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There is also clearly the possibility of what one might call a “half-height space-frame” design: a partial space frame used in lieu of a ladder frame:





For some interesting short engineering essays on the optimization of tubular space-frame design for (a) a student race car, and (b) a solar powered vehicle, using computer modeling, see http://mate.tue.nl/mate/pdfs/12814.pdf and http://www.fisita.com/students/congress/sc08papers/f2008sc048.pdf



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2. Most MAN-Neoplan Buses use Ladder-Frames and Space-Frames, and are not True Monocoque


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Already back in 1953, MAN-Neoplan started making buses with a semi-monoque design. And in 1988, MAN introduced the “MetroLiner”:

The first full monocoque bus in the world which no longer needed any supporting chassis or skeleton. This carbon design vehicle was made as a complete cell entirely of plastic. The exterior of the new NEOPLAN, which was given the name Metroliner, was just as futuristic as the concept as a whole. The Metroliner's low weight made it ideal for alternative drive systems such as hybrid or fuel cell concepts.

The MetroLiner's monocoque design was 50 % lighter than more typical bus designs – see http://en.wikipedia.org/wiki/Neoplan , http://web.archive.org/web/20080602...f_NEOPLAN/History/Milestones/1982_to_1991.jsp , http://www.man.eu/man/media/en/cont.../presse_und_medien_1/BUSLIFE_1_10_Neoplan.pdf , http://www.neoplan-bus.com/cms/media/en/content/downloads/marke/jubilaeum75jahre.pdf , http://www.coachbuilt.com/bui/n/neoplan_usa/neoplan_usa.htm . Here are some images of the MetroLiner:







But apparently the MAN MetroLiner had some problems, and the design was not followed up with future model derivations – see http://www.traditionsbus.de/Fahrzeuge/neo_mic.htm , and http://translate.google.co.uk/trans...://www.traditionsbus.de/Fahrzeuge/neo_mic.htm . If you type “MAN + Neoplan + Monocoque” into google, you will get pretty much nothing, except for references to this 1988 Metroliner.


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However, MAN Neoplan does make buses with tubular space-frame designs. See for instance the CityLiner description, at http://www.neoplan-bus.com/cms/en/skyliner/sicherheit/skyliner_sicherheit.html , http://www.neoplan-bus.com/cms/en/cityliner/cityliner_galerie/galerie.html , and http://www.corporate.man.eu/en/company/production/man-truck-and-bus/Starachowice.html :









[video=youtube;9zY8biWGUCg]https://www.youtube.com/watch?v=9zY8biWGUCg [/video]



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3. The Pros and Cons of Ladder Frames versus Tubular Space Frames in Buses


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Now it would be a mistake to think that all MAN Neoplan Buses use tubular space-frames.

In its literature for the sale of chassis-only products, MAN still seems to offer quite a few ladder-frame designs – see http://www.corporate.man.eu/en/products-and-services/commercial-vehicles/man-bus/MAN-Bus.html and http://www.corporate.man.eu/man/med...rodukte_und_services_1/man_bus_chassis_de.pdf :





If a tubular space-frame were hands-down superior, one would think that MAN-Neoplan would offer only tubular space-frame designs? And yet as the MAN product literature just posted indicates, this is simply not the case.

The following very short webpage description of “Types of Buses and Frame Design” provides a really useful summary of the advantages and disadvantages of “Ladder Frame Design” versus “Tubular Space Frame Design” – see http://autobei.com/blog/type-of-buses-and-frame-design/ :


Advantages:




Disadvantages:




But granted, as this article makes clear, more buses used around the world are now tubular-space-frame designs, than ladder-frame designs:





As for materials, there is some argument to be made that even though weight is a consideration, a tubular space-frame structure should ideally be made of light-weight stainless steel, and not aluminum – see http://articles.sae.org/12734/ , and also see the discussion of Prevost further along in this series of posts. Prevost constructs all of their buses out of a lattice of tubular stainless steel.


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4. VW “Synchro” T3 Rally Bus: Tubular Space Frame


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As luck would have it, I just came across a VW “Synchro” Microbus conversion that nicely illustrates another issue: internal volume. Yes, a tubular space frame design might increase available space for passengers and goods in a “normal” kind of bus, the kind intended for only for use on good paved roads. But it's an open question whether a tubular space frame design can generate the same benefits in an expedition motorhome intended for bad-road and occasional off-road travel, without compromising internal volume with transverse struts.

