Camper Thermal Engineering for Extreme Cold & High-Altitude: Arctic Antarctica Tibet

[Gatsma]

Biotect- You are most welcome! I did not realize how much impact my short post above would have, but after all I have learned from everyone here, anything I may contribute is but a small token of my appreciation for all the knowledge available in these forums on this board. People like Biotect and Campo are the reason this is such a great source of information about expeditionary travel.
Again, thank all of you!

 

[campo]

Thanks !
The lots of nice reactions you make are motivating me.
We had an overlander meeting this weekend so I did not find time to answer.
Let's go on with some thermal engineering:
We know that we need heating capacity (or cooling) to cover the thermal losses through the walls.
The better word could be the outer peel of the box, because sometimes insulation is doubled by internal walls or furniture.
There is more:
A lot more thermal capacity will be needed for the first heat up starting from cold/warm outside temperatures.
Remember that we have something like 300kg wooden furniture inside.
I calculated that you need about 2.290 Watt to heat up 300kg wood from 0°C to +22°C in 2 hours.
Always trying to calculate practical reality situations and not the ones on the moon.
So we also have the ventilation losses.
Yes it is not a submarine. We will have to make some breathing refreshment holes.
The theory is that we ventilate a lot more in normal conditions and less in extreme.
For the calculations it is easy to average the calorific ventilation losses at 500 Watt for 2 persons living on board.
These 2 persons will generate body heat (125 Watt per person).
Of course it depends from the moment (reading a book it is only 70 Watt for the tiny lady)
We have some equipment on board that generates heat.
The fridge, inverter, lights and others are heaters with total thermal capacity of 100 to 300 Watt depending of their status.
And last but not the smallest heat capacity is needed for the warm water calorifier and the frost protections of the outside water tanks.
With the spiral loop that I welded in these stainless steel tanks I estimate that it can transmit up to 2000 Watt heat in the insulated black and grey water tank situated outside under the vehicle.

 

[Gatsma]

And the education continues.....

 

[campo]

All this calculations are only because I want to know which type of heater and airconditionning I have to use for the world tour.
After the sizing I will have the problem to find components that cover the whole thermal range as indicated and not only the extreme situation.

 

[dwh]

View attachment 244351

Looks like they had to relocate the radiator. Though some of those trucks (older ones?) have an air-cooled engine, so maybe it's just for ducting...

 

[campo]

The thermal calculations show us that we will have to install a system with a maximum heater capacity from something like 7.000 Watt.
This heater will have to run for very long periods between 1000 and 2000 Watt and even lower.

For the air-conditioning we need a maximum cooling capacity up to 2.500 Watt.
The air-conditioning will be used for long periods between 1.000 and 2.000 Watt.
My first opinion is that all these capacities are low, I would have thought more.
So this is what I will install in my RV expedition truck
Than I have still to adapt the 2 values were Biotect had remarks:
The calculations winter extreme outside temperature is now -30°C and he proposed -40°C
The side walls are only 40mm thick and he proposed more so I will make them 60mm to see if it changes the results considerably or not.

I repeat here (with Fahrenheit) what I did calculate:
What is the outside temperature in winter times?
The heater supplier Eberspächer says that it’s gasoil heaters will work down to -40°C (-40°F)
But we calculate as extreme with -30°C (-22°F) . If more heat power is available no problem.
The normal cold winter conditions will be like -10°C (+14°F)
AND 70 % of the time the heaters will have to work at ambient +5°C(+32°F)
Inside calculation temperature is chosen +22°C (+72°F)
We would like the system to cover all the above mentioned range.

Summer temperatures (same idea)
Extreme outside +45°C (113°F) cool down to interior +28°C (82°F)
Summer warm +28°C (82°F) cool down the interior to +24°C (75°F)
This last one is what the AC system will have to deliver in 70% of the time that it is wanted to function.

 

[biotect]

Hi Campo,

Very interesting calculations.

I just wanted to add two things here:


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1. Blue Thunder


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Blue Thunder is a MAN-KAT conversion that belongs to egn, and it was designed for most climatic zones.

egn defines "most climactic zones" as follows:

As we want to go in the not to far future on a long voyage through most climate zones, our truck is designed to go into environment for a temperature range of about -40 C to +50 with enough supplies to stay there for weeks. Alone for the supplies like water, food, fuel we can spend a few metric tons of payload, and we try to save supplies by using them efficiently, where it is practical.

