Slow ships

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Slow ships

December 25, 2009, 07:36:51 am

Following the 7.1 release, the RVG Tanker, with a capacity of 750m3, travels at an extremely slow speed when fully loaded (4km/h), and the MHz Oil Barge (205m3 capacity) only travels at a speed of 4km/h even when empty. I'm guessing this might have something to do with the new physics engine and the weight of those shops and so on.

Re: Slow ships

Reply #1 – December 25, 2009, 11:20:13 am

Junna,

thank you indeed for your feedback! The new physics engine was written by Bernd Gabriel, so I shall leave it to him to look into this issue. Thank you very much for raising it, though.

May I ask which pakset that you are using, incidentally?

Re: Slow ships

Reply #2 – December 25, 2009, 09:21:42 pm

pak128; it is also problem with various custom vehicles.

Re: Slow ships

Reply #3 – December 28, 2009, 03:35:32 pm

I checked a lot of pak64, pak128 and pak128.Britain.Exp vehicles/convoys and changed the params of the new physics model to values, which allow all these checked vehicles to move at given top speed with full load on a flat ground. These changes will be part of release 7.2. Until then you might want to raise global_power_factor_percent in simuconf.tab.

@jamespetts
The postal bicycle of pak128.Britain.Exp cannot move, but this is independent from any settings in the model. The man power of 1 kW produces a force of 0.1 kN, which is rounded to 0 kN

. I will change the vehikel_besch_t to remember the force/tractive effort in N instead of kN and will load/save it as floating point value in kN.

I suggest to add the 'model params' to ways and vehicles, which actually are the origins of these values. A Shinkansen or Thalys definitly has a smaller wind resistance than a freight steamer. Frictional resistance could be the sum of a way portion and a vehicle portion. The existing constant values will be used, if way or vehicle do not define own values (e.g. for all non experimental paks).

@jamespetts
Even with the smaller FR_ROAD the Scammell Mechanical Horse cannot pull any of its trailers except the one for livestock.

Re: Slow ships

Reply #4 – December 28, 2009, 03:39:09 pm

Bernd,

thank you for looking into this! Much appreciated. As to being able to move at full speed with a full load - could all of these vehicles do that in real life? Which vehicles have you checked for these purposes?

As to the model parameters - which particular parameters do you suggest be added to ways and vehicles? I am very cautious about adding parameters to ways and vehicles, as each additional parameter that needs to be applied to all vehicles or ways creates a truly gargantuan amount of work for pakset maintainers.

Re: Slow ships

Reply #5 – December 28, 2009, 03:58:42 pm

James,

I think all trucks, busses and ships are constructed to run at its top speed with maximum load. As the engineers know the maximum load while constructing the vehicle, they dimension the engine to fit the demands.

The model uses CF_xxx and FR_xxx, where CF_xxx is a wind resistance factor and FR_xxx a friction resistance factor. CF_xxx depends on the vehicle geometry and the density of its environment (air/water) and FR_xxx depends on the contact surfaces of way and vehicle.

Re: Slow ships

Reply #6 – December 28, 2009, 04:28:03 pm

Bernd,

I am not sure that that is necessarily right, for road vehicles, in any event: I suspect that some early 'buses might not have been able to make their top speed when fully loaded, and some lorries might well only be able to go at their maximum speed when not quite full or when empty. Not all engineering decisions are well-made or accurate.

As to the resistance factors - that is a huge amount of work for pakset authors. I was thinking of adding a simple "streamlined=1" parameter to vehicles to indicate whether they are streamlined, and to adjust the air resistance accordingly, the default being zero (not streamlined), so that pakset authors would only have to alter those relatively few streamlined vehicles. Incidentally, on the subject of streamlining, only the leading vehicle of a convoy should have the full air resistance effects: subsequent vehicles should have only a tiny fraction of the leading vehicle's air resistance. Is that modelled?

Re: Slow ships

Reply #7 – December 28, 2009, 05:56:21 pm

a) I am also not quite sure that that is always necessarily right, but for gameplay it looks a bit strange and it is very, very complicated to balance it between 'slows down a bit' and 'friction does allow to start'. I changed the speed preview in gui_convoy_****embler and convoy_info to show a maximum speed of null, if the convoy will not start (that's why some run 4 km/h only. To prevent them from stucking e.g. at slopes, they ~~run~~ creep very slow).

b) Due to the default values (the current constants) the way and vehicle params will be optional. Only ways/vehicles with extraordinarily differing figures need to overwrite them with own values.

c) Yes, the air resistance is mainly a matter of the leading vehicle as long as it's front area is greater than that of all following vehicles. The model respects the air resistance of the leading vehicle only. If we add an air resistance param to the vehicles we should ****ume, that both ends of the vehicle have the same air resistance, if at all both ends can lead the vehicle.