The VW "Synchro”, which first appeared in 1985, is basically a T3 Microbus redesigned with 4-wheel drive, and hence off-road or bad-road capable. The resulting “T25” was developed in the 1970's and early 1980's, by German engineers who had used VW Microbuses to travel to far-flung destinations in Africa and Latin America. They recognized the need for a more robust, 4WD version of the Microbus – see http://www.club80-90syncro.co.uk/Syncro_website/TechnicalPages/_THE SYNCRO STORY.htm , https://www.flickr.com/groups/t25/ , and https://www.flickr.com/groups/t25/pool/ , and https://www.facebook.com/vwt25 .

In 2012, Bernd Jaeger, a social worker by day, a rally enthusiast and specialist car builder by night, completely redesigned his old T25 Microbus (also used in previous rallies), to become a truly robust, rally-capable racing vehicle for the future, with a tubular space-frame – see http://www.syncro-bernd-jaeger.de/DEUTSCH/index.html , http://www.syncro-bernd-jaeger.de/DEUTSCH/html/personliches.html , http://www.syncro-bernd-jaeger.de/DEUTSCH/html/rallyebus.html , http://translate.google.co.uk/trans...www.syncro-bernd-jaeger.de/DEUTSCH/index.html , http://translate.google.co.uk/trans...ernd-jaeger.de/DEUTSCH/html/personliches.html , http://translate.google.co.uk/trans...o-bernd-jaeger.de/DEUTSCH/html/rallyebus.html , http://translate.google.co.uk/trans...o-bernd-jaeger.de/DEUTSCH/html/werkstatt.html , http://www.marathonrally.com/news/b..._den_gelben_t3_synchro_rally_bus.23116.0.html , http://www.auto-motor-und-sport.de/...es-vw-bus-t3-der-irre-rallye-bus-7968262.html , https://www.flickr.com/photos/kullekuck/7236015034/ , http://translate.google.co.uk/trans...es-vw-bus-t3-der-irre-rallye-bus-7968262.html :









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There is a brief discussion and more high-res imagery on ExPo, at http://www.expeditionportal.com/forum/threads/37713-An-expedition-truck-on-portals/page82 .

And here are some videos:




These images of Berned Jaegar's T25 conversion all suggest a possible downside of tubular space-frame construction. The triangulated braces you see in these images, running transversally across the camper, are not possible in a large bus or motorhome, where maximal usable internal volume is an absolute priority. dave.com summarizes the problem nicely:

Obviously, not every gap between tubes can be braced (you need enough room for the driver to sit in the car etc), so in reality the chassis members must retain some resistance to bending. However, you still have a structure that is much, much stiffer than a ladder-frame chassis at a far lower weight. The downside is, with all those tubes running everywhere, you aren't left with much space, which isn't good for carrying loads. Also, the design relies on even distribution of loading, so isn't suited to carrying a couple of tons on the back of a truck, for instance.

A secondary problem is that a spaceframe is an utter nightmare to build. Even leaving aside the difficulty of ensuring that all required bracing has been designed in, the trouble is that at some point you're going to actually have to weld all the sections together accurately. Even for a relatively simple spaceframe, such as the Gordon Keeble chassis pictured right, this is a hugely labour-intensive exercise - far more so than any ladder-frame design. 


On the plus side, there's nothing that exotic about the materials and principles used, and if you're willing to dedicate the time to it, a very stiff, light structure can be assembled without any special techniques. It is for this reason that, although now overshadowed in terms of ultimate performance by other designs, the space-frame chassis remains a very popular way of building high-performance vehicles where speed of production, interior space, and ultimate stiffness & weight-reduction can be sacrificed in exchange for being able to use relatively basic materials and techniques: Most kit cars, as well as many racing vehicles, use space-frame construction.

Again, see http://www.initialdave.com/cars/tech/chassisbasics01.htm .