And you shouldn't rate the comfort to low. On a long-term trip it has similar importance as the other ones. Because the vehicle is becoming your home only if you feel comfortably.

BTW, the intended use is also an important design factor. A expedition camper used only part-time for vacation for a few weeks during the year can be designed totally different as a expedition camper used as mobile home all over the earth.

See post #103, at http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page11 .

I've now had well over one hundred exchanges with egn on this forum, always on the "Fully Integrated Man or Tatra" thread. As near as I can tell, he is a German automotive engineer by training. So egn's claims are not to be taken lightly: he really knows what he is talking about. And of course it also helps that he owns Blue Thunder, a very impressive, 6x6 MAN KAT:










For further technical information about Blue Thunder and lots of pictures, see http://www.expeditionportal.com/forum/threads/11614-MAN-6x6-camper , http://www.enfatec.de/index.php?id=54 , http://translate.google.co.uk/translate?hl=en&sl=de&tl=en&u=http://www.enfatec.de/index.php?id=54 , and http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/20933867/srt/pa/pging/1/page/1.cfm .

Here are the technical specifications on the Enfatec website for Blue Thunder's walls:

Building construction

• Self-supporting sandwich plate panels ENFATEC- of fiberglass composite plate thickness 60 mm with 55 mm PU foam insulation, insulation value 0.44 W / m² K.
• Fabric reinforced layers 3 mm / 2 mm
• Glued to ENFATEC ALU SYSTEM PROFILES
• Corners reinforced with ENFATEC ALU SYSTEM CORNER
• Base plate with integrated welded steel frame reinforcement

And here is a partial description of the heating system: the first from the Enfatec website, and the second from the "Fully Integrated Man or Tatra" thread:

Heating

• Hot water central heating (9 kW) diesel operation
• Cab heating
• High radiant heat share due to radiators in living area, shower and toilet room
• Additional electric heater 220V 2kW with antifreeze circuit

We have a Webasto Thermo 90 ST diesel heater for both space heating and warm water. For warm water we have a boiler that is heated by a heat exchanger or electrically.

For the second, see post # 164, at http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page17 .

I should add here that egn's boiler is an Isotemp Isotherm Basic 40 double-coil with 750 W/230 V heating element -- see http://www.indelwebastomarineusa.com/Products/us/html/7957.html .

In short, as indicated earlier, 6 cm wall thickness seems a reasonable assumption for a "round the world" expedition motorhome. But it would still be very interesting to know whether increasing the wall thickness from 4 cm to 6 cm changes your calorific calculations very much!!


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CONTINUED IN NEXT POST
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[biotect]

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CONTINUED FROM PREVIOUS POST

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2. The DoLeoni MAN KAT


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I also wanted to mention the the technical specifications for the DoLeoni MAN-KAT. Like egn's Blue Thunder, this too was designed as a "round the world" expedition motorhome. Here are the measurements for the thicknesses of the walls, the roof, and the floor:

Features of the Passenger Cell:

• Royalplastic construction in Vinilestere resin with smooth edges
• Thickness of side and front walls – 6 cm
• Thickness of rear wall and roof – 10 cm
• Thickness of floor – 14 cm
• KCT double glazed windows with dimmers and insect screens

See http://www.doleoni.com/wp/en/man-kat-1-a1/ . And here are some images of the Doleoni MAN-KAT:








In other words, here again we have 6 cm thick walls. But we also have a much thicker roof and floor, respectively 10 cm and 14 cm, similar to the Mongolian Zetroses that were mentioned earlier. It seems that increasing the thickness of the walls and the floors beyond 6 cm would be important in order to improve insulation? But if I am wrong about this, please correct me.

All best wishes,



Biotect

 

[campo]

