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Outerra Apps => Games => Topic started by: ZeosPantera on July 31, 2012, 02:17:23 am

Title: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on July 31, 2012, 02:17:23 am
Lets use this as a general thread concerning JUST the current demo's and games 8x8.

(http://i.minus.com/ilwCutd2qWY5Y.png)

First I will state that the physics are in no way final and the center of gravity is set to an immensely unrealistically low position. (like a weeble) If it were realistic you would be on your side constantly so assume that this is the Arcade version.

Despite this I have been in the testing version messing with the 8x8's new handling variables and have come up with something I feel best matches my impression of the vehicles climbing/acceleration possibilities.

-Vehicle.cfg---------------------------------------------------------

wheel = {
    suspension_rest_length  = 0.48
    max_suspension_travel   = 0.75
    stiffness               = 6.5
    damping_compression     = 0.10
    damping_relaxation      = 0.03
    friction_slip           = 0.57
}

max_engine_force        = 25000
max_braking_force       = 13750
redux_coef              = 0.2
max_kmh                 = 5

I timed it and it takes roughly 50 seconds to hit 28m/s (AKA 100km\h or 62mph) with an absolute salt flat max speed of 33m/s or 73mph. I have tried to find the "tatra 813's" 0-100km/h times but I don't think it is listed.

Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: Peca on July 31, 2012, 10:05:36 am
I have tried to find the "tatra 813's" 0-100km/h times but I don't think it is listed.
I it not listed because max. speed is 85 km/h for Tatra 813 (some say it can go faster, but this is from factory specs).
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: cameni on July 31, 2012, 11:13:48 am
First I will state that the physics are in no way final and the center of gravity is set to an immensely unrealistically low position. (like a weeble) If it were realistic you would be on your side constantly so assume that this is the Arcade version.
I've been trying to adjust the center of gravity but the effect was almost unnoticeable. After some digging around it seems there's an artificial roll prevention force that's strongly counteracting any rolling.

So yes it's arcadeish at the moment, but since the chassis doesn't collide yet, any roll would just make the truck fall under the ground.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on July 31, 2012, 11:17:06 am
It is nice to know that you have at least looked. What aspect of this whole setup would put that erector force on? Is it hidden in the bullet code or something in the properties of the model?

I it not listed because max. speed is 85 km/h for Tatra 813 (some say it can go faster, but this is from factory specs).

I thought it was 100kmh max. I am pretty sure it can reach highway speeds.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: cameni on July 31, 2012, 11:29:48 am
It's in the vehicle code, I based it off some Bullet example initially and then modified and added to it. I remembered there was a "roll influence factor" mentioned, but that part I didn't modify yet.


I thought it was 100kmh max. I am pretty sure it can reach highway speeds.
Old T813 8x8 KOLOS was slow. Here are some specs (in Czech): http://www.tatra813.ic.cz/data.htm (http://www.tatra813.ic.cz/data.htm)
The maximum speed with overdrive was 80km/h. Screaming like hell at that speed.

T817 (T815-7) can reach 110km/h, 8x8 variant probably less.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on July 31, 2012, 04:08:26 pm
Those maximum speeds will have to be limited with an additional factor. If the engine power is lowered too much it can't climb realistically. Transmission emulation will need to be implemented at some point it seems.

Edit: Also I am not sure if this is a throttle handling bug or physics but I spent about 30 minutes driving the 8x8 across the russian tundra to try and crash it like it was (wasn't crashing) and when I let off the key throttle and alt-tabbed the truck drove for several minutes with only a moderate decrease in speed over the flat-ish terrain. Is their no/very low rolling resistance or is that some sort of keep alive throttle until brake that is implemented?
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: cameni on July 31, 2012, 04:15:40 pm
No rolling resistance. That's also related to the friction of the transmission I guess (tire + transmission friction).
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: Timmo on July 31, 2012, 10:44:55 pm
As a hack perhaps a general drag/resistance value could be added which summarises trans/tyre/aerodynamic retardation in one?

I'm assuming it will slow down more when travelling up an incline?
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: cameni on August 01, 2012, 01:15:27 am
It should not affect slow speeds as much as the higher ones, when the engine force is low. With the varying transmission you can accelerate until the engine torque cannot overcome the global rolling friction anymore.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on August 05, 2012, 01:14:14 pm
OK. I know that some sort of internal combustion engine model is needed for "other" aspects of the OT engine modding career but I think we should take the Anteworld future vehicle in a different power delivery direction.