Now I suspect that tubular space-frame construction is possible in buses, like the NeoPlan CityLiner pictured previously, because they do not have to withstand nearly the same degree of stress as a "bad-road" or "off-road" vehicle. But once you throw “bad-road” or “off-road” capability into the mix of specifications, I wonder how robust a tubular space-frame would be, without additional transversal struts? Furthermore, if one wants the vehicle to have abundant large windows, and a deck opening in the rear, as well as a Uni-Cat-style pop-up, every such opening will be space not spanned by a strut.

Of course, Corona in India does make tubular space-frame buses for Indian roads, buses that have huge amounts of glass. Again, see http://coronabus.in , http://coronabus.in/about.html , http://www.motorindiaonline.in/buses/corona-bus-riding-successfully-on-monocoque-technology/ , and http://www.skyscrapercity.com/showthread.php?p=101323701 . And Indian roads are notoriously bad. So I am not saying that it can't work. I just have some questions that I would first want to ask an automotive engineer.


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5. Hybrid Backbone Tube + Space-Frame


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So I have to confess that I am still not quite ready to give up on the idea of a Tatra “backbone tube” providing fundamental structural rigidity – see http://en.wikipedia.org/wiki/Backbone_chassis .

Furthermore, according to the following very interesting pdf-book about chassis design, available on-line, backbone tube designs are almost always combined in “hybrid” configurations with space-frames – see http://www.keithwakeham.com/Files/ChassisDesign.pdf :

7.1 Introduction to Backbone

This is a direct application of the tube theory. The idea is to create a front and rear structure that connect to a tube that runs the entire lenght of the car. Unlike a transmission tunnel the backbone is fully enclosed to be a ridgid structure and handle all loads. It is normally very continous with few holes. Since it is so narraw the wall is generally thicker.

Some chassis intergrate this type of design into the primary structure such as cars like the “locost”. Others build on this, relying on the backbone but adding additional structure to stiffen the backbone such as the DP1 from dpcars.net.
It should be noted that the backbone can be created through many types of construction. Triangulated space frame, angular monocoque, or continous tube. All been used in production cars. Almost all are rear wheel drive and front engine allowing the backbone to double as a transmission and drive shaft tunnel.

Or as david.com writes:

A backbone chassis.... can actually be slightly stiffer than a space-frame of the same weight. However, because the chassis has to fit within the confines of the centre of the body, it can only be made so stiff. As such, it tends to lend itself better to small or medium sized vehicles, as large, powerful cars do not necessarily have enough of a proportional increase in the room available for the central backbone to allow it to be scaled up to cope with the increased loads. This is not so much of an issue for extremely large vehicles, though, and Czechoslovakian manufacturer Tatra has successfully used a backbone chassis on large military trucks (right), although in this case the chassis structure is tubular rather than square. Although Colin Chapman is often credited with inventing the backbone design, it's actually Tatra who first developed it.

A side note on backbone chassis is that, with the structural component of the car in the centre, the outer body panels can be made from very light material such as composites or aluminium. While this is good for weight-reduction, it also means that a backbone chassis car is not necessarily the place you want to be in the event of a side impact, as there isn't a lot there to protect you. Saying that, the DeLorean was designed using a backbone chassis (with the help of Lotus, as it happens), and was designed from the outset to be an extremely safe car, with good side-impact protection. The secret here is that the DeLorean was part backbone chassis, and part monocoque. In fact, this is true for most backbone-chassis vehicle designs. Monowhat? We'll talk about that later...

For instance, the DeLorean DMC-12 was originally supposed to be a “pure monocoque” design, but it was soon revealed that this would fail crash tests. So DeLorean sought outside engineering help, from Lotus engineering. The redesigned DeLorean combined a backbone-tube, wishbone-style chassis frame, with a GRP (glass-fibre reinforced plastic) composite body, over which was stretched a decorative stainless steel skin – see http://antholonet.com/EngineersCars/DeLorean/delorean.html , http://netpeers.com/DeLorean club/web-content/Bloom.html , http://www.deloreanmuseum.org/car.html :








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The exterior styling of the DeLorean was by Giorgetto Guggiaro, who I revere -- see http://en.wikipedia.org/wiki/Giorgetto_Giugiaro . But Guggiaro designed the DeLorean when "the wedge" was all the rage:







And again, I am just not a fan of flat panels, sharp angles, and this sort of "future-macho" look.

