, like the Earthroamer, will be visually at home everywhere. But a vehicle that, unlike the Earthroamer, might have a UniCat-style pop-up; and that, like the Hymer, will have swivel seating and a fully integrated interior; and that, like the SX-45, will have a rigid, torsion-free box-frame, with progressive coil suspension, to make that interior possible.
All best wishes,
Biotect