There is a prototype Jaquar that has been discussed on top gear and the youtube DRIVE channel that has peaked my interest in hybrids due to its sheer awesomeness. Essentially this Jag will have two small turbine engines in the rear 7"x30" each connected directly to electric generators and also thrusting the exhaust out the rear of the car for propulsion. These generators will spin at HIGH rpm and create a constant build-up of electrical energy for the drive-train-less individual four wheel drive electric motors. Some sort of reserve system of capacitors is likely going to be used to store energy for quick bursts and to make modifying the idle of the two turbines less dramatic and more likely determined by extended use or manual control. (Give me all she's got Mr Scott!)

So now look at this 8x8 from the future we are all driving. Isn't it just BEGGING to have an M1abrams style/sized (http://usarmy.vo.llnwd.net/e2/-images/2008/08/11/20692/army.mil-2008-08-11-084249.jpg) turbine 16"x50" (that will run on any combustible liquid at nearly any ALTITUDE...) strapped sideways behind the cab churning away at a huge electrical generator. Subsequently feeding either a simple High/Low gearbox placed before the standard tatra drive-train  OR  Four motors/reduction, one for each pair of left right wheels therefore still using the differentials both in-line and side to side but with detachable clutches so that 8 wheel drive can be disabled for road driving economy or all locked for extreme up hill climbidness(new word pat pending)!

The torque curve will be a bit of a guess and this system would require some special coding to handle initial power buildup times and reserve generation/holding but just think of the sound (http://tinyurl.com/8z4nthe) it will make instead of a rattling old diesel.. Plus higher speeds might then be possible with the simpler drivetrian even if just slightly.


As an added gameplay mechanic you could use the parked vehicle as a power source at remote locations.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: cameni on August 06, 2012, 08:30:17 am
I like that idea, we knew something had to be done about the truck and the futuristic setting. Since nobody knows what fuel will be available, it's important to have an engine capable of burning almost anything, while being reliable.

Torque can be easy, actually similar to the simplistic model there is now. Electric motors have a neat torque curve. Like this:

(http://lancet.mit.edu/motors/colorTS1.jpg)

Think locomotive :)

We could, for example, assume that there are going to be modern electric motors directly in the wheel hubs, propelling the wheels individually.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on August 06, 2012, 02:12:01 pm
It will also be a good place to showoff any heat haze distortion effect with the exhaust of the turbine out the top of the truck.

(http://cdn-www.airliners.net/aviation-photos/photos/9/5/8/1286859.jpg)

Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: User_name on August 26, 2012, 11:02:00 pm
Without knowing what “redux_coef” does (can guess), the 8x8 likely has lots of torque multiplication through gearbox and differential.

Modeling gearbox (transmission) need not be excessively complex at this point, but a understanding of gear ratios would help allot. With that said, so should be power transmission losses:
- Good manual transmission on passenger car (rear wheel drive) is ~85-88% efficient.
- 4x4 (full time) is 65-70% on a good day.
- 8x8, wouldn’t want to guess, because tire condition (varying diameters in contention) and many other variables come into play.

A simple mathematical equation that factors in gear multiplication (torque) versus speed (m/s or KPH or MPH ) would help. Highly loaded vehicles like 8x8 likely have many gears to keep engine in optimum power band, so  step changes encountered during shift are minimized.

Also a 8x8 should not coast for that long, too many tires engaged, too many fictional losses.

Also, last thing you want is a turbine for a power source. A pig to say the least, especially at low power. The M1 tank has the lowest range of any modern tank. As RPM drops on turbine, so does compression ratio, with that efficiency. Turbines do best being pushed hard and not idling.
 
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on August 27, 2012, 12:02:45 am
Also, last thing you want is a turbine for a power source. A pig to say the least, especially at low power. The M1 tank has the lowest range of any modern tank. As RPM drops on turbine, so does compression ratio, with that efficiency. Turbines do best being pushed hard and not idling.