Re: Slow ships

Reply #8 – December 28, 2009, 06:12:40 pm

Quote from: Bernd Gabriel – on December 28, 2009, 03:35:32 pm

I will change the vehikel_besch_t to remember the force/tractive effort in N instead of kN and will load/save it as floating point value in kN.

I won't do that unless other changes to the data model are planned. I forgot, that pak files are in a binary format. In a text format this change would have been compatible with existing integer formatted values.

Re: Slow ships

Reply #9 – December 28, 2009, 06:35:42 pm

Perhaps the reader should simply round up to 1 instead of rounding down to zero?

Re: Slow ships

Reply #10 – December 28, 2009, 06:48:48 pm

Quote from: Bernd Gabriel – on December 28, 2009, 03:58:42 pm

James,

I think all trucks, busses and ships are constructed to run at its top speed with maximum load. As the engineers know the maximum load while constructing the vehicle, they dimension the engine to fit the demands.

Not really. In factory specs there is usually a "fully loaded top speed", which is *not* the same as the "top speed". Sadly we don't usually have factory specs to work from :-) There are good reasons for this particularly with freight: it often makes sense to have a vehicle which can run faster empty than full (since it runs half the way empty), and with some types of engines the higher "empty speed" just happens naturally when you design an engine for the 'fully loaded top speed'.

Ships and barges, however, usually can go at their top speed fully loaded. Water resistance is much more significant than inertia, so a ship engine doesn't usually get a "bonus" for running empty.

Road and rail vehicles are different, because air resistance is a lot less than water resistance. Heavy engines designed to haul huge freight loads usually can go a bit faster running "light" (though sometimes it is not safe). However, the existing vehicles in most paks seem to have been mostly balanced for a "top fully loaded speed" rather than a "top speed" -- especially since in standard they are allowed to exceed "top speed" in some circumstances. It shouldn't be a difference of more than, say, 15 km/h in most vehicles anyway.

---
EDIT:
BTW, I like the idea of simply rounding all numbers below 1 up to 1 when reading. It's sort of simplistic, but it works (and I'm OK with bicycles suddenly getting a BURST of SPEED

)

Re: Slow ships

Reply #11 – December 28, 2009, 08:33:07 pm

Ships are very much hindered by load, especially small ships, since the water to be displaced is much higher. Nevertheless, this is most square, while load is linear.

And for trains the max speed is usually given by the brakes. Thus empty trains are allowed for higher speeds than heavy loaded ones.

Re: Slow ships

Reply #12 – December 29, 2009, 06:37:10 pm

Quote from: jamespetts – on December 28, 2009, 06:35:42 pm

Perhaps the reader should simply round up to 1 instead of rounding down to zero?

Yes, that will help the postal bike for now, but image those calves!

I'll fix the code that way.

Re: Slow ships

Reply #13 – January 02, 2010, 11:17:25 am

Quote from: Bernd Gabriel – on December 28, 2009, 03:58:42 pm

James,

I think all trucks, busses and ships are constructed to run at its top speed with maximum load. As the engineers know the maximum load while constructing the vehicle, they dimension the engine to fit the demands.

The model uses CF_xxx and FR_xxx, where CF_xxx is a wind resistance factor and FR_xxx a friction resistance factor. CF_xxx depends on the vehicle geometry and the density of its environment (air/water) and FR_xxx depends on the contact surfaces of way and vehicle.

Bernd - can I check: do you envisage pakset authors being able to set precise CF_xxx and FR_xxx values in vehicles' .dat files? If so, in what situations, other than a streamlined vehicle, do you envisage pakset authors needing to specify these values, and where is such information obtainable?

Re: Slow ships

Reply #14 – January 02, 2010, 01:38:47 pm

James,

some example drag coefficients can be found at http://de.wikipedia.org/wiki/Str%C3%B6mungswiderstandskoeffizient and http://en.wikipedia.org/wiki/Drag_coefficient. You see differences of about 100%. That should be worth thinking about indiviual CF_xxx figures.

some example rolling frictions can be found at http://en.wikipedia.org/wiki/Rolling_friction and http://de.wikipedia.org/wiki/Rollwiderstand. Here you see differences of about 500%-800% for car tires on various grounds. That should be worth thinking about indiviual FR_xxx figures.

Obtaining exact values might be difficult, but at least matching the order of magnitude, will help to model vehicles (and ways) closer to the real originals.

Re: Slow ships

Reply #15 – January 02, 2010, 05:27:54 pm

Bernd,

I cannot see a great deal of information suggesting a significant difference in either the drag coefficients or rolling resistance levels of different vehicles of the same basic cl****. Indeed, the rolling resistance gives one value for each cl**** of vehicle, with no information as to variance between different vehicles in that cl****. I only read the English pages, as I cannot read German - is different information provided on the German page?