Hi Biotect
I know both trucks, the Blue Thunder from EGN as well as the Doleoni who is for sale.
They are huge, beautiful and certainly impressive.
These massive vehicles are more than 30 years old and that is not what I wanted to do.
Both vehicles are recently re-equipped with high end luxuous living compartments.
Be aware that from the other side they do not have modern on board electronic driving management,
no fault diagnostic with OBD2, no ABS, no disk brakes, no air suspension, no cruise control and so on.
On the highway the MANCAT 1A's red zone ends where my green zone starts.
The fuel consumption there is double, the maintenance cost triple, the exhaust gasses quadruple and the noise soo nice but very loud.
They suffer and the old timer vehicles can be forbidden or highly taxed in a few years.
Probably they can do the same extreme environments as my modern truck.
The maniability and weight will be a dis advantage.
One failure of the only one big Webasto unit and the fun is over.
I have several redundant small units and continue my travel in case of failures.
And can they cover a wide thermal range for example in heating from 600 Watt up to +7.000 Watt ?
And can they overnight in silence with AC, for more then 12 hours on batteries ? Genset is not an option for me, too loud to sleep with.
Probably some parts of their insulation, heating and cooling system are overdone and not really calculated.
OK me too I love these "cult" vehicles.
You have to compare it with a Harley Davidson purchase.
More expensive, slow, not very useful for most driving but such a nice sound.
I have more focus on today and tomorrow solutions and I am working on the front side.

I made a note that I have to compare in my calculations between -30°C and -40°C.
As I have to do with the wall insulation thickness.

 

[campo]

@Biotect
Maybe you can compare some pictures...

 

[biotect]

Hi Campo,

I agree with you: a 30-year old MAN-KAT A1 as a "base" is a very distinct kind of choice. Like buying an old Harley Davidson.

However, let me be very clear: in my designs for a "concept vehicle", this is not what I have been imagining! Rather, I have been imagining a completely new base chassis. And of course an advanced propulsion system, some kind of serial hybrid arrangement.

I only referenced these vehicles above for their campers, their wall-thicknesses, and their "targeted" temperature ranges: -40 C to +50 .


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But I also referenced them for their size overall, because I am designing a 6x6 concept vehicle, and not a 4x4 concept vehicle. I am designing a concept vehicle roughly the same length overall as Blue Thunder, or the "Concorde" Liner Plus: 9.5 m. Except that, unlike Blue Thunder, my design will be "fully integrated". The cab will not be separate from the camper.

For an explanation of what I mean by "fully integrated", please see page 1, at http://www.expeditionportal.com/for...-8x8-Expedition-RV-w-Rigid-Torsion-Free-Frame . This explains the idea, and it explains how a large, fully integrated expedition motorhome is possible from an engineering standpoint. As you know, torsion-free chassis frames that can support fully integrated, expedition motorhomes do exist: the MAN SX-44 and SX-45, and the Tatra 815.

But I should also note, just in case you jump to the wrong conclusion, that I am not interested in the 8x8 versions of these vehicles. I am only interested in the 6x6 versions.

Now in my own opinion, 9.5 m is not too long. You may disagree. But there is a range of opinion about this matter in the world of expedition motorhomes. Some say that 7 m should be the maximum possible length. Others say 8 m. Others say that the best vehicle is an SUV with a Roof-Top Tent. Others say that nothing beats overlanding by motorbike. However, there is also something in addition to be said: the largest 3-axle UniCat and ActionMobil vehicles are even longer than 9.5 m. The longest 3-axle vehicles that UniCat and ActionMobil produce are 10 m - 11 m long.

And even longer, four-axle, 8x8 vehicles also exist, made by ActionMobil. The "Desert Challenger", for instance, is 12 m long -- see http://actionmobil.com/en/4-axle/desert-challenger. But again, I have no interest in a 12 m 8x8. I am designing a 9.5 m 6x6.

So perhaps I should emphasize that I really have no interest in doing a concept design for a 4x4 expedition motorhome that is just 6 or 7 m long..... ....If you read the "Fully Integrated MAN or TATRA" thread, you will see why. It's best not to go over all of those arguments again here, in this thread. I have already stated my position very clearly, in that thread. So if possible, please just accept that I will be designing a concept expedition motorhome that is 9.5 m long, and that is 6x6.


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Now if it's not too much trouble to ask, it would then be great if you might be willing to do a set of calculations for a vehicle that is very much like a "fully integrated" ordinary motorhome..... ....You know the kind: a Hymer or a Concorde that is a "one room design". No separation between cab and camper, and roughly 9.5 m long. See post #72 at http://www.expeditionportal.com/for...xpedition-RV-w-Rigid-Torsion-Free-Frame/page8 , and here are some images:


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But again, same basic temperature parameters: -40 C to +50 .