In terms of engineering, the DeLorean was certainly interesting, and it suggests a possible solution for a large expedition motorhome: a Tatra backbone tube (and just the tube, nothing else), combined with either a monocoque or a tubular space frame shell. But notably, the DeLorean DMC-12 did not even make it into the Top 25 short-list for "Car of the Century", an international award which polled a jury of 132 professional automotive journalists, from 33 different countries -- see http://en.wikipedia.org/wiki/Car_of_the_Century . Many Americans seem to have a soft spot for the DeLorean, perhaps because it figured so prominently in the "Back to the Future" movie trilogy. But from a global perspective the DeLorean is a minority taste. Whereas the BMW 328, a category of car that includes the Kamm Coupé, did make the short-list.

Note that the finished DeLorean DMC-12 was, in effect, a redesigned Lotus Esprit – see http://en.wikipedia.org/wiki/Lotus_Esprit , http://cnx.org/contents/84009280-522e-4fde-894f-82b818570e72@2 , and http://www.lotusespritworld.com/EHistory/DeLorean.html . Although DeLorean went bankrupt, Lotus engineering benefited greatly from the arrangement, winning subsequent consulting contracts based on its experience developing the DeLorean.

The DeLorean then demonstrates that design precedents exist for a structural solution that combines a backbone tube with either true monocoque construction, or a tubular space-frame. There are lots of other examples, but thought I would focus on the DeLorean, because it is so familiar.


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6. High-End American Class-A Motorhomes with Semi-Monoque Designs


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In closing, I'd like to note that American high-end manufacturers of the chassis frames used in diesel-pusher motorhomes, will advertise that their chassis-designs are more nearly like a tubular space-frame.

The following is something I just came across: it is probably the most useful guide available on the web to American manufacturers of motorhome chassis. I've pasted it both as an image, and as text, because it's so well-written, compact, and thorough – see http://serenitysys.com/rv/diesel_pusher_motorhome_chassis.htm :

Diesel Pusher Motorhome Chassis Comparison

We have a friend that says he can't tell the difference between the way his Buick Century and a BMW drive. Another friend thinks his small Toyota pickup rides really nice. They are nice folks, but they simply don't notice the difference between extremely different vehicles. 

Then there are some of us, like myself, that notice significant differences between very similar cars; like between our 1984 Mercedes 300SD and 1984 Mercedes 300CD, even though they have the same chassis and suspension design. They're even the same color! 

Some people have suggested comparing specifications of the different chassis. That only works to a limited extent. Some auto & RV manufacturers are experts at cloning specifications yet the results are dramatically different than the vehicle being copied. How many car makers would have you believe that their compact sporty sedan drives like a BMW 3-Series? All of them! But, none can match the little Bimmer.

The same holds true with motor homes. The manufacturers of less expensive MH's go to a great deal of effort to convince the prospective buyer that their $175,000 DP is virtually the same as a competitor's $250,000 DP. The truth is that the differences between brands is less than the difference between price points.

Entry-level DP [diesel pusher] chassis are similar: steel springs, small engines, light GVWR, etc.

Mid-level DP [diesel pusher] chassis are similar: air bags, air drum brakes, medium-size engines and GVWR.



High-end DP [diesel pusher] chassis . . . yes, they are similar too: air suspension, side radiator, large engines and heavy GVWR, usually semi-monocoque, disc brakes and tag axles.

What I've noticed that each chassis manufacturer tends to it's own characteristics (think personality) that reflect both the overall design and the sum of the parts. Here's my spin on the players. Partially to avoid Ford/Chevy (or Mercedes/BMW) arguments, I've used all GM brands as an automotive comparison.



Dynomax: A proprietary chassis of Country Coach began in 1998 after Gillig left the RV market. Semi-monocoque, all-welded all-steel construction, including suspension mounting and adjustment, all IFS. A premium chassis with excellent ride & handling.



Freightliner: A dependable chassis with a focus on price, like a Chevrolet. Freightliner got into the RV business in the mid-90's when it purchased Oshkosh. Very popular in the entry level to mid-range DP's. Tends to ride softly and wallow more than the other chassis in its price class. 