And that would be the case if we were direct powering the wheels with a transmission and the turbine. In this rendition we are going for a more diesel locomotive setup where the turbine is just there to generate electricity. A storage system whether batteries or capacitors will build up and be tapped for the electric motor driven wheels. Which can be switched on and off as needed. (ie smooth road 30mph) you can probably get away with 2 wheel drive. In a high use scenario like climbing mountains to escape packs of wild cheetah's the turbine would need to be spooled up to replenish the capacitors faster. Using more fuel.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: User_name on August 27, 2012, 02:17:05 pm
First, hope you didn’t take my comment about last thing you want is a turbine personally. It was directed at how poorly turbines do with respect to fuel consumption and how it gets worse the slower you run/turn it.

Now I used the term compression ratio because most people can relate to that. In actuality it is pressure ratio that is correct term, so let’s start with a turboshaft (turbine like in M1 tank) and say it has a pressure ratio of 10:1 at full power, at 50% RPM it will have a pressure ratio ~5:1, this results in a lowering of efficiency  and with that higher fuel consumption.

Now I’m not a huge fan of Wiki but refer to link http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption (http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption) and scroll down to table.

The aircraft turbo prop is a good example of what I was describing.
-aircraft engine at idle = 2390 g/(kW•h)
-aircraft engine at ground roll = 1270 g/(kW•h)
-aircraft engine @ 0.30 Pmax = 508 g/(kW•h)
-aircraft engine @ 0.70 Pmax = 328 g/(kW•h)
-aircraft engine at Pmax (100% RPM) =294 g/(kW•h)

The reason most people don’t talk about this, is turbomachinery (jet engine, turbo fan, turbo shaft) usually spends most of it’s time at high power levels in which it is working in efficiency sweet spot.

I’m going to switch to standard engineering for now (not metric).
0.70 lb/hp/hr = Turbo shaft (good modern design)
0.39 lb/hp/hr = Stratified combustion (good modern gas design)
0.32 lb/hp/hr = good modern diesel design

So let’s say you are on a flat/smooth surface and it takes 100HP to maintain 62 MPH (100 KPH), turbo shaft will consume 70 pounds of fuel, gas engine 39 pound and diesel 32 pounds in one hour.  So regardless of drivetrain type you are burning twice the fuel (same fuel) for turbine vs. diesel.

Turbines have great power density and are very reliable, but a small application like 8x8 a diesel or gas engine would be more practical. Especially if truck was used as generator for people when not on the move (this is what several militaries have as a future goal).

Not sure if you want to get into drivetrain conversation, but there are also losses when going from generator-to-battery-to-electric motor. 

 :)
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on August 27, 2012, 02:42:46 pm
You seem far more knowledgeable in this field than I and I will take you word on all the figures. If you have any suggestions on how to modernize or universalize the power/systems for bases and vehicles PLEASE share them. We need more people that actually know the engineering sides of things to help with designs. I hate when games base nothing on science and just gut feeling everything.

Let's get science up in here.

(http://laserpointerforums.com/attachments/f54/32592d1304702808-three-cheers-albert-nasa-farnsworth-science.jpg)
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: User_name on August 27, 2012, 03:34:26 pm
From reading forum comments it seems that the setting would be somewhat in the future… So with that said, many things can be possible.

Sounds like a do everything exploration vehicle is what you are after.

Couple of questions;
-Would amphibious capabilities be required?
-Using it as a generator to power other things when not on the move be a benefit?
-Is emphasis on good fuel economy or brute force?
-Would a semi-realistic power/fuel consumption model be required?
-Magic fuel OK (something that does not exist)?
-Batteries with 10x the power density of today’s technology OK? Can trade space on truck for range with insertable modules.

Lots of possibilities, perhaps make a few suggestions and can help on technical end. 
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on August 27, 2012, 08:30:27 pm
-Would amphibious capabilities be required?

I think some fording would be needed but I wouldn't want it as a replacement for an actual boat/hovercraft vehicle.

-Using it as a generator to power other things when not on the move be a benefit?

Personally YES. I think that would be an excellent resource to make the vehicle the center of attention when out in the wilderness or forging new territory.

-Is emphasis on good fuel economy or brute force?

I think a sliding scale. Traveling across long distant roads/plains should be economy but mountains are mountains after all.

-Would a semi-realistic power/fuel consumption model be required?