For additional information about large Concorde “Liner class” motorhomes, please see http://www.concorde.eu/de/modelle/ , http://www.demo.spherovision.de/me/concorde_cruiser/0_spherovision_webpan3/sv_wp3_viewer.html , http://www.concorde.eu/de/modelle/liner-plus/beschreibung/ , http://www.concorde.eu/de/modelle/liner-plus/ausstattung/ , http://www.concorde.eu/de/modelle/liner-plus/grundrisse.html , http://www.concorde.eu/media/filestore/1/1/8/2_c68542918dea18c/1182_c7e333f6747fe73.pdf , http://www.demo.spherovision.de/me/concorde_liner/0_spherovision_webpan3/sv_wp3_viewer.html , http://www.concorde.eu/de/modelle/liner-centurion/beschreibung/ , http://www.concorde.eu/de/modelle/liner-centurion/ausstattung/ , http://www.concorde.eu/de/modelle/liner-centurion/grundrisse.html , http://www.concorde.eu/assets/files/kataloge-2014/14319_Liner Centurion_RZ.PDF ,http://www.demo.spherovision.de/me/...ion/0_spherovision_webpan3/sv_wp3_viewer.html , http://www.concorde.eu/de/modelle/centurion/beschreibung/ , http://www.concorde.eu/de/modelle/centurion/ausstattung/ , and http://www.demo.spherovision.de/me/concorde_centurion/0_spherovision_webpan3/sv_wp3_viewer.html.


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Now yes, I know that this is not a standard design for an expedition motorhome. I know that in most expedition motorhomes the cab is almost always separate from the camper. That way the camper can be mounted on a separate, 3-point pivoting sub-frame, so that the underlying base chassis can flex and twist.

In short, what I am proposing is not a standard design. But that is exactly the point. That is the whole reason for doing my MFA Thesis to begin with: to suggest that a very different kind of fully integrated, 9.5 m long, 6x6 expedition motorhome could be possible. What I am designing is a concept vehicle, after all.....

A concept vehicle is not supposed to resemble almost every other expedition motorhome that has ever been built, in which the cab and camper remain separate. If I designed a very standard sort of expedition vehicle for my MFA thesis, I would fail the course. They would kick me out of Art School.....:sombrero: Because from a concept point of view, there is nothing interesting and nothing original about an expedition motorhome that has a cab that is still separate from the camper. It has been done hundreds of times before. Whereas what has rarely been done, for an expedition motorhome, is a fully integrated vehicle.

One of the few, rare examples is Peter Thompson's Mañana. For a full description of Mañana, see post #212 at http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page22 .

Here I should note that Mañana is 10.74 m long, and has travelled all over Australia, including some very challenging bad roads, like the Gibb River Road, and the Tanami Track. Peter Thompson built Mañana on top of a rather ordinary kind of MAN civilian truck chassis, which was probably a mistake. Peter has written to me that if he were to build Mañana again today, he would build it on top of a new MAN SX-45 or Tatra 815 torsion-free chassis.


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Now as you say, it is very possible that in the DoLeoni MAN KAT and Blue Thunder vehicles just referenced above, the insulation, the heating, and the cooling systems are "not really calculated". So that's what makes this dialogue with you so interesting!

So again, if possible, it would be great if you might be willing to do calculations for a fully integrated "one room design" that is 9.5 m long, 2.45 or 2.5 m wide, and with a roof topping out at 3.9 or 3.95 m..... A one-room design that could handle temperatures as low as -40 C, and as high as +50 . And sure, I realize that the glass used will have to be thermally superb. And even then, insulating "shades" of the sort shown in some of the images above would probably still be necessary in weather below -15 C. Or perhaps window-covers that are even more powerfully insulating would be necessary.....?

In closing, I hope that the above was not too direct. But thought I should make it clear where I am coming from, and the kind of design parameters that I am personally most interested in.

If you don't have time to make these calculations, no worries! Furthermore, it will still be very interesting to see your calculations for a smaller, much more ordinary kind of expedition camper box: the kind of camper box that goes on top of a 4x4 motorhome, and that remains separate from the cab. And it would be great to see you develop your thoughts on that, for whatever temperature ranges you prefer, and for whatever thicknesses of wall, roof, and floor insulation you prefer. But just thought I should make the kinds of design parameters that I personally have in mind, also very clear.....