Gillig: A popular chassis for expensive, high-end DPs (Beaver, Country Coach & Foretravel) until 1997 when they left the RV market to focus on their school busses. Each of these DP makers responded by developing their own proprietary chassis. A very heavy-duty traditional raised-rail chassis with a Cadillac kind of ride and handling. 



Magnum: A proprietary chassis brand of Safari. Starting with the Safari line in the mid-90's and migrating up the Beaver line in the late 90's. A wide variety of innovative chassis ranging from lower-middle level to the very high-end Prevost wannabe Beaver Solitaire. The higher end Magnum chassis used on the Beaver Patriots, Marquis & Solitaire were equipped with 8-bag like the Monaco, but with larger air bags for a better ride. 



Newell: Proprietary chassis semi-monocoque chassis for very high end Newell DP's. 



Peak: A proprietary chassis for Alpine. A relatively new design Huck-bolted raised-rail chassis with rugged features similar to the old Gilligs. Uses heavy-duty 4 wheel hydraulic disc brakes. Touted as a high quality mid-range coach that appears to have hit its target.



Roadmaster: The proprietary chassis brand of Monaco Coach. Purchased from Chrysler Corp in 1984. Makes the widest variety of chassis from entry-level through high-end semi-monocoque DP's. The entry level RSR & RR4R chassis are similar to their entry-level competitors--nothing wrong with them but nothing remarkable. Their mid-range & up chassis are known for their 8 air bag suspension (10 with tag axles), yet their high-end S-Series doesn't have IFS. The widely spaced, but small air bags provide crispest handling as well as the firmest ride of any DP I've driven. I prefer calling the Roadmaster RR8R & up chassis the Pontiacs of MH's. There is no such thing as a 30,000# Porsche! 



Spartan: A specialist chassis builder that makes MH & fire engine chassis exclusively. Very good customer support. While they do make an economy chassis, they are more known for their high quality components in the mid-range to high-end DP's. I think of the Spartan as the traditional Buick; well-built with a good compromise of ride and handling. 



TravelRide: Foretravel's proprietary semi-monocoque chassis that came after Gillig. Another 8-bag premium chassis with excellent ride & handling characteristics.

Notice for instance that Newell Coach, probably the most “premium” luxury coach manufacturer in the United States, who I've discussed several times in this thread, has a completely proprietary chassis, one that this short article describes as “semi-monocoque”. What this really means, is that much like a MAN Neoplan CityLiner bus, the tubular space frame of the body of a Newell Coach provides structural support as well. See http://www.newellcoach.com .

Along similar lines, when it was still in business, Country Coach built a proprietary semi-monoque design called the “Dynomax” – see http://www.giantrvonline.com/chassis/DynoMax Chassis.htm , http://www.tablerockhome.com/allure1/ , http://www.countrycoach.com/2010/11/ccc-in-the-news/ , http://www.countrycoach.com/2011/01/country-coach-we-are-back/ :







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7. The Monaco/Roadmaster Chassis


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Next, it's worth taking a close look at the literature available online produced by Monaco Motorhomes, and its proprietary chassis subsidiary, Roadmaster. The author of the article comparing diesel pusher chassis thought so highly of Monaco/Roadmaster, that he or she was tempted to call it the "Porsche" of diesel pushers.

Monaco Motorhomes advertises that its “raised frame rail” Roadmaster system has steel trusses that are engineered as integral parts of the chassis – see http://www.monacocoach.com/returntopower/ , http://giantrv.addr.com/products/monaco/roadmaster/roadmaster.htm , http://guaranteerv.com/upload/media_element/503/01/roadmaster-brochure.pdf , http://www.roamingtimes.com/rvreports/7/monaco-cayman-luxury-motorhome.aspx , and http://www.roamingtimes.com/rvreports/6/monaco-diplomat-luxury-motorhome.aspx :







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It's not really clear in Monaco's more recent literature to what extent the space-frame of the Monaco camper body is also structurally relevant to the “raised frame rail” chassis underneath. The last three images shown immediately above, and the images that appear most recently on Monaco's website, suggest that the camper frame may not be that structurally integral or relevant.