I would want impeccable attention to reality paid. Too often this is ignored and if Outerra is to be the home of all simulators it should simulate things like this foremost.

-Magic fuel OK (something that does not exist)?

Well, I think the ability to use multiple naturally occurring and easily refined fuel sources should be expected. When returning to earth I don't expect there to be any oil resources left (at least large ones) and self sustaining colonies will need to function without the benefit of large fuel harvesting operations. (that would come later when the mountain town expands and needs more power)

-Batteries with 10x the power density of today’s technology OK? Can trade space on truck for range with insertable modules.

I think we are assuming a far enough leap into the future (500-1500 years) to assume when the ship left earth technology would be certainly more advanced. How far is a matter of speculation but I don't think anything not foreseen on the horizons now should be used as a Magic Widget to fix our engineering problems.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: User_name on August 27, 2012, 10:12:54 pm
For now fossil fuels are hard to replace and no real technological leaps in the near future. Look at fuel cells, they have yet to deliver on promises. Batteries are getting better (more abuse tolerant), but still power or energy density remains low by comparison to fuel.

Hybrids are good for stop and go, but VW diesel actually gets better mileage at highway speeds then Prius or it did a few years ago. What was discussed earlier is a “series hybrid” the train locomotive example which does better at low speeds. At mid to high speeds parallel hybrids do better, that is in which both electric motor and internal combustion engine share load, or electric motor handles getting it moving and engine augments power as required and also charges battery. At high speed say 80+ MPH a well designed engine is best.

I guess from a “fun” standpoint a series hybrid would be the way to go. Motor in each wheel hub and it could turn on a dime like a tank (wheels turn opposite to each other and it almost spins in place).  Perhaps 2 gen sets (engine generator combination) giving it some redundancy while being able to be economical when needed or serve as power station for small community. Diesels will run on vegetable or reasonably easily derived oils, so that would be fuel of choice I would guess.
The advantage to electric motor in wheel hub would be that it is more efficient then all 8 wheels mechanically coupled. The inverters could be set up to deliver torque as required or send power to the wheel that is not spinning. Then there are also active handling possibilities, but beyond the scope of conversation here.

Battery pack size, that’s a tough one. Perhaps treat it like city bus and use it for initial acceleration and store some regenerative braking energy. Also have a small quiet range in which truck is almost silent, because it is running on batteries only. But remember your discharger to charge ratio, usually 5:1 or you can discharge battery 5x faster than charge. You mentioned super-capacitors, those are still very unproven at high energy levels that would be required for 8x8 (never mind the size).
 
As far as diesel noise, not sure if have heard new Volvo truck, when that turbocharger gets spooled up it sounds more like a turbine than anything else, it surprised me first time I heard it. 

Now if you want to go out on the fringe, Purdue has shown aluminum with something added (can’t remember details) will split water into hydrogen and oxygen which can be burned. The aluminum gets reduced to an oxide when done…  But I wouldn’t go there.

Not sure what if anything was added, so sorry if this got dragged off topic.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on August 27, 2012, 11:59:51 pm
No this is fine. We need this sort of discussion to weed out ideas that make no sense. Perhaps a pure technology post just discussing what future tech should be available in all aspects. Everything from camera scanning to future weaponry.

Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: Peca on August 28, 2012, 02:50:45 pm
I think the best energy source for the postapocalyptic version of Tatra 8x8 would be small nuclear reactor. It has enough power, it lasts for years and it is a real technology. We could be using this technology even now, if there weren´t some safety and political reasons.

http://www.treehugger.com/renewable-energy/the-answer-to-detroits-problems-build-mobile-nuclear-reactors.html (http://www.treehugger.com/renewable-energy/the-answer-to-detroits-problems-build-mobile-nuclear-reactors.html)
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on August 28, 2012, 02:58:51 pm
eh.. I watched a full special on the "Nuclear Bomber" and the danger of it is insane. I don't think I would want to drive around anything using nuclear power other than a large ship with several hundred feet from it to me and steel bulkheads.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: Peca on August 28, 2012, 03:37:27 pm
If you mean project http://en.wikipedia.org/wiki/Tupolev_Tu-119 (http://en.wikipedia.org/wiki/Tupolev_Tu-119) , it is stone age and flying it was very close to commiting suicide. Nowadays we are able to create reactors which are selfregulating and automatically shut down if broken.