Re: Slow ships

Reply #16 – January 02, 2010, 06:37:35 pm

Please look at the tables.
"Autoreifen" = "car tire"

Re: Slow ships

Reply #17 – January 02, 2010, 07:43:18 pm

Quote from: Bernd Gabriel – on January 02, 2010, 06:37:35 pm

Please look at the tables.
"Autoreifen" = "car tire"

The tables in the German page or the English page?

Re: Slow ships

Reply #18 – January 02, 2010, 10:06:55 pm

Both english and german tables.

Together they give a wide range of c_w resp. c_d values for cars and airplanes and for car tires on several kinds of roads:

cd/cw    Item
0,8       Ford Model T
0,54       Mercedes G-Kl****e (W463, langer Radstand)
0,50       Citroen 2CV
0,48       VW Käfer
0,41       VW Golf I (1974)
0,38       VW New Beetle (1998)
0,37       Renault Twingo I (1995), Smart Fortwo (1998)
0,36       Citroën DS (1955), Tatra 87 (1937)
0,35       NSU Ro 80 (1967)
0,34       Ford Sierra, VW Golf II
0,33       Peugeot 206, Mercedes-Benz 190 E (1983)
0,32       Fiat Grande Punto (2005), Seat Leon (Typ 1P)
0,31       Renault 19, Citroën C4 Pic****o, VW Golf VI
0,30       Audi 100 C3 (1982), Citroen SM (1970), Škoda Octavia (Limousine 2008)
0,29       Opel Vectra (Vectra A 1988–1995), BMW 1er (2004), BMW 7er (2008)
0,28       Mercedes E-Kl****e (W124, 1984), Opel Vectra (Vectra C 2002–2008), Audi A2 (1999–2005)
0,27       Audi A4 (2007), Mercedes-Benz CL-Kl****e (2006), Opel Insignia (2008)
0,26       BMW 3er (2008), Mercedes C-Kl****e (2000), Opel Calibra (1990)
0,25       Panhard CD (1962), Audi A2 1.2 TDI (2000), Mercedes E-Kl****e (W212, 2009)
0,24       Mercedes-Benz E-Kl****e Coupé (C209, 2009)
0.9    a typical bicycle plus cyclist
0.021    F-4 Phantom II (subsonic)
0.022    Learjet 24
0.024    Boeing 787 [15]
0.027    Cessna 172/182
0.027    Cessna 310
0.031    Boeing 747
0.044    F-4 Phantom II (supersonic)
0.048    F-104 Starfighter
0.095    X-15 (Not confirmed)

Crr             Description
0.0002 to 0.0010       Railroad steel wheel on steel rail
0.0022 to 0.005       production bicycle tires at 120 psi and 50 km/h, measured on rollers
0.0025          Special Michelin solar car/eco-marathon tires
0.005          Tram rails standard dirty with straights and curves
0.0055           Typical BMX bicycle tires used for solar cars
0.0062 to 0.015       Car tire measurements
0.010 to 0.015       Ordinary car tires on concrete
0.055 to 0.065       Ordinary car tires on gr****, mud, and sand
0.3             Ordinary car tires on sand
0,001–0,002       Eisenbahnrad auf Schiene (Railroad steel wheel on steel rail)
0,0035          Fahrradreifen auf Asphalt (bicycle tires on asphalt)
0,006–0,010       Autoreifen auf Asphalt, Lkw (Truck tire on asphalt)
0,011–0,015       Autoreifen auf Asphalt, Pkw (Car tire on asphalt)
0,01–0,02          Autoreifen auf Beton (... concrete)
0,020          Autoreifen auf Schotter (... gravel)
0,015–0,03          Autoreifen auf Kopfsteinpflaster (... cobblestone)
0,03–0,06          Autoreifen auf Schlaglochstrecke (... pothole road)
0,050          Autoreifen auf Erdweg (... earth road)
0,04–0,08          Autoreifen auf festgefahrenem Sand (... compacted sand)
0,2–0,4          Autoreifen auf losem Sand (... not compacted sand)

Re: Slow ships

Reply #19 – January 02, 2010, 10:38:58 pm

Ahh, yes, I saw those, but that doesn't seem to show much information on differentiation between different sorts of commercial transport - all of the road vehicles listed are private cars, no different types of trains are listed, and the aircraft values do not fluctuate a great deal.

Re: Slow ships

Reply #20 – January 02, 2010, 10:56:54 pm

they forgot to list the simutrans relevant vehicles

I'm sure, that a modern truck has less air resistance than the good old Ford T and an ICE train less than an early electric loco.
These comparisons sound like 'the younger the vehicle the less the air resistance' but a modern commuter train has a greater air resistance than an ICE.