Furthermore, I can't help notice that even in the earlier images, in which a Monaco chassis frame + camper frame seem fully fused as a single unitary design, there are still two, long, much thicker ladder rails running the full length of the vehicle. So it's quite possible that what's needed in a fully integrated expedition motorhome design is something similar, but with the ladder rails replaced instead by a Tatra backbone tube.

campo, you will love the first video below, in which a representative from Monaco/Roadmaster makes fun of the idea of simply throwing a motorhome on top of truck chassis:




But this video also suggests just how complicated it is to create a structurally sound semi-monocoque motorhome design from scratch.

And perhaps even harder to create one for an expedition motorhome…..


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8. The Prevost Chassis


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Although the above comparison of American diesel pusher chassis is by far the best I've yet come across, it is by no means complete. For instance, it fails to mention the Workhorse chassis (perhaps now out of business?), as well as Prevost. Prevost is important because the buses it creates serve as the base vehicles for the other four "premium" luxury motorhome fabricators in the United States (i.e. in addition to Newell), namely, Millennium, Featherlite, Liberty, and Marathon Coaches – see http://motorhome.prevostcar.com/where-buy , http://www.millenniumluxurycoaches.com , http://www.featherlitecoaches.com , http://www.libertycoach.com , and http://www.marathoncoach.com .

Apart from product literature in pdf form, there are not that many images of the Prevost chassis available on-line. But there is no question that Prevost constructs its buses and motorhomes as a fully integral stainless steel tubular space frames, covered by a fiber-composite body. Prevost advertises their design as an:

Integral Structure -- Strongest, Safest, Most Durable in the Industry. Unparalleled vertical, lateral, and torsional rigidity compared to body-on-chassis constructions..... Inherent torsional rigidity enables levels of handling precision and vehicle responsiveness that enhance dynamic safety.

In contrast to Monaco/Roadmaster, there is no ambiguity here: Prevost vehicles are not "body-on-chassis" constructions:









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See http://motorhome.prevostcar.com , http://motorhome.prevostcar.com/product/models , http://motorhome.prevostcar.com/product/innovation-and-enhancements , https://www.prevostcar.com/content/prevost-h3-45-vip , https://www.prevostcar.com/content/prevost-x3-45-vip , https://www.prevostcar.com/content/prevost-xlii , https://www.prevostcar.com/content/safety , https://www.prevostcar.com/content/motorhome-very-special-experience , http://www.millenniumluxurycoaches.com/prevost-innovations/ , https://www.prevostcar.com/conversion-coach-brochures , https://www.prevostcar.com/sites/default/files/motorhome_brochure.pdf , https://www.prevostcar.com/sites/default/files/prevost_conversion_coach_brochure_04-13.pdf , http://www.millenniumluxurycoaches.com/wp-content/uploads/PrevostPDF/2011_prevost_brochure.pdf , https://www.prevostcar.com/sites/default/files/prevost_top_15_features_brochure.pdf , https://www.prevostcar.com/sites/default/files/prevost_conversion_coach_brochure_04-13.pdf , https://www.prevostcar.com/sites/default/files/x3-45_vip_spec_sheet_11-2013_0.pdf , https://www.prevostcar.com/sites/default/files/h3-45_vip_spec_sheet.pdf , https://www.prevostcar.com/sites/default/files/x3-45_vip_entertainer_spec_sheet_11-2013_0.pdf , https://www.prevostcar.com/content/converters-dealers , and http://motorhome.prevostcar.com/where-buy .

Because Prevost is also a high-end manufacturer of touring buses – a kind of North American equivalent of MAN Neoplan or Van Hool – Prevost can invest heavily in the R & D necessary to create a completely integral space-frame chassis, just like MAN Neoplan. Prevost's product for motorhome conversion is then not "just" a chassis. It's not just an undercarriage as per the motorhome chassis that are sold by Spartan, Freightliner, or Workhorse. Rather, it's a fully completed bus shell, factory-fitted with slide-outs. Millennium, Featherlite, Liberty, and Marathon Coaches then take this bus shell and turn it into a motorhome. So as the literature from Prevost posted above suggests, this means that a Prevost motorhome will have a structural integrity that other manufacturers simply cannot match. Not, that is, unless they build their own semi-monocoque propriety chassis, a per Newell or Monaco/Roadmaster.