All best wishes,



Biotect

 

[campo]

Hi Biotect
I understand your ideas to design a fully integrated 6x6 concept vehicle.
Remember that I have been inside the 8x8 Unicat's, several times on the Eurosatory fair, BK and many others.
I have met variants of trucks with the MANKAT chassis but other cabins than the ones that EGN and Doleoni have.
You can find them today in the VEKA racing team and already in the very past in the OMAN military versions with the
same as MANKAT spiral spring, but the already “modern” F80 cabins.
The blue thunder and deleoni are for me not fully integrated concept as what you want to do.
Neither the family Tatra 6x6.
Look closely to the fixation of the RV box on the chassis frame.
As you have to look to find the attachments between driver cab an RV body.
But that is for your other thread.
There in the very north where the above pictures are made, we had also the TGS 6x6 26430 who had some manoeuvrability
troubles so the driver abandoned it and toke the quad to follow us.
The longer 19ton 6x6 vehicle with 6m box could not cross the same rivers as we did with the lighter 4x4 with weights between 10 and 11 tons.
We had also the 4x4 family TGM doka 18340 with 6 persons on board.
This 10m long and weight 12,5 ton 4x4 with 14R20 had no problems to get through.
Of course we cannot go with the 13290's there where others can go with smaller vehicles.
For the thermal discussion I will help you with the calculations for your concept vehicle.
I made a spread sheet and can introduce other parameters than the ones I used for my expedition RV.
The results are of course related to the theories that you have in mind.
It are the translations to English that take me most energy.
Change the length, wall thickness or ambient temperatures is not a problem.
Would your front wind screen in the concept vehicle be double thermic glass and does that exists?
I found out that I had to make the walls not thicker than necessary. You lose space and win no strength.
The extra cost is negligible for thicker walls with more insulation. But every door opening becomes a heavy struggle.
Normally also on an extreme thermic vehicle has to be finger light.
What is the percentage of thermal losses through the walls compared to the losses through, windows, cold bridges, ventilation and the rest ?
Best wishes Campo

 

[biotect]

.

It is the translations to English that take me most energy.

Hi Campo,

Many thanks for your reply.

First off, thought I should mention that Google Translate tends to be fairly good, especially for translation between Indo-European languages – see https://translate.google.com . Perhaps you are already familiar with it? Google Translate becomes a bit less reliable when the languages are more “linguistically distant” from each other, as per Chinese and French, or Arabic and English.

But English and French share a huge common vocabulary: about 28 % of all English words come from French. Another 29 % of English words come from Latin (mostly medical, scientific, and legal words), and 26 % of English words come from German. However, most of the commonly used, everyday words in English come from German. And the structure of English is more Germanic than French. Which is why linguists classify English as a “West Germanic” language – see http://www.grammarphobia.com/blog/2010/01/why-is-english-a-germanic-language.html , http://en.wikipedia.org/wiki/West_Germanic_languages , and http://en.wikipedia.org/wiki/Germanic_languages .

So when you write in English on forums like this, just imagine that you are talking to a bunch of geographically displaced Germans.....:sombrero:

About 8 years ago when I was still completing my B.A., I taught in a ESL (English as a Second Language) summer program in Switzerland, where students came from all over the world. By the far the best English-learners were the Germans and the Scandinavians, because for them English is very linguistically similar to their native languages. Whereas learning English was the most challenging for the Chinese and the Japanese. And so too, oddly enough, for Spanish speakers.

Why Spanish speakers? The explanation usually runs that Spanish speakers are the least motivated to learn English, because they already speak an international language, namely, Spanish. Spanish speakers can travel all over Central and South America and be understood. So even though Spanish is linguistically “closer” to English than Chinese, the average level of Chinese competence in English is actually superior to the average level of Spanish-speaker competence. The Chinese know that very few people outside China know how to speak Chinese. And so if the Chinese want to be understood by foreigners, they have to learn English. The same is not true for Spanish speakers. After Mandarin, Spanish is the most widely spoken language in the world. Yes, there are even more native-born Spanish speakers than English speakers – see http://en.wikipedia.org/wiki/List_of_languages_by_number_of_native_speakers . And throughout Latin America, Spanish functions as the de facto "lingua franca". So one could argue that the world currently has two “international languages”, or two “lingua francas”: Spanish and English.

In any case, Google Translate should be able to translate all ExPo pages, and it should be able to help you translate your French or German sentences into English ones….

See for instance -- http://translate.google.co.uk/trans...old-amp-High-Altitude-Arctic-Antarctica-Tibet and http://translate.google.co.uk/trans...old-amp-High-Altitude-Arctic-Antarctica-Tibet .