For example http://phys.org/news145561984.html (http://phys.org/news145561984.html) - this has 27MW sou our reactor could much smaller.

Or if we want something supersafe, there is http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator (http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator) Only problem with this is low efficiency, without some major improvement it is too inefficient for our purposes.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: PytonPago on September 03, 2012, 11:07:16 am
For example http://phys.org/news145561984.html (http://phys.org/news145561984.html) - this has 27MW sou our reactor could much smaller.

Still the old Uranium source seems to be ... would be interesting to go Th ! : P In other hand, thanks for the link. Pretty interested to know how the operation, its high temp. requirements and its needed fuel uranium state (the fission products too as for the "fuel recycling candidate" claim). Doe, would take the temp. and its designated underground usage as a high risk in automotive solutions.

Or if we want something supersafe, there is http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator (http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator) Only problem with this is low efficiency, without some major improvement it is too inefficient for our purposes.

Nice stuff. How much radioactive material would be needed to fuel our actual transportation world needs ?  ??? (not bad for an colony of course and with an stable source of such materials - trough a lot better nuclear reactors (for static wide-use purposes as of a mothership-reactor) and after production separation/enrichment systems) ... maybe coupled trough an modified variant of russian planed space propulsion: http://www.space-travel.com/reports/Plutonium_to_Pluto_Russian_nuclear_space_travel_breakthrough_999.html (http://www.space-travel.com/reports/Plutonium_to_Pluto_Russian_nuclear_space_travel_breakthrough_999.html)  http://www.theregister.co.uk/2011/04/05/russia_nasa_nuclear_spacecraft/ (http://www.theregister.co.uk/2011/04/05/russia_nasa_nuclear_spacecraft/) ... where the actual radioactive waste would be used for small transports after separation/enrichment (if possible, still don´t know the reactions they have in mind for this drive) ... like they ion acceleration way of thinking doe.  ;D
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: GHAO on February 17, 2013, 02:02:32 pm
According to the physics A-Level course I'm on (A-Levels are just before university, so ages 17-18), under EU laws maximum output of a large truck is 6kW per tonne. So for a Tatra, I'm guessing it's about 4-5 tonnes? That's only 30kW in total, so that's about 1000x smaller power than the little nuclear reactor linked above. Even being approximate, a reactor 100x smaller would fit on the Tatra. Approximately, the reactor would fit between the rear and front wheels, not intruding on cabin space at all. It's possible, but if we're talking of having algae farms, it's gotta have some form of combustion engine.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: cameni on February 17, 2013, 02:31:08 pm
Tatras are heavy trucks. T817 8x8 (http://www.deagel.com/Military-Trucks/T-815-7-8x8_a002521003.aspx) has max weight 38 tonnes.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on February 17, 2013, 04:23:49 pm
According to that page the cargo weight is 24700 so that is heavier than the truck isn't it?.. Are the units in the editor KG?

Actually if you don't mind could you briefly go over some of the units used in the editor? EF probably doesn't convert easily to a single HP/TQ figure but some of the other items must have a real world grounding.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: cameni on February 17, 2013, 04:38:10 pm
Most of the units are in the SI standard system. I tried to put the units in square brackets on the wiki, where possible. For some parameters I don't know the units, or they are so crude approximations that the units don't help anyway. I will need to go over them analyzing the sources. I think the suspension is expressed in a normalized form, independent of vehicle mass.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: GHAO on February 19, 2013, 02:15:28 pm
38 tonnes! Blimey! Fits within my vague approximations still though, nuclear fuel is still an option. :P
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on February 19, 2013, 03:03:49 pm
Well if the truck is coded at 14000 SI (Standard Imperial) than the truck only weighs 7 tons. Which seems low.
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: cameni on February 19, 2013, 03:10:40 pm
LOL, that's not standard imperial, but International System of Units (http://en.wikipedia.org/wiki/International_System_of_Units) (abbreviated SI from French: Le Système international d'unités)
Title: Re: 8x8 Discussion (Let's Talk Specs)
Post by: ZeosPantera on February 19, 2013, 03:22:24 pm
Doh.. Metric is how an American would know it. Damn SI...