Here are some Prevost videos that, on occasion, provide some glimpses of tubular space-frame construction:


[video=youtube;mV15ySsFR0A]https://www.youtube.com/watch?v=mV15ySsFR0A#t=40 [/video] [video=youtube;avOyCjGzCM8]https://www.youtube.com/watch?v=avOyCjGzCM8 [/video]
[video=youtube;HtiUjOv-H-4]https://www.youtube.com/watch?v=HtiUjOv-H-4#t=35 [/video] [video=youtube;pukz_q-kxhs]https://www.youtube.com/watch?v=pukz_q-kxhs [/video]
[video=youtube;Hh9CvIessAU]https://www.youtube.com/watch?v=Hh9CvIessAU [/video] [video=youtube;e1-1Lp7_5L4]https://www.youtube.com/watch?v=e1-1Lp7_5L4 [/video]
[video=youtube;_Ctqm27lcGw]https://www.youtube.com/watch?v=_Ctqm27lcGw [/video] [video=youtube;_GYQuKiojDs]https://www.youtube.com/watch?v=_GYQuKiojDs [/video]



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Finally, it's worth noting that that when President Barack Obama toured the Midwest in 2011, he travelled in a Prevost -- see http://www.examiner.com/article/the-obama-presidential-bus-tour-another-win-for-prevost , http://www.examiner.com/slideshow/the-obama-presidential-bus-tour-another-win-for-prevost#slide=1 :





[video=youtube;NvKL73DLkzo]https://www.youtube.com/watch?v=NvKL73DLkzo [/video]


In any case, once again, many thanks for your post, campo. I had already collected much of this material, and your post simply "provoked" me into doing a bit more research, and finally presenting it. As must be clear from the above, I am well aware of various chassis possibilities, and the use of tubular space-frame "semi-monocoque" construction in high-end buses and motorhomes in particular.

I am simply not completely convinced that a tubular space frame alone – especially the kind that has lots of big "holes" in it for windows, slide-outs, and a Unicat-style pop-up – will have the structural integrity necessary to handle bad-road and off-road travel. Perhaps I am being too skeptical. But the Tatra backbone tube is proven technology. Combining that Tatra backbone tube (and again, just the tube), with space frame construction, as per MAN Neoplan's CityLiner, Newell Coaches, or Prevost Buses, may seem like overkill. But until I talk to a few friends who have great backgrounds in automotive engineering, that's how I am currently leaning.....

All best wishes,



Biotect

 

[optimusprime]

C

..



Hi optimusprime,

Did you get a chance to read the summary specification? It's post #686, at http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page69 ? campo also re-posted the summary specification directly above your post....... It's a reasonably thorough list. Perhaps you didn't see it, before posting your message?

Or perhaps you mean something else by "a review now and then"? I can see the idea: take this specifications list, and then write a short 1 - 3 sentence description and justification after each one. That might be a good exercise to engage in, for all sorts of reasons. Will see what I can do over the next few weeks.





Hi thajakits: Yes, I can see your point too. After I've created a kind descriptive short-list, post it at the beginning of this thread, with the caveat as you've stated it: that it will updated on an ongoing basis, so don't get too attached to any particular version. Or, save the first page as many times as might prove necessary to keep up with my changes......:sombrero:

Many thanks for describing the thread discussion as "epic". A really good concept vehicle that pushes boundaries should raise a wide variety of issues.

Will address your other points after I've posted in response to campos.


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As for a break from this thread: gosh, it will happen shortly whether I like it or not! Art College recommences in a week, and my posts will reduce to a trickle. I've just been trying to get as much stuff that I've already written uploaded from my computer before the time-crunch really hits, in October. You will only have to put up with my crazy ideas for just a few more days......:coffeedrink:

All best wishes,



Biotect

Yes i did read the the summary, but to my mind,that was a summary of what you are trying to achieve.

I was thinking that you now need to summerise those design parameters that have been discussed,and how they have been chosen/
Resolved/changed etc.
Otherwise i fear the thread will have to many loose ends,and will simply end up being a confusion of too many recurring posts,and information overload.

A good example could have been the discussion on whether to have Propane on board,you have decided not to have Propane on board
So you could do a brief paragraph on how you came to that decision.