Don't worry about getting your grammar or lexicon completely right. What matters is not perfection, but rather, communication. As long as you understand me reasonably well, and I understand you reasonably well, that's all that matters.

All best wishes,



Biotect

 

[biotect]

Campo,

Now, continuing with the substance of your post:

I understand your ideas to design a fully integrated 6x6 concept vehicle.

Remember that I have been inside the 8x8 Unicat's, several times on the Eurosatory fair, BK and many others.
I have met variants of trucks with the MANKAT chassis but other cabins than the ones that EGN and Doleoni have.

You can find them today in the VEKA racing team and already in the very past in the OMAN military versions with the
same as MANKAT spiral spring, but the already “modern” F80 cabins.

The blue thunder and deleoni are for me not fully integrated concept as what you want to do.
Neither the family Tatra 6x6.

There in the very north where the above pictures are made, we had also the TGS 6x6 26430 who had some manoeuvrability
troubles so the driver abandoned it and toke the quad to follow us.

The longer 19ton 6x6 vehicle with 6m box could not cross the same rivers as we did with the lighter 4x4 with weights between 10 and 11 tons.
We had also the 4x4 family TGM doka 18340 with 6 persons on board.

This 10m long and weight 12,5 ton 4x4 with 14R20 had no problems to get through.

Of course we cannot go with the 13290's there where others can go with smaller vehicles.

Yes, I agree: the standard format of a Tatra 815 6x6 truck, or a MAN SX-44 truck, is not what I want. And the format of egn's Blue Thunder is also not fully integrated. This is all very obvious.

But I only want the chassis frame of a Tatra 815 6x6, or a MAN SX-44 truck. I do not want the cab, and I do not want the complete truck.

For instance, did you know that Tatra sells vehicles with just a frame and an engine, and no cab attached? See http://www.tatratrucks.com/underwood/download/files/tatra-t815-790r99-8x8-chassis_en.pdf and http://www.tatratrucks.com/underwood/download/files/tatra-t815-790rk9-6x6-chassis_en.pdf .

Again, I am only interested in the chassis frame. I want to build something completely new on top of the frame. And I am only interested in the MAN or TATRA chassis frame because it is torsion-free, and it does not twist. That way a fully integrated design for an expedition motorhome becomes possible. When Peter Thompson built Mañana, the first thing he did was remove the cab from the chassis frame. He had no use for it. He only used the MAN chassis frame + engine -- see http://www.thompsons.au.com/motorhome/ .

campo, if you check out the "Fully Integrated Man or Tatra" thread, you will see that literally everything has been discussed in tremendous detail there -- see http://www.expeditionportal.com/for...-8x8-Expedition-RV-w-Rigid-Torsion-Free-Frame . Probably almost every possible objection that you could ever think of, has already been raised and discussed in detail in that thread....

Please trust me on this: I have been thinking about and discussing this idea for a "concept expedition motorhome" for more than a year. And for almost 6 months here on ExPo, in the "Fully Integrated Man or Tatra" thread.


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1. A Few More Thoughts on Size......


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The longer 19ton 6x6 vehicle with 6m box could not cross the same rivers as we did with the lighter 4x4 with weights between 10 and 11 tons.

Yes, I know there is always a trade-off between size + weight, versus geographic reach. But when it comes to imagining the design of a vehicle that one will live in full-time, for years on end, travelling the world at great length, I tend to lean in the direction of more size and more weight. And my sense is that many people who have seriously considered what it might be like to live in the same motorhome for year after year, also tend to favor bigger vehicles. Even if this means less geographic reach.

Granted, an expedition vehicle based on an SX-44 or Tatra 815 6x6 chassis would not be small. But it would not exactly be huge either. Again, egn’s “Blue Thunder” is 9.3 m long – see http://www.expeditionportal.com/forum/threads/11614-MAN-6x6-camper , http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/20933867/srt/pa/pging/1/page/1.cfm , http://www.enfatec.de/index.php?id=54 , http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page25 . This may seem very large for an expedition motorhome, but it would still be considered "small" when compared to the wider world of German "Liner"-class motorhomes, or American Class-A motorhomes.