Re: Slow ships

Reply #21 – January 02, 2010, 11:59:44 pm

I very much doubt that the same would apply to commercial road vehicles as it would to cars; commercial road vehicles are almost never streamlined. Some trains are indeed streamlined; but I am not aware of there being a truly significant difference between different streamlined trains, or different non-streamlined trains; only between streamlined trains and non-streamlined trains. What I was planning is simply having an option in the .dat file "streamlined=1" for those cases.

There does not seem to be a significant difference in rolling resistance, either.

Re: Slow ships

Reply #22 – January 03, 2010, 12:57:29 am

I see no imperative to simplify the CF_xxx figure to a boolean value and riding a bike on sand isn't as easy as on concrete.

Re: Slow ships

Reply #23 – January 03, 2010, 10:52:09 am

Quote from: Bernd Gabriel – on January 03, 2010, 12:57:29 am

I see no imperative to simplify the CF_xxx figure to a boolean value and riding a bike on sand isn't as easy as on concrete.

The reason to use a boolean value is that the only significant differences are between streamlined and non-streamlined vehicles, and because it is virtually impossible to get accurate air resistance data for specific commercial vehicles.

As to different surfaces - are you suggesting that the rolling resistance values be set in the ways' .dat files, not in the vehicles' .dat files?

Re: Slow ships

Reply #24 – January 03, 2010, 11:27:31 am

Quote from: jamespetts – on January 03, 2010, 10:52:09 am

The reason to use a boolean value is that the only significant differences are between streamlined and non-streamlined vehicles, and because it is virtually impossible to get accurate air resistance data for specific commercial vehicles.

As CF_xxx will be an optional figure, there is no need to find accurate values. Skip it and there will be the common default. If you know, your vehicle has an extraordinary greater or lesser value, set it.

Quote from: jamespetts – on January 03, 2010, 10:52:09 am

As to different surfaces - are you suggesting that the rolling resistance values be set in the ways' .dat files, not in the vehicles' .dat files?

Rolling resistance (rr) is an effect of the interacting surface of way and vehicle. Thus a carriage with a steel rimmed wheel on cobblestone has a lesser rr than a car's pneumatic tire and the horses themselves nearly about no 'rolling' resistance at all, although it is more difficult to ride in sand. Therefore I suggested to add an optional rr figure to both way and vehicle and to add the rrs of way and vehicle to obtain the actual effective rr. This is a compromise avoiding a separate table or list of combinations of ways and vehicles with related rrs.

Re: Slow ships

Reply #25 – January 03, 2010, 12:35:04 pm

Quote from: Bernd Gabriel – on January 03, 2010, 11:27:31 am

As CF_xxx will be an optional figure, there is no need to find accurate values. Skip it and there will be the common default. If you know, your vehicle has an extraordinary greater or lesser value, set it.

The reason that I suggested simply having "streamlined=1" is that the only information that anyone will ever be able to get about commercial vehicles will be whether they are streamlined or not. It will be easier for pakset authors to understand and implement this than for all of them to try and fail to find vehicle specific data, and end up falling back on the same generic data that we can hard-code in the first place.

Quote

Rolling resistance (rr) is an effect of the interacting surface of way and vehicle. Thus a carriage with a steel rimmed wheel on cobblestone has a lesser rr than a car's pneumatic tire and the horses themselves nearly about no 'rolling' resistance at all, although it is more difficult to ride in sand. Therefore I suggested to add an optional rr figure to both way and vehicle and to add the rrs of way and vehicle to obtain the actual effective rr. This is a compromise avoiding a separate table or list of combinations of ways and vehicles with related rrs.

Ahh, this is an interesting idea - to add the two values. Where do you think that we can find data for that? The Wikipedia article has data for certain combinations (e.g., steel railway wheel on steel railway track), but does not split them (what would be the result of a steel railway wheel on cast iron track? A cast iron wheel on steel track? A wooden wheel with a wrought iron rim on cast iron track? Etc.). Do you know where this data might be available?

Re: Slow ships

Reply #26 – January 03, 2010, 12:47:09 pm

James,

you don't find these data anywhere like you don't find data for maintenance costs anywhere. But you added such a figure and the vehicle designers must find a value suitable for gameplay.

This is my final statement to the discussion, whether we need these figures or not. There is nothing more to say about the relation between model and reality.

Re: Slow ships

Reply #27 – January 03, 2010, 01:52:01 pm

Actually, I am in the process of sourcing information about realistic relative maintenance and purchase costs for Pak128.Britain-Ex.

Re: Slow ships

Reply #28 – January 09, 2010, 02:30:05 pm

you could just use a float value for drag and use it like a boolean for the extreme values 1.0 and 0.0. A hardcoded default value will be used in that case. If anyone knows or guesses the excact value he could enter the float value and override the defaults.