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Bio
I think you are going to have to start making descisions soon,otherwise there is a danger of this thread really spiraling out of context.
As i have mentioned before, we need a retrospective of where we are now,what has been decided and what the next 'item' to be decided will be...
So far we know that : it will be of a 'space frame' tubular design.it will be 6x6 and thats about it...
So we need to choose ...
Drivetrain, hub motor,tradition axle/ shaft,portals.
Suspension,independant, leaf,coil,air,hydraulic,hydro pneumatic.
Powerplant,diesel,diesel electric,jet turbine,warp reactor.
This will then get us to a stage where we can say we have a 'rolling' chassis design,we know what we NEED to be able to get this vehicle moving,so now we can design the rest of the vehicle round it!
Hi
optimus,
Gosh, that was a positive firestorm of engineering discussion! I will respond in item-by-item detail in my next post, which I hope to get on the thread before 10 more engineering posts appear....:sombrero:
In short order:
(1) Straight-Axle versus IS.
I find myself being convinced in favor of straight axles, and no IS.
Haf-E seems to be deciding in favor of straight axles, too, and this
is an overlanding vehicle. So the complexity entailed by IS seems a potential problem, and
campo is perhaps only interested in IS because he currently has leaf springs, and wants a smoother ride. According to all, straight axles
can deliver that smoother ride, with coil/air suspension.
So unless I hear some really convincing counter-arguments soon from
NeverEnough and
campo, as to why IS is still preferred to straight axle, that's where I am now headed.
thjakits has made a really good case for straight-axle; I need the other side to make a really good, summary, point-form case for IS. The TerraLiner will be a serial hybrid (more on that below), so as even
thjakits admits, in the serial hybrid scenario perhaps IS might make sense because it might allow a long, uninterrupted space in the center of the truck. But even in IS, the links in the suspension function better when long, so one probably won't gain that much uninterrupted space in the center of the vehicle in any case. Sounds like a good enough argument to me.....:ylsmoke:
(2) PowerTrain
Sorry,
dwh, but microturbines are out, at least for now.
My engineering friends and I have been designing the space for the motor/generator so that it
could accommodate a pair of Capstone C65's, if necessary; and a slide-out tray that could take the weight. A while back someone (I forget who) advised me to design a generator compartment in such a way that the motor/generator could be easily swapped as technology advances. That's what I am doing.
As present, I am leaning in the direction of a Jepotnik-sized diesel engine and generator, 3.2 L, 182 HP, 6 cylinder, with 120 KW of electrical output – see post #673 at
http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page68 . But the Oshkosh 4x4 L-ATV used in Baja had a a 400hp 6.6L Duramax engine, so who knows? And the Oshkosh L-ATV is a much smaller vehicle than the TerraLiner, just a 4x4 – see posts #671 to #673, at
http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page68 .
So I am erring on the side of caution, and designing the engine compartment to accommodate an engine/generator even as large as the 750 HP Volvo F16 – see
http://www.google.co.uk/url?sa=t&rc...-l1GMOG4L_L0DOaVzgK9oyg&bvm=bv.82001339,d.bGQ and
http://www.volvotrucks.com/trucks/u.../key-features/Pages/volvo-diesel-engines.aspx . Or something like that. Sure, this may be complete overkill, and totally unnecessary. But until someone does a convincing power calculation, the size of the engine compartment will have to remain a bit vague.
Think of the TerraLiner as a motorhome version of the Abrams Tank: a completely modular design, so that the TerraLiner's mechanical and electrical elements could be easily rebuilt and/or replaced, as technology advances – see post #516 at
http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page52 , and see
http://channel.nationalgeographic.com/channel/ultimate-factories/videos/abrams-tank/ :
[video=youtube;dG4CLaBMfVU]https://www.youtube.com/watch?v=dG4CLaBMfVU [/video]
The United States has not built a completely new Abrams tank from scratch since 1993.
(3) Power Calculation
The power calculation should be easy enough to do, one would think, at least for a trained electrical engineer (
Haf-E?). The TerraLiner will be a full serial hybrid, not parallel; with 6 separate electric hub motors, as per
Haf-E's recommendation. It will be 10 m long, and 20 tons, so just stipulate a power size for the electric hub motors, and the power requirement of the generator should be easy enough to calculate?
Sure, batteries in between could lower the necessary generator size, the batteries draining a bit faster than they charge, thereby making a small diesel engine/generator possible. That's the basic principle behind the "range extender" format: that the batteries allow a significant reduction in the size and power output of the generator. But it would be good to begin with an “extreme case” scenario: no batteries at all, just the diesel engine + generator, directly powering the hub motors, as per the PistenBully 600 E+ snow groomer shown earlier – see posts #934 to #939, at
http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page94 . Recall that the current model of the Pisten Bully 600 E+ has no batteries; these will only be added in later models.
And after this "no batteries" calculation,
then throw batteries into the mix.....
(4) Supplementary 20 KW generator.
The TerraLiner will also carry a supplementary 20 KW turbocharged generator. But
not to act as "backup" for the main engine-generator. But rather, to charge the batteries efficiently and quietly when parked, as suggested earlier in the thread.
(5) No Portals.
Last but not least, no portals. The TerraLiner will be big enough, and its tires big enough, that portals are another unnecessary complication. The TerraLiner is a 6x6, so the largest inter-axle distance will be much smaller than any of the commercial overlanding vehicles posted a while back. And its breakover, approach, and departure angles will all be much better, even with the second and third axles clustered in back.
Think of it this way. I will want side-lockers between the first and second axles, of the kind pictured in these images of Zetros trucks:
In a standard staight-axle configuration with XZL tires, the center of the tire is either 58 cm (14.00R20) or 61 cm (16.00R20) above the ground. At least theoretically. When under load, or when deliberately deflated, it will of course be less. This then suggests that side-lockers could descend as low as just 80 cm above grade on either side, between the first and second axles, without significantly impairing the inter-axle breakover angle. In the following schematics of MAN-KAT 6x6s, the "peak" of the breakover angle between the first and second axles, seems no better than 80 cm above grade; not much higher than the wheel centers:
So if one wants side-lockers that can descend on either side to 80 cm above grade, then the only thing that portals might add, is an additional 20 cm of clearance, because the straight axles across the vehicle could now locate at 80 cm above grade, instead of 60 cm. That additional clearance may be important in a mog-sized vehicle that wants to rock-crawl off-road. But would it really be important in a bad-road expedition motorhome? I'd like to hear the argument that the additional complication of portals is really worth it, in a vehicle the size of the TerraLiner.
More on the topic of comparative breakover angles anon.
Hope that clarifies matters, for now.....
All best wishes,
Biotect
PS -- Personally, I really enjoy reading the engineering banter, even when it gets a bit chaotic and out of control. I am not an engineer, so this banter always provides enlightening information, at least for me. After all, I created the thread precisely so that I could get practical, engineering, and overlanding advice / feedback for an innovative transportation
design exercise. I can do the design; but it's great to learn that I should be designing a vehicle that includes a truck-sized
"rock-slider".
On that topic:
optimusprime, many thanks for the pictures of rock-sliders. Would you know of any good
videos that show rock-sliders in action with SUVs?
....