German "Liner” motorhomes are typically 9 - 12 m long, and American Class-A motorhomes are considered “small” if they are 35 feet long (10.67 m), “medium-sized” if they are 41 feet long (12.5 m), and only truly “large” if they are 45 feet long (13.71 m). But even if they are 45 feet long, it seems that American Class-A motorhomes still manage to find campsite spaces in most North American natural parks, for instance.


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2. A Tatra 815 6x6 weighs no more than a Zetros 6x6


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As for weight, as near as I can tell, there is no significant difference in weight between a Zetros 6x6 chassis, and a completely new Tatra 815 6x6 “Phoenix” chassis. See post #84 at http://www.expeditionportal.com/for...xpedition-RV-w-Rigid-Torsion-Free-Frame/page9 , and see grizzlyj’s reply in post #85. However, the Zetros 6x6 chassis twists and bends, whereas the Tatra 815 chassis is completely torsion-free. So it is possible to build a fully integrated motorhome on top of the Tatra chassis, but not on top of the Zetros. And yet the Tatra will weigh no more than the Zetros.

There are literally hundreds of webpages that discuss the pros and cons of different sizes and types of mainstream motorhomes – see for instance http://changingears.com/rv-checklist-rv-types.shtml?sec-learn , http://www.rvbeachbum.com/types-of-rv.html , http://www.your-rv-lifestyle.com/motorhome-versus-fifth-wheel.html , http://www.campingroadtrip.com/tips-and-articles/what-type-of-rv-is-right-for-you , http://www.familiesontheroad.com/resources/choosingRV.html , http://www.familiesontheroad.com/resources/buyingRV.html , http://technosyncratic.com/2011/05/16/rv-pros-cons/ , http://www.technomadia.com/excuses/ , http://www.technomadia.com/2012/02/family-aspects-of-a-nomadic-lifestyle/ , and http://www.rvlifestyleexperts.com/free-rv-info/getting-started/rving-the-long-and-the-short-of-it/ .

But what seems to come up again and again, is that if one really intends to use one’s motorhome full-time, as one’s primary residence, then bigger really is better, even if this means coping with the parking and drivability issues that beset larger vehicles. The following is a statement by the owner of a Class-A who lives in their motorhome full-time:

Pack light! We've lightened our load a dozen times so far, and are still trying to streamline even more. But don't cut necessities - if you love your toaster, keep it. Don't skimp so much you're miserable - this is not camping, it's living, and even though they call them "recreational vehicles," this is life, not a vacation. You'll need more than you think and less than you think all at the same time.

See http://www.familiesontheroad.com/resources/choosingRV.html.


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3. Towing a Car, "Dinghy", or "Toad"


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In the world of mainstream RV's, Americans who have large Class-A motorhomes for full-timing typically get around the drivability problem by towing a car, “dinghy”, or “toad” – see http://www.motorhome.com/rv-how-to/dinghy-towing-guide/dinghy-towing-fever/ , http://www.motorhome.com/rv-travel-news/its-dinghy-time/ , http://www.motorhome.com/rv-how-to/dinghy-towing-guide/dinghy-towing-basics/ , http://www.motorhome.com/rv-reviews/motorhome-reviews/dinghy-towing-ranger-fx4level-ii/ , http://www.examiner.com/article/rv-101-flat-towing-checklist-for-your-toad-vehicle , http://dinghytowing.rvtravel.com/2012/01/dinghy-towing-guide-for-2012-available.html , http://roadmasterinc.com/index.php , and http://roadmasterinc.com/products/towbars/all_terrain.html :





So I am thinking the same: I am imagining the 6x6 vehicle as a kind of “base camp”.

I really liked Peter Thompson’s arrangement, in which Mañana also had a “TOAD”, i.e. a “towed vehicle”. That way the Thompsons could still explore places where their 35 foot long, 10.74 m motorhome could not go – see http://www.thompsons.au.com/motorhome/ , and post #212 and #214 at http://www.expeditionportal.com/foru...e-Frame/page22 .

Mañana towed a Jeep 2001 Wrangler/Renegade hardtop:













But of course other options exist, like carrying a motorbike in back, or a small 4x4 dune buggy, as per Jago Pickering’s Tatra 6x6 – see posts #236 to #241 at http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page24 and http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page25 .


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4. Image Gallery of Veka Racing 6x6 Rally Support Vehicles


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I have met variants of trucks with the MANKAT chassis but other cabins than the ones that EGN and Doleoni have.

You can find them today in the VEKA racing team.....

Many thanks for this reference to Veka Racing – see http://www.veka-racing.nl/en . The official website of Veka Racing seems to only have images of 4x4 rally racing trucks see – http://www.veka-racing.nl/en/pictures.html . But on pages 5 and 6 of the “CaptainsVoyage” web-forum, there are some terrific images of Veka’s 6x6 rally support trucks – http://www.captainsvoyage-forum.com...ars-buses-trucks-trains/945-sporttrucks/page5 and http://www.captainsvoyage-forum.com...ars-buses-trucks-trains/945-sporttrucks/page6 :





Indeed, this particular thread in the “CaptainsVoyage” forum is more packed with more great images of 4x4 rally racing trucks, than I’ve yet seen posted anywhere else….

All best wishes,




Biotect

 

[biotect]

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1. Thermal Engineering


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Now getting back to thermal engineering……:wings:

For the thermal discussion I will help you with the calculations for your concept vehicle.

I made a spread sheet and can introduce other parameters than the ones I used for my expedition RV.
The results are of course related to the theories that you have in mind......

Change the length, wall thickness or ambient temperatures is not a problem.

Would your front wind screen in the concept vehicle be double thermic glass and does that exists?

I found out that I had to make the walls not thicker than necessary. You lose space and win no strength.

The extra cost is negligible for thicker walls with more insulation. But every door opening becomes a heavy struggle......

What is the percentage of thermal losses through the walls compared to the losses through, windows, cold bridges, ventilation and the rest ?

Best wishes Campo

Many thanks for agreeing to do a separate set of calculations for a 9.5 m long “fully integrated” expedition motorhome.

It's also very interesting that increasing the wall thickness from 4 cm to 6 cm does not dramatically improve the thermal properties of the vehicle. Is the same true about increasing the thickness of the floor and the ceiling?

If this is true, then I wonder why the Mongolian Zetroses and the DoLeoni MAN KAT have such thick floors and ceilings -- 14 and 10 cm thick respectively. And I wonder why UniCats always seem to have walls that are 6 cm thick. ActionMobil does the same. Here is the specification for the Global Cruiser 7400 “Robusto”, a 6x6 that has travelled pretty much all over the world:

The ACTION MOBIL-body:

Construction:

Self supporting sandwich plate panels of fibre glass composite.
Panel connections made by adhesive bond to custom extrusions eliminates metalic heat conduction paths.


Wall thickness 2,40” (61 mm) with polyurethane foam insulation, reinforces polyester.

As far as I know, these pdfs are no longer available on-line, so I cannot give you a direct web-link. For more photos of the vehicle, see ActionMobil's website at http://actionmobil.com/en/3-axle/globecruiser . And for even more photos of this large vehicle travelling the world, see the owner's blog at http://www.waypoints.ch .

So I was just wondering why almost all such vehicles have 6 cm thick walls?

Perhaps mainly for structural reasons, if not for thermal ones? Or is there some other explanation. It does seem strange that they all use 6 cm walls, even though as you've just said, 6 cm walls are really not necessary.


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2. KCT Double-Glazed Windows


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Would your front wind screen in the concept vehicle be double thermic glass and does that exist?......

What is the percentage of thermal losses through the walls compared to the losses through, windows, cold bridges, ventilation and the rest ?

I was thinking that most of the windows would be made by KCT, which seems to be the specialist window manufacturer most widely used by expedition motorhome fabricators – see http://www.kctechnik.com/en/index.html , http://www.kctechnik.com/en/catalogue.pdf , http://www.kctechnik.com/en/retailers.html , and http://www.kctechnik.com/en/gallery/index.html . KCT windows are double-glazed with tempered safety glass, they have a special thermal and sun-protection coating, and they achieve the insulation values of a modern house window – according to KCT….:






In the United States double-glazed windows will also be called “dual pane” or “thermopane” windows. And there are lots of American manufacturers who make them specifically for RVs. See for instance http://www.motionwindows.com , http://www.rvwindows.com/applications/rv-elite-series/ , http://www.rvwindows.com/applications/bus-van-conversion-windows/ , and http://www.motionwindows.com/products/elite-dual-pane-windows-series-1800/ . Ideally these windows would even be triple-pane (three layers). But I have not been able to find a website for a manufacturer that makes triple-pane windows for RVs.

Perhaps you know of a manufacturer who makes triple-pane windows for motorhomes?


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CONTINUED IN NEXT POST